Answers to the practical questions and problems contained in the fourteen weeks courses in physiology, philosophy, astronomy, and chemistry (old and new edition). By J. Dorman Steele ...
Steele, Joel Dorman, 1836-1886.

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Page  2 THE FOURTEEN WEEKS' COURSES IN NATURAL SCIENCE, BY J. DORMAN STEELE, A.M., PHI.D. Fourteen Weeks iq Natural Philosophy, Fourteen Weeks iq Ctlenqistry, Fourteen Weeks iq Descriptive Astroqonqy, Fourteel Weeks iq Popular Geology, Fourteeq Weeks iQ2 Human P1ysiology, Fourteen Weeks iq Zoology, Fourteeq Weeks iq Botany, A Key, containing Answers to the Questions and Problems in Steele's I4 Weeks' Courses, 4 1ISTORIC4L SERIES, ON THE PLAN OF STEELE'S 14 WEEKS IN THE SCIENCES. A Brief History of the Urlited States, A Brief History of France, The same publishers also offer the following standard scientific vworks, being more extended or difficult treatises than those of Prof. Steele, though still of Academic grade. Peck's Ganot's Natural Philosophy, Porter's Principles of Chemistry, Jarvis' Physiology and Laws of Healtl, Wood's Botanist and Florist, Clanlbers' Elenments of Zoology, lcIqtyre's Astroqomy and tle Globes, Page's. Elen~ents of Geology, Entered according to Act of Congress, in the year 1869, by A. S. BARNES & CO., In the Clerk's Office of the District Court of the United States for the Southern District of New York. sTERLE'S KEY.

Page  3 PREFACE. THIS little work is designed to aid teachers who are using the Fourteen Weeks Course. The problems contained in all the books are fully, and, it is thought, accurately solved. Great pains have been taken to revise and compare them carefully. The practical questions are answered, often not in full, yet enough so to give the key to the more perfect reply. The use of the text-books is presupposed, and the statements merely supplement, or apply the fuller theories therein contained and explained. On many points there may be a difference of opinion. The author often finds in his own classes a wide diversity. On mooted questions he has merely advanced one view, leaving the subject open for the discussion of other theories. Minute directions are given, pages 71-82 inclusive, for performing a course of experiments in Chemistry. It is hoped that these may be of service to teachers who, with incomplete appadatus, are trying to illustrate to their pupils some of the principles of that science. In all cases of doubt or misunderstanding with regard to the answers or solutions, the author will be pleased to correspond with any teacher using the Series ELMIRA, Mdrch 19, 1870

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Page  5 ANS WERS TO THE PRACTICAL QUESTIONS IN THE FOURTEEN WEEKS COURSE NATURAL PHILOSOPHY. LThe bold-faced figures refer to the pages of the Philosophy; the others to the number of the Practical Questions.] INERTIA. 26. I. If one is riding rapbidly, in which direction will he be thrown when the horse is suddenly stopped f. In the same direction in which he is going. He has the inotion of the carriage, and his inertia carries him forward. 2. Wkhen standing in a boat, why, as it starts, are we thrown backward? Because the inertia of our bodies keeps them stationary, while the boat carries our feet forward. 3. WIhen carrying a cup of tea, if we move or stop quickly, why is the liquid liable to spill? The inertia of the tea tends to keep it still or in motion, as the case may be. If we move the cup quickly, the motion is not imparted to the liquid soon enough to overcome the inertia. When, therefore, we start, the tea spills out backward; or, when we stop, it spills out forward. We understand this if we can tell why a cup of tea is more liable to spill than one of sugar.

Page  6 6 ANSWERS TO BRACTICAL QUESTIO.NY 4. Why, whzen closely Jbursued, can we escape by dodging? We turn sharply. Our pursuer, ignorant of our design, cannot overcome his inertia so as to turn as quickly, and hence is carried past. 5. tWhy is a carriage or sleigh, when sharply turnino, a corner, liable to tiz over? Because its inertia tends to carry it directly forward. A puzzling question in this connection is-Why is a sleigh more liable to tip over than a wagon? 6. Why, if you Pklace a card on your fnger, and on to q/ zit a cent, can you snap the card fi-om under the cent without knockinfg the latter offyourfingcr? Because the friction between the card and the cent is so slight that, by a quick snap, you can overcome the inertia of the former without imparting any fbrce to the latter. 7. Why, after the sails of a vessel are furled, does it s;ll continue to move; and why, after the sails are all spread, does it require some time to -et under full headway? Its inertia must be overcome in the one case by the resistance of the air and water, and in the other by the force of the wind. COHESION. 40. I. Why can we not weld a piece of copper lo one oj iron? Cohesion acts only between molecules of the same kind. 2. 4Why is a bar of iron stronger than one of wood? Because its force of cohesion is stronger. 3. WVhy is a piece of iron, when perfectly welded, stronger than before it was brokcn? By the hammering, more particles are brought within the range of cohesion. 4. Why do drops of dz/]'ie-eunt liquids vary in size? Because they vary in cohesive force. 5. Why, when you drop medicine, will the last few dr'fp. contained in the bottle be of a larger size fhan the others?

Page  7 IN AA NTURAL PHIILOSOPHY. 7 The pressure of the liquid in the bottle is less, and therefore they form more slowly. 6. Why are drops larger if you drop them slowly f There is more time for the adhesive force of the bottle to act on the liquid, and so a larger drop can be gathered. 7. Why is a tube stronger than a rod of the same weight? a rod supported at both ends be broken in the middle. \Ve shall see that it yields first on the circumference. So true is this, that long beams heavily loaded have been broken by a mere scratch of a pin on the lower side. The particles along the centre break last. They rather aid in the fracture, since they afford a fulcrum for the rest of the rod, acting as the long arms of a lever, to act upon. In a tube the particles at the centre are removed and all concentrated at the outside, where the first strain is felt. (See Physiology, p. 20). 8. Why, if you melt scraps of zinc, will they form a solid mass when cooled? The heat overcomes, in part, the attraction of cohesion, so that the particles flow freely on each other. They now all come within the range of cohesion, so that when the metal cools they are held by that force in a solid mass. 9. In what liquids is the force of cohesion greatest? Mercury, molasses, etc. io. Name some solids that will volatilize without melting? Arsenic, camphor. ADHESION. 47. I. Why does cloth shrink when wet? By capillary attraction the water is drawn into the pores ot the cloth. The fibres are thus expanded sidewise and shortened lengthwise. The cloth "fulls uIf" or thickens while it shortens and narrows (shrinks) in the process. 2. IWhy do sailors at a boat-race wet the sails? The pores being full and expanded make the sails more compact. They will therefore hold the wind better.

Page  8 8 ANSWERS U'0 PRACTICAL QUESTIONS 3. Why does not writing-ipaer blot? Because the pores are filled with size. (See Chemistry, p. I6I.) 4. Why does iainztprevent woodfrom shrinking? Because it fills the pores of the wood. 5. ihat is the s/hate of the surface of a glass qf water and one of mercury? Ordinarily the former is concave and the latter convex. 6. Why can we not dry a toweltierfectly by wringing? Because of the strength of the capillary force by which the water is held in the pores of the cloth. 7. Why will not water run through a fine sieve when the w7ires have been greased? Because the grease repels the water and so prevents capi!. lary action. 8. Why will camnihor dissolve in alcohol and not in water? Because there is a strong adhesion between the alcohol and camphor, and little, if any, between the water and camphor. 9. Why will mercury rise in zinc turbes as water does zn glass tubes? Because of the strong adhesion between zinc and mercury. io. Why is it so diffcult to lift a board out of water? Because of the adhesion between the board and the water. i I. Why will ink spilled on the edge of a book extendfurther inside than f stsilled on the side of the leaves? Because the capillary pores of the paper are short, being only the thickness of a leaf, while the capillary spaces between the leaves are longer and continuous. 12. If you should hali ten to spill some ink on the edge of,your book, ought you lo press the leaves togfether?.No. Because you would make the capillary spaces between tlie leasves smaller, and so the ink would rise in them further. 13. WZhy can you not mix oil and water? Because there is no adhesion between them.

Page  9 IN NATURAL PHILOSOPHiI. 9 15. Why will water we/tyour hand while mercury will noat! Because in the former case there is an adhesion, in the latter none. I 6 Why is a tub or fail liable to fall to pieces if noalflled with water or kefpt in the cellar? Because the moisture dries out of the pores, and the wood shrinks so as to let the hoops fall off. 17. NAame instances where the attraction of adhesion is stronger than that of cohesion. WXTood fastened by glue will often split before the glue will yield. Paper stuck with paste, and bricks with mortar, are also examples. GRAVITATION. 63. I. When an afttle fills to thegroulrd, how izmuch doesthe earth rise to meet it? The earth falls as much less distance than the apple, as its mass is greater. 2. Uthat causes the sawdust in a mill-ofind to collect in large masses? The attraction of gravity which exists between all bodies, whereby they attract each other. All bodies on the earth would tend to approach each other, and the big ones would gather all the little ones around them were they as free to move as the sawdust floating on water. 3. Will a body weigh more in a valley than on a mountain P It will, because the attraction of the earth is greater. 4. Will a pfound weight fall mIore slowly than a tzwo-fiound Veight? They will both fall in the same time, except the slight difference which is caused by the resistance of the air. Galileo propounded this view and proved it, in the presence of a xast crowd, by letting unequal weights fall from the leaning towez of Pisa.

Page  10 [0 ANSSWERS TO PRACTIUAL QUESTIONS 5, How deey5 is a well, if it takes three seconds for a stone to fall to the bottom of it? (2) equation of falling bodies, d = 16t2; hence d = 16 x 32 = 144 feet. 6. Is the centre qf gravity always within a body-as, fao examiple, a ring.? It is not. In the case given it is at the centre of the circle. 7. If two bodies, weighing respectively 2 and 4 pounds, be coznneced b't a rod 24 inches long, where is the centre of ravity? To be in equilibrium the weight of one multiplied by its distance from the centre of gravity iust equal the weight of the other mtltiplied by its distance. 24. 6 = 4; hence 4 in. is the unit for each pound. Therefore the centre of gravity is 8 in. from the larger weight and 16 in. from the smaller. 8. In a balli of equai density throughout, where is the centre of gravity? At the cefitre of the ball. 9. Why does a ball roll down hill? Because the line of direction falls without the small base of the ball. Io. Why is it easier /o roll a round body than a square one? Because the base of the ball is so much smaller, and therefore the centre of gravity need not be raised to bring the line of direction without. I I. Why is it easier to tifz over a load of hay than one of stone? Because the centre of gravity in a load of hay is very high, and in a load of stone very low. Therefore the centre of gravity in the former need not be raised much to bring the line of direction without the base, while in the latter it must be. I2. Why is a fyranmid the stablest of structures? Because the base is so broad and the centre of gravity so low. The centre of gravity must therefore be lifted very ligh before the line of direction will fall without the base. 13. When a hamner is thrown, on which end does it always strike? On the heavy end or head, because that part is attracted by the earth more strongly.

Page  11 IN NATURAL PHILOSOPHY. I 14. WIhy does a rope-walker carry a heavy balancing-oleI Because in this way he can easily shift his centre of gravity. I5. What would become of a ball if droApied Zilto a hoie bored through the centre qf the earth? In falling, it would gain a momentum which would carry it past the centre of the earth. But as it is constantly coming to a part having a slower axial revolution than itself, it would scrape on the east side of the hole until it reached the centre; beyond that point it would scrape on the west side. This friction would prevent its reaching the opposite side of the earth. It would therefore vibrate to and fro, each time through a shorter distance, until, at last, it would come to rest at the centre of the earth. i6. Would a clock lose or gain time if carried to the top of a mountain? It would lose time, because the force of gravity would be lessened. At the North Pole it would gain time, because there the force of gravity would be increased. I7. In the winter, would you raise or lower the pendulzumbob of your clock? I would lower it, since the cold of winter shortens the pendulum, and this movement of the bob would counteract that change. i8. Why is the iendulum-bob always madeflat? To decrease the friction of the air. i9. What beats off the time in a watch? The vibration of the balance-wheel. 20. Is solved in the book. 21. WIhatshould be the leI^t/h of a fiendulum at New YorA to vibrate half-seconds? (1 sec.)2: (/, sec.)2:: 39.1 in.: x = 9.7 + inches. To vibrate quarter-seconds? (1 sec.)2: (1/4 sec.)2:: 39.1 in.: = 2.4 + inches. To vibrate hours? (1 sec.)2: (3600 see.)2:: 39.1 in.: x -: 7!97.7 miles.* ~lNearly the ditineter of the earth.

Page  12 I2 ASVSWERS TO PRACTICAL QUESTIONS,' 22. What is the profiortionate time of vibration of two pen. duzirns, I6 and 64 inches long, respectively? According to the 2nd. law of pendulums, Time of vib. of 1st: Time ofvib. of 2d::./16: 4/6:: 4: 8:: 1: 2 23. Why, when you are standing erect against a wall, and a piece of money is placed between your feet, can you not stoyV forward and ftick it upf? By leaning forward you bring the centre of gravity in front of your feet, and, as on account of the wall, you cannot throw any part of your body back to preserve the balance, you fall forward. 24. If a tower were i 98 feet high, with what velocity would a stonle droPifiedfromn the summnit, strike the ground? According to equation (3), v2 = 61 d. v2 = 64 x 198. v=112.5 feet. 25. A bodyfalls in 5 seconds: with what velocity does zi rtrike the grozund? According to equation (1), v = 32 t. v =32 x 5. v =160 feet. 26. How far will a body fall in Io seconds? According to equation (2), d = 16 t2. d = 16 x 102 = 1600 feet. Witih what velocity will it strike the ground? According to equation (1), v = 32 t. v = 32 x 10 = 320 feet. 27. A body is thrown iujward with a velocity of 192 feet the,irst second, to what height will it rise? Equation (1), v = 32 t. 192 = 3-2 t. t = 6 sec. (2), d = 16 t2. d = 16 x 62=57f feet. 28. A ball is shot ufiward with a velocity of 256 feet;, t what height will it rise? How long will i cottiznuze to ascend Using equations (1) and (2), as in the last problem, we have: t = 8 sec. d = 1024 feet. 30. Are any two plumb-lines parallel? Thev are not, since they point to the earth's centre of gravity. No twvo spokes of a wheel can be parallel.

Page  13 IN 1NATURAL PHILOSOPHY. 1 3 3r. A stone let fallfromi a bridge strikes the water in three seconds. What is the hezght? Equation (2), d = 16t2. d = 16 x 32 = 144 feet. 32. A stonefallsfrom a church steeple in 4 seconds. What is the height? Equation (2), d = 16t2. d = 16 x 42 = 256 feet. 33. How far would a body fall the first second at a hez-ght of I2,000 miles above the earth's surface? (16,000 mi.)2: (4000 mi.)2:: 16 feet: x = 1 foot. 34. A body at the surface of the earth weizghs oo tons. what would be its weight I,ooo miles above?,(5000 mi.)2 (4000 mi.)2:' 100 tons: x = 64 tons. 35. A boy wishing to find the hezght of a steetle les fly an arrow thatjust reaches the toti and then falls to the ground. It is in the air 6 seconds. Required the hezght. Equation (2), d = 1612. d = 16 x 32 = 144 ft. 36. A cat let fall fronm a balloon reaches the ground it io seconds. Required the distance. Equation (2), d = 16 x 10' = 1600 ft. 37. In what time wzll a tpeznduinu 40 feet long make a vzibration? According to the 2nd. law of pendulums, and taking the length of a seconds pendulum as 39 in., we have: lsec.:x:: /39: /40x12in. x= /-g=1 2.:o+ x = 3.5+ sec. -In what time will a tendulunz 52 feet long make a vz; bration? 1 sec.: x:: /3in.: /52x 12 in. - = 4 seC.

Page  14 14 A.NSTI'ERS TO PRA C77CAL QUESTIONS -How long would it take for apendulum one mile in leng'th tA, make a vibration? — How long would it take for a fpendulum reac Itingfrom the earth fto the moon to make a vibration? -Required the length of a pendulum that would vibrate centuries. ( 7 be solved likeprobl/em 20.) 38. Two mneieoric bodies in space are 12 miles apart. They weigh Ioo and 200 lbs. respectively. If they siould fall toaether by force of their mutual attraction, what Plortion of the distance woluld be passed over by each body? The distance passed over by the two bodies is inversely as their mass; hence one moves 8 miles and the oth er 4 miles. 39. I/a body weighs 2,000 lbs. ufpon the surface of the earth, what would it weigh 2,000 miles above? (6000 mi.)2: (4000 mi.)j:: 2000 lbs.: x = 888,/9 lbs. /Low much 500 miles above? (4500 mi.)2: (4000 mi.)2:: 2000 lbs.: x = 1580+lbs. The weight of bodies below the surface of the earth decreases as the distance increases. Ex. Ex. What would the above body weigh if carried 2,000 mziles below the surface? i,ooo lbs. — I,ooo miles belowe? 1,500 lbs. (See Physics, page 5, note.) 40. At what distance, above the sufwace of the earth will a body fall, the frst second, 21 inches? A body falls 16 ft.* (192 inches) at the surface of the earth. 211/3 inches are */9 of 192 inches: Now as the attractioil is inversely as the square of the distance. the distance must be V/, or 4 times that at the surface. Hence the body must be 12,000) miles from the centre, or 8,000 miles from the surface of the earth. The problem may be solved directly by proportion, thus: x2: 40002:: 192 inches: 21'/3 inches. x = 12000 miles (distance from the centre) 12000 miles-4000 miles=8000 miles. 41. How far will a bodyfall in 8 seconds? I,o24 ft. —II t/e 8fz second? 240 ft. —-In Io seconds I, 6o0C ft. —in tht. 3oth second? 944 ft. According to the best authorities tl)e dist,:acte is more exactly 16t1/, f

Page  15 IN NA TURA L PIHILOSOPIt.. I 5 MOTION. N0. I. Can a rifle-ball befred thr-olgi a handkerchief sus. pended looselyfrom one corner? Yes. The wind of the ball will lift the handkerchief somewhat. 2. A rife-ball thrown against a board standing edg6ewise will knock it down; the same bullet fired at the board vill pass through it without disturbizng its position. Why is this? The ball which is thrown has time to impart its motion to the board; the one fired has not. 3. Why can a boy skate safely over a piece of thin ice, when, if he should pause, it would break under him directly? In the former case there is time for the weight of his body to be communicated to the ice; in the latter, there is not. 4. Why can a cannzon-ball be fred through a ldoor standing ajar, without moving it on its hin-ges? Because the cannon-ball is moving so quickly that its motion is not imparted to the door. 5. Why can we drive on the head of a hammzer by sinuply strikinzg the end of the handle? This can only be done by a quick, sharp blow which will drive the wooden handle through the socket before the motion has time to overcome the inertia of the iron head. A slow, steady blow will be imparted to the head, and so fail of the desired effect. 6. Suzipose )o'u were on a train of cars movin, at the rate of 30 milesper hour: with what force would you be thrown forward if the train were stopped instantly? With the same velocity which the train had, oi 44 feet pet second. Your momentum would be your weight avoirdupois multiplied by this velocity. 7. IZ what line does a stone fall from the nast-head of a vessel in motion? In a curved line, produced by the two forces-gravity and the forward motion of the vessel.

Page  16 L D ANSWERIS TO PRA b'UICAL QUESTION1'S 8. If a ball be droa5i)ed from a hzigh tower' it'ill striev /tIe earth a little east of a vertical line. Why is this? In the daily revolution of the earth on its axis, from vwest to east, the top of the tower moves faster than the bottom, because it passes through a larger circle. When, therefore, the ball falls, it retains that swifter easterly motion and so strikes east of the vertical. 9. If is staled that a suit was once brought by the driver of a light-wagon against the owner of a coach for damcages caused by a collision. The comn laint was that the lattfr was drivingl sofast, that wheln the two carriages struck, fte drivcr Zf the former was thrown-forerard over the dash-board. S'how how his own testimolny pSroved him to have been at f/ullf. WThen the light-wagon was suddenly stopped, its driver went on by his inertia with the same speed at which the wagon was moving. That this threw him forward over the dash-board, proves his speed to have been unusual. io. Supiose a train moving at the rate of 30 miles per hour; on the rear jplaforzm is a cannon ained parallel with the track and in a direction precise/y opposile to the motion of the car. Let a ball be discharged wit/h /e exact speed of the train, where would it fall? In a vertical line to the track. The two equal, opposite motions would exactly destroy each other. t. Su5ppose a steamer in ralpid motion and on its deck a man jumping. Can he jumnpi further by leapigs the w'ay the boat is moving or in the ofpiosile direction? It will make no difference as long as he jumps on the deck. Should he jump off the boat, then the effect would be different. 12. WHhy is a runnlintgjuniz lont er than a standing one? Because the motion gained in running is retained in the jump and adds to its distance. I3. If a stone be dr(ojpped from the mast-head of a vessel in motion, will it strike the same spot on the deck that it would if the vessel were at rest? It will. It falls with the motion of the vessel, and goes just as far forward while falling as the vessel does.

Page  17 IN NA I URAL PHILOSOPHY. 1 7 I4. Coltd a party play ball on the deck of the Great Eastern when steaming along at the rate of 20 miles per hour, without making allowance for the motion of the ship.? They could. The ball would have the motion of the ship, and would move with it in whatever direction they might throw it. I 5. Since "action is equal to reaction," why is it not as dangerous to receive the "' kick" of a gun as the force of the bullet? The striking force is as the square of the velocity; and the velocity with which the gun moves backward is as much less than that with which the bullet moves forward, as the gun is heavier than the bullet. For this reason a heavy gun will kick much less than a light one. I6. If you were to jumZn from a carriage in rapid nZotion, wouldyou leap directly toward the spiot on which you wished to alzghlt? No; because as one jumps from the wagon he has its forward motion, and will go just as far ahead, while leaping, as he would if he had remained in the carriage. He should, therefore, aim a little back of the desired alighting-place. I 7. If you wished lo shoot a bird in swift fzight, would you aim directly at it? No. The bird will fly forward while the bullet is going to it. One should, therefore, aim a little in advance. i8. At what parts of the earth is the centrifugalforce the least? The poles. They simply turn around in 24 hours. 9. What causes the mud tojfy from the wheels of a carriage in rapid motion? The centrifugal force (the inertia of the mud). 20. What proof have we that the earth was once a soft mass? It is flattened at the poles. This effect is produced upon a ball of soft clay by simply revolving it on a wire axis. 21. On a curve in a railroad, why is one track always higher than the other?

Page  18 18 AXSWERS TO PRACTICAL Q Z7ESTIONS The outer track is raised that gravity may balance the cen. trifugal force. 22. I4What is the pirincijple of the sling? The sling is whirled until a strong centrifugal force is generated; the string, the centripetal force, is then released, when the stone flies off at a tangent. 23. The mouth of the Mississzppi river is about 24 miles fulrther from the centre of the earth than its source. What causes its water to thus " run Au hill?" The centrifugal force produced by the revolution of the earth on its axis tends to drive the water from the poles toward the equator. Were the earth to stand still in its daily rotation, the Gulf of Mexico would empty its waters back through the Mississippi to the northern regions. 24. Is it action or reaction that breaks an egg wheen I strike it against the table? The reaction of the table. 25. Was the man philosophical who said "it was not the falling so far but the stofiping so quick that hurt him?" He was. 26. If oneferson runs against another, which receives the greater blow? Action is equal to reaction: hence the blows must be equal. 27. Would it vary the effect if the two persons were running in otbtosite directions? The blow would then be the sum of both their momenta. If they were running in the same direction? The blow would be equal to the diference of their momenta. 28. [eWhy can you notfire a rifle-ball around a hill? Because a single force always produces motion in a straight line. 29. Why does a heavy gun " kic/" less than a light one? See problem I5. 30., ma on on the deck of a large steamer draws a small

Page  19 IN NATURAL PHIL OdOPHY. 19 boat toward hint. How much does the shipz move to meet the boat? The ship moves as much less distance than the boat, as it'3 heavier than the boat. 31. Suppose a string, fastened at one end, will just sut5p5or a weight of 25 lbs. at the other. Unfasten it, and let two persons pull uipon it in opfilosite directions. How mu, /i can each pull without breaking it? 25 lbs. The second person, in the latter case, can pull as much as the nail did in the former. 32. Can a man standing on a pilatfor;-scale make himself Iighter by ifting uip on himself? He cannot; because action is equal to reaction, and in an opposite direction. As much as he lifts up, so much must he press down. 33. Why cannot a man lift himself by fiulling utp on his boot-straps? See last problem. 34. If ifrom a gun pilaced vertically, a ball were fired into perfectly still air, where would it.fall? It would return into the gun. 35. With what momentum would a steamboat weighing I,ooo tons, and moving with a velocity of I o feet per second, strike against a sunken rock? 1000 tons x 101 = 100,000 tons. 36. With what momentum would a train of cars weighing Ioo tons, and running Io miles per hour, strike against an 7bstacle? The velocity per second is 142/3 ft. 100 tons x (142/3)2 = 21,5111/, tons. 37. What would be the copfiarative striking-force of tzwc hammers, one driven with a velocity of 20feetfer second, ana the other Io feet? 02 = 400. 102 = 100. 400: 10O.: 1: 4. Hence one will strike four times ae ht,rd a blow as the other. This principle is of great impertance in chopping wood, splitting rails, and in all cases where percussion is concerned.'he highest attainable velocity is to be souOg.t.

Page  20 20 AI/' WERS TO PRA CTJCAL QUESTIONS -There is a story told of a man who erected a huge pair of bellows in the stern of his pleasure-boat, that he might alwayi have a faiir wind. On trial the plan failed. In which di rection should he have turned the bellows? In the manner adopted at first, of turning the nozzle toward the sails, the action of the wind against the sails and the reaction of the bellows against the boat just balanced each other. If the man had turned the nozzle backward he could have saved the reaction of the bellows to move the boat. This would, however, have been a most costly and bungling way of navigation. -If we whirl a pail of water swiftly around with our hand, why will the water all tend to leave the centre of the piail? Why will the foam all collect in the hollow at the centre? THE MECHANICAL POWERS. 99. I. Describe the rudder of a boat as a lever. The water is the F, the boat the V, and the hand the P. As the W is between the F and the P, it is a lever of the second class. 2. Show the change that occurs from the second to the third class of levers, when you take hold of a ladder at one end and raise it against a building. At first the ground is the F at one end, the hand the P at the other, and the ladder the W hanging between; hence this is a lever of the second class. After a little, the F remaining the same, the P is applied at one end, near the F, and the ladder is the WV hanging, at the other; hence this is now a lever of the third class. 3. Why is a piinch from the tongs near the hinge more severe than one near the end? Because in the former case the tongs are a lever of the first class-in the latter, of the third. In the first class there is a gain of power, in the third a loss. 4. Two 5ersons are carrying a weight of 250 lbs., hanging

Page  21 IN NATURAL PH2LOSOPf7l 21 between them from a pole io feet in length. Whe e should it be suspended so that one will lift only 50 lbs.? One lifts 50 lbs.; the other 200 lbs. The proportionate length of the arms of the lever should be the same as the proportionate weights-i. e., 1 to 4. 10 + 5 = 2, the unit of measure. lIence one arm is 2 feet long and the other S feet long. PRooF.-(See Prob. 7, p. 10.) 50 x 8 = 200 x 2. This is the substance also of the equation P x Pd = XV x Wd. 5. In a lever of the first class, 6 feet long, where should the F be fplaced so that a P of I lb. will balance a Woof 23 lbs.? 6 feet = 72 inches. 72 + 24 = 3, the unit of distance. The W must be placed 3 in. and the P 69 in. from the F. PRooF. 23 x 3 = 1 x 69 (Prob. 4). 6. What P would be required to lift a barrel of fiork with a windlass whose axle is one foot in diameter and handle 3 ft. gong. P: W: rad. of axle:: rad. of wheel. x: 200 lbs:: 1/2 ft.: 3 ft.: = 331/s lbs. 7. What sized axle, with a wheel 6 feet in diameter, would be required to balance a W of I ton by a P of Ioo lbs F P: W:: rad. of axle: rad. of wheel. 100 lbs.: 2000 lbs.:: x: 3 ft. x = /20o ft. = the rad.; hence the diameter = 3/10 ft. 8. WHhat number of movable pzulleys would be required to;ift a W of 200 lbs. with a P of 25 lbs.? W= P x twice the no. of mov. pulleys; hence p-= twice the no. of mov. pul's. 200 + 25 = 8. 8 + 2 = 4 = the no. required. 9. How many lbs. could be lifted with a system of 4 zmovable pulleys, and one fixed pulley to change the direction of the force, by a P of oo lbs.? W= P x twice the no. of mov. pulleys. 100 lbs. x (4 x 2) = 800 lbs. = the W. io. What weight could be lifted with a single horse-15owe, (33,000 lbs.) acting on the tackle-block? (Fig. 62.) This block has 3 movable pulleys, and using the equation of the pulleys given in the last two problems, we have, making no allowance for friction, 33,000 lbs. x (3 x 2) = 198,000 lbs.

Page  22 22 ANSWERS TO PRACTICAL QUESTIONS I I. What distance should there be between the threads oj a screzwe, that a Pof 25 lbs., acting on a handle 3 ft. long, may lift I ton weight? F: W:: Interval: Circumference. 25 lbs.: 2000 lbs.:: 7: 72 in. x 3.1416. x = 2.83 -in. 12. How high could a P of 12 lbs., movinfg I6 ft. along an indcined plane, lift a W of 96 lbs.? P: W:: height: length. 12 lbs: 96 lbs.:: 16 ft. x = 2 ft. 13. I wish to roll a barrel of flour into a wagon, the box of which is 4ft. from thegroulnd. l can lift but 24 lbs. How Ionff a plank should I get? P: W:: height: length. 24 lbs: 196 lbs.:: 4 ft.: x = 322/s ft. 14. The "evenzer" of apair of whifclrees is 3 J. 6 in. loin,, how much must the whifzzetree be ntov'ed to give one horse the advantag-e of a over the other? For every 3 lbs. one horse pulls, the other must pull 4 lbs.: hence 7 represents the proportion in which the load is to be divided. 3 ft. 6 in. = 42 inches. 42 in. + 7 = 6 inches. the unit of measure. Hence one arm of the evener must be 6 in. x3 = 1S in. long, and the other 6 in. x 4 = 24 in. long. Or, if we prefer, we may say 21 in. - 3 in. = 18 in. lonz. and 21 in. + 3 in. = 24 in. long. Pnoon.(See Prob. 4, p. 20.) 18 x 4 = 24 x 3 = 72. 15. In a set of three horse wshiffletrees, haing an "evene"?' 5 ft. long, at what:point should the pfilough-clevis be attached that the single horse may drawv the same as each one of the spfan of horses? For every lb. drawn by the single horse the span should draw 2 lbs.: hence 3 represents the proportion in which the load is to be divided. 60 in. ~ 3 = 2(0 in., the unit of measure. 20 in. x 1 = 2(1 in., and 20 in. x 2 = 40 in. Hence one arm mast be 20 in.. and the other 40 in. long. To give ~ advantage? The single horse should draw 3 lbs. and each of the others 4 lhs.: hence the span should draw 8 lbs. 60 in. - 11 = 56/1, in., the unit of measure..6/,l in. x 3 = 164/,l in., and 55/11 in. x S = 437/1, in. I6. What W can be lifted with a P of 0oo lbs. actino cn a screw having threads i of an inch apart and a lAver handle,1 f!. ad a v

Page  23 IN NATURAL PHILOSOPHY. 23 P:'W:: Interval: Circumference. 100 lbs.: x: 1/4 in.: 96 in. x 3.1416. x = 120,637+ lbs. 17. What is the object of the big balls cast on the ends of the Fandle of the screw used in cohying-firesses? By their inertia and centrifugal force they make the motion more uniform and continuous. I8. In a steelyard 2ft. long, the distancefrom the weighthook to the fulcrum-hook is 2 in. How heavy a body can be weighed with a I lb. weight at the further end? 24in.-2-in.=22in. lib. x 22=221bs.=P. 221bs. -+ 2 = lllbs. = W. i9. Describe the changefrom the Ist to the 3d class of levers, il the ditSerent ways of using a spade. When digging, the ground at the back of the spade is the F; the ground lifted is the W; and the hand at the other end is the P. As the W is at one end, P at the other, and the F between, this is a lever of the ISt class. When throwing dirt, the left hand at one end of the spade is the F; the dirt at the other end is the W, and the right hand between the two is the P. As the P is between the F and the W, this is a lever of the 3d class. 20. W Vhy are not blacksmiths' and fire tongs constructed on the same princihle P The former are of the Ist class, as power is required: the latter of the 3d class, as rapidity only is necessary. 2 i. In a lever of the 3d class, what y will a P of 50 lbs. balance, if one arm is 12 ft. and the other 3 ft. lon? P: W:: Wd: Pd. 50lbs.: x:: 12 ft.: 3 ft. x = 121/2 lbs. 22. In a lever of the 2d class, what IV will a P of 50 lbs. balance, with a lever I2 feet long and W 3 feetfrom the Ff 0 lbs.: z:: 3ft.: 12ft. t = 200 lb*

Page  24 24 AINSSTERS TO PRACTICAL QUtESbl'ONS 23. In a lever of the Ist class, what Wgwill a P of 50 lt.A balance. with a lever I2 ft. long and the F 3 ft. from the W 9 50 lbs.: x:: 3ft.: 9ft. x = 150 lbs. 24. In a wheel and axle, the P= 40 lbs., W= 36o lbs., diameler of axle =8 in. Required the circumference of thu wheel. P: W:: diameter of axle: diam. of wheel 40 lbs.: 860 lbs.:: 8 in.: x = 72 in. = 6 ft., the diameter of wheel. 6 ft. x 3.1416 = 18.85 ft., the circumference of the wheel. 25. In a wheel and axle the P = 20 lbs., the W= 240 lbJ., and the diameter of wheel = 4ft. Required the circumference of the axle. 20 lbs: 240 lbs:: x: 48 in. x = 4 in. (diameter of axle). 4 in. x 3.1416 = 12.56 in. (circumference). 26. Required, in a wheel andaxle, the diameter of the wheel, the diameter of the axle being IO inches, P= Ioo lbs. and W I to0n. 100 lbs.: 2000 lbs.:: 10 in.: x = 200 in. = 162/3 ft. 27. What P would be necessary to sustain a weight o0 3,780 lbs., with a system of 6 movable ulleys and one rote Y W = P x twice the no. of mov. pulleys. 3,780 lbs. = P x (6 x 2). P = 315 lbs. 28. Iowr many movable pfilleys would be required to sustain I Wof 420 lbs. with a P of 2 Io lbs.?-Ans. I. HYDROSTATICS. 121. I. Why do housekeepfers test the strength of lye, b) trying whether or not an egg will float on it? The potash dissolved in the water to form lye increases the density of the liquid. When enough has been dissolved to make its specific gravity greater than that of the egg, the egg will float. This becomes, therefore, a simple means of testing the amount of potash contained in the lye.

Page  25 1A AATURAL PHILOSOPHY. 25 2. How much water will it take to make a gallon of strong brine. A gallon. The salt does not increase the bulk of the liquid. 3. Why can afat man swim easier than.a lean one? Because muscles and bones are heavier than fat. The specific gravity of a fat man is therefore less than that of a lean one. 4. Why does thefiring of a cannon over the watersometimes bring to the surface the body of a drowned person.f One answer is given in the Philosophy. It is probable, also, that the firing of the gun produces a partial vacuum, or in some way takes off, for an instant, a part of the pressure of the air on the water. The gases in the body would then expand and bring it to the top. 6. if we let bubbles of air fpass uj5 through a jar of water, why will they become larger as they ascend? The pressure of the water is less as they near the top, and so they expand. 7. What is the pressure on a lock-gate 14 feet high and Io feet wide, when the lock is full of water f 14 x 10 x 7 x 1000 oz. = 980,000 oz. = 61,250 lbs. S. Will a iail of water weigh any more with a live fish in it than without? If the pail were full before the fish was put in, then it will make no difference, since the fish will displace its own weight of water, which will run over. If the pail is only partially filled, then, though the fish is upheld by the buoyancy of the water, since action is equal to reaction, it adds its own weight to that of the water. -If a man and a boy were riding in a wagon, and, on conming to the foot of a hill, the man should take up the boy in his arms, would not that helP the horse? 9. If the water filtering down through a rock should collect in a crevice an inch square and 250 feet high, opening at the bottom into a closed fissure having 20 square feet of surface, what would be the total pressure tending to break the rock? 2

Page  26 26 ANSWERS TO PRACTICAL QUESTIONS. The pressure is the same on every square inch of the twenty square feet of surface. 250 x 1000 oz. x 20 x 144 = 312, lbs. 144 Io. Why can stones in water be moved so mnuch more easily than on land? Because the water oaoys up about one-half of their weight. I I. Why is it so difficult to wade in the water where there is any current? Because the buoyant force of the water makes us so light that we are easily carried away from our footing. I2. Why is a mill-dam or a canal embankment small at the tofp and large at the bottom? Because the pressure of the water increases with the depth. 13. In digging canals and building railroads, ozught not the engineer to take into consideration the curvature of the earth? Certainly. If he should build on a true level he would find his embankment pointing up to the stars. I4. Is the water at the bottom of the ocean denser than thal at the surface? The immense pressure must condense it very much at great depths. There is a certain point beyond which divers cannot penetrate. I5. Why does the bubble of air in a spzrit-level move as the instrument is turned? Because the air is lighter than the alcohol and rises constantly to the highest point. For this reason, also, the tube is curved upward at the centre. i6. Why can a swimmer tread on glass and other sharp substances at the bottom of the water with ithttle harm? See problem I I. 17. Will a vessel draw more water in salt or in fresh water! In fresh, because its specific gravity is less. 18. Will iron sink in mercury? No. It will float, like a cork on water. 19. The water in the reservoir in New York is about 8ofeel

Page  27 IN NATURAL PHILOSOPHY. 27 aboe thefountain in the City Hall Park. What is tihe pressure on a single inch of the pi]pe at the latterpoint? (1000 oz. x 80) + 144 = 34.7 lbs. 20. Why does cream rise on milk? Because it is lighter than the milk. 2. Ifa ship founders at sea, to what dei5th will it sink? Until its specific gravity becomes equal to that of the water? 22. There is a story told of a Chinese boy who accidentally dropped his ball into a deep hole, where he could not reach it. He filled the hole with water, but the ball would not quite lat. Hefinally bethought himself of a lucky expedient, which was successful. Can you guess it? He put salt in the water. 23. Which has the greater buoyantforce, oil or water? Water, because its density is greater. 24. What is the weight of 4 cu. ft. of cork.? 1000 oz. = the weight of 1 cu. ft. of water..240 = the spec. grav. of cork. 240 oz. = the weight of 1 cu. ft. of cork. 4 960 oz. = 4 " " = 60 lbs. 25. How many oz. of iron will a cubic foot of corkfloat in water? 1000 oz. = weight of a cubic foot of water..240 = spec. grav. of cork. 240 = weight of a cubic foot of cork. 1000 oz. - 240 oz. = 760 oz., the buoyant force of a cubic foot. 26. What is the specific gravity of a body whose weight ix air is 30 grs. and in water 20 grs.? 30 grs. - 20 grs. = 10 grs. 30 grs. + 10 grs. = 3. The body is three times as heavy as water. 27. Which is heavier, a pail of fresh water or one of salt. atErr? A pail of salt-water is as much heavier than one of freshwater as the weight of the salt added to make the brine.

Page  28 28 ANSWERS TO PRACTICAL QUESTIONS 28. The weights of a piece of syenite-rock in air and tn wa/er were 3941.8 grs. and 2607.5 grs. Find its sjiec. grav. — Ans. 2.954. 29. A sfiecimen of green safifhire from Siam weighed in air 2I.45 grs., and in water I6.33 grs. Required its sjiec. grav.-Ans. 4. I 89. 30. A specimen of granite weighs in air 534.8 grs., and in wuater 334.6 grs. What is the sj5ec. grav.?-Ans. 2.67 1. 31. What is the bulk ofa ton of iron? 1000 oz. = weight of 1 cu: ft. of water. 7.8 = spec. grav. of iron. 7800 oz. = weight of a cu. ft. of iron. 82,000 oz. (a ton of iron) -+- 7,800 (weight of a cu. ft.) = 44/s za. ft A ton of gold? 1,000 oz. = weight of a cu. ft. of water. 19.34 = spec. grav. of gold. 19,340 oz.* = weiht of a cu. ft. of gold. 32,000 oz.* + 19,340 oz. = 1.6, the no. of cu. ft. A ton of coAS5er? 1000 oz. x 8.9 = 8900 oz. 32,000 oz. + 8900 oz. = 3.6 (nearly) the no. of cu. ft. 32. What is the weight of a cube of gold 4 feet on eacA ride? 43 = 64, the no. of cu. ft. 19,340 oz.* (no. of oz. in 1 cu. ft.) x 64 = 77,360 lbs. 33. A cistern is 12 ft. long, 6 ft. wide, and o Jft. deep When full of water, what is the firessure on each side? On one side, 12 x 10 x 5 x 1000 oz. = 600,000 oz. = 37,500 lbs. On one end, 6 x 10 x 5 x 1000 oz. = 300,000 oz. = 18.750 lbs. 34. Why does a deadfish alwaysloat on its back? It has its swimming-bladder located just under the spine; and this is the lightest part of its body, and, of course, comes to the top as soon as the fish dies. * In these solutions the student should notice that avoirdupois weight is used in weighing the gold. To be exact, 1,000 oz., the weight of a cu. ft. of water, should be reduced to Troy weight, and the lb. gold taken as 12 oz. Troy, whenr the ans. would be about 1.36 cu. ft.

Page  29 IN NATURAL PHILOSOPHr. 29 36. A vessel holds Io lbs. of water-: how much n.rcurmy would it contain? Mercnry is 13.5 times heavier than water. Hence the vessel would contain 10 lbs. x 13.5 = 135 lbs. of mercury. 37. A stone weighs 70 lbs. in air and 50 in water [Whal is its bulk? 70 -50 = 20. 20 x 16 oz. = 320 oz., the weight of water displaced. 320 oz. is 8/25 of a cu. ft. 38. A hollow ball of iron weighs Io lbs.: what must be its bulk, to foat in water? 10 lbs. = 160 oz. As a cubic ft. of water weighs 1,000 oz., the ball must displace such a part of a cu. ft. of water as 1,000 oz. is contained times in 160 oz which is.16 cu. ft. HYDRAULICS. 121.. How much more water can be drawn from a faucet 8 feet, than from one 4 feet below the surface of the water in a cistern? = 2gd; hence v = 2 V16 x8 = 2Q.6. v = 2 J16x4 = 16. Hence 6.6 cu. ft. more would flow from one than from the other in each second..2. How much water would be discharged ijer secondfr-om a shortpfipe having a diameter of 4 inches and a depth of 48 feet below the surface of the water? 42=16. 16 x.7854=12.57 sq. inches=.087 sq. ft. (area of the tube). v = 2gd = 2V16 x 48 = 55.4.087 x 55.4 = 4.8 cu. ft. 3. When we pour molasses from a jug, why is the stream so much larger near the nozzle than at some distance from it p Because, according to the law of falling bodies, the further the molasses falls the faster it falls. The stream, therefore, becomes smaller as it moves more swiftly, until, at last, it breaks up into drops.

Page  30 30 ANSWERS TO PRACTICAL QUESTIONS 4. Ought afaucet to extend into a barrel beyona the staves-t No; because cross currents would be produced, which would interfere with the free passage of the liquid. 5. What would be the effect if both the openings in one of the arms in Barker's Mill were on the same side? It would cease revolving. The pressure in each direction would then be equal, and the arms would balance. PNEUMATICS. 148. I. Why must we make two openings in a barrel of cider when we taf it? One to let out the cider, and one to admit the air. 2. What is the weight of ro cubic feet of air? 100 cu. in. weigh 31 grs.; hence 10 cu. ft. will weigh 31 grs. x 172.8 =.7652 lbs. avoirdupois. 3. What is the pressure of the air on one square rod of land? 2721/4 x 144 x 15 lbs. = 588,060 lbs. 4. What is the pressure on a pair of Magdeburg hemispheres 4 in. in diameter, when the air is entirely exhausted? 3.1416 x 42 x 15 lbs. = 753.9 lbs. 5. How high a column of water can the air sustain twhen the barometric column stands at 28 in.? 28 in. x 131/2 = 311/2 feet. 6. If we should add a fressure of two atmospiheres, what.would be the bulk of ioo cu. in. of common air? The pressure is trebled, and according to Mariotte's law, the volume will be reduced in the same proportion; hence it will be 100 cu. in. + 3 =.31/, cu. in. 7. If, while the water is running through the sizphon, we quickly lift the lonlg arm, what will be the effect on the water in the sipthon? It will all run back through the short arm into the vessel. 8. If we lift the entire sipthon? The water will all run out the long arm.'rhe reason of this

Page  31 IN NATURAL PHILOSOPHIY. 3 difference is, that when we lift the long arm we make it in effect the short arm, and the other arm the long one. 8. When the mercury stands at 29~ in. i'z the barometer, how high above the surface of the water can we place the lower pumf-valve? In theory, 29. in. X xI3 - 398~ in.; in practice, the distance is much less than this. 9. Why cannot we raise water, by means of a sipfhon, to a higher level? There is no power in a siphon; it is only a way of guiding the flow of water to a lower level. Io. If the air in the chamber of a fire-engine be condensed to 1c6 its former bulk, what will be thefiressure due to the ex!pansive force of the air on every sguare inch? —Ans. 240 lbs. I x. What causes the bubbles to rise to the surface, when we put a lump of loaf-sugar in hot tea? The bubbles of air contained in the pores of the sugar rise because they are lighter than the water. 12. To what height can a balloon ascend? Until its specific gravity is the same as that of the air in which it floats. -What weight can it lift? A weight equal to the difference between its own weight and that of the air it displaces. 13. Why is the air lighter in foul and heavier in fair weather? This question is answered in the Philosophy. Another reason may be, that the upward currents of air partly remove the pressure in foul weather. 14. When smoke ascends in a straight line, is it a proof o1 the rarity or density of the air? Of its density, because it shows that the smoke is much lighter than the air, and so rises immediately to the top. I. Why do we notfeel the heavy pressure of the air on out bodies?

Page  32 32 ASNSWERS TO PRACTICAL QUESTIONS Because it is equally distributed within and without our bodies. The pressure on a person of ordinary size is about 16 tons. I6. Is a bottle empSty whenfilled with air? No; because we must empty the air out before we can fll the bottle with anything else. I8. How does the variation in the pressure of the air affect those who ascend lofty mountains? The outward pressure is there partly removed, and the inner pressure remaining the same, the blood is often forced through the ears, nostrils, etc. When one descends into a deep mine the conditions are reversed: the outer pressure becomes in excess of the inner; severe pain is felt in the eardrum, and ringing noises in the head become almost intolerable. These, however, disappear after a time, where the equilibrium between the internal and external pressure is restored. It is said that Humboldt ascended where the mercurial column fell to 14 inches, and descended in a diving-bell where it rose to 45 inches-thus making a variation of 3I inches, or a difference of 3 I,ooo lbs. pressure on his body. -If the atmosphere in a diving-bell were of the same density as that at the surface of the earth, how deep in the water would it be necessary to sink the bell in order to reduce the volume of the air one-half, or, in other words, for the bell to half fill with water?-Ans. 34 feet. How near would the bell be filled at a depth of 1,020 feet. Ans. 29/so. If the bell were then raised, would the water stay in till it reached the surface? The elasticity of the air would cause it to gradually expand and drive out the water as it rose. ACOUSTICS. 184. I. Why cannot the rear of a long column of soldiers keep time to the music ~

Page  33 IN NA TURAL PHiLOSOPHY. 33 Because it takes time for the sound-wave to pass down the column, and hence those in the rear do not hear the music as soon as those in front. 2. Three minutes elap5se between theflash and the rejiort of a thunderbolt: how far distant is it? If the air is at the freezing point, the distance is 1090 ft. x 60 x 3 = 196,200 ft. 3. Five seconds expire between theflash and report of a gun: what is the distance.? 1090 ft. x 5 = 5450 ft. 4. Suippose a speaking-tube should connect two villages Io miles apart. How long would it take a sound to pass that distance? 52,800 ft. -+ 1090 ft. = 48.4 (sec.) 5. The report of a pistol-shot was returned to the earfrom theface of a cliff in 4 seconds. How far was it? 1090 ft. x 2 = 2180 ft. 6. What is the cause of the difference in the voice of man and woman? It may be a difference in the length of the vocal chords, or in the power of lengthening and shortening them; but it is not yet fully understood. The difference between a bass and tenor, as between a contralto and soprano voice, is probably that of quality only, like that between different kinds of musical instruments. 7. What is the number of vibrationsfier second necessary to produce the fifth tone ofthe scale of C? (p. 176.) C, = 128 vibrations. G of that scale = 192 vibrations per second. 8. What is the length of each sound-wave in that tone when the temperature is zeroa? 1090 ft.- 32 ft. =1058 ft. 1058 ft. +192=5 ft. 6 + in. (the length of each vibration). 9. What is the number of vgbrations in the fourth tfne above middle C (Cj)? C, = 256 vibrations.36, = (the proportionate no. for the 5th of the scale). 256 x = 384 (the number of vibrations per second). 9*

Page  34 34 ANSWERS TO PRA CTICAL QUESTIONS 10. A meteor of Nov. 13, I868, is said to have exfiloded at a height of 6o miles: what time would have been necessary for its sound to reach the earth? 52SO ft. x 60 = 316,800 ft. 316,800 ft. + 1090 ft. = 290 (sec.) = 4 min. 50 sec. I I. A stone was let fall into a well, and in 4 seconds was heard to strike the bottom. How deep was the well? (See p. 48.) d = 16 x t2. d = 16 x 42 =256 ft. I2. What time would it require for a sound to travel 5 mites in the still water of a lake? 5280 ft. x 5 = 26,400 ft. 26,400 ft. + 4700 ft. = 5.6 (sec.) 13. How much louder will be the report of a gun to an observer at a distance of 20 rods than to one at half a mile? 160rods are8times 20 rods. The intensity of the sound is inversely as the square of the distance = 1/64. Hence the sound is 64 times louder to the observer at 20 rods that to the one at half a mile. 14. Does sound travel faster at the foot or at the tofi of a mnountain? The density and elasticity of the air vary in the same proportion; hence if the temperature were the same on the top of a mountain that it is at the foot, the velocity of sound would be the same, but as it is always colder, the velocity is less. 15: Why is an echo weaker than the original sound? Because the intensity of the sound-wave is weakened at each reflection. i6. Why is it so fatiguing to, talk through a sfieakingtrumpet? Because so much more air must be set in motion by the vocal chords. The column of air in the resonant cavity of the throat is re-enforced by all the air in the trumpet. -— When we hear a goblet omr a wine-glass struck with the blade of a knife, we can distinguish three sounds, the fundamental and two harmonics.* * Is not the ear the most perfect sense? A needlewoman will distinguish by the sound, whether it is silk or cotton that is torn. Blind people recognlze

Page  35 IN NATURAL PHIILOSOPIY. 35 OPTICS. 224. I. Why is a secondary bow fainter than the jprimary I The primary is produced by one reflection and two refractions; the secondary, by two reflections and two refractions. The additional reflection weakens the ray. Why are the colors reversed? We can understand this by looking at Fig. 159. In one bow we see that the rays enter the drops at the top, and are refracted at the bottom to the eye; in the other, that the rays enter at the bottom, and are refracted at the top to the eye. 2. Why can we notsee arounda house or through a bent tube? The rays of light move in straight lines. 3. What color would a painter use if he wished to represent an opening into a dark cellar Black. 4. Is black a color? No; it is the absence of color. Is white? Yes; it is the presence of all color-i. e., it is the compound effect produced on the brain by seven different impressions. 5. By holding an object nearer a light, will it increase or diminish the size of the shadow? It will increase it, because more rays are intercepted. 7. Where do we see a rainbow in the morning? In the west. the age of persons by their voices. An architect, comparing the length o' two lines separated from each other, if he estimate within the 30th part, we leem very accurate; but a musician would not be considered very precise who only estimated within a quarter of a note. (128-30 = 4, nearly.) In a large orchestra, the leader will distinguish each note of each instrument. Wc recognize an old-time friend by the sound of his voice, when the other senses utterly fail to recall him. The musician carries in his ear the idea of the musical key and every tune in the scale, though he is constantly hearing a multitude of sounds. A tune once learned will be remembered when the words of the song are forgotten. Prof. Pepper tells us that he tuned a fork which corresponded to 64,000 vibrations per second. The first harmonic is produced by one-half the whole cord, the second by one-third, &c.

Page  36 36 ANSVWERS TO PRACTICAL QUESTIONS 8. Can any two sp5ectators see the same rainbow? They cannot, because no two persons can be at the right angle to get the same color from a drop. 9. Why, when the drofps of water are falling through the air, does the bow appear stationary? Because the drops succeed each other so rapidly that they keep a constant impression on the retina. Io. Why can a cat see in the night? Because the pupils of its eyes are larger, and so admit more light. Why cannot an owl see in daylight? The pupils of its eyes are large enough to admit of cleal vision in the night, but they cannot be contracted, and so in daylight the owl becomes dazzled with the excess of light received. I2. Wshy are we blinded when we pass quickly from a dara into a brilliantly lighted room? The pupils of our eyes admit too much light, but they soon contract to the proper dimensions, and we can then see distinctly. When we pass out from a lighted room into the dark street, the conditions are reversed. I3. If the light on a distant planet is only ylog that which we receive, how does its distance from the sun compare with ours? As the light is inversely as the square of the distance, the distance is V ioo = I times greater than ours. 14. If when I sit 6 feet from a candle I receive a certain amount of light, how much will I diminish it if I sit back 6 feet further? As my distance from the light is doubled, the light is inversely as 22, or only i as bright. I5. Why do drops of rain, in falling, appear like liquid [hSoads? The impression the drop makes on the retina remains until the drop reaches the ground. i6, Why does a to-wal turn darker when wet?

Page  37 IX NATURAL PHILOSOPHY. 37 More of the light is transmitted, and less reflected. We see this illustrated in greasing a bit of paper. It becomes semitransparent because more light passes through it, but looks darker itself because less light is reflected to the eye. 17. Does color exist in the object or in the mind of the observer? In the mind. Color in the object can be only a peculiar property whereby a body absorbs some colors, and reflects or transmits others. 18. Why is lather opaque, while air and a solution of soap are each transparent? By repeated reflections and refractions in passing through the unhomogeneous mass of lather, the rays are weakened. The principle is the same as that of deadening floors with tanbark. (Phil., p. i6x.) I9. Why does it whiten molasses candy to jull it? Water is given up both in cooking and pulling. This causes more light to be reflected (Q. i6), while the crystals formed, especially on the surface, hide the impurities. 20. Why does plastering become lighter in color as it dries? Because, as the water evaporates, the mortar transmits less light, and reflects more light to the eye. q I. Why does a photographer iuse a kerosene oil-lamp in the' dark-roomz?" Kerosene oil-flame emits only heat and color, but no actinic rays. Some " dark-rooms" are lighted with yellow glass windows. 22. Is the common division of colors into "cold" and "warm" verified in philosophy? Yes; red contains more heat than violet. 23. I Why is the image on the camera, Fig. I67, inverted? The rays cross each other at the focus of the double convex len. 24. WJhy is the second image seen in the mirror, Fig. 134, bngrtgter hani.,.e f, r The first is formed by reflection from the glass, and the second from the mercury. As the latter is a beter reflector,

Page  38 38 ANSWERS TO PRACTICAL QUE'STIONS the second image will be brighter. Each image after that will be weakened by the repeated reflection. 27. Which can be heard at the greater distance, noise or music? Other things being equal, music will penetrate much further than noise. Boatmen call to each other, at a distance, in a musical tone. A band is heard above the noise of the rabble. It seems to be a wise arrangement of Providence that all harsh, discordant noises should perish as soon as possible, and only harmonious ones survive. 28. Why are some bodies brilliant, and others dull? Some reflect the light better than others. A piece of stone coal lying in the sun's rays will shine so brilliantly that one will cease to see the coal at all, and will judge it to be a bright metal. 29. Why can a carpenter looking along the edge of a board tell whether it is straight? If the edge is straight, the light will be reflected uniformly to his eye from the whole length. Any uneven places will make dark and light spots. 30. Why can we not see out of the window after we have lighted the lampf in the evening? The glass reflects the light of the lamp back to our eyes, and they adapt themselves to the increased amount. 3 I. Why does a ground-glass globe soften the light? It scatters the rays. 32. Why can we not see through.grozund-glass or painted wvindows? They transmit the light irregularly to the eye, and not uniformly, like a transparent body. 33. Why does the moon's surface appear flat? Because it is so distant that the eye cannot detect the difference between the distance of the centre and the circumference.

Page  39 IN NATURAL PHILOSOPHY. 39 34. Why can we see further with a telescope than with the naked eye? Because it furnishes us more light with which to see a distant object. 35. Why is not snow transparent, like ice? Because it is unhomogeneous. See problem I8. 36. Are there rays in the sunbeam which we cannot see? We cannot see the heat or the chemical rays. 37. (x) Make two marks on a sheet of white paper, at a distance of about three inches from each other. Then closing one eye and looking steadily at one mark (though we can see both), move the paper toward the eye. A point will be reached where the eye can perceive only one of the marks; on coming nearer, both will be seen again. 38. (2) Prick with a pin, through a card-board, two holes:loser together than the diameter of the pupil of the eye. Holding the card pretty near the eyes, look through these holes at the head of a pin. There will seem to be two pin-heads. 39- (3) Press the finger on one eyeball and we shall see objects double. Since an impression is made on the retina of each eye, it would seem that we ought always to see objects double. The nerves from both eyes are so joined, however, before they reach the brain, that this effect is avoided. If, now, we cause the image on the retina to be made on parts of the eye which do not correspond to each other, we shall obtain a double image. 40. Why is a rainbow in the morning a sign of foul, and in the evening of fair weather? In the morning it indicates a formation of clouds when the temperature is rising, and therefore shows a determination to moisture. In the evening it indicates a clearing away when the temperature is falling, and hence shows a determination to dryness. 41. Why is a red, lowering sky in the morning a sign of rain, and a brilliant red sky at night, of fair weather?

Page  40 40 ANSWERS TO PRACTICAL QUESTIONS 42. Why does a distant light, in the night, seem like a star! 43. Why does a bright light, in the night, seem so much nearer than it. is? 44. Why does a ray of light, j5assed through a small hole, of any shape, inz a card, make a round, bright spot? 45. Why are these siots crescent-shaped during an eclipse? 46. VWhat color predominates in artificial lights? Yellow. 47. Why does yellow seem white, and blue green, when seen jby artificial light? Because the white takes on, in the yellow rays. a yellow hue, and the yellow added to the blue gives a green, hence there is no white for comparison. So, also, dark blue becomes purple, and red has a tawny hue. Magnesium light possesses all the colors of the spectrum, and hence all objects retain their natural appearance when illuminated by it. 48. Why are we not sensible of darkness when we wink? Because the impression of the light is retained upon the retina during the brief interval of darkness. HEAT. 258. I. Why will one's hand, on a frosty morning, freeze to a metallic door-knob sooner than to one of porcelain? Because the metal is a better conductor of heat than the porcelain, and hence conducts the heat from the hand faster. 2. Why does a piece of bread toasting curl up on the side toward the fire? The water being expelled from the pores on that side causes the bread to shrink. 3. Why do double windows protect from. the cold? The non-conducting air enclosed between the window-panes keeps in the heat and keeps out the cold. 4. VWhy do fur;nace-men wear flannel shirts in summet to kefie cool, and in winter to keep warm?

Page  41 IV LVATURAL PHILOSOPHY. 4 1 In summer the non-conducting flannel keeps out the furnace heat, and in the winter keeps in the body-heat. 5. Why do we blow our hands to make them warm, and our soup to make it cool? Our breath is warmer than our hands, but cooler than our soup. 6. Why does snow iprotect the grass? The air enclosed between the flakes of snow is a non-conductor. No infant in its cradle is tucked in more tenderly than the coverlet of snow about the humble grass that nestles down for its winter's nap on the bosom of mother Earth. 7. Why does water "boil away" more rapiidly on some days than on others? Because the atmospheric pressure varies. 8. What causes the crackling sound ill a stove, when a fire is lighced? The expansion of the iron by the heat. 9. Why is the tone of a iiano higher in a cold room than in a warmn one? The steel wires lengthen in a warm room, and so lower the tone. io. Ought an inkstand to have a large or a small mouth? A small mouth, to prevent evaporation. I. Why is there a space left between the ends of the rails on a railroad track? To allow room for the expansion and contraction of the railq with the changes in temperature. I2. Why is a person liable to take cold when his clothes are daimnf? The water which evaporates from his clothes, in drying, absorbs heat from his body. 13. What is the theory of corn-iofpfiing? The air in the ceiis oi the corn expands by the heat and bursts the outer coating of the corn.

Page  42 42 A NS EWRS TO PRA CTI CA L Q UFS TIO NS I4. Could vacuum-pans be employed in cooking? They could not, because the heat would not be sufficient to cook the food. I5. Why does the air feel so chilly, in the spring, when snow and ice are melting? When the ice is passing into the liquid state, it absorbs heat from all surrounding objects. I6. Why, in freezing ice-cream, do we put the ice in a wooden vessel, and the cream in a tin one? The non-conducting wooden vessel prevents the ice from absorbing heat from the external air, and the conducting tin vessel enables it to absorb the heat from the cream. 17. Why does the temperature generally moderate when the mnow falls? The vapor passing into the solid form gives off heat. 9. Why does sjrinkling a floor with water cool the air? The water turning to vapor absorbs heat. 2o. How low a degree of temierature can be reached with a mercurial thermometer? Nearly to the freezing point of mercury, -39~ F. 2.. If the temperature be 700 F., what is it C.? -0~- 328=38~. 38-X-1.8=21.1- C. -If the temperature be 70~ C., what is it F.? 70~ x1.8=126~. 126~+32~=158' F. 22. Will dew form on an iron bridge? Yes, because iron is a good radiator. On a wooden bridge? Not so readily, because wood is a poorer radiator. 23. VWhy will not corn ipo when very dry? The pores shrink, and the corn becomes compact; only porous, tender-celled corn will pop. 24. The interior of the earth being a melted mass, why do we get the coldest water from a deep well?

Page  43 IN NATURAL PHILOSOPHY. 43 The well extends below the influence of the sun, and not deep enough to reach the internal heat of the earth. 25. Oughtl the bottom of a tea-kettle to be polished? No, since a polished surface would reflect the heat. We need a black, rough, sooty surface to absorb the heat rapidly. 26. Which boils the sooner, milk or water? Milk, because it is so adhesive that the bubbles of steam which are formed at the bottom of the dish cannot easily escape. They therefore pile up on top of each other, and the milk boils over readily. 27. Is it economy to keep our stoves highly polished? The stove-blacking used is a good radiator, but the surface should not be highly polished, as that hinders radiation. 28. If a thermometer be held in a running stream, will it indicate the same temperature that it would in a pailful of the same water? It will. For the same reason that a thermometer, in the wind, will indicate the same temperature as in the still air. although the former seems to us much colder. 29. Which makes the better holder, woollen or cotton? Woollen, because it is so poor a conductor of heat. 30. Which will give out the more heat, a pilain stove or one with ornamental designs? The latter, since it has more radiating surface 3 I. Does dew fall? No; it forms directly where it is found. The vapor merely collects on the cold surface. 32. What causes the " sweating' of a pitcher? The vapor of the air condenses on the cold pitcher. It is often a sign of rain, since it shows that the air is full of vapor easily deposited. 33. VWhy is evaporation hastened in a vacuum? Because the pressure of the air is removed.

Page  44 44 AJ.5',VEERS TO PRACTICAL QUESTION1S 34. Does stirring the ground around plants aid in the dqefa sition of dew? It does, since it facilitates radiation. 35. Why does the snow at the foot of a tree melt sooner than that in thze oi5en field? The dark-colored tree absorbs the sun's heat, and then radiates it out in slow, dull waves, which are absorbed by the snow. 36. Why is the opening in a chimney made to decrease in size from bottom to top? Because as the heated air rises it cools and shrinks. If the chimney did not diminish in size correspondingly, currents of cold air would set down from the top. 37. Will tea keefi hot longer in a bright or in a dull tea-pot e In a bright one, since a polished surface retards radiation. 39. Why is one's breath visible on a cold day? The vapor in the breath is condensed by the cold air. 41. Why is light-colored clothing cooler in summer and warmer in winter than dark-colored? It does not absorb the heat of the sun in summer, nor the heat of the body in winter; dark-colored clothing has neither of these desirable properties. 42. How does the heat at two feet from the fire compare with that at four feet? 22: 42:: 1:4. Hence it is four times greater. 43. Why does the frost remain later in the morning uipon some objects than iupon others? Those objects which are good absorbers of heat soon become warm enough to melt the frost upon them: poor absorbers heat more slowly, and so retain the frost longer. 44. Is it economy to me green wood? It is not, since the sap must be changed to vapor, and wate,

Page  45 INV A TUBRAL PHIL OSOPHY. 45 in turning to vapor renders latent over goo~ of heat. This is, of course, entirely lost to the consumer. 45. Why does not green wood snap? The pores are filled with water instead of air. The water does not expand rapidly enough to burst off the coverings of the cells, and so simply oozes out gradually and is vaporized. 46. Why will a fiece of metal droipped into a glass orjorcelain dish of boiling water facilitate the ebullition? The rougher surface of the metal aids in the formation and disentanglement of the steam-bubbles. The bubbles cling longer to a smooth than to a rough surface. This is one cause of that bumping sound often noticed when liquids are boiling in glass dishes. 47. Which can be ignited the more easily with a burningglass, black or white papier.P Black paper, since it is a much better absorber of heat. 48. Why does the air feel colder on a windy day.? Because fresh portions of cold air are brought constantly in contact with our bodies. 49. In what did the miracle of Gideon's fleece consist? The hard threshing-floor was a better conductor of heat than the porous fleece; hence, naturally, the dew would collect on the latter more readily than cn the former. In the miracle, the conditions remaining the same, the results in the two cases were reversed. (Judges, vi. 37-40.) 50. Could a burning-lens be made of ice? Burning-lenses have been made of that material. The rays have no heating power until the waves of ether are stopped. They do not elevate the temperature of the medium through which they pass. 5 I. ZVhy is an iceberg frequently envelop5ed by a fog? The moisture of the air is condensed upon its cold surface. 52. Would dew gather more freely on a rusty stove than on a bright kettle? It would, because the rusty iron surface is a good radiator. 53. Why is a clear night colder than a cloudy one f

Page  46 46 ANSWERS TO PBRA CTICAL QUESTIONS On a cloudy night the clouds reflect the radiated heat of the earth back again, and thus act as a blanket to keep the earth warm. On such a night there can be no frost or dew. On a clear night, the heat which the earth radiates passes out freely into space, and thus the earth cools rapidly. 54. Why is no dew formed on cloudy nights? See last question. 55. Water boiled at a certain place at 200~ F.: what was Sfe height above the sea? 56. On Mont Blanc boiling water is only 84~ C.: what is the height? 57. Why do we use a longer tube of mercury for a baromzter than a thermometer? 58. Which is the hottest jart of a room? 59. Why is it hotter above a flame than at the side? 6o. What is the difference between dew and rain? 6I. Why will ashes keep fire overnigzht? 62. If a piane of glass and a similar late of polished s4eel were laid upon the ground, in the night, zpon which would the dew form most abundantly? The glass is a poor conductor of heat, and so would absorb little heat from the earth, while the metal would absorb it freely; the glass is a better radiator than the polished metal, and thus would become drenched with dew, while the metallic surface would be scarcely dimmed. 63. Why is there but little dew forzmed in cities? 64. Is an abundant dew a sign of rain? It is. See question 32. 65. Is there any dew formed out at sea 66. Why are gardens in a valley often t&uched with frost, while those on the hills escape unharged.! The cold air settles into the valley, while the warm air rises to the hills.

Page  47 IN N1A TURAL PHILOSOPIHY. 4x7 67. How are hailstones formed? There are two separate currents of air, one hot and charged with moisture, the other cold. The former is displaced by the latter and driven up in the atmosphere. There its vapor is condensed at the centre of the cloud into snow, and at the extremities into ice-cold water. In this cloud there is a whirling motion which collects the snow into little balls, each of which is the nucleus of a hailstone. Each of these is carried, alternately, by the whirling currents, into the snow-cloud at the centre, and the ice-cold water outside. Both give it a coating, one of snow-like, spongy ice, and the other of transparent ice. This is done with great rapidity, until at last its weight overcomes the violent upward motion which sustains it in the air, and the hailstone falls to the ground. When a hailstone is carefully examined we can see this nucleus, and these concentric layers, like the coats of an onion.* 68. Why do we have hailstorms in summer, and not in winter? The small spongy hail or sleeo of winter has the same origin as hailstones in summer, but there is not enough vapor in the cold air to give them the size of summer hailstones. 69. Is the sweating of a ipitcher a sign of rain? See question 32. 70. Where should ice be applied, to cool wa/er? At the top, because cold water falls. 7 I. Why is evaporation hastened in a vacuum? Because the pressure of the air is removed. 72. Is a dusty boot hotter to the foot than a polished one p It is, because it is a better absorber of heat. * The above theory is that advanced by Prof. Loomis, in his "Treatise on Meteorology." Th 3 teacher will find this work invaluable on all meteorologi. cal questions.

Page  48 48 ANSWERS TO PRA CTICAL QUEST7JONS. (Key, p. 34, Prob. I.) The method adopted in solving this problem is merely the rough one in common use, and gives only an approximate result. If an exact answer is desired, we should take in account the time required for the sound to reach the ear. The following method may be employed: x = No. sec. for stone to fall. 4 —x = " "sound to reach the ear. 16x2 - (4 —x)1090. l6x2 = 4360-1090x. From this, by completing the square, we have - = 3.7892 + second>. Then the equation (2) d= I6t2 gives the depth. d = 16(3.7892+)2 = 229 ft. and 8.795 in., which is the answer exact within a small fraction. A- second method (more exact)d = depth of the well = 16tP. t=-V/d=, v. 16 4 4-i vd = No. of sec. for sound to reach the,L (4-i vcd)1090 =4360- 6 - V 4360 - vd = d. 1d-i - d = 4360 - d. - gAeA-4 d = — 19OO960 d = WUL + feet.

Page  49 ANS WERS TO TIlE PRACTICAL QUESTIONS, AND SOLUTIONS OF THE PROBLEMS, fm THE FOURiTEEN WEEKS COURSE C H E M I S T R Y r[ he bold-faced figures refer to the page of the Chemistry; the others to the number of the Practical Questions.] I. Is it likely that all the elements izave been discovered? It is not, since several have been found lately by means of spectrum analysis. The ancients held that there are but four elements-earth, water, air, and fire; the first representing the solid form of matter, the second the liquid, the third the gaseous, and the fourth the force which changes matter from one form to another. Few of the sixty-five elements are common. Those italicised, in the table on page 14, are rare. The remarkable phenomena of allotropism would seem to indicate that, perhaps, what we now consider distinct elements may be only allotropic states of the same element. Indeed, it is possible to conceive that all substances are only allotropic forms of one universal essence. In the present state of chemistry this view cannot be proved, and is only a speculation as to what mav be discovered in the future. 2. What is the origin of the tern- "gas?" This word was first used in the 17th century. Explosions, strange noises, and lurid flames had been seen in mines, caves, &c. The alchemists, whose earthen vessels often exploded 2

Page  50 50 AIVSIAWEIRS TO PRA CTICAIL QUESTIONS with terrific violence, commenced their experiments with prayer, and placed on their crucibles the sign of the crosshence the name crucible from crux (gen. crucis), a cross. All these manifestations were supposed to be the work of invisibl' spirits, to whom the name gahst or geist, a ghost or spirit, was applied. The miners were in special danger from these unseen adversaries, and it is said that their church service contained the petition, "From geists, good Lord, deliver us!" The names-spirits of wine, nitre, &c., are a relic of the superstitions of that time. 3. If the air were luZire 0, what bodies would escae cornmbzsyioun in a co;agaration.? The stones, mortar, &c., which being already combined with 0 and other elements, and thaving their chemical affinities satisfied, are hence termed " burnt bodies." 4. Why will lime added to hard water often soften it? The lime will combine with the free carbonic acid absorbed by the water. This renders the water incapable of holding in solution as much carbonate of lime as before, which is then precipitated, and the water thus partly softened. 5. Wl'hy will stirring a wood fire quicken the flamze, but at coaltrire, will deadean it.? Stirring a fire lets in more 0, which quickens a wood fire but reduces the temperature of a coal fire below the point of union between 0 and coal. It is really based on the fact that a higher temperature is requisite to burn coal than wood. 6. /Why does blowing on a fire quicken the faame, but on a lamp e-tintz,-'ishes it? The same principle applies as in the last question. In addition, the force of our breath often drives the flame off the wick mechanically. 7. I4'hy will oyster-shells Jlaced on the grate oaf a coal fire pfrevent the formation of clinkers? The lime of the shells forms a flux with the silicates contained in the coal, and thus renders them more fusible.

Page  51 IV CHEMISTR Y. 51 8. What alkali abounds in sea-weed? Soda. 9. WVhat alkali abounds il land-plants? Potash. The former salt is a constituent of sea-water, and the latter of rocks which decompose to form the soil. Io. How is limne-water made fromn oyster-shells? The oyster-shells, in burning, lose their CO_. This leaves the lime uncombined; hence it readily dissolves in water. ii. Tl/hat other tests of lead than IfS? KI gives a yellow precipitate, NH4S a black, and SO;3 a white one. 12. Will not lime lose its benefcial effect zpons soil after a time? Lime acts in various ways to improve thy fertility of a soil. It corrects its acidity, aids in the decomposition of the rocky constituents, hastens the decay of the humus, and also makes the soil more porous. It does not, however, benefit the growing plant directly, but works up other materials in the soil. It therefore loses its effect after a time. The Belgian farmers have a proverb: "'Much lime and no manure Make falrm and farmer poorer." 13. UL/hzat is the derivatioMi of the term zinc 9 The name is probably derived from the Giernari zinken, signi. fying " nails," and is applied to this metal on -account of its fre. quently forming pointed particles somewhat resembling nails, when melted and suddenly poured into water. (Griffiths.) I4. /halt is the actionh of permatgancte of potash (chameleon mineral) as a disinfectant? It gives up its O to oxydlize the organic impurities of the water in which they collect. I5. Do all fish die whecz takent out of the wZater.? No. Some fish have an apparatus for moistening their gills. They can therefore crawl about in the grass, and even migrate from one stream to another.

Page  52 52 ACNStWES TO PRA CT1CAL QUESTIO.NS I6. What proof have we that H is a metal? Besides that given in the Chemistry, the " sodium amalgam" is thought by some to be an additional proof. Heat moderately in a test-tube a little mercury with a grain or two of sodium. The two metals will combine, forming a pasty amalgam. When cold, pour over it a solution of sal-ammoniac. The amalgam will immediately swell up to eight or ten times its original bulk, retaining, however, its mnetallic lustre. It is thought that H is the metal which puffs out and combines with the mercury, since otherwise we would be compelled to suppose that NH4 is a metallic element, instead of a compound radical, as is generally believed. 17. WhKy does not frozen meat spoil? The cold protects from chemical change. The bodies of mammoths have been found in the frozen soil of Arctic regions so perfectly preserved that the dogs ate the flesh. How long the animals had been there we cannot tell, but certainly for ages. In I86I the mangled remains of three guides were found at the foot of the Glacier de Boissons, in Switzerland. They had been lost in an avalanche on the grand plateau of Mont Blanc, forty-one years before. i8. Give an illustration of the effect of food on the dishosz. tion of animals. Bears which feed on acorns are mild and tractable, while those of the polar regions, which live on flesh alone, are fierce and ungovernable. 19. Confnpare the chemical action of the animal with that of the flant. The animal lives on organized materials, taking up O and evolving CO2, and other oxydized products. The plant lives on unorganized materials, CO2, HO, NH,, and salts, organizing them and evolving O. The function of the animal is oxydation; that of the plant, reduction. The food of the plant serves merely to increase its bulk; that of the animal is employed to replace the material worn out by the active operations of life. The animal obtains the energy necessary for its

Page  53 : CIIEISTR 1Y. 53 existence from the oxydation of its own body; the plant obtains the energy necessary for the organization of its food di rectly from the sun. 20. Show how man is made mainly of condensed air. Science has demonstrated that man is formed of condensed air; that he lives on condensed as well as uncondensed air, and clothes himself in condensed air, that he prepares his food by means of condensed air, and by means of the same agent moves the heaviest weights with the velocity of the wind. But the strangest part of the matter is, that thousands of these tabernacles formed of condensed air, and going on two legs, occasionally, and on account of the production and supply of these forms of condensed air which they require for food and clothing, or on account of their honor and Dower, destroy each other in pitched battles by means of condensed air. LIEBIG. 19. I. In making 0 fromt chlorate of Jotash (KO. C05), haw much can be obtained from two pounds of the salt? 60=48=eqiivalent of constituent. KO.C105=122.5= " conmpound. x=weight of constituent. 2 lbs.=.'' compound. 60: KIO.C105:: x: 2lbs. 48: 122.5:: 2 lbs. x= 25=. 781lb. (0). 2. In makino H, zi'ic is used. HIow much sulphate of zinc (ZnO.SO, + 7H0) will be formed from 2 lbs. of the metal? Zn = 382.5 = equivalent of the constituent. ZnO.SO 3+7110 = 143.6 = " " compound. 2 lbs. = weight of the constituent. x = " " compound. Zn: (ZnO.SO,+7IIO):: 2 1)bs.: x. 32.5: 143.6:: 2 lb.:. x=8.8 lbs. (white vitriol, sulp. zinc). 3. How much SO, will be required to make 50 lbs. sutlhate of iron (FeO. SO, + 7 /0)?

Page  54 54 ANS WERS TO PRACTICAL QUESTIOi~S SO3 = 40 - equivalent of the constituent. FcO.809 +7110 = 13!) = " compound. x = weigh.' of the constituent. 50 lbs. = " " compound. SO3: (FeO.SO3 +t-1iO)::: 50 lbs. 40: 139:: x: 50 lbs. x = 14 -%-4g lbs. (SO8.) 4. The equivalent of the chloride of sodiumZL (salt) is 58.5, In io0 bs. there are 6 —l lbs. qf chlorine ~ what is the cquiva. lent of Cl? x = equivalent of the given constituent. 58.5 = " " " compound. 6 - 817 lbs. = weihght of the given constituent. 10 lbs. = " " " compound. x 58.5:: 6 q g- lbs.: 10 lbs. x = 35.5. 5- [~n 20 grains of bromide of potassium. there are 6f1I% g'rains (f jo/assinum the equivalent of oftassium being 39, what is the equivaleznt of the bromide of potassium? 39 = equivalent of the given constituent. x = " " " compound. 6 -[lj grs. = weight or the given constituent. 20 grs. = " " compound. 39: x:: 6- igrs.: 20 grs. x= 119. 6. In 14 lbs. of iron-rust (Fe2 0/ hoeo much 0? 30 = 24 = equivalent of the given constituent. FeO = 80 = " " compound. x = weight of the given constituent. 14 lbs. = " " " compound. 24: 80:: x: 14 lbs. x=4 1/ lbs. (0). 7. In 2o lbs. of glass (Na 0.Si + CaO. Si02) how manzt lbs. of sand (SiO,)? 2 SiO2 = C:0 = equivalent of the given constituent. (NaO.SiO2 +CaO.SiO2) = 119 = I " con pound. x = wveight of the given constituent. 20 lbs. = " compound. 60: 119:: x: 20lbs. =lO 10 -l-0 lbs. (SiO2)

Page  55 IXN CIEM'ISTR Y. 55 8. In a 25 lb. sack of salt (NazaC) how many lbs. of the metal sod(iumz? Na = 2.3 = equivalent of the constituent. NaC1 = S.5. " " compound. x = weight of the constituent. 25 )lbs. = " " compound. 2.3: 5S.5:: x: 25 lbs. x = 9 -l(7~ lbs. (Na). 229. 5. Wh/at wezigt of 0 is cozntained in 60 grs. of KO. ClOj?,O = 48 = equivalent of constituent. KO.C105 = 122'1/2 = "compound. x = weight of constituent. 60 grs. = " "compound. 48 1221/2 x: 60 grs. x = 23 2 rs. (O). 6. How zmuch KI zill ie feormned in prehiartng 80 grs. of 0 P First find how much KO.C106 will be required to make 80 grs. of 0, and then subtract the So grs. of 0 from the amount, and the remainder will be the KC1. The constituent and compound are the same as in the last problem. 48: 122 l/2: So rs.: x x = 204.16 grs. 204.16 grs. - 80 grs. = 124.16 grs. (KCI). 7. How much H can be mzade from Io lbs. of Zn? First find how much ZnO Io lbs. of Zn will form; second, subtract the Io lbs. of Zn, and the remainder is the 0 which came from the water. This 0 formed' of the water, and the remaining 5 is the H set free. Zn = 32.5 = equivalent of the constituent. ZnO = 40.5 = "." compound. 10 lbs. = weight of the constituent. x = " " compound. 35.5: 40.5:: 10 lbs.: x. x = 12.461 Ibs. (ZnO). 12.461 lbs. ZuO - 10 lbs. Zn = 2.461'bs. (O). 2.461 lbs. + 8 =.307 lbs. (H). 8. How mtuch H can be made froMn 50 lbs. of water?

Page  56 56 ~ANSWERS TO PIRATlICAL tUESTTI'ONS 1I = 1 = equivalent of given constituent. HO = 9 = " " compound. x = weight of given constituent. 50 lbs. = " " compound. 1: 9:: x: 50 lbs. x =5 5/9 lbs. (I1). More simply, I of water is H; hence 50 lbs. + 9 = 5 5/9 lbs. (II). 9. Hozw much salbettre will be required lo make i8 lAt o.f aquazforis? NO5 = 54 = equivalent of given constituent. KO.NOr = 101 =' " colpI)ound. 18 lbs. = weight of given constituent. X = " " conpound. 54: 101:: S1 lbs.: x. x = 33 2/3 lbs. (saltpetre). io. H-ow m uchZ oil of vitriol will be required to decomfpose 6 lbs. of sal/tfcre? First find how much KO in 6 lbs. of KO.N05, next how much KO. SO, that amount of KO will make, and lastly subtract the KO from the KO. SO3, and the remainder will be the SO.. In both cases we neglect the HO combined in the salts and the acid. KO: KO.NO5:: x: 6 lbs. 47: 101:: x: 6 lbs. x = 2.79 lbs. (KO). KO: KO.SO3:: 2.79 lbs: x. 47: 87:: 2.79 lbs.: x. x = 5.16 lbs. (KO.S03). 5.16 lbs. (KO. SO3) - 2.79 lbs. (KO) = 2.37 lbs. (S03). I. How niztchZ HO will be decomfosed by one drach/m c k', and how much KOA will be formed? First find how much KO I dr. of K will form, then subtract from the KO the drachin of K, and the remainder is the 0, which must be a of the water from which it is obtained.

Page  57 z- CHE MISTR Y. 57 K: KO:: ldr.: x. 39: 47:: 1 dr.: x. z = 1-.y drs. (KO). 1ih drs. — 1 dr. = 5-. dr., the amount of 0. The HO is 9/8 of 8/39 dr. = 3/,3 dr. (110). 12. What weig-ht of nitrous oxyd will be forned front the decomposition of 6 oz. of nitrate of ammonia? 2 NO: NH40.NO5:: x: 6 oz. x = 3 3/,o oz. (NO). 13. How much sal-ammoniac would be required to make 2 As. of NH,? NH13: NII4Cl:: 2 lbs.: x. 17: 53.5:: 2 lbs.: x. x = 6 5/17 lbs. (sal-ammoniac). 14. How much CO, will be formed in the combustion of 30 grs. of CO? CO: CO,:: 30grs.: x. 14: 22:: 30 grs.: x. z = 47 1/7 grs. (C02). [5. What weight of carbonate of soda (sal-soda) would be required to evolve I2 lbs. of CO2? CO2: NaO.CO:: 12 lbs.: x. 22: 53:: 12 lbs.: x. x = 28 /ll lbs. (NaO.CO2). i6. What weight of bicarbonate of soda (NVaO.2CO,, "soda") would evolve 12 lbs. of CO,? 2CO2: NaO.2CO:: 1'2 lbs.: a. 44: 7B:: 12 lbs.: x. x = 20 6/1, lbs. (" soda"). 17. What weight of C is there in a ton of CO,? C: CO2:: x: 2000 lbs. 6: 22:: x: 2000 lbs. x = 545,5/1 lbs. (C). 18. How much 0 is consumed in burning- a ton of C? 3*

Page  58 58 ANSWERS TO PRACTICAL QUESTIONS C: CO:: 2000lbs.: x. 6: 22:: 2000 lbs.: x x = 7333 1/3 lbs. (CO2). 733 37/ - 2000 lbs. = 5333 1/s lbs. (O). More simply:C: 20:: 2000 lbs.: x. x = 53331/s lbs. 19. In burning a charge of Io lbs. of gunz owder, find the weight of the several products formed. (See page 107.) (1.) KS: (KO.NO,+S+3C):: x: 10 lbs. 55: 135:: x: 10 lbs. x=42/27 lbs. (KS). (2.) N: (KO.N0,+S+3C):": x 10 lb. 1-: 135:: x: 10 lbs. x = 1 1/27 lbs. (N). (3.) 3CO2: (KO.NO,+S+3C):: x: 10 lbs. 66: 135:: x: 10 lbs. x =4 24/27 lbs. (C02). 20. WH iat weihl of common salt would be requlired to for, n 2: lbs. of mluriatic acid (HCl)? Cl: 1C1: x:: 25 lbs. 35.5: 36.5:: x: 2.5 lbs. x = 2-1.3 lbs. (C1). C1: NaCl:: 24.3 lbs.: x. 35.5: 58.5:: 24.3 lbs. x. x = 40.C44 lbs. (NaCl). 2z. HC1 of a s5eciflc gravity of 1.2 contains about 40 per cent. of the acid. This is v'ry strong commercial acid. What weight of this acid could be formed by the HCl acid gas ro(,. duced in the reaction named in the preceding problem? If 25 lbs. = 40 per cent., then 100 per cent. = 2.5 times 25 lbs. = 62 1/2 lbs. 22. HMhat w-eight of hydriodic acid (1/I) is j dtrachm of iodine? L: HI:: 1 dr.: x. 126.8: 128.8:: 1 dr.: x. x = 1634 drs. (11I).

Page  59 1N CHEMISTR Y. 59 23. WIhat weight of Glauber salt can be formzed from loo lbs. of oil of vitriol? * SO:'NaO.S03:: 100 lbs.: x. 40: 71:: 100 lbs.: x. x = 177.5 lbs. (NaO.SO3). 24. TV/sla /eight of S is there in 1o rs. of sulzihide of kydrov,,. S: 11s:: x: o10 grs. 16: 17:: x: 10U grs. x=97/17 grs. (S). 25. How much 0 is required to chanZge a lb. of SO, to SO. S0.2 S03:: 1 lb.:x. 932: 40:: 1 lb.: x. X 1 1/4 lb. (SO3). 1 /4 lb. -1 lb. = 1/4 II)- (0). 26. How nuc C. phosphorus in 4d0 lbs. of Phoaslshate of lime t (See page 245.) I': 3CaO.rO:: x: 40 lbs.:11: 155:: x: 40 lbs. = 8 lbs. (P). 27. itow munch J in 40 lbs. of the sSyciphosfphate of lime? P: CaO.PO,:: x: 40 lbs. 31: 99:: x: 40 lbs. x = 12 52/,, lbs. (P1). 28. Howt tIuch t;hosfihate of lime will an os. of P make t': 3CaO.P0,:: 1 oz.: x. 31: 153:: 1 oz.: x. x = 5 oz. (3CaO.PO5). 29. How many lbs. of 110 iin I86 lbs. of SO,.3H0? 3110: S03.31O11:::186 lbs. 27: 67:: x:186 lbs. x = 44 64/67 lbs. (110). * In this, as in the other problems, the HO contained in the cid and in the salt is neglected, since it is a variable quantity, and the examp4es are merely for practice.

Page  60 60 ANSWVERS TO PRAC'TICAL QUE.STIONS 30. How much CO, isformed il the combustion of l ton of C? C: CO2: 2000 lbs.: x. C0: 22:: 2000 lbs.: x. x 73333 1/3 lbs. (C02). 31. What weight of S is there ils a ton of iron iyrztes f 2S: FeS,:: x: 2000 lbs. 32: 60:: x: 2000 lbs. x= 10662/8 lbs. (S). 32. WZhat weight of cospieras could be made from 500 lbs.,f iron pyrites? In forming FeO. SO3 from FeS2 only one atom of S is required; hence the 500 lbs. of iron pyrites really contain but 366 2/, lbs. of FeS, which will, at a single reaction, form copperas; by oxydation from the air, the remaining atom of S would doubtless be used afterward. The problem might be solved as well, perhaps, by taking either the Fe or the S alone as the constituent. FeS: (FeO.SO3+7HO):: 3662/3 lbs. (FeS):. 44: 139:: 3662/3 lbs.: x. z = 1158.3 lbs. (FeO.SO3 +7HO). 33. What weight of H is there in a pound of heavy car. buretfed hydrogesn? 411: C4114:: x: 1 lb. 4: 28::: lb. = 1/7 lb. (11). 34. RHzo much O would be required to o.rydize the metallic v-ojper which could be reduced from its oxyd by passing over it, when white-hot, 20 grs. of Hgas? The same amount of 0 would be required to oxydize the copper that was taken from it when it was reduced from its oxyd. The H passing over it when white-hot takes out its 0 and forms HO. H is always -L of the HO. The H = 20 grs.; hence the H0 =9-times 20 grs. = I8o grs. 180 grs. (HO) - 20 grs. (H) = 16o grs. (0). 35. How much 0 would be required to c:rydize the metalitc iron which could be reduced in the sanre manner by Io grs. of H g as?

Page  61 1Y CHEfIISI'~ Y. 51 Following the same reasoning as in the last problem, we have H = 19 grs.; hence the HO = 9 times 10 grs. = 90 grs. 90 grs. (HO)- 10 grs. (I-1) = 80 grs. (0). 36. IW'hat weiht of N is there in Io lbs. of NH3.HO? N: NH3.HO:: x: 10 lbs. 14: 26:: x: 10 lbs. x= 5 5/, lbs. (N). 37. /olw much KO. CIO5 would be required to evolve sufficient 0 to burn the H produced by the decomiposition of 2 lbs. of 1O? 9 of HO is 0; hence 2 lbs. of HO will produce, when decomposed, I-1 lbs. 0. The problem is, then, how much KO.C10O would be required to furnish I- lbs. 0? 60: KO.C105: 1.77 lbs.: x. 48: 122.5:: 1.77 lbs.: x. x= 4.51 lbs. (KO.C105). (If the common fractions are used in solving this problem, the answer is 454 lbs.) 38. How much H zmust be burned to ptroduce a ton ol wvafter? 11: HO: x: 2000 lbs. 1: 9:: x: 20001bs. x = 2222/9 lbs. (II). 39. How much S is there in a lb. of SO, S: SO,:: x: llb. 16: 32:: x 1 lb. x = l/2 lb. (S). 40. Finzd how much "soda" is formed from 500 lbs. of salt. 4I. Find the amount of Glauber salt produced in he firsl step, with the charge just named. 42. Find the amount of HCl prodzuced. 43. Find how much sulphuret of sodium is formed in the skcond step.

Page  62 62 ANS'WEIZS TO PRACTICAL QUESTIONS 44. Find how much suljhurel of calcium is made 45. Frind how much sulPhur could be saved (if none were lost) fS'om the CaS. The following reactions show the chemical changes which take place in the various stages: 2) NaO.SO3 + 2C = NaS + 2C02. NaS + CaO.CO2 = CaS + NaO.CO,. From the (i) reaction we find how much Glauber salt will be made froll 500 lbs. of common salt. To do this we first find how much Na there is in 500 lbs. NaCi; and, secondly, how much NaO. SO3 that amount of Na will make. Na: NaC:: x: 500 lbs. 23: 58.5:: x: 500 lbs. x = 196 -ij ji- lbs. (Na). Na: NaO.SO,:: 196 16-,4 lbs.:. 23: 71:: 196 -filx,. =60- {i a-9 lbs. (NaO.SOs). Ans. to lst tf)ob. Na: NaO.CO,:: 196-l6l- lbs. (Na): x. 23: 53: 196 A6'8 lbs.: x. S = 4i 21- lbs. (NaO.CO2, "Soda'). Ans. to 40th pro. Cl: Na('l:: x 500 lb)s. 35.5: 58.5::: 500 l1)s. x = 3030 -iy Ms. (C1). Cl: IIC1:: 303!- 97 lbs.: x. 85.5: 36.5:: 303 -1r lbs.: x. =311 ~1_1j- lbs. (HC1). Ans. to 42d prob. Na: NaS:: 196-f6f8l- lbs. (Na): x. 23: 39:: 196 fi-6- lbs.: X. x = 333 1/3 l)bs. (NaS). Ans. to 43d prob. 3/s lbs. (NaS) -196 — y lbs. (Na) =136 ys lbs. (S). Ans to Ipob. 15. S: CaS:136 -_-_ lbs. (S): x. x = 307 9/~, lbs. (CaS). Ans. to 44th prob

Page  63 IN CHEM'IS TR Y. 63 46. How many lbs. of HCl would be required to neut-alize szqllcient carbonate of ammonia to form a 30 lb. cake of salamlinoniac (NH4. Ci)? First find how much C1 there is in a 30 lb. cake of salammoniac; second, how much HC1 would contain that amount ef Cl. Cl: NII4C1 l: 30 lbs. 35.5: 53.5:: x 30 lbs. x = 19!.) lbs. (C1). C(': [IC1:: 19.9 lbs. x. 35.5: 36.5:: 19.9 lbs.: x. x = 20.4 lbs. (HC1). 47. ltow ruach S is there in a ton of plaster (gypsum) f S: CaO.S03::: 2000 lbs. 16: (;6: x': 20t)0 lbs. x = 470.58 lbs. (S). 48. I/ow much alumiznum is tcere in a ton of clay P 2A1: A120,.SiO2:: x: 2000 lbs.'.4: 81.4:: x: 2000 lbs. x = 673.2 lbs. (Al). 49. lowu mucl/' A is there in 10 lbs. of alun? K: (KO.SO + A1203.3SO3+'iII0): x: 10 lbs. 39: 474.4:: x: 10 lbs. x =.21 lb. (K). 50o. Iow mucLh wzhitc-lead (PbO. CO2) could be made from I lb. of litkha;-,e? Pb: PhO:: x: 11). 10.3 11 1.6:: x 1 b11). =.!92 11). (I'bl)) in 1 lb. of litharge. P!): PbO.C02::.92 lb.: x. 103: 133::.92: x. x= 1.1 lb. (PbO.CO2). 5i. How many lbs. qf C would be required to reduce 4u ions of browzn hematite (2Fe2 0. 3 HO0)? In the intense heat of the furnace the 3HO would be decomposed, and so only sufficient C would be required to burn

Page  64 04 A NLSWVE.RS TO PRACTICAL QUESTIONS, &c. the 6 atoms of O in the 2Fe20s. In 40 tons of brown hemlatite there are 34.22 of the base. 60: 2Fe2O3:: x: 34.22 tons. 48: 1(60:: x: 34.22 tons. z = 10.26 tons (0). Eight-elevenths of CO, is O; if Io0.26 tons is-,L-, it would require 3.84 tons of C to burn 10.26 tons of 0, and thus reduce 40 tons of hematite. 52. In 60 lbs. of heavy star (snlzantle of baryla) how mucfA S is there? S: BaO.SO3::: 60 lbs. 16: 116.5:: x: 60 lbs. x = 8.2 lbs. (S). S3. How much alum can be made from I cwt. of potash t KO: (KO.SO0 + A20.3SO3 + 24HO): 100 lb.: 1. 47: 474.4:: 100 lbs.: x. = 1009.8 + lbs. (alum).

Page  65 AN SWER S TO TIHE PRACTICAL QUESTIONS IN THE FOURTEEN WEEKS COURSE DESCRIPTIVE ASTRONOMY. Di. Tycho Brakhe have a telescofe? No. Galileo invented the telescope. 2. Sufz5ose one should watch the sky, on a winter's evening, from 6 P. M. to 6 A. M., what portion of the celestial sphere would he see? All that is ever seen in his latitude. 3. How do we find whazt proportion of the sun's heat reaches the earth? Calculate the surface of a sphere whose radius is the distance of the earth from the sun, and then estimate what proportion of that area the earth occupies. 4. How many real mzotions has the sun? Two. One around its axis, and one with the solar system around the Pleiades. 5. How many ati5farent motions has the sun? Three. One along the ecliptic,-its yearly motion; one through the heavens,-its daily motion; and one N. and S. 6. How many real motions has the earth? Three. One on its axis; one around the sun; au4 a tfhird its " wabbling motion," which causes Precession.

Page  66 66 4NSW'RS TO PRACTICAL QUESTIOIN'S 7. Can vny inferior planet have anl elongfatioz of go~? No. Venus recedes only 48~ from the sun. 8. How do we know the heat of the suin's rays at any planet.? Tlhe intensity of the heat and light varies inversely as the square of the distance. 9. Can you give any other proof than that named in the book, of the rotundity of the earth? Aeronauts, when at a proper height, can distinctly see the curving form of the earth's surface. Io. In what way is the force which acts on a spiinning-tap ofpfsile to that which produces precession (p. 125)? Gravity, acting on the top, tends to draw C P (Fig. 34) Iram the perpendicular. The attraction of the sun, acting on the bulging mass of the earth's equator, tends to draw C P toward the perpendicular. _ I. Wlhy is the Tropic of Cancer placed where it is? Because it is the farthest place north where the sun is evex seen directly overhead. 12. W4hy is the Trvopic of Cancer so called? When named, the sun was probably in that constellation at the time of the summer solstice. Now, owing to the precession of the equinoxes, the sun is in the constellation Gemini, and to be exact, it should be called the Tropic of Gemini. It is still, however, the sign Cancer, as before. The same reasoning applies to the Tropic of Capricorn, which is now in the constellation Sagittarius. I3. lit Greenland, at what part of the year will the midnight suzn be seen due north? At the summer solstice. 14. How do we know that the moon has little if any atmostbhere? Because when the moon occults a star, there is no refraction of the star's true place. I5. When is the moon seen high in the eastern sky in the afternoon, long before the sun sets?

Page  67 IN DESCRI'PTIVE ASTRONOMY 67 During the second quarter before it comes into opposition. i6. IWzhy is the Ecliptic so called? Because eclipses always occur within it. 17. Why is it thal the suzt in summer shines on the north side of some houzses both at rising and setting, but in wiinte7 never does? Since at the summer solstice the sun rises and sets north of the E. and XW. points, it will rise and set on the north side of a house which stands exactly N. and S. At the winter solstice the sun rises and sets S. of the E. and W. points

Page  68 TABLE OF THE MINOR PLANETS. Sidereal No. 2tName. Date of Discovery. Discoverer. Revolution __ __ __ __ _ __(Days.) 1 Ceres............ 1801, January 1 Piazzi......... 1680 2 Pallas............ 1802, March 28 Olblers.......... 1682 3 Jwino............ 16041, Sept. 1 Harding........... 1596 4 Vesta............ 1807, Mlarch 29 Olbers............. 1326 5 Astreea........... 1845, December 8 Hencke............ 1512 6 Hebe............. 1847, July 1 Hencke............ 1379 7 Iris.............. 1847, August 13 Hind........ 1346 8 Flora.......... 1847, October 18 Hind............. 1193 9 Metis.......I 1848, April 25 Graham......... 1346 10 Hygieia.......... 184-19, April 12 Gasparis......... 2043 11 Partilenope.... 1850, May 11 Luther............. 1403 12 Victoria......... 1850, Sept. 18 3 tind............. 1303 13 Egeria 185 ), Nov. 2 Gasparis........... 1511 14 Irene......... 1851, May 19 Hind............... 1519 15 Eunomia........ 1851, July 29 Gasparis........... 1570 16 Psyche.......... 1852, llarch 17 Gasparis........... 1828 17 Thetis........... 1852, April 17 Luther............. 1421 18 lelpomene...... 1852, June 24 Hind............. 1271 19 Fortuna.......... 1852, August 22 Ilind.............. 1393 20 AfMassalia.......... 1852, Sept. 19 Gasparis........... 1365 21 Lutetia.......... 1852, Nov. 15 Goldschmidt....... 1388 22 Calliope.......... 1852, Nov. 16 Hind.............. 1813 23 Thalia.......... 1852, Dec. 15 Itind.............. 1556 24 Themis.......... 1853, Ap)ril 5 Gasparis.......... 2036 25 Phocema...... 18.53, April 7 Chacornac......... 1358 26 Proserlina...... 1853, May 5 Luther............. 1580 27 Euterpe......... 1853, Nov. 8 Hind.............. 1313 28 Bellona.......... 1854, MIarch 1 Luther............. 1692 29 Amphitrite...... 185-, March 1 Marth............. 149!)2 30 Urania........... 1854, July 22 Hind.............. 1329 31 Euphrosyne..... 1854, Sept. 1 Ferguson.......... 2048 32 Pomona.........18654, October 26f Goldschmidt....... 1521 33 Polyhymnia.... 1854, October 28 Cllacornac......... 1778 34 Circe............ 1855, April 6 Chacornac........ 1609 35 Letucothea....... 1855, April 19 Luther............. 1903 36 Atalanta......... 1855, October 5 Goldschmidt....... 16(64 37 Fides............ 1855, October 5 Luther............. 1569 38 Leda............. 1856i, January 12 Chacornac......... 1657 39 Lmtitia.. 1856, February 8 Chacornac...... 1684 40 Harmonia....... 18)i;, March 31 Goldschmidt....... 1247 41 Daphne...... 185, May 22 Goldschmidt.........81 42 Isis..............15i, Iay 23 Pogson............ 13)2 43 Ariadne......... 1857, April 15 Poerson......... 1195 44 Nysa............. 1857, May 27 Goldsclmidt....... 1379 45 Eugenia.......... 1857..June 7 Goldschidt.......... 8 46 Hestia............ 1857, August 16 Pogson............ 1470 47 Aglaia........... 1857, Sept. 15 Luther............. 1788 48 Doris........... 1857, Sept. 19 toldschmidt....... 2003 49 Pales 1857, Sept. 19 Goldschmidt....... 175 50 Virginia. 1857, October 4 Ferguson......... 1576 51 Nemasa........ 1858, January 22 Laurent............ 1338 52 Europa......... 1858, February 4 Goldschmidt....... 1993 53 C'alypso......... 1858, April 4 Luther............. 1548 4 Alexandra...... 1858, Sept. 10 Goldschmidt. 1634 55 Pandora.........1858, Sept. 10 Searle.............. 1674 -~~~~~~~~~~~~~~

Page  69 4A BLE OPF TI'HE MllOR PLANE1'S. 69 Sidereal No. Name. Date of Discovery. Discoverer. 1Revolution ____ ____ ____ ____ _______ _(D ays.) 56 Melete*.......... 1857, Sept. 9 Goldschmidt....... 152'r 57 Mnemosyne I... 1, Sept. 22 Luther............. 58 Concordia........ 1860, March 21 Luther............ 1615 59 Elpis........... 1 60, Sept. 12 Chacorac......... 16:34 60 Echo........... 1880, Sept. I5 Ferguson.......... 1352 61 Dana6........... 1860, Sept. 93 Goldschmidt.. 19()2 62 Erato........ 1860, Sept. 14 F6Orster and Lesser. 2023 63 Ausonia.......... 1861, February 10 Gasparis........... 1355 64 Angelina......... 1861, March 4 Tempel............ 1601 65 Cybele........... 1861, March 8 Tempel............ 2311 66 Maia........... 1l61, April 9 Tuttle.............. 1588 67 Asia............. 1861, April 17 Pogson............ 1375 68 Leto............. 1861, April 29 i Luther............. 1695 69 Hesperia......... 18);1, April 29 Schiaparelli........ 1893 70 Panopea......... 1861, May 5 Goldschmidt....... 1542 71 Niobe............ 1861, August 13 Luther.. 1671 72 Feronia.......... 1861, May 29 Peters and Safford. 1245 73 Clytie........... 18t;2, April 7 i Tuttle............. 1590 74 Galatea.......... 1862, Au rust 29) Tempel............. 1691 75 Eurydice......... 1862, Sept. 22 Peters............. 1594 76 Freia............ 1862, October 21 d'Arrest.......... 2080 77 Frigga............ 1862, Nov. 12 1 Peters............. 1596 78 Diana............ 1863, March 15 i Luther............. 1554 79 Eurynome....... 18i3, Sept. 14 Watson............ 1399 81) Sappho.......... 1864, May 2 Pogson........... 1270 81 Terpsichore..... 1864, Sept. 30 Tempel............ 1.93 8' Alcmene......... 1864, Nov. 27 1 Luther............ 1659 83 Beatrix........... 186ti5, April 26 Gasparis....... 881 84 Clio............. 1865, August.26 Luther............ 1830 85 Io................ 1865, Sept. 19 Peters........... 158 8i Semele.......... 1866, January 4 Tietjen............ 1983 87 Sylvia............ 18ti6, May 16 Pogrson............ 2:384 88 Thisbe........... 18ti66, June 15 Peters............ 675 8'3 Julia............. 1866, August 6 Stephan......... 1472 91 Atiope.......... 166, October Luther............. 1 031 91 A2Egin........... 1866, Nov. 4 Stephan........... 1495 92 Undina.......... 1867, July 7 Peters 2086 93 Minerva........ 1867, August 24 Watson........... 1669 94 Aurora........... 1867, Sept. 6 Watson............ 2050 95 Arethusa......... l867, Nov. 23 Luther............. 1964 9 t Egle............. 1868, February 17 C(,ggia............. 1950 97 Clotho... 1868, February 17 Tempel............ 1592 98 Ianthe.......... 1868, April 18 Peters.......... 16()7 99 Dike........ 8.... 1868, ay 28 Borelly............ 100 tIecate.......... 18;8, Jilly 11 Watson............ 1892 101 Helena...... 1868, August 15 Watson............ 15018 10()2 Mirial.......... 1868, August 22 Peters............ 1587 10:3 Hera............ 1868, Sept. 7 Watson............ 1622 104 Clymene......... 186s, Sept..3 Watson............ 2071 105 Artemis.......... Sept. 16 Watson.......... 1341 106 Dione............ 1868. October 10 Watson............ 2092 107 Camilla.......... 1868, Nov. 17 Pogson.......... 108 |lecuba.......... 1869, April 2 Luther............. 210 109 Felicitas......... 1869, Oct. 9 1 Peters.............. 1615 * Goldsclhmidt at first believed it to be Dapt)he (41), but Schubert finding its perioQ different, called it Pseudo-Ditphne. It was not seen from 1857 to 1861, wLen Luhor redlecovered it, and named it Mlelete. The numerical order is that adopted bx the authority of the Berlin Ephemeris.

Page  70 7o TABLE OF THE MINIOR PLANYETS. No. Namlec. Date of Discovery. Di-scoverer. Log. a. 110 Lydia............ 1870, April 19 Borelly............ 0.4371261 111 Ate............ 1870, August 14 Peters.............. 0.413183 112 Iphigenia...... 1870, Sept. 19 Peters........... 0.386324 113 Amalthea........ 1871, March 12 Luther... 0375971 114 Cassandra....... 1871, July 23 Peters..............l 0 4242 115.............. 1871, Alngust 6 \Watson........... 0.376540 116 Sirona.......... 1871, Sept. 8 Peters.............. 0.441912 117 Lomia.......... 1871, Sept. 12 Borelly..... 0.475643 118 Peitho.......... 1872, March 15 Luther............ 0. 86977 119.................. 1872, April 3 Watson........... 0.410364 120 Lachesis....... 1872, April 10 Borelly............ 0.4958110 121............1...... 1872, May 1'2 Watson........... 0.538967 122 Gerda.......... 1872, July 1l Peters........... 0.508118 1'23 Brunhilda....... 1872, July 31 Peters........... 0.430151 12.1 Alcesto......... 1872, August 23 Peters.. 0.419063 125................. 1872, Sept. 11 Prosper Henry.... 0.48219 126.................. 1872, Nov. 5 Paul Henry....... 0.386778 127.................. 1872,:Nov. 5 Prosper Henry..... 0.44377 128..1872, Nov. 25 Watson................... 129 Antigone..... 1873, Feb. 5 Peters........... 0.457822 4 139 Electra........ 1873, Feb. 17 Peters................... * LOg. a = logarithm; of m:ljor semiaxis of orbit, taking the earth s distance from the sun as unit.

Page  71 SIMPLE DIRECTIONS S TO A BEGINNER FOR PERFORMING THE EXPERIMENTS IN THE FOURTEEN WEEKS COURSE IN CHEM I ST R Y. (OLD NOMENCLATURE.) [The large figures refer to the page of the Chemistry, and the small ones tc the number of the experiment. Read for additional directions, Chemistry, pp. 235-248, and new edition, pp. 24L5-267.] 11. I. Put as much chlorate of potash (potassic chlorate) as will lie upon the point of a knife-blade, and half as much sulphur, into the mortar. Grind them slowly with the pestle until the ingredients are thoroughly mixed and distributed over the bottom of the mortar. Hold the mortar so that the loose particles cannot fly into your eyes, nor the flame burn your clothes, and then grind heavily with the pestle, when rapid detonations will ensue. The mixture will last for days. After use, clean out the mortar carefully for other experiments. The powder can be wrapped with paper into a hard pellet and exploded on an anvil by a sharp blow from a hammer. Sometimes small bits of phosphorus are used instead of sulphur. Great care is then necessary, as the particles of burning phosphorus are apt to fly to some distance. 12. I. Two teaspoonfuls of common carbonate of soda and one of tartaric acid should be dissolved separately in a wineglass of water. On being poured together in a larger glass, they will violently effervesce. Use a glass large enough to

Page  72 72 DIRECTIONS FOR PERFORMING' prevent any running over upon the table. Neatness in experiments is essential to perfection3 and often to success. 15. I. The cabbage solution is made by steeping purple cabbage leaves in water. A little lemon-juice or vinegar will turn it to a bright red, and a little of the potash solution to a deep green, Add a little alcohol to the red solution, to keep it from freezing, and bottle it for use. Dissolve a little of the dry litmnus in water, filter and bottle it. These are to be used in testing the alkalies and acids. Dissolve also a stick of the potash in water, filter and bottle. Fill two test-tubes nearly full of water; color one with the cabbage and the other with the litmus solution. Add a few drops of the potash solution and of the sulphuric acid alternately to each. The color can be changed at pleasure. Take a small bit of tubing, and heating the ends in the flame of the spirit-lamp (the greatest heat is near the tip of the flame), seal up the opening. This will be useful to dip into the acid or alkali, as it will remove a drop more readily than by dropping from the bottle. 20. Pulverize an ounce of the potassic chlorate very carefully; stir in it one-fourth of its weight of the black oxyd of manganese and place the mixture in the copper retort, attach the tubing and gas-bag as shown in the figure of p. 234; or in the Florence flask, attaching a delivery tube, as shown in figure on p. 20. The glass tubing may be heated in the flame of the alcohol-lamp and bent to the desired shape, or it can be broken into short lengths by simply starting the break in the tube by a mere scratch with a three-cornered file and then connecting the pieces of glass tubing with a short bit of the small rubber tubing, as in the figure on p. 20. The gas may be passed off from the gas-bag, or directly from the retort into the pneumatic cistern, C, across which is placed a shelf perforated, to permit the gas to bubble up into the receiver, J. The pneumatic cistern may consist of a tub of water. The bottles for collecting the gas are sunk into the water until filled, inverted, and then lifted up on the shelf, carefully keeping the lower edge of the bottle beneath the water. A large tin pan, without any shelf, may be used as a cistern by filling the bottles full of water in a deep

Page  73 EXPERIMENTS IN THE'UIEMISTRY. 73 pail, and then slipping a plate underneath each one, as shown in the second figure on p. 22, leaving enough water on the plate to cover the edge of the bottle; it may then be lifted out and placed in the cistern. In the same way the bottles, when filled with gas, may be remc ved and kept for use. Gas may be passed from one bottle to another by inverting one over the other beneath the water in the pneumatic cistern, or in a large pail, when the gas will bubble up from the lower one into the upper one. Apply the heat to the glass retort very carefully at first, holding the lamp in the hand and moving it around so that the flame may strike all the lower part of the flask, and thus expand it uniformly. Be careful also that there is no draft of cold air to strike against the heated retort. With the copper retort no care of this kind is necessary. When the gas ceases to come off, remove the stopper or lift the end of the tube out of the water; otherwise, as the retort cools and a vacuum is formed, the water in the cistern will set back into the flask, and, if of glass, will break it. An ounce of the salt will make over six quarts of oxygen gas. When the retort is oartly cooled, pour in some warm water to dissolve the residuum, which may then be poured out and the retort drained and Jet away for future use. In order to test the purity of the materials, and thus avoid any danger of an explosion, place a little of the mixture for making oxygen in an iron spoon and heat it over the spirit-lamp. If the gas passes off quietly, no langer need be apprehended. 22. I. The experiment with the candle can be performed most strikingly by filling a common fruit-jar with nitrogen see page 32) and another with oxygen. The covers will preLerve the gases until wanted for use. The covers may then be laid loosely on top cf the jars, and the lighted candle passed quickly from one jar to the other. It will be extinguished in one and relighted in the other. With care, it may be passed and repassed a dozen times. This strikingly illustrates the difference between oxygen and nitrogen. Test the carbonic acid, in this as in all similar experiments, with the blue litmus and the green cabbage, or a slip of blottingpaper wet with the litmus solution. A few drops of the solu

Page  74 74 DIRECTIONS FOR PERFOR.T NO tion may be poured into the jar, and then the jar shaken, so as to permit the water to absorb the gas. The candle may be simply stuck upon the end of a bent wire, but it is much neater to have the tinsmith fit a little cup for its reception, as shown in the figure. 2. The worn-out watch-springs which can be obtained gratis of any jeweller, may be easily straightened by drawing them between the fingers. If the end of each spring be heated and then pounded with a hammer on any smooth hard surface, the temper may be thoroughly drawn and the edge sharpened. Make a slit with a knife in the side of a match, into which insert the edge of the spring. Take a piece of zinc or tin large enough to cover the mouth of the jar containing the oxygen, and make a hole through it with a nail. Pass the other end of the spring through this hole, and then through a thin cork. The spring is now ready for burning. The metal cover will prevent the flame from coming out of the jar and burning one's hand, and the cork will hold the spring in its place. When the match is ignited, and then lowered into the jar of oxygen, the spring should not reach more than half-way to the bottom, and should be pushed down as it burns. If a specie-jar be used, do not fill it quite full of gas, as a little water left in the bottom will prevent the melted globules of iron from breaking the glass. 23. I. If brimstone be used in this experiment, and it fails to light readily, pour upon it a few drops of alcohol, and then ignite it. 2. If you have not a deflagrating spoon to contain the phosphorus, one may be readily extemporized. Hollow a small piece of chalk and attach it to a wire, which may then be secured to a metal top, as in the case of the watch-spring. This need not be pushed down into the jar as the burning progresses. At the close of the experiment, test for the acid formed in the combustion. The fumes are very disagreeable, and should not be inhaled or allowed to escape into the room. 3. If a piece of bark charcoal be ignited, and then lowered into a jar of oxygen, it will deflagrate with bright scintillations. 31. I. Put in an evaporating-dish a little starch; cover it

Page  75 EXPERIME.NTS I.N THE I CiIE'lIST'RY. 7c with water in which a few crystals of iodide of potassium have been dissolved, and heat. Stir the liquid, to prevent lumps. When cooked, immerse in the paste slips of blotting-paper. Use while moist. Be careful not to heat the glass tube too hot, lest the ether vapor may ignite. Keep the jar well filled with vapor by frequently shaking it. Lower into the ozone a bit of silver-leaf moistened with water; it will quickly crumble into dust, the oxyd of silver. 34. I. To make the iodide of nitrogen, cover a few scales of iodine with strong aqua ammonia. After standing for a half-hour, pour off the liquid and place the brown sediment in small pieces on bits of broken earthenware to dry. This will require several hours. They may then be taken to the classroom very carefully and exploded by a slight touch of a rod, or even a feather. 37. I. For making NO, a special apparatus is necessary for complete success. The Florence flask may, however, be used, and the heat of the spirit-lamp will be sufficient. The fumes may be caught in the evolution flask, which is kept cool by a towel frequently wet. When the retort is partially cooled, at the conclusion of the process, pour in a little warm water, to dissolve the sulphate of potash, otherwise the retort may break by the crystallization of the salt. 2. Mix equal parts of nitric acid and oil of vitriol (perhaps a teaspoonful of each), and pour the mixture on hot finelypowdered charcoal, or on a little oil of turpentine. It will be oxydized with almost explosive violence. This should be performed out of doors. 3. Bits of tin may be obtained of any tinsmith. Put them in a tumbler and nearly cover them with the NO,. In using copper, the apparatus shown on page 39 is excellent. The acid may be turned in gradually through the funnel tube. Before putting in the acid pour into the flask warm water to cover the lower end of the funnel tube, which should nearly reach the bottom of the flask. When a jar is filled with the NO, it may be lifted out of the water and inverted, when the NO4 will pass off in blood-red clouds. If the jar be left in the cistern and one edge be lifted so as to admit a bubble of air, red fumes will fill the jar. By standing a moment the

Page  76 76 DIRECTIONS i'OR PERFOR31ING water will absorb the red vapor. This process can be re. peated several times with the remaining gas. 40. I. The finely-powdered sal-ammoniac and lime may be mixed in an evaporating-dish. The -escaping ammonia should be tested with a glass rod or tube wet with hydrochloric acid. 2. Heat a little aqua ammonia in the Florence flask. Collect the vapor in an inverted bottle, to which is fitted a cork and tube, with the inner extremity drawn to a fine point over the spirit-lamp. Insert the cork, and then plunge the bottle into a vessel of water. The water which passes in first will absorb the gas so quickly as to make a partial vacuum, into which the water will rush so violently as to produce a miniature fountain. 42. I. In making H, the directions given on pages 236-7 should be carefully observed. For purifying the gas a solution of potash should be placed in the flask d (page 42). If a junk bottle be used the acid should be added slowly, as the heat generated is liable to break the bottle. Pour the water into the flask a until the lower end of the funnel is covered, before adding the acid. The flow of gas may be regulated by additions of acid, as may be wanted. One part of acid to ten or twelve of water will liberate the gas very rapidly. If it comes off very fast, the liquid is liable to froth over. The philosopher's lamp, page 237, is very interesting. The jet may be a straight glass tube drawn to a fine point over the spirit-lamp. Large glass tubes or the beaks of broken retorts, held over this flame, will produce the singing tones, though not as well as the apparatus figured in the book. The tone may be regulated by the size of the flame, i. e. the rapidity with which the gas comes off, the size of the jet as well as the length and size of the tubes. The H can be collected over the pneumatic cistern, or, since it is lighter than air, in inverted bottles. As soon as the bottles are turned right side up the gas will escape. To measure the H and O for the "mixed gases," a receiver, with a stop-cock on top, which may be connected by rubber tubing with the gas-bag, is very useful. The oxygen may be passed directly into the gas-bag, however, as on page 234, until it'is about one-third full, when

Page  77 EXPERIIMEIVS IXIN THE C6HEMISTRY. 77 the bag may be removed and attached to the hydrogen ap. paratus to be filled. 50. I. In lieu of a small crucible, fill a common tobaccopipe with crystals of blue vitriol, and heat them over the lamp or in a common fire until the water of crystallization i3 expelled. Alum may be rendered anhydrous in the same manner. 56. I. Small paste-diamonds may be obtained of a jeweller, to illustrate the forms of cutting the diamond. 60. I. Place a filtering paper in the glass funnel, and in it a couple of ounces of bone-black or finely-powdered chdrcoal. Filter through it water colored with ink, litmus, or any other impurities. In pouring the liquid into the filter hold a glass rod against the edge of the pouring vessel, so as to direct the stream into the funnel. The funnel may be placed in the nozzle of a bottle, but must not fit closely. A bit of wood or a thread inserted between the stem of the funnel and the nozzle will leave an opening sufficient for the egress of the air. 64. I. Break some marble into small bits; place them carefully in the evolution-flask, and, inserting the cork and tube, pour in HC1 slowly. The gas, on account of its weight, may be passed directly into a bottle or jar. 2. Lower a lighted candle into a jar of the gas, or, lowering the candle into an empty jar, pour the gas into the jar, as if it were water. Test the acid with litmus paper. 3. Place a piece of lime as large as an egg in a pint of water; let it stand overnight; pour off the clear liquid-it is lime-water. Place a little in a tumbler and breathe through it by means of a tube, or pass a current of CO, from the evolution-flask until the liquid, at first milky, clears. 4. Breathe through a tube into an empty bottle. Lower into it a lighted candle-it will be immediately extinguished. Pour in some lime-water, shake it thoroughly and it will become milky. 5. Twist a wire around the neck of a small wide-mouthed vial, to answer as a bucket. Lower it by the wire into a jar of CO:,, our ideal well foul with the gas. Raise it again, and test for the CO2 by m ans of a lighted match. The bucket will be found to be full of the gas.

Page  78 78 DIRECTIONVS FOR PER'FORMING 6. Fill a jar with hydrogen, and in a similar way dip the gas downward and burn it over a lamp. This shows in a very striking manner the difference between H and CO2 in respect to specific gravity. The one, we see, is dipped upward, the other downward. 7. Balance a large paper bag or box on a delicate pair of scales, or in any simple manner one's ingenuity may suggest. Empty into the box a large jar of CO2, and the box will quickly descend. 8. Arrange little wax-tapers in a wooden or pasteboard trough, as on page 65. Light them, and then pour in at the top a bottle of carbonic acid gas. If the proper slant is given to the trough, all the candles will be extinguished. 72. I. Olefiant gas may be made by heating in the flask one part, by measure, of alcohol and two parts of sulphuric acid. Pass it through a solution of potash, as shown on page 88, and then collect in the gas-bag. Fit a piece of glass tubing, drawn to a fine point at one end, to the stop-cock of the gas-bag by means of a bit of the rubber tubing. On turning the stopcock and forcing out the gas it may be ignited, when it will burn with a clear white light. 2. Fill a tall jar one-third full of olefiant gas, and the remainder with chlorine gas. On lighting, the mixture will burn with a dense cloud of smoke. HC1 is the product of the combustion. 3. Mix with oxygen anc explode in soap-bubbles. It produces a greater noise even than the " mixed gases." Great care must be taken not to let the light approach the gas-bag containing the mixture. 4. Fit a large test-tube with a cork and a piece of glass tubing, drawn to a fine point at the outer end. Fill the tub with fine dry pine-shavings. On heating, the gases from the wood will pass off, and can be ignited at the jet-tube. The test-tube can be held by a strip of twisted paper or wire. 59 At the close of the Ist exp. perform the one figured on page 79. A small piece of wire-gauze, 4 or 6 inches square, for this purpose can be purchased of any tinsmith. If you do not force the gas out too rapidly, you will be able to burn it on either side of the gauze at pleasure.

Page  79 EXPERIMENTS IN TlHE CHEMISTRY. /9 79. Place on top of the gauze a bit of camphor-gum. Ig. nite it, and the flame will not pass through to the lower side. Then ignite on the lower side, and extinguish the flame on the upper side. 77. The carbonic acid of a burning candle may be passed through lime-water in the following manner. Take a bottle arranged with tubes, as in the middle one shown in the figure on page 87. From the tall tube at the left suspend a glass funnel with the stem coupled to the tube by means of a piece of rubber tubing. Place under this funnel a burning candle. Partly fill the bottle with lime-water. Then placing the mouth to the right-hand tube, draw out the air from the bottle. This makes a draft over the candle, and draws its invisible smoke through the funnel, down the long tube, and up through the lime-water, which soon becomes milky. SO. The compound blow-pipe with gasometers, as shown on page 238, is the most serviceable. If gas-bags are used, the one for hydrogen should be twice the size of the one for oxygen. A board should be laid on each bag, upon which weights may be placed, when ready for use, so as to force out the gas steadily. Turn the stop-cock so that the H will pass out twice as fast as the 0. Always ignite the H first, and then turn on the O slowly until the best effect is produced. If gasometers are used, press the inner receivers down to the bottom, and then pour in water till it reaches nearly the top. The rubber pipes may then be attached to the hydrogen or oxygen apparatus, and the gases passed directly into the gasometers. Proper pressure is produced, when the jet is to be ignited, by unloosing the strings from the inner'receivers, and thus taking off the " lift" of the weights which equipoise them. Additional pressure is secured by bearing down upon the receivers. All the metals burn in the blow-pipe flame with their characteristic colors. Narrow slips should be prepared for this purpose. A mirror, and a cup for holding the chalk, are necessary to show the lime-light. A piece of hard chalk or lime, whittled to about the size of a pencil, may be held in the flame to illus. trate the principle. S7. Put in the flask two ounces of common salt and an ounce and a half of black oxyd of manganese. Pour on

Page  80 So DIRECTIONS FOR PERFORM't~G enough water to reduce the mixture to a thin liquid Shake the flask until the whole interior is moistened. Insert the cork and delivery-tube; the middle bottle shown in the figure is not necessary. Fill the pneumatic cistern with warm water, unsing just as small a quantity asfpossible, since water absorbs the gas. Pour in an ounce of the oil of vitriol through the funnel-tube, or directly at the nozzle, by removing the ground stoDper; if a kind of flask be used which has one. The gas will come ofi at once, even before the heat is applied. Collect the gas in bottles and use directly, if convenient, otherwise put corks in them and rub the nozzles well with tallow. Pass the gas through cold water, as shown on page 88, or more simply, through a tumbler of water. This will form chlorine water, which should be bottled and kept in a dark place. 2. Fill a test-tube nearly full of pure rain or snow watei, and let fall into it a drop or two of thle nitrate of silver solution. A drop of HC1 will form a cloudy white precipitate. 91. I. Place on a clean white dish a few scales of iodine and a bit of phosphorus as large as a pea. It will soon ignite. 2. Fill three test-tubes nearly full of soft water. Pour in one a few drops of a solution of bichloride of mercury, into the second of sugar of lead, into the third of subnitrate of mercury (formed by pouring NO5 on mercury). Add to each of these a few drops of the solution of iodide of potassium. The first especially will produce a brilliant color (iodide of mercury); the rapid change from yellow to red is very marked. On continuing to add the iodide of potassium, the red precipitate will be dissolved and disappear. 3. Make an additional quantity of the iodide of mercury, as in the 2d exp. Let it settle. Pour off the liquid, and then spread the sediment on a piece of heavy card-board. making a red spot as large as a silver dollar. Dry it care. fully. Then heat very strongly, when it will turn yellow. Rub over the yellow spot the point of a knife several times, bearing on very firmly, and a red mark can be seen. Lay away the paper for a day or two, and the red color will spread ovei the whole spot. 4. Dissolve a few scales of iodine in fifteen or twenty tines its bulk of alcohol.?our a few drops of this solution on a

Page  81 EXPERIMEtETS IN -T'IrE CUHEM'ISTR. 81 freshly cut potato or apple. Blue specks will show the presence of starch. 96. I. Melt a quantity of sulphur, either the flowers or brimstone, in a test-tube. It is at first thick and dark-colored, but after continued heating becomes thin and dark-colored. Pour it now into water and it will form an elastic gum, which can be moulded into any desired form. 2. Heat a piece of brimstone in a test-tube. After a little the sulphur will sublime and collect in the upper part of the tube as flowers of sulphur. 3. Fill a cup with brimstone and melt it with a gentle heat. Set it aside to cool. When a crust has formed on top, break it and pour out the liquid contents. If the cup be broken, the bottom will be found covered with crystals of sulphur. 100. Place in the evolution-flask half an ounce of sulphuret of iron. Cover this with water, and then pour in oil of vitriol through the funnel until the gas comes off freely. It may be passed through a glass of cold water. This solution must be bottled and closely corked. The gas may be tested directly; see page 137. 102. I. Cover a stick of phosphorus with dry, fine-pow. dered charcoal. It will soon ignite. 2. Put in a vial half an ounce of sulphuric ether and a halfdozen pieces of phosphorus not larger than grains of wheat. Thoroughly shake and then. set away. Repeat the shaking often. When the phosphorus is dissolved, pour a little of the solution on the hands, and when briskly rubbed together in a dark place they will glow with a ghostly light. 3. Pour some of the solution on a lump of loaf-sugar. Drop this in hot water, when the ether will catch fire. 4. Place in a wine-glass a few crystals of chlorate of potash and a small bit of phosphorus. Fill the glass nearly full of water. By means of a funnel-tube, pour a little oil of vitriol to the bottom of the glass. A violent deflagration will immediately take place, and, in a dalk room, flashes of green light will be seen. 119. Cut off three or four inches of magnesium ribbon, and holding. one end with a -pair of pincers, thrust the otbf]r into

Page  82 82 DIREUCTONS FOR PERFORMIALG, ETC. the flame of the spirit-lamp. The metal will almost instantly ignite, when it may be removed and held up to the view of the class until the Mg is consumed. 124. To make a saturated solution of alum, drop crystals of the salt into boiling water, until a drop of the liquid taken out on the end of a glass rod and put on a bit of glass will crystallize as soon as it cools. 134. Fill a test-tube nearly full of water. Pour in it a few drops of the solution of sulphate of copper. Add ammonia, and a blue precipitate will be formed. Notice the change from green to blue. The sulphate of copper may be readily made for this experiment by covering a copper cent with dilute oil of vitriol. This experiment may be made to show the divisibility of matter by weighing the cent, then seeing what proportion of the whole solution you use, and then experiment to find what quantity of water can be taken and yet have the blue color perceptible in the ammonia test. 185. Fill a test-tube one-sixth full of sweet oil, add a little ammonia, and nearly fill with water. The constituents remain separate. Shake thoroughly, and they will combine, forming a thin, soapy liquid. Add an acid, and they will dissolve partnership at once. SUGGESTIONS. Melted snow, or very clear rain-water, will answer the place of distilled water in making solutions, &c., for experiments. Whenever corks leak gas they may be wrapped with thin strips of wet paper to make them fit more tightly, or the entire nozzle maybe smeared with tallow, or covered with sealingwax, if heat is not used. In that case a little plaster of paris may be wet up and quickly applied. The experimenter will find a retort-stand for holding the retorts, a test-tube holder, a set of tin cork-borers, several Florence flasks of different sizes, the copper retort for making oxygen, and the gas-bag, with its tubing and connectors, almost indispensable. After these, the compound blow-pipe is of the greatest value. A few drops of a solution of magenta (j dr. in a gill of HO) will color the water beautifully, and add to the effect of certain experiments.


Page  84

Page  85 ANSWERS TO THE PRACTICAL QUESTIONS AND PROBLEMS IN THE FOURTEEN WEEKS IN CHEMISTRY, REVISED EDITION, WITH NEW NOMENCLATURE. [ The large figures refer to the fage of tze Chemistry, and the small ones to the number of the Question.] 24.-I. I.Z a 25-lb. sack of common salt, how manylt pounds of t/he metal sodium? Na = 23 = atomic weight of the given element. NaCl = 58.5 = molecular weight of the compound. x = weight of the given element. 25 lbs. = - " "compound. Na: NaCI:: x: 25 lbs. 23: 58.5:: x: 25 lbs. 58.5 x 575 lbs. 7r = 997 lbs. (Na). 2. I/ 14 lbs. of iron rust (Fe2O3), how muich 0? 03 = 48 = atomic weight of the given element. FeO0 = x6o = molecular weight of the compound. x = weight of the given element. 14 lbs. = " "compound. 0: Fe2Os:: x: 4 lbs. 48: 6o::: x4 lbs. x6o x = 672 lbs. x = 4- lbs. (O).

Page  86 86 ANSWERS TO PRACTICAL QUESTIONS 3. How much S is there in 2 lbs. of SO2? S = 32 = atomic weight of the given element. SO2 = 64 = molecular weight of the compound. x = weight of the given element. 2 lbs. = " " compound. S: SO2: 2 lbs. 32: 64: x: 2 lbs. 644 = 64 lbs. x = lb. (S). 4. lrowz much S is there in 2 lbs. oJ H2SO4? S: HSO,:: x: 2 lbs. 32: 98::: 2 lbs. 98 x = 64 lbs. - ='- lb. (S). 5. Hfow much 0 is there in 5 lbs. of HNO3? 03 = 48 = atomic weight of the given elemen:. HNO3 = 63 = molecular weight of the compound. x = weight of the given element. 5 lbs. = " " compound. 0,: HNO3:: x: 5 lbs. 48: 63:: x: 5 lbs. 63 x = 240 lbs. x = 31[ lbs. (O). 6. w07v much H is there in 6 lbs. of HC1? H: HC:: x: 6 lbs. I: 36.5:: x: 6 lbs. 36.5 x = 6 lbs. x= o = 2 = lb. (HI). 7. Hlow much K20 could be made/from 3 lb)s. oJ K? K2: KO0:: 3 lbs.:x. 78: 94: 3 lbs.: x. 78 x = 282 lbs. x = 3?a lbs. (K20). 40.-. Are all acids sour? (See Chemis2ry, page 22, note, and also page xxo.)

Page  87 IN CHEMIS TRY. 87 2. What is the difference between an -ate, an -ite, and an -ide compound? An -ate compound is a union of an -ic acid with a base; an -ite compound is a union of an -ous acid with a base; and an -ide compound is a union of two elements, a binary compound. EXAMPLES.-Iron sulphate, FeSO4; calcium sulphite, CaSO3; potassium chloride, KC1. 3. Why does not canned fruit decay? Because the O of the air is excluded. 4. Where is the higher oxide formed, rt lthe /fr-ge or in the pantry? (See Czenzistry, page 33, note.) 5. Why is the blood red in the arteries anld dark in the veins? XWhen specimens of venous and of arterial blood are subjected to chemical examination, the differences presented by their solid and fluid constituents are found to be very small and inconstant. As a rule, there is rather more water in arterial blood, and rather more fatty matter. But the gaseous contents of the two kinds of blood differ widely in the proportion which the carbonic acid gas bears to the oxygen; there being a smaller quantity of oxygen and a greater quantity of carbonic acid, in venous than in arterial blood. And it may be experimentally demonstrated that this difference in their gaseous contents is the only essential difference between venous and arterial blood. For if arterial blood be shaken up with carbonic acid, so as to be thoroughly saturated with that gas, it loses oxygen, gains carbonic acid, and acquires the hue and properties of venous blood; while, if venous

Page  88 88 ANSWERS TO PRACTICAL QUESTIONS blood be similarly treated with oxygen, it gain's oxygen, loses carbonic acid, and takes on the color and properties of arterial blood.-HUXLEY's Lessons in Physiology. 6. Why do we need more ox3gen in winter than in summer? Because there is a brisker fire going on in our corporeal -stoves. 7. Which would starve sooner, a fat mant or a lean one? (See Chemistry, page 35, note.) A superabundance of flesh, in a time of scarcity, is taken up by the absorbents and thrown into the circulation, thus supplying the place of food in nourishing the body. 8. How do teamsters warm themselves by slapping their hands together? To produce the motion, additional O is supplied, and increased oxidation is the result. This liberates heat to warm the body. Besides, the blood sets to the arms and the general circulation becomes more rapid. This extra supply, both by its presence and the friction of the swiftly moving currents, fu:nishes heat, and thus raises the tern perature of the body. 9. Could a person commit suicide by holdingf his breath? Respiration is entirely independent of consciousness, as is seen in sleep, coma, etc. It may be interrupted fo, a few minutes, but no effort of the will can enable one to hold his breath until life is extinct. The desire for 0, the besoin de respiresr, or the respiratory sense, as it is called, becomes at last so great that the strongest resolution yields the struggle.

Page  89 I.~ CHEMIISTR Y. 89 Io. Why do we die when our breath is stopped? "In asphyxia it is difficult to say which destroys life, the absence of oxygen or the presence of carbonic acid." -FLINT. There is an absence of oxygen, so essential to every vital operation, and also an accumulation of carbonic acid * in the system. I i. WIhy do we breathe so slaowly when we sleep? (See Chemistry, page 35.) Because so little muscular action is going on in the body. 1 2. Hzow does a cold-blooded animal differ from a warmblooded one? In the imperfection with which the blood is oxygenated. The lungs are often of small capacity, and loose texture, and are sometimes wanting entirely. In reptiles a portion of the blood is not sent to the heart, and hence in the vessels there is a mixture of arterial and venous blood. The breathing is therefore slow, the motions are languid, and there is little heat. I3. fVhy does not the body burn out like a candle? Because it is renewed by the processes of assimilation and nutrition as rapidly as it is destroyed by the waste of oxidation. Whenever the former are in excess we gain flesh, when the latter, we grow poor. I4. Do allparts of the body change alike? * This gas remains fixed in the blood-corpuscles, and renders them incapable of furnishing any oxygen to the system. CO is a deadly poison, because it clings to the disks more tenaciously.

Page  90 9~ ANSWERS TO PRACTICAL QUESTIONS The rate of change varies with the amount of oxidation, and that depends on the use of the organ. The right arm of the blacksmith must be transformed much more rapidly than the left. I5. What objects would escape combustion? Burnt bodies, i. e., those which are already combined with oxygen. i6. How much oxygen can be obtained fronz 6 oz. q KClO03? 0,: KC10,:: x: 6 oz. 48: 122.5:: X: 6 oz. 122.5 X - 288 Oz. X = 2.35 oz. (0). Or (see Chemistry, page 28), "2s x 6 oz. = 2 OZ 45 oz. (0). 17. How much KC103 would be needed to produce 2 lbs. of O? 0,: KC10,:: 2 lbs.: x. 48: I22.5:: 2 lbs.: x. 48 X = 245 lbs. x = 5458 lbs. (KC10). I8. How much KCI would be formed in preparing I lb. of O (See Chemistry, page 28, diagram.) If I lb. is " of a compound, what are 14? Ans. -III lbs. = lx: Ibs. (KC1). 19. Name a substance from which the 0 can be set free by the stroke of a hammer. Potassium chlorate. 20. lame one from which it is liberated with great dZfficulty. Sand, carbonic anhydride. (See Chemn., p. 98, note.)

Page  91 IN CHEMISTRY. 9I 2. Is it probable that all the elements have been discovered? (See Key, page 49, Question I.) 22. Is heat PRODUCED by oxidation? (See Chemistry, pages 36 and Ioo.) All forms of force-electricity, heat, muscular energy, chemical attraction, gravitation, etc., are now considered as movements of molecules; the particles being in continuous, undulatory motion, the swiftness and width of the vibrations determining the character of the force. These forces are interchangeable, but cannot be created or annihilated, increased or diminished. 23. What is the difference between dynamic and potential force? A potential force is one that is latent; a dynamic, one that is sensible. The former is hidden; the latter is in full action. Potential force is a weight wound up, a loaded gun, a river trembling on the brink of a precipice, a giant waiting the word, an engine with the valve closed. Dynamic force is the weight falling, the river tumbling, the giant striking, the engine flying along the track. 24. Why does running cause paanling? As soon as we begin to perform any unusual exercise, we commence breathing more rapidly-showing that, in order to do the work, we need more O to unite with the food and muscles. In very violent labor, as in running, we are compelled to open our mouths, and take in deep inspirations of oxygen. 25. fow does 0 give us strength? (See Ckhemnstry, page 35.)

Page  92 92 AN1SWERS TO IRACTICAL QUESTIONS Our muscles, as well as the food from which they are formed, consist of complex molecules, and the tension of the forces is very great. When they oxidize, the potential force becomes a dynamic one. 26. Does the plant PRODUCE force? (See Chemistry, page Ioo.) It only gathers up the solar force. 27. If,we burn an organic body in a stoave, it gives oft: heat; in the body it produces also motion. Explaint. The force set free by the oxidation of the muscles, and food within the body is, by the principle of the correlation of forces, converted into muscular energy. 28. In preparing N a thin, white cloud remains in the jar for a long time. IZhat is it? Probably an antozone cloud. 49. —I. ow could you detect any free 0 in alar of N? B3y passing into the jar a bubble of NO, and watching for the production of the red fumnes of NO2. 2. Row would you remove the product of the test I By letting the jar stand over water. 3. In the experimtent shown in Fiig. I i, why is the gas red in the flask, but colorless when it bubbles zp into the jar? Because the NO2 formed by the air present in the flask is absorbed by the H20 in the pneumatic tub. 4. How much H3N can be obtainedfrom 3 lbs. of salammoniac?

Page  93 IN CHEMISTR Y. 93 (i). HN: H,N,C1:: x: 3 lbs. I7: 53.5:: x: 3 lbs. 53.5 x = 55 lbs. x = I~~ lb. (H,N). (2). From the formulae it is seen that any amount of sal-ammoniac will yield ~ its weight of ammonia: hence, 3 lbs. will give 3 lbs. x ~l~ = 7 lb. (HN). 5. How much H 20 will be formed in the process? By examining the reaction given in the Chemistry, page 48, it will be seen that i of the H in each molecule of H,N,CI goes to form H1O. Hence, find (I) how much H there is in 3 lbs. of sal-ammoniac, and (2) how much H0O would be formed by ~- that amount of H. (I) *1 H4N,Cl::: 3 lbs. 4: 53.:: x: 3 lbs. 53.5 X = 12 lbs. x = 7 lb. (HI). (2) f. lb. + 4 = i-lb. Tg lb. x 9* = - lb. (t110). 6. hozw, much CaO will be needed? Find (I) how much O there is in -0~ lb. of H20; and (2) how much CaO would be needed to furnish that amount of O. (I),is%- lb. x 5 * =,f lb.; hence, there are?r4 lb. of O in the water produced. (2) 0: CaO:::i- lb.: x. I6: 56:: 2 lb.:. x6 x = 107. x = 1.57 + lbs. (CaO). 7. In separating N, how much air will be needed to furtish a gallon of the gas? About - of the atmosphere is N: hence, i of a gallon of common air would be required to furnish one gallon of N. ~ See Chemistry, rage 24.

Page  94 94 ANSVTEERS TO PIA CTICAL Q UESTIO:NS 8. How much N20 canl be made fromz i lb. of ammonium nirate? N20: H,N,N03:: x: lb. 44: 80:: I lb. 80 x = 44 lbs..x= 11 lb. (N,0). 9. How much nitric acid canl be formed from 50 lbs. of sodium nitrate (NaNO3)? Find (r) how much N there is in 50 lbs. of sodium nitrate (Chili saltpetre), and (2) how much HNO3 could be made from that amount of N. (:) N: NaNO3:::50 lbs. 14: 85:: x.: 5o lbs. 85 x = 700 lbs. x = 8~- lbs. (N). (2) N: HNO,:: 8i- lbs.: x. I4: 63:: 8 A lbs.: a. 14 - = 5I87 lbs. x = 37,x lbs. (HNOJ). Io. What causes flesh to decompose so much more easily than wood? It is partly owing to the greater complexity of its molecule, and partly to the presence of the fickle N. i. If a ltuft of hair be heated in a test tube, the liquid farmelt will turn red litmus-paper bhue. Exfplain. Ammonia is formed by the decomposition of the hair, and this acting on the red litmus-paper turns it blue. 12. Wh[y should care be used in opening a bottle of strong H N in a warm room? The volatile gas sometimes drives out the liquor ammonia with great force.

Page  95 IN COEE-MISTI 1. 95 13. What weit of N is there in io lbs. of HNOa? N: HNO3:: x: so lbs. 14: 63:: i: Io lbs. 63 x = 140 lbs. x - 2, lbs. (N). I4. Hiow much sal-ammoniac 7wEould be required to make 2 lbs. ofH3N? H2N: ItN,CI:: 2 lbs.: x. I7: 53.5:: 2 lbs.: x. r7 -= I07 lbs, X = 6,5 lbs. (HN,C1). 15. Give illustrations of the replacement of the H in an acid by a metal. (See C/emitstry, page 44, note; page 5I, reaction; and page I28, note.) I6. What is the tdlierence between liquid ammonia and liquor ammonice? Liquid ammonia is the gas condensed into a liquid by cold: liquor ammoniae is a solution of the gas in H20. 63.-I. WhyI,, in fillinag the hydrog-en gun, do we use 5 parts of common air to 2 of H, and only one part of 0 to 2 of H? Because the air is only ~ oxygen, and hence 5 parts of common air are equivalent to i part oxygen. 2. Why are coal cinders often moistened with H2 0 before Using (See Chemistry, page 57, note.) The H20 being decomposed by the heat of the fire increases the combustion. 3. WVhat injury may be done by throwing a small quantity of H20 on afire? " No more heat is produced by the action of the H20,

Page  96 96 ANSWERS TO PRACTICAL QUESTIONS but it is in a more available form for communicating heat. The steam in contact with incandescent charcoal is decomposed-the O going to the C to formn CO2, and the H being set free. If the C is abundant, and the heat high, the CO. is also decomposed, and double its volume of CO formed. The inflammable gases, H and CO, mingled with the hydrocarbons always produced, are ignited, making the billows of flame which sweep over a burning building." —S. P. SHARPLES. 4. Why does the hardness of wa/er vary in different localities The hardness of the water will necessarily vary with the solubihity of the minerals in different localities. 5. What causes thze variety of minerals in fhe ocean? Is the Vquantity increasing? The ocean contains the washings of the land. Every mineral soluble in water is borne to the sea. The quantity of mineral matter in the ocean would therefore seem to be increasing, yet there is a compensation in the return to the soil, of guano, marine plants, and fish, which are driven on shore by winds and waves, or carried by the industry of man. Analysis of sea-water (Schweitzer): Water.................................................... 963.74 Sodium chloride......................................... 28.05 Potassium chloride.......................................76 Magnesium chloride..................................... 3.66 Magnesium bromide.................................02 Magnesium sulphate..................................... 2.29 Calcium sulphate........................................ x.40 Calcium carbonate..................................... 03 Iodine.................................................. traces Ammonia................................................ traces I000.02

Page  97 IN CIIEMIS TR Y 97 6. Is there not a compensationl in the sea-plants, fish, etc., which are washed back on the land? (See Answer to Question 5.) 7. Since "all the rivers flow to the sea," why is it not full? Because of the constant evaporation from its surface. 8. Wh/at is the cause of the tonic influence of the sea breeze? There are traces of certain mninerals which probably give to the sea breeze a bracing influence. The air from the ocean is also, dqubtless, highly ozonized. Persons with delicate lungs, therefore, find the sea breeze too corrosive. In England, rheumatic and other inflammatory diseases are more abundant near the coast than inland. 9. WFlhen fish are taken out of the water, and thus brought ilnto a more abundanlt atmosphere, why do they die? Fish inhale O through the fine silky filaments of their gills. When a fish is drawn out of H20, these dry up, and it is unable to breathe, although it is in a more plentiful atmosphere than it is accustomed to enjoy. I o. Do allfish die when brought on land? (See Key, page 5I, Question I5.) Ix. that weeiht of water is there in I00 o bs. of sodium sulphate (Na2SO4,ioH2O), or Glauber's salt? xoHO: NaSO,,IoH2O x:: oo lbs. 180: 322 x: xoo Ilbs. 322 x = i8ooo Ibs. x = 55.9 lbs. (H,O).

Page  98 98 ANSWERS TO PRACTICAL QUESTIONVS I2. [lihat weight of water in a ton of alum (KA1,2S04, 121120)? 12H,O: KA1,2SO,, I2H,O: x: 2000 lbs. 216: 474.5:: x: 2000 lbs. 474-5 x = 4320oco lbs. X = 90Io.4 lbs. (H20). I 3. How much water would it require to furnish enough H to change 5 lbs. of nitric anhydride to nitric acid? Find (I) how much HNO3 could be made from 5 lbs. of N205 (see Chemistry, page 44, note); (2) how much H20 is contained in that amount of HNO3. The difference between the weight of the nitric anhydride and that of the nitric acid will show the amount of water required to furnish the H. (I). N.0: 2(H-Oo): 5 lbs.:. Io8: 125:: 5 lb.:x. Io3 x = 630 lbs. x = 5.833 lbs. (HNO,). (). 5.833 lbs. (HNO0) - 5 lbs. (N2O,) =.833 lb. (HO2). I 4. How does the air purify running water? The O contained in the air absorbed by the H 20 oxidizes the organic substances, which are the most dangerous impurities. 5. What is the action of potassium permanganate as a disinfectant? It gives up its O to oxidize the organic impurities. i6. Why does lime sometimes soften hard water when added to it? (See Key, page 50, Question 4.) I7. What weigkt of H can be obtained from a gallan of water?

Page  99 IN CHEMISTR Y. 99 The standard gallon of the United States weighs 8.3389 lbs. of distilled water. H:, H,O0:: x:8.3389 lbs. 2: i8:: x: 8.3389 lbs. 9 x = 8.3389 lbs. x =.9265 lb. (H). 18. In decomposing H 2 O, 65 parts by weight of Zn yield 2 parts by weight of H. How much Zn must be emzployed to obtain Ioo lbs. of H? If we look at the equation HSO, + Zn = ZnSO, + H,. we see that H, signifies 2 parts by weight of hydrogen, H,20 " 8.. i' "water, S i; 32.. i; sulphur, 0, 64 " " " "oxygen, H,SO, " 98 " " " "sulphuric acid, Zn " 65 " " " " zinc, ZnSO, 6I " ".6i zinc sulphate. The equation, therefore, shows that 98 parts by weight of sulphuric acid added to 65 parts of zinc will form i6I parts of zinc sulphate, and, decomposing i8 parts of water, liberate 2 parts of hydrogen. For every part of H we must have S6ZE parts of Zn: hence, to obtain Ioo lbs. of H we should need ioo lbs. x -M5- 3250 lbs. Zn. In a similar way we can find the amount of each of the other constituents needed. I9. How much KC103 would be required to evolve sufficient 0 to burn the H produced by the decomposition of 2 lbs. of H20? (See Key, page 6I, Question 37.)

Page  100 I00 ANSWERS TO PRACTICAL QUESTIONS 20. Hbow much 0 would be required to oxidize the metallic Cu which could be reduced from its oxitde by passing over it, wzhen white-hot, 20 gr. of H gas? (See Key, page 6o, Question 34.) 2 I. How much 0 would be required to oxidize the metallic Fe which could be reduced in the same manner by Io grs. of H gas? (See Key, page 6i, Question 35.) 2 2. WZhy are rose-balloons so buoyant? They are filled with hydrogen or coal-gas, which is lighter than common air. 23. How much H must be burned lo produce a ton of water? Find how much H is contained in 2000 lbs. of water. (I). H2: H,O:: x: 2000 lbs. 2: i8:: x: 200oo) lbs. i8 x = 4000 lbs. X = 222- lbs. (H). 2d Method.-One-ninth of any weight of water is hydrogen; hence, 2000 lbs.. 9 = 2222 lbs. (H). 94. —I. Why does not blowing cold air on a fire with a bellows extinguish it? More heat is liberated by the O which combines with the fuel than is withdrawn from the fire by the current of cold air. Yet the temperature of the fire must be sufficient to elevate that of the O to the point of union with C and H, else the fire will be extinguished. 3. Why is fire-damp more dangerous than choke-damp? Fire-damp, or marsh-gas, is inflammable, while chokedamp, or " carbonic acid," is not.

Page  101 IN CIIEMISTR Y. I 0 I 4. Represent the reaction in making C02, showing the atomic weights, as in thepreparation of 0 Oil pJag, 28. In this experiment the acid exchanges its hydrogen for the calcium, producing calcium chloride (CaCI2) on the one hand, and carbonic acid (H2CO3) on the other. But the carbonic acid is so unstable that it immediately becomes decomposed into water, which remains behind, and into carbonic anhydride, which comes off as a gas with brisk effervescence. The decomposition may be represented as follows: CaCO3 + 2HC1 CaCI2 + H20 + CO2. (Calcium Car- + (Hydrochlo- = (Calcium + (Water)+ (Carbonic bonate) ric Acid) Chloride) Anhydride) Ca C 0 2(H C1) Ca C12 + H20 + C 02 40 + 12 + 3 x I6 2(I +-35.5) 40 - 2(35-5) 2 + 16 I2 + 2 X 16 100 73 III I8 44 173 I73 The CO liberated = -~3 of the materials used; the H.O =,?~, and the CaCl, = 1- 3. 5. Should one take a light into a room where the gas is escaping? Great care should be used, since coal-gas is combustible, and when mixed with O in the proper proportion explodes with great violence. Severe accidents frequently occur from a neglect of this precaution. 6. What causes the difference between a No. I and a VNo. 4 pencil? (See Chemistry, page 67.) 7. Why does it dull a knife to sharpen a pencil? (See Chemistry, page 67.)

Page  102 102 ANSWERS TO PRACTICAL QUESTIONS 8. Why is slate found between seams of coal? (Sce Geology, page I50.) The coal represents a period of vegetation, and the slate, one of convulsion. During the former, a deposit of the leaves, branches, trunks of trees, etc., was made; during- the latter, one of gravel, sand, etc., accumulated. 9. Wfzy zwas /ie coal hidden in the earlz? It is natural to think that one object was to protect it from accidental combustion. Io. WViere as the C, noz0 contained in thze coal, before the Carboniferous age? (See Geology, pages I5o-i.) In the atmosphere, which was then so full of CO2 that, according to certain authorities, it contained 7 to 8 parts in IOo. i i. Must /ihe air have then contained more pl/antfood (See Chem7istry, page 7I, and Geology, page I50.) I 2. /ialf is t/he principle of t/he Vuaariumz 2 The inter-dependence of animals and plants, whereby each supplies the wants of the other. The aquarium is a microcosm -a world in miniature. * I have read somewhere a beautiful Persian fable in which a nightingale and a rose are represented as being confined in a cage together, and being dependent upon each other for life. The fable is truth symbolized. The idea has now become more practical, but not less beautiful. In the modern aquarium, or drawing-room fish-pond, we see the world in miniature. It is a self-regulating, self-subsisting establishment, and is constructed on the most perfect principles of chemical economy. "Before this truth of compensation between animals and plants was discovered, many attempts were made to keep fish in small glass globes. A.

Page  103 IV CIIEEIISTR I 03 13. Wthat test should be employed before going down in an old well or cellar? A lighted candle should be lowered. If that is dimmed or extinguished it is not safe for one to descend. 14. What causes the sparkle of wzine and the foam of beer? The CO2 formed in the process of fermentation. I 5. What causes the cork lofy out of a catsup bottle? The CO2 which is produced when the catsup ferments. they soon exhausted the oxygen, and impregnated the water with carbonic acid, it was necessary to change it daily. In this operation they suffered the most intense fear. For a few weeks they would drag out a dubious existence, seemingly anxious only to find out before they died where they were and how they got there. Finally, but a fiew years since, it was discovered that plants evolve oxygen and consume carbonic acid in the water as well as in the air. Starting out with this idea, about the year i85o, a Mr. Warrington, an Englishman, set about breeding fish and mollusks in tanks by the aid of marine plants. He succeeded admirably for a few days, but after a time, a change came over his little world. Without apparent reason, the water became suddenly impure and the fish died. Here was a new agency at work. With the aid of a microscope, Mr. Warrington explored his tank for the poison that was evidently latent there. He soon discovered that some of his plants had reached maturity and, in obedience to the law of nature, had died..The decaying matter was the poison of which he was in search. How was this to be counteracted? In nature's tanks-seas, rivers, and ponds-reflected Mr. Warrington, plants must die and decay, yet this does not destroy animal life. We must see how nature remedies the evil. I-e hastened to a pond in the vicinity and examined its bottom with care. He found, as he had anticipated, an abundance of vegetable matter decayed. He likewise found swarms of water-snails doing duty as scavengers, and devouring the putrefying substances before they had time to taint the water. Here was the secret; so beautiful a contrivance that it is said Mr. Warrington, with the emotion of a true man of science, burst into tears when it flashed upon him like a revelation. " He, however, quickly dried his eyes, gathered a quantity of snails, and threw a handful into his little tank at home. In a single day the water was clear and pure again. The fish throve and gamboled, grew and multiplied; the plants resumed their bright colors, and the snails not only rollicked in an abundance of decaying branches, but laid a profusion of eggs, on which the fish dined sumptuously every day."

Page  104 I04 ANVSWERS TO PRACTICAL QUESTIONS I6. What ihilosophical princzIpe does the solidzfication of CO2 illustrate? (See Philosophzy, page 242.) That evaporation is a cooling process. A portion of the liquid CO2 turns to vapor, and thus abstracts so much heat from the remainder as to freeze it. I 7. Why does the division in the chimney shown in Fzg. 28 produce tzo czrrents? For a few moments there is an uncertainty-a condition of unstable equilibrium. The heated air is endeavoring to rise, and the cold air trying to come in to supply its place. The situation of the candle in the jar determines the length of time before the currents start. If the candle be placed on one side of the jar they will be established almost instantly. i8. What causes the unjleasant odor of coal-gas? Is it useful? Impurities which it contains. Olefiant gas has a faint sweetish odor, while carbonic oxide and hydrogen, when pure, are inodorous. The disagreeable smell is due in part to acetylene (C2H2). The unpleasant odor warns us of the presence of coal-gas. 19. What caulses the sparkling often seen in a gas-lz,ht Particles of lime taken up mechanically in the process of purification. 20. Why does H in burning give out more heat than C? I lb. of H burned in O emits heat sufficient to melt 315.2 lbs. of ice; and T2 lbs. of carbon converted into CO2 enough to melt 700 lbs. of ice. (This subject is

Page  105 IV CRHEMISTR Y. 105 quite fully treated in Miller's Chemical Physics, page 294, et seq.) The cause is not as yet fully determined, although it is perhaps safe to say that in ordinary combustion the heat depends on the amount of O which enters into combination with the fuel. " Thus hydrogen in burning takes up three times as much O as C does, and hence gives off three times as much heat."-YOUMANS. 2 1. Why does blowing on afire kindle it, and on a lighted lamp extingulish it? (See Key, page 50, Question 6.) 22. Why can we not ignite hard coal with a match / Because it is a good conductor of heat. 23. What causes the dripping of a stove-pipe? The condensation of the water formed in the combustion of the fuel. 24. Why will an excess qfcoalput out a fire? Because it will absorb the heat, and thus reduce the temperature of the fire below the combining point of C and 0. 25. Why do not stones burn as well as wood? Because they are already burned, i. e., combined with 0. 26. Why does not hemlock make good coals? Because (I) of its lack of C, and (2) its porous structure. 27. What adaptation of chemical affinities is shown in a Zlght? If 0 had the same affinity for C that it has for H, they would be consumed at once, with little light. The fact

Page  106 Io6 ANSWERS TO PRACTICAL QUESTIOnS that the H burns first, and thus heats up to the luminous point the particles, of C as they float outward to the air, causes the illuminating power of the hydrocarbons. 28. Is there a gain or a loss of zeight by combustion 1 The products of combustion weigh as much as the fuel and the O which enters into combination with it. 29. Why ldoes sniffing a candle brighten the flame? Because it removes the charred wick, which diminishes the heat of the flame both by conduction and radiation. 30. Why is the flane of a candle red or yellow, and that of a kerosene oil-lamp wehite? (See PhilosopqAy, page 225.) The heat of a candle-flame is much less than that of kerosene, and thus the colors characteristic of a lower temperature are produced. 3 I. Why does blowing on a light extinguish it? Because it lowers the temperature of the flame below the point of union between O and C. 32. Why will water put out a fire? (See Chemistry, page 93.) Partly by absorbing the heat of the fire, and partly by shutting out the 0. 33. What should we do if a persons clothes takefire? The best course is to wrap the person in a blanket, carpet, coat, or even in his own garments. This smothers the fire by shutting out the 0.

Page  107 IN CIIE2IIS TR Y. I07 34. Ozught we to leave ojpen the doors or wizndows of a burning house? (See Chemistry, page 93.) No. Open doors or windows will make draughts of air to feed the flame. 35. IWhy does a street gas-hitht burn blte oa a zowindy nzrlt I? /s the light thenZ as iltense? The heat? O is mingled with the flame in sufficient quantities to burn the H and C simultaneously. Thereby the heat is increased, but the light diminished. The principle is that of Bunsen's burner. 36. Whzy does not the lime burn z i a calcium-lizzt Lime is a burned body; its symbol is CaO. 3 7. Whgy is a candle-ftame tapering? (See Chemzistry, page 88.) The currents of air rushing toward the flame from all sides give it the conical form. 38. Why does a draught of air cause a lamp to smoke? It lowers the heat of the flame below the point of union between C and 0, and thus the C is precipitated. 39. What makes the coal at the end of a candle-wick? The wick at the edge of the flame comes in contact with the 0 of the air, and therefore burns. 40. Which is the hottest part of aflame? Toward the point of the cone, where the gaseous envelopes meet and make a solid flame.

Page  108 io8 ANSWERS TO PRACTICAL QUESTIONS 41. gtWhy does not a candle-wick burn? There is no O at the centre of the flame. 42. How does a chimney enable us to burn higzZhly carbon ferous substances like oil without smoke? (See C(hemistry, page 88.) It keeps out the cold air, and elevates the temperature of the 0, which supplies the flame. Thus more C can be consumed. 43. How much CO2 in 200 lbs. of chalk? CO,: CaCO,:: 200 lbs. 44: 100::: 200 lbs. o00 x = 88oo lbs. x = 88 lbs. (CO,). 44. What weight of CO2 in a ton of vmarble? CO: CaCO3:x: x2000 lbs. 44: oo:.: 2000 lbs. soo x = 88,ooo lbs. x = 880 lbs. (CO,). 45. TbVhat is the (i'ference between marble and chalk? Marble is a compact, crystallized carbonate of lime, while chalk is a porous kind of limestone. 46. IWhy tdoes not a cold saucer held over an alcohoflame blacken, as it does over a candle or gas-light? There is less C in alcohol than in tallow or in coal-gas. 47. Could a light be frozen out, i. e., extingutished, by merely lowering the temperature? It is said to have been done in Arctic regions.

Page  109 IN CUIIEMISTRY. 09 48. How;Aclz CO, is formed in the combustion of one ton of C? C: CO:: 2000 lbs.: x. 12: 44:: 2000 lbs.: x. 2 X = 88,0ooo lbs. x = 7333.33 + lbs. (CO,). 49. What weig,,ht of C is fhere in a ton of CO2? C CO,::: 200ooo lbs. I2: 44::: 2000 lbs. 44 X = 24,000 lbs. x = 545.45 + lbs. (C). 50. How much 0 is consumed in burning a ton of C? In any quantity of CO2, -T%- of the compound is 0, and r C. If -- = 2000 lbs. (CO2), then " =- of 2000 lbs. 5333-33 + lbs. (O). 5 I. haznt weirhit of sodium carbonate (Na2CO3, IoH 20, "ccar'bonate of soda ") would be required to evolve I2 lbs. of C02? CO,: Na2CO,, IoH2O:: I2 lbs.: x. 44: 286:: I2 lbs.: x. 44 x = 2432 lbs. x = 50.72 lbs. (Na2CO,, IoHO). 52. How much CO will be formed in the combustion of 30 grs. of CO? CO: CO,:: 30 grs.: x. 28: 44:: 30 grs.: x. 28 X = I320 grs. X = 47.14 grs. (CO,). 53. W1hatwetight of hydrogen sodiuzm carbonate (H NaCO3, "bi-carbonate of soda ") would be required to evolve 12 lbs. of C02? CO2: HNaCO3:: I2 lbs.: x. 44: 84:: 12 lbs.: x. 44 x = Ioo8 lbs. Xr =2.9 lbs. (HNaCOs).

Page  110 I IO ANSWERS TO PRACTICAL QUESTIONS 54. Write in double columns the different properties of carbonic anhydride and carbonic oxide. I. CO,2. I. CO. 2. Atomic weight-44. 2. Atomic weight-28. 3. Specific gravity —I.529. 3. Specific gravity-.967. 4. Will not burn. 4. Burns with a blue flame. 5. A negative poison. 5. A direct poison. 6. Liquefies at 32~, and a pressure 6. Has never been liquefied. of 38.5 atmospheres. 7. Sparingly soluble in water. 7. Freely soluble in H,,O. &c., &c. 8. Forms salts. &c., &c. I8. —I. If chlorine water stands in the sunlifflit for a time, it will only redden a litzmus-solution. Why does it not bleach it? Hydrochloric acid is formed, which reddens the litmus. 2. Why do tinsmiths moisten with HC1, or sal-ammoniac, the surface of metals to be soldered? It dissolves the coating of oxide and leaves the surface of the metal free for the action of the solder. 3. Hozel much HCI can be made Jfrom 25 lbs. of common salt? Find (i) how much C1 there is in 25 lbs. of NaCl, and (2) how much HC1 that amount of C1 would make. (I). C1l: NaC1::x: x25 lbs. 35.5: 58.5::: 25 lbs. 58.5 x = 887.5 lbs. X = I5 I7094 lbs. (C1). (2). C1: HC1:: I5.I7094 lbs.: x. 35.5: 36.5:: I5. 7094 lbs.: x. 35.5 X = 553.7393I lbs. = I55.5980056+ lbs. (HCI).

Page  111 IN CHEMISTRY. I I I 4. What weight of NaCl would be required to form 25 lbs. of muriatic acid? (See Key, page 58, Question 20o.j) 5. HC1 of a speczfic gravity of I.2 contains about 40 per cent. of the gas. This is very strong commercial acid. What zweight could be formed by the HC1 acid gas produced in the reaction named inz the preceding problem? (See Key, page 58, Question 21.) 6. fhat is the difference between sublimation and distillation? A body is said to sublime when it rises as vapor and condenses in the solid form; when it condenses as a liquid it is said to distil. 7. Why do eggs discolor silver spoons? The sulphur of the egg combines with the Ag, forming silver sulphide —the black sulphuret of silver. 8. Explain the principle of hair-dyes. The two principal chemicals used for dyeing the hair are lead and silver nitrate. The S in the hair combining with the Ag makes silver sulphide, or with the Pb, lead sulphide, either of which stains the hair: the former colors the skin as well as the hair, while the latter is absorbed through the skin, causing colics and other diseases such as are common among painters. The "golden yellow color" lately in fashion is produced by a solution of arsenic with the hydrosulphate of ammonia. In order to dye the lighter tints, it is necessary to bleach the hair with an alkaline solution. See Fireside Science, page 77.

Page  112 I I2 ANSWERS TO PM2A CTICAL QUESTIONS 9. Why is new flannel apt to turn yellow when washed? New flannels, washed in strong soap, turn yellow, because the alkali of the soap unites with the SO2 used in bleaching the cloth, and thus sets free the original color. Io. Is it safe to mix oil of vitriol and water in a glass bottle? The heat produced by the combination of the two will be liable to break the glass. i i. What is the color (f a sulphuric acid stain on clot/i? How would yolu remove it? It is generally red, especially on black cloth. The color may be restored by a few drops of a solution of common "soda." 12. What causes the milky look when oil of vitriol and water are mixed? Pb from the stills in which the acid is condensed, and which is soluble in strong HSO4, is precipitated when the acid is diluted with H2O. 13. What is the relation between animals and plants? Which perform the offlce of reduction, and which that qf oxidation? (See Key, page 52, Question i9.) 1. Hrow many fpounds of S are contained in Ioo lbs. of HSO4? S: HSO:: x: Ioo lbs. 32: 98: x: Xoo lbs. 98 x = 32O3 lbs. x 32" lbs. (S).

Page  113 IN CHEMISTRY. I 13 5. How mulch 0 and H 20 are needed to change a ton of S02 to H2SO4? One ton of SO2 will make Ij3 tons of H2SO4: of which 4i is H, 4- is S, and 3 is O. i of this O, or -, comes from the air, and I = A from the water. (See process of manufacture, Chemistry, p. II6.) Hence -A (0) and:3 (H) -:9 of the acid was furnished by the waters of I~- tons - ton (H O). The process of reasoning may be seen more clearly, perhaps, by preparing the formulae as in Question i8, page 99, of this Key. i6. How much 0 in a ldb. of H2SO4? R3v of any quantity of sulphuric acid are 0; i is H; and 1j are S. Hence in I lb. of H2SO2 there are j-lb. (O). 17. State the analogfy between the compounds of 0 and S. O s HO I H,S H2.0 (hydrogen dioxide) H.2S co, Cs, The corresponding compounds possess not only an analogous composition, but also similar chemical properties. I46.-I. In tlhe experiment with Na2SO4, on page I33, an accurate thermometer will show that inl making the solution, the temperature of the liquid willfall, and in its solidification, will rise. Explain. (See Philosoaphy, page 233.) The solid salt passing into a liquid takes up heat, and, in returning from a liquid to a solid again, gives up heat. The latter is illustrated in next question.

Page  114 114 ANSWERS TO PRACTICAL QUESTIONS 2. If, in making a so/auion of Na SO4, we use the salt which has effloresced, and so become anhydrous, the temperature will rise instead offalling as before. Explain. This is because a solid hydrate is formed before the salt dissolves in the H20. The same holds true of other anhydrous bodies, as the chlorides of Zn, Fe, and Cu. 3. fW. hy is KNO3 used instead of NaNO3 for making guinpozeder? Sodium nitrate is imported from Chili in large quantities, and attempts have been made to use it for making gunpowder,* but its tendency to attract moisture has frustrated the plan. It is now extensively used as a fertilizer, and is said to be the cheapest form in which N can be furnished the soil. A4. Why is a potassium saltpreferable to a sodZiuzr one in rlass-zmaking? Sodium salts give a greenish tint to the glass. * Gunpowder is an intimate mechanical mixture of about I part nitre, I part sulphur, and 3 parts charcoal. These proportions, however, vary somewhat in different countries, as well as in different sorts of powder. More charcoal adds to its power, but also causes it to attract moisture from the air, which of course injures its quality. For blasting rocks, where a sustained force, rather than an instantaneous one, is required, the powder contains more sulphur, and is even then often mixed with sawdust to retard the explosion. The nitre, sulphur, and charcoal, having been ground and sifted separately, are thoroughly mixed and then made into a thick paste with water. This is ground for some hours under edge-stones, after which it is subjected to immense pressure between gun-metal plates, forming what is known as hresscake. These cakes are then submitted to the action of toothed rollers, whereby the granulation of the powder is effected. The grains thus formed are sorted into different sizes by means of a series of sieves, and thoroughly dried at a steam heat. The last operation, that of polishing, is accomplished in revolving barrels, after which the powder is ready for market. The heavier the powder, the greater is its explosive power. Good powder should resist pressure between the fingers, giving no dust when rubbed, and have a slightly glossy aspect.-Yo MAN.s.

Page  115 LV CHEMISTRY. I I5 5. EWhat is the glassy slag so plentiful about a furnace? * A silicate of lime or some other base contained in the ore. Ordinary Slag from Blast Furnace (Bloxam). Silica...................................................... 43.07 Alumina.........4....................................... I4.85 Lime.................................................. 28.92 Magnesia............................................... 5.87 Oxide of iron............................................. 2.53 Oxide of manganese....................................... I37 Potash...........................................84 Sulphide of calcium....................................... I.9o Phosphoric acid......................................... trace I00.35 6. State the formule of nitre, saleratus, carbonate and bicarbonate of soda, plaster, pearlash, saltpetre, plaster of Paris, cgypsum, carbonate and bicarbonate ofpotash, sal-soda, and soda. Nitre, saltpetre.................................. KNO,. Saleratus, pearlash.................................. HKCO,. Carbonate of soda, sal-soda........................ NaCO,. Bicarbonate of soda, " soda"................ HNaCO,. Plaster, gypsum.............................. CaSO,,2H,O. Plaster of Paris...................................... CaSO,. 7. Explain how ammonium carbonale is formed in the process of making coal-gas. Nitrogen exists in small quantities in coal, and when that is distilled at a high temperature, the elements in their nascent state combine to form this compound. * The slag is commonly employed for road-making in the neighborhood ot the iron-works. Some attempts have been made to turn the slag to account by employing it as a manure for soils deficient in potash, of which it will be seen that the above slag contains nearly lth of its weight, in a form which would be easily rendered available for plants by the combined action of air and moisture. When the slag is run into water, or blown into a frothy condition by the blast, it resembles pumice-stone, and is easily ground to a powder fit for applying to the soil.

Page  116 I I6 AIANSW ERS TO PRAC TICAL QUESTIONS 8. Upon what fact epends the formation of stalactites? Water containing carbonic acid in solution will dissolve carbonate of lime freely, but when, on exposure to the air, the gas escapes, the carbonate is deposited. 9. Why is HF kept in gutta-percha bottles? Because it will dissolve silica, and so destroy a glass bottle. io. Explain the use of borax in softening hard water? It softens hard water by uniting with the soluble salts of lime or magnesia, and making insoluble ones which settle and form a thin sediment in the bottom of pitchers in which it is placed. I I. forlow are ptriftctions formed? Certain springs contain large quantities of some alkaline carbonate; their waters, therefore, dissolve silica abundantly. If we place a bit of wood in them, as fast as it decays, particles of silica will take its place-atom by atom-and thus petrify the wood. The wood has not been changed to stone, but has been replaced by stone. 12. InZ what -part of the bold,, and in what forms, is phosphorus fozund? As a phosphate it is the principal earthy constituent of the bones. It is also a never-failing ingredient of the brain and nervous system. The susceptibility of phosphorus to oxidation especially adapts it to the rapid changes incident to the structure and offices of the brain.* * Phosphorus is an element which can imperceptibly and quickly pass from a condition of great chemical activity to one of equal chemical inertness. In

Page  117 IN2 CIIEMISTiY I I' 13. Why are matches poisonous? What is the antidote? (See Physiology, page 209.) Because of the phosphorus in the mnatch. virtue of this character, it " may follow the blood in its changes, may oxidize in the one great set of capillaries, and be indifferent to oxygen in the other; may occur in the brain, in the vitreous form, changing as quickly as the intellect or imagination demands, and literally flaming that thoughts may breathe and words may burn; and may be present in the bones in its amorphous form, content like an impassive caryatid, to sustain upon its unwearied shoulders the mere dead weight of stones of flesh. And what is here said of the brain as contrasted with the bones, will apply with equal or similar force to many other organs of the body. All throughout the living system, we may believe that phosphorus is found at the centres of vital action in the active condition, and at its outlying points in the passive condition. In the one case it is like the soldier with his loaded musket pressed to his shoulder and his finger on the trigger, almost anticipating the command to fire; in the other it is like the same soldier with his unloaded weapon at his side standing at ease." " Further, phosphorus forms with oxygen a powerful acid, capable even of abstracting water from sulphuric acid, and yet perfectly unirritating to the organic textures. Taking up varying quantities of water, phosphoric acid assumes no fewer than three distinct forms, which will unite with one, two, or three atoms of alkali respectively, giving an acid, neutral or alkaline reaction. Thus it is available for the most varied uses in the body. A child is beginning to walk, and the bones of its limbs must be strengthened and hardened; phosphoric acid, accordingly, carries with it three units of lime to them, and renders them solid and firm. But the bones of its skull must remain comparatively soft and yielding, for it has many a fall, and the more elastic these bones are, the less will it suffer when its head strikes a hard object; so that in them we may suppose the phosphoric acid to retain but two units of lime, and to form a softer, less consistent solid. And the cartilages of the ribs must be still more supple and elastic, so that in them the phosphoric acid may be supposed to be combined with but one unit of base. On the other hand, its teeth must be harder than its hardest bones, and a new demand is made on the lime-phosphates to associate themselves with other lime-salts (especially fluoride of calcium), to form the cutting edges and grinding faces of the incisors and molars. All the while, also, the blood must be kept alkaline, that oxidation of the tissues may be promoted, and albumen retained in solution; and yet it must not be too alkaline, or tissues and albumen will both be destroyed, and the carbonic acid developed at the systemic capillaries will not be exchanged for oxygen when the blood is exposed to that gas at the lungs. So phosphoric acid provides a salt containing two

Page  118 I I8 ANSWVERS TO PRA CTICAL QUESTIONSL 14. Will the burning phosphorus ignzite the wood of the matc/? It does not give off enough heat in its oxidation to raise the temperature of the wood to the igniting point. Many, however, claim the true reason to be that, in burning, it produces an ash (P205) which covers the wood as with a varnish and so protects it from oxidation. I5. What philosophical prinzcile is illustrated in the ignition of a match by friction. (See Philosotlhy, page 230.) The conversion of motion into heat. I6. How much H 20 would be required to dissolve a pound of KNO 3? 3~ lbs. of cold water and 1 lb. of hot water. I7. Ihalt causes the bad odor after the discharge of a g7in? The potassium sulphicle gradually gives up its S to form HS. i8. Write in parallel columns the properties of common and of redphosphorus. units of soda and one of water, which is sufficiently alkaline to promote oxidation, dissolve albumen, and absorb carbonic acid, and yet holds the latter so loosely, that it instantly exchanges it for oxygen when it encounters that gas in the pulmonary capillaries. Again, the flesh juice must be kept acid (perhaps in opposition to the alkaline blood, as affecting the transmission of the electric currents which traverse the tissues), and phosphoric acid provides a salt, containing two units of water and one of potash, which secures the requisite acidity."-DR. G. WILSON, Edinburgh Essays, i856.

Page  119 INr CHEEMISTR. I 19 Common phosphorus. Amorphous phosphorus. i. Specific gravity-I.83. I. Specific gravity-2.1x4. 2. Burns at IxI~. 2. Burns at 500. 3. Odor of garlic. 3, Odorless. 4. Soluble in CS2. 4. Insoluble in CS,. 5. Colorless, or straw-yellow. 5. Red often rivalling vermilion. 6. A deadly poison. 6. Harmless. 19. What causes the difference between fine and coarse salt? (See Chemistry, page I32.) The rapidity of evaporation in the process of manufacture. 20. Why do the fiures ill a glass paper-weight look Target' when seen from the top than from the bottom? The form of the glass acts like a convex lens to magnify the apparent size of the figures. 2 I. What is the diferezrce between water-slacked and airslacked lime? The former is simply calcium hydrate, CaO, H20, while the latter is hydrated calcium carbonate, CaO, CO2, 1120 (?). 22. Why do oyster-shells on the,grate of a coal-stove prevent the forzmation of clinkers? The lime of the shells acts as a flux with the iron in the coal, thus dissolving the clinkers, if any form. 23. Hoaw is lime-water made from oyster-shells? The shells are burned, driving off the CO2 combined with.the CaO in the CaCO3, and the lime thus formed is slightly soluble in water.

Page  120 120 ANSWERS TO PRACTICAL QUESTIOASg 24. Why do newly plastered zwalls remain damp so long? The plaster or mortar in drying gives off the water the lime took up in slacking. 25. Will lime lose its beneficial effect Upon a soil after frequent a.pplications (See Key, page 5S, Question I2.) 26. What causes Plaste.r of Paris to harden again after being moistened? (See Chemistry, page 139.) It recombines with the water which was driven off in the process of its manufacture. 27. UWhat is the difference between sulphate and suzphite of lime? The former is a compound of sulphuric acid; the latter of sulphurous acid. 28. What two classes of rays are contazied in the magnesium lizght? (See Philosofphy, page 206.) The actinic or chemical, and the colorific or luminous rays. 29. What rare metals would become useful in the arts, if theprocess of manufacture were cheapened? AMagnesium, aluminum, sodium, etc. 30. What is the rational formula for calcium carbonate i Calcium sulphite? Calcium sulphate? I. CaCO3 - CaO,C02. 2. CaSO3 = CaO,S02. 3. CaSO4 = CaO,SO.

Page  121 IN CHEMISTR Y. I 2 I 3 1. Why is lime placed in the bottom of a leach-tub? The potash of the ashes is generally in the form of a carbonate, the acid neutralizing in part the strength of the alkali. The lime combines with the CO2. 3 2. Is saleratus a salt of K or qyf Na? It should be a carbonate of K, but, on account of its cheapness, the corresponding salt of Na is often sold instead. 33. Why will Na burst i/nto a blaze w.ken thrown on hot water? The heat of the water raises the hydrogen to the igniting point. This catches fire, and the volatilized Na colors the flame. 34-. Why are certazin kintzs of brick white?'IThey contain no iron, this being the substance which by its oxidation gives the color to common brick. 35. Illusrate the force of chemical affinity. The tremendous force of chemical affinity forms with O half the crust of the earth. Yet when the chemist sets the O free fi-om its prison-house, it comes before him a transparent, invisible gas, and he cannot condense it to a solid or liquid state by any mechanical process. I76. —I. Pb is softer than Fe; why is it not mnort malleable? The facility with which a mass of metal can be hammered or rolled into a thin sheet without being torn, must depend partly upon its softness, and partly upon its tenacity. If it depended upon softness alone, lead should be

Page  122 122 ANSWERS TO PRACTICAL QUESTIONS the most malleable of ordinary m.etals; but, although it is easy to hammer a mass of lead into a flat plate, or to squeeze it between rollers, any attempt to reduce it to an extremely thin sheet fails from its want of tenacity, which causes it to be worn into holes by percussion or friction. On the other hand, if malleability were entirely regulated by tenacity, iron would occupy the first place, whereas, on account of its hardness, it is the least malleable of metals in ordinary use; whilst gold, occupying an intermediate position with respect to tenacity, is the most malleable, which appears surprising to those who are only acquainted with gold in its ordinary forms of coin and ornament, in which it is hardened and rendered much less malleable by the presence of copper and silver. I.-Relative,alleability of the Metais. z. Gold. 4. Tin. 7- Zinc. 2. Silver. 5. Platinum. 8. Iron. 3. Copper. 6. Lead. I.-Relative Tenacity of the Metals. Lead............................ I Silver........................... 124 Tin. I Platinum........................ 5....................... I........................ Zinc...................... 2 Copper........................ I8 Palladium..................... I Iron........................... 27Gold............................ 2 Steel....................... 42 III.-Relative Ductility of the Metals. i. Gold. 5. Copper. 8. Zinc. 2. Silver. 6. Palladium. 9. Tin. 3. Platinum. 7. Aluminum. io. Lead. 4. Iron. — BLOXAM. 2. What is the cause of the changing color ofLen seen in the scum on standing water? (See "Interference of Light," Philosoofhy, page 209.) The thin pellicles of iron-rust on standing H20 pro

Page  123 IN CHEMISTRY. 123 duce a beautiful iridescent appearance, the color changing with the thickness of the oxide. A soap-bubble exhibits in the same way a play of variegated colors according to the thickness of the film in different parts. 3. RHow can the spectrea of the metals be obtained? (See Astronomy, page 285.) By looking through a prism at a flame containing minute portions of the volatilized metal. 4. Ought cannon, car-axles, etc., to be used until they break or wear out? Cannon are condemned and recast after being fired a certain number of times, even though they show no flaw, as the jarring to which they are exposed causes the iron to take on a crystalline form and become less fibrous and tough. A cast-iron gun of io-inch bore or less, ought to stand Iooo rounds; larger calibres, a smaller number. 5. Why is " chilled iron" used for safes? The iron being cooled so instantaneously, the crystals are exceedingly small, and the metal is correspondingly harder than when cast in the ordinary way. 6. Does a blacksmith plung-' his work into water merely to cool it? The metal is harder when cooled quickly and therefore resists wear longer. 7. What causes the ewhite coating made when we spill water on zinc? The oxide of zinc which is formed on the surface of the metal through the favoring influence of the water.

Page  124 124 ANSWERS TO PRACTICAL.QUESTIONS 8. Is it well to scald pickles, make sweetmeats, orfry cakes int a brass kettle? (See Chemistry, page I59.) 9. What danger is there in the use of Icad ipcs? Is a lining of Zn or Sn a protection? (See Chemistry, pages 156 and i6o, and Fireside Science, page x49.) Zinc and tin are corroded by oxygen, though less readily than Pb, and, while their salts are poisonous, the lead is soon laid bare, and this also oxidizes. io. Is water which has stood in a metal-lined ice-pitcher healthful? (See Chemistry, page 157.) The dissimilar metals fastened with solder which corrodes in the presence of water, develop a galvanic current which hastens the oxidation. The salts thus formed are very dangerous. i i. If you ask for " cobalt " at a drug-store, what will you get? If for " arsenic? " Impure metallic arsenic is sold as "cobalt," while arsenious anhydride is called "arsenic."' I2. What two elements are fluid at ordinary temperatures? Bromine and mercury. 13. Should we touch a gold ring to mercury? The mercury will form with the gold an amalgam.

Page  125 IN CHEMISTR r. 125 14. Why does silver blacken if handled? The perspiration of the body contains S, which combining with the metal forms silver sulphide-the black sulphuret of silver. I5. Why does silver tarnish rapidly where coal is used for fires? S, which is present in coal, is set free by combustion and forms a silver sulphide. I6. Why is a solution of a coin blue? From the Cu which is contained in silver coin. I 7. Why will a solution of sizler nitrate curdle brine? A white, curdy precipitate of silver chloride is formed. I8. Why does writing with indelible ink turn black when exposed to the sun, or to a hot iron? By the decomposition of the silver salt contained in the ink, and consequent production of Ag2O, which stains organic matter black. I 9. What'alloys resenble gold? Oreide, aluminum-bronze, etc. 20. Why does a fish-hook " rust out" he line lo which it is fastened? Ferric oxide and ferric hydrate act as conveyers of 0, absorbing it from the air and giving it up to organic bodies with which they are in contact. 2 I. Why do the nails in clap-boards loosen? (See Question _o.)

Page  126 126 ANSWERS TO IPRACTICAL QUESTIONS 22. S/how that the earth's crust is mainly composed of burnt metals. (See Cooke's Religion and Chemistry.) It consists largely of potassium, magnesium, calcium, aluminum, sodium, etc., in combination with 0. These compounds are the products of combustion. The elements 0, Si, Al, Mg, Ca, K, Na, Fe, C, S, H, C1 and N —I3 in all-probably make up -_o9_ of the earth's crust. 23. What kind of iron is used for a magnet? For a magnetic needle? Steel. 24. Why does a tin pail so quickly rust out when once the:in is worn through? The iron rusts rapidly in the presence of water, which favors oxidation. 25. Why is the zinc oxide found in NVew 7ersey red, when zinc rust is white? The oxide in New Jersey is colored by compounds of iron and manganese. 26. Should w: Jfilter a solution of permanganate of polash through paper? (See Chemistry, page I55, note.) No. The salt will give up 0 and corrode the filter. 27. Why is wood, cordage, etc., sometimes soaked in a solution of corrosive sublimate? This salt possesses strong antiseptic properties.

Page  127 IN CHE4lISTR Y. I27 28. Why does the white paint around a sink turn black? H2J is set free, which, acting on the paint, forms lead sulphide-the black sulphuret of lead. 29. Why is aluminum, rather than platinum, used for making the smallest weights? Because of its bulk as compared with that of platinum. 30. How would you detect the presence of iron particles in black sand? By a magnet. 3'. Which metals can be welded? (See Philosophzy, page 37.) Iron and platinum. 32. When the glassy slagfrom a blast-furnace has a dark color, what does it show? It might be anticipated that the appearance of the slag would convey to the experienced eye some useful information with respect to the character of the ore and the general progress of the smelting operation. A good slag is liquid, nearly transparent, of a light grey color, and has a fracture somewhat resembling that of limestone. A dark slag shows that much of the oxide of iron is escaping unreduced. Streaks of blue are commonly found when ores containing sulphur are being smelted, possibly from the presence of a substance similar to ultramarine, the constituents of which are all present in the slag. Again, the slags obtained in smelting ores containing titanium generally present a peculiar blistered appearance.BLOXAM.

Page  128 I 28 ANSWERS TO PRACTICAL QUESTIONS 33. Aii welding iron the surfaces to be joined are onmes times sprinkled with sand. Expainz. The silica acts as a flux with the oxide upon the surface and lays bare the metal for welding. 34. What is the difference between an alloy and an amalgam? An amalgam is composed of mercury and some other metal. An alloy consists of any metals whatever. 35. Steel articles are blued to protect from rusting, by heating in a sand-bath. Explain. A thin coating of oxide is. formed on the surface of the metal. 36. Give the rational forrmul for coperas and whiite leadt. i. FeSO4 = FeO,SO3. 2. PbC03 = PbO,C02. 3 7. Wthy is Hg usedforf illing thervnomefers? (See Phi'osoAhy, page 235.) Because it is fluid at all ordinary temperatures. 38. Ihat oxide is formed by the combustion of Na, K, Zn, S, Fe, Pb, Cu, P, etc.? Which are bases? Acids? Give the common namze of each. (I). NaO0 is formed when Na oxidizes in dry air, or oxygen at a low temperature. This takes up water with great avidity, forming HNaO (NaHO), sodium hydroxide. Na2O2 is made when Na is heated to 2000 C. HNaO is the caustic soda of commerce, and is an alkaline base.

Page  129 IN CHEMISTRY. I29 (2). K in a similar manner, depending upon the temperature, forms K20, K.O2, and K204. The first, with water, forms the ordinary caustic potash, HKO, of commerce. It is an alkaline base. (3). ZnO is the only known oxide of zinc. It forms salts. (4). Seven compounds of S and O are known, but only two are of interest-the familiar anhydrides, SO2 and SO3. (5). The oxides of iron are four in number: (i) the monoxide, or ferrous oxide, FeO, from which the green ferrous salts are derived; (2) the sesquioxide, or ferric oxide, Fe203, yielding the yellow ferric salts; (3) the magnetic or black oxide, Fe304, which does not form any definite salts; (4) ferric acid, H2FeO4, a weak acid, forming colored salts with potassium. (6). Pb forms two oxides, the monoxide and the dioxide. The former is the well known litharge, which is the base of the lead salts. (7). Cu has two oxides-the cuprous (Cu2O) and cupric (CuO), both of which form salts, thus giving rise to two series, the cuprous and the cupric salts. The two oxides are commonly known as the red and the black. (8). Phosphorus forms two oxides, phosphorous anhydride (P203) and phosphoric anhydride (PO,5). 39. Is charcoal lighter than H 20? Charcoal appears at first sight to be lighter than water, as a piece of it floats on the surface of this liquid; this is, however, due to the porous nature of the charcoal, for if it be finely powdered it sinks to the bottom of the water. RoscoE.

Page  130 130 ANSWERS TO PRACTICAL QUESTIONS 40. Name the vitriols. The compounds of sulphuric acid and oil of vitriol, commonly called "the vitriols," are as follows: i. Sulphate of iron, Green vitriol. 2. Sulphate of copper, Blue vitriol. 3. Sulphate of zinc, White vitriol. 41. Is Mg a monad or a dyad? Zn? Mg belongs to the zinc class of metals which comprises magnesium, zinc, cadmium, and indium. These are all dyads. 42. JVame some dibasic acid. Sulphuric acid, carbonic acid, etc. 43. namze a neutral salt. An acid salt. (See Chemnzistry, page 128, note.) 44. Calculate the percentage of water contained in crystalt lized copper sulphate. Sodium sulphate. Calcium sulphate. (I). CuSO,, 5H,O = 249.5. 5H,O = 9o. Hence, /-~ =.36 = 36 % of copper sulphate is water. (2). Na2SO,, IoH,O = 322. IoH20 = 80o. Hence,.- 5 =. 55 % of sodium sulphate is water. (3. CaSO,, 2HO = x72. 2H20 = 36. Hence, T'v. =.20 = 20 % of gypsum is water. (4). A12K2, 4SO + 24H20 = 949. 24H20 = 432. Hence, Sj.45 = 4%5 of potash alum is water.

Page  131 INv CHEMISTRY. I3 45. What is the testfor Ag? Cu? Ag can be easily detected when in solution by the precipitation of the white curdy chloride, insoluble in H20 and HNO3, and soluble in H3N: the metal can be obtained in malleable globules before the blowpipe, and is reduced from its solutions by Fe, Cu, P, and Hg. Ag is estimated quantitatively either as the chloride or as the metal. Copper may be tested (i) by the black insoluble sulphide; (2) by the blue hydrate turning black on heating; (3) by the deep blue coloration with ammonia; (4) by the deposition of red metallic copper upon a bright surface of iron placed in the solution. 46. What weezght of crystallized " tin salts" (SnCl2, 2 H 2) can be preparedfrom one ton of metallic tin? Sn: SnCI,, 2HO2:: 2000 lbs.: x. 18: 225:: 2000 lbs.: x. zI8 x = 450000 lbs. x = 38I3.56 lbs. (SnC12,,2H,O). 47. ioo parts by weighlt qf silver y'ield I32.8 + parts of silver chloride. Given the combiniing weight of chlorine, required that of silver. X: 35.5:: oo: 32.8+. 328 X = 3550. x = io8+. 48. What is the composition of slacked lime? (See Chemisiry, page I37.) CaO,H 20. 49. How is ferrous sulphate obtained? How many tons of crystals can be obtained by the slow axidation of 230 tons of iron pyrites containing 3 7.5 per cent. of sulphur? (See Ckemistry, page 155, and Keay page 6o; Question 32.)

Page  132 I:32 AYSWlERS TO PRA CTICAL QUESTIONS Find (I) how much S there is in the given weight of iron pyrites; (2) how much ferrous sulphate could be made from that amount of S, if it wer-e all oxidized. (I). 230 tons x.375 = 86-23 tons (S). (2). S FeSO2, 7HO2:: 86.25 tons: x. 32 278:: 86.25 tons: x. 32 X = 23977.5 tons. x - 749.296 tons (FeSO,,7HO). 50. Reizired 500 tons of soda crystals, what will be the w~,eibght of salt and pure suhphuric acid neededt? Find (I) how much Na there is in 500 tons of " soda," and (2) how much NaCl would be needed to furnish that amount of the metal in case all were utilized. (I). Na: Na2CO,IoH0:: x: 500 tons. 46: 286:: x: 500 tons. 286 x = 23,000 tons. x = 80.42- tons (Na). (2). "-!o of any amount of NaCl is Na; hence, to furnish 80.42 tons of Na would require ag x 80.42 tons = 204.546 tons (NaCI). (3). By comparing the atomic weights of the substances it will be seen that for 46 parts of Na thecre must be 98 of pure H20S0. a" x 204.546 tons = 435-77I tons (H..SO). 5. Dcsc-ib the tscs of lim e in afg-irclt[ulre. (Scc IKey, page 5I, Question I2.) 52. Hflow many tons f oil (,f Titriol, conlahining 70 per cen t. of pure acid (H 2 S()4), carn lie pr'epax'el from 2 50 tons of iron pyrites, containini 42 p5:- cctn. of sutlihur? (i). (See QuestIon 49.) 25, tons x.a2 = io5 tons (S). (2). S: H2SO0:: 05 tons: x. 32 98:: 105 tons: x. 32 X = io29o tons. x = 32.56 tons (H2SO). (3)- If 32I.56 tons (H2SO,) is 70 g of the given oil of vitriol. the entire armount vculd be 321;56 tons x F 459.28 tons (oil 6f vitriol).

Page  133 IN CHEM$ISTRY. I: 33 i. How would you prove the presence of tannin in tea? By adding a few drops of a solution of ferrous sulphate. This would form a dark precipitate of iron tannate. 2. Hoaw would you test for Fe in a solution? (See Miller's Inorganic Chemristry, page 525.) A solution of nutgalls will give a bluish-black, inky precipitate. The ferrous- or proto-salts are distinguished by their light green color, and by their solutions giving (I) a white precipitate, with caustic alkalies; (2) a light blue precipitate, with potassium ferrocyanide, which rapidly becomes dark: whilst the ferric- or per-salts are yellow-colored, and their solutions yield (i) a deep reddish-brown precipitate, with the caustic alkalies; and (2) a deep blue precipitate (Prussian blue), with potassium ferrocyanide. 3. Why can we settle coffee with an efgg? The albumen of the egg coagulates by heat, and entangling the particles of coffee, mechanically carries them to the bottom. 4. prow would you show the presence of starch ivz a potato? A solution of iodine will form the blue iodide of starch. 5. Why is starch stored i fthe seed of a plant? For the growth of the young plant. 6. Why are unbleached cotton goods dark-colored? Because of the dirt gathered in the process of manufacture. The cotton balls arie snowy white.

Page  134 I 34 ANSWERS TO PRACTICAL QUESTIONS 7. Why do beans, rice, etc., swell when cooked? By the bursting of the starch granules. 8. Ithy does decaying wood darken? By the formation of humus which contains carbon in excess. 9. Why does smoke cure hams? The creosote of the smoke has powerful antiseptic properties. i o. Hiow would you show that C exists in sugar? By the experiments described in the Chemistry on page 117, note; page I9o, note; and page I91 in the formation of caramel. I r. Why do fruits lose their sweetness when over-ripe? (See Miller's Organic Chemistry, page 875.) The vegetable acid contained in the fruit when green, oxidizes as the ripening process continues, O being absorbed and CO2 evolved. If this continues too long, the sugar itself becomes oxidized. 12. Why does maple-sap lose its sweetness when the leaf starts? The sugar of the sap is applied to the wants of the growing tree. I3. Should yeast-cakes be allowed to freeze? A cold of 320 will kill the ferment.

Page  135 IN CHEMlISTR Y. I35 I4. Why will wine sour if the bottle be not well corked? The presence of air will cause the continuation of the oxidizing process into the second or acetic stage. 15. Why can vinegar be made fromz sweetened zwater and brown paper? The paper acts as a ferment, while the sugar or molasses is oxidized into alcohol and thence into acetic acid. I6. VWhy should the vinegar-barrel be kept in a warm place? Heat promotes chemical change. 17. Why does "scalding" check the "working" of preserves? The ferment which causes the fermentation is killed by the heat. I 8. Is the oxalic acid in thepie-plant poisonous? It is neutralized by the alkaline base, with which it is combined in the plant. I9. now nmay ink-stains be removed? By a solution of oxalic acid, forming an iron oxalate which is soluble in water, and hence may be washed out. 20. Why is leather blzck on only one side? (See Chemistry, page 21I.) The solution of copperas, which blackens the leather, is applied on only one side.

Page  136 136 ANSWERS TO PRACTICAL QUESTIONS 2 1. Why do droyps of tea stain a knife-blade? (See Chemistry, page 2I1.) The tannic acid of the tea combines with the iron, forming an iron tannate.* 2 2. Why will not coffee stain it in the same way? (See Miller's Organic Chemistry, page 549.) The modification of tannin contained in coffee, unlike that in tea, turns a solution of ferrous sulphate green, and will not precipitate one of gelatin. 23. Why does writingfluid darken on exposure to the air? (See Chemistry, page 262.) It absorbs 0, the iron changing to ferric oxide. 24. What causes the disagreeable smell of a smoldering zwick? A volatile substance, termed acrolein, is produced in the decomposition of the oil. 25. Why does ink corrode steepens? The free sulphuric acid of the ink combines with the iron of the pen. 26. How does a bird obtain the CaCO3 for its eggshells? (See chemistry of a hen's egg in Fireside Science.) A common hen's egg is 95 per cent. carbonate of lime, * The tannic acid of the tea tans the albumen of the milk used in seasoning the tea, forming flakes of real leather. It has been calculated that an average tea-drinker, in this way, makes and drinks enough leather each year to make a pair of shoes. The albumen of milk uniting with the tannic acid of tea. softens its flavor. This is generally preferred to the harsh, clea/ Lvcekrtagre.

Page  137 INR CHEMIST~ Y. I37 one per cent. phosphate of lime and magnesia, and two per cent. animal matter. The shell would weigh over Ioo grains, so that a hen laying ioo eggs in a season would require nearly I-1- lbs. of CaCO3. The hen must in part secrete this fromn her food, and in part gather it from the sand, pebbles, etc., she picks up amid her incessant scratching and searching. 27. Why will tallow make a harder soac than lard.? Tallow contains more palmitin, and less olein, than lard. 28. Why does new soap act on the halnds more than old? The spent lye, which contains the excess of alkali, gradually separates from the soap, leaving only the salts in which the alkali is neutralized by the fatty acids. Also a more complete combination takes place, whereby some free alkali is taken up by the acids, perhaps before uncombined. The former statement is especially true in the case of soft or home-made soap. 29. What is the shiny coat on certain leaves and fruits? A species of wax secreted by the plant. 30. Why does turpentine bur;l with so much smoke? Because it contains an excess of carbon. 3. WIhy is the nozzle of a turpentine bottle so stick), The turpentine on exposure to the air oxidizes, turning to rosin. 32. Why does kerosene give more ligh-t than alcohol? It contains more carbon, which, when heated in the flame of the burning H, gives out a white light.

Page  138 I38 ANSWERS TO PEA CTICAL QUESTIONS 33. Ihat is the antidote to oxalic acid? IVhy? Magnesia or chalk, forming an insoluble oxalate. 34. Would you weaken camphor spirits with water? (See Chemistry, page II7.) No; since camphor is insoluble in dilute alcohol. The principle is the same as that of the precipitation of lead from dilute oil of vitriol. 35. What is the difference betw:ven rosin and resin? Rosin is an oxidized resin. Rosin is a species, and resin a genus. 36. Wh.y tdoes skim-milk look blue and new milk zehite? The globules of butter contained in new milk reflect the light, and so make it look white; but when they are removed, by the separation of the cream, more light is transmitted, and only the blue is reflected to the eye. 37. 17Why does an ink-spot turn yellow after washingg with soap? The free alkali of the soap combines with the tannic acid of the ink, leaving the oxide of iron (ferric oxide), which stains the cloth yellow.

Page  139

Page  140 Atomic Molecular Specific Specific Quan- Electrical Fusing olvent _Name SmoQa-Eetil Color Solvent Name Symbol Weight Weight Gravity Heat tivalenceCharacterPoint Aluminum......... Al 27.5 A1l=55 2.67.2143 II or IV + 12 white 1292 F HCI Antimony (Stibium) Sb 122 Sb,=488 6.71.05077 III or V - 16 bluish-white 8122 F. HCI + HNO, Arsenic............As 75 As,=300 5.95.08140 III or V - 9 steel-gray 774' F HNO' Barium............ Ba 137 Ba2=274 1.85...... I II + 5 yellow Bismuth.......... Bi 210 Bi =840 9.799.03084 III or V + 28 reddish-white 507; F. HNO, Boron............ B 11..... 2.680.2500 III - 14 brown. KCO3 hot Bromine........... Br 81, Br2= 160 3.187.1060 I - 5 brownish-red 45' F. Ether Cadmium.......... Cd 112 Cd=2'24 8.604.05669 II + 24 bluish-white 4420' F. H2SO4 Cuesium............ Cs 133j Cs2 = 266 unknown..... I +............................ Calcium............ Ca 43 C=80 1.578 II + 7 light-yellow HC1 dil. Carbon............C 12 C,=24? 2.35.02411 IV - 15 black infus. insol. 8 Cerium............. Ce..... II + 15............ Chlorine........... C1 35.5 C12=71 2.435.1214 I — 4 green........ O Chromium......... Cr 52.5 Cr, =105 6.810..... 1I or IV - 10 gray 1(1 Cobalt............. Co 59 Co,=118 8.95.10696 II + 2; steel-gray 20 F'. HCl Copper (Cuprum)... Cu 63.5 Cu2 = 127 8.90.09515 II + 30 red 19!)42 F. H1SO c0 Didymium...... ).... 96 D II 16 ~~~CDidmUm.....D D, = 192..........I + 16.................... Erbium............E 112 E =224... II + 11 Fluorine...........F 19 F,=38 1.31 I - 3........ Glucinum.......... 9.5 G2=19 2.10..... II + 9............ Gold (Aurum)...... A 197 Au,=394 19.34.03244 III -23 yellow 2015 F. (-) HC11N0, Hydrogen.......... 1 112H=2.069 3.4046 I - 22 colorless Indium............ In 76 7.20..... II + 26 white' 49. F...her' Iodine.............. I 127,12,=254 4.94.05412 I - 6 bluish-black 225 F. Ether iridium............. Ir 197 21.80.03259 II or IV - 25 white 011 insol. Iron (Ferrum)...... Fe 56... 7.80.11379 II or IV + 20 gray-white 1900 to 2901) Acids Lanthanum......... La 92II + 17...'w ht 2.0,"F... Lead (Plumbum).. Pb 27.. 11.36.0314 II 25 hluihs:white 6202i F. hNO Lithium............ IL 7 L.=14 0.59.9408 I +4 white 324' F. Magnesium........ Mg 24 17........ 1.249!) II + 8 white 446'0 F. Acids Manganese. Mn 55.... 8.00.1217 II or IV + 18 gray-white........ HC1 Mercury (Hydrargyrum)........ r gyrum)........ Hg 200.... 13.596.03332 II - 30 white -39 F. HNO Molybdenum....... Mo.96 8.64...... VI - 12 1 gray.. HNO,

Page  141 Nickel.......... i Ni 59........ 8.90.10863 II + 21 white 32 I1 Niobium...... Nb.94.3.V 1. 9 whi........ V - 19 Nitrogen........... N 14 N=28 71.2440 III or V - 2 colorless............... Osmium............I Os 199 2 21.400.03063 IIorIV -24 bluish-white infus....... Oxygen.. 0....... 16'- 3 1.1056.2182 II colorless Palladium..... d 106....... 11-12.05927 II or IV -29 white 40C0 () Phosphorus... P 31 1.83.187 III or V - 8 colorless 110~ CS, Platinum........Pt 197........ 21.53.03243 IIor V -26 white 4591 F. (.) fC + HTNO Potassium (Kalium) K 39 K =78.865.1695 I + 2 bluish-white 136. Rhodium........ Ro 104 11.00.05803 II or IV - 27....... Rubidium......... Rb 85 i 170 1.52 I + white ".... Ruthenium........ Ru 104 11-12 II...... or IV - 28.............. Selenium......... Se 79.5 Se,=1 59 4.80.0 IorV -7 brown "4 S Silicon...... Si 28........ 249.... I - 21 brown IINO, + HF Silver (Argenttin).. Ag 108 Ag2, =216 10.50.05701 I ~ 31 white 18'3`r. HNO3 Sodium (Natrium).. Na 23 Na2=46.972.2934 I + 3 white 195.... Strontium........ Sr 87.5 2.54 II +6 pale-yellow dil. HNOd 3 Sulphur............ S 32 S'=64 2.00.1776 II or VI - yellow 22S CS2 Tantalum...... Ta 182 10.78...... V - 18........... Tellurium....ITe 129 T =258 6.65.04737 II or VI - 17 reddish-white 7 HSO, Thallium..... T 204....... 11.86.03355 I or III + 23 white 554 HENO. Thorium........... Th 238................... IV + 14................ Tin (Stannum).. Sn 118.......3.05623 II or IV + 27 white 442' F. lCI Titanium........... Ti 50 5.3 II or IV - 20 gray HC1 Tungs~ten (Wtol-! fmTungsten (.1- W 184 17.50.0342 VI - 13 steel-gray.HNOs framium)...... Uranium......... U 120.... 18.40 II or V + 29 gray....... Vanadium.......... V 51 3.64 III or V - 11.......... Yttrium.......... Y 62... II + 10... Zinc............... Zn 65.....15.9555 II + 19 bluish-white 773' F' Zirconium. Zr 89..... 4.15... IV 13 black 1tF NoTE. —The names of metals are printed in Roman, non-metals in italics. The electrical character of an element is relative; although aluminum is positive towards a majority of the elements, it is negative towards 12 elements. Oxygen is the most electro-negative of all; sulphur is the most negative with one exception, hence marked — 1. Coesium is the most electro-positive of all and takes a plus sign. Silver is in middle numerically, there being 31 elements more strongly negative and 31 more strongly positive. Temperatures above 2000~ F. are only approximate.

Page  142

Page  143 AN SWERS TO THE PRACTICAL QUESTIONS IN THE FOURTEEN WEEKS IN HUMAN PHYSIOLOGY. 38.-I. Why does not a fall hurt a child as much as it does a grownz person? The bones of a child are largely cartilaginous, and so do not transmit a shock, or readily yield to a blow. They are also well padded with fat. 2. Should a young child ever be ur,ed to stand or walk? No; bow-legs are often caused by the premature use of the lower limbs in standing or walking. Nature is the best guide in such matters. 3. WVhat is meant by " breaking one's neck?" The dislocation of the vertebra and consequent injury of the spinal cord. 4. Ofught chairs or benches to have straight backs? The backs should conform to the natural shape of the spine. This tends to prevent curvatures and other distortions of the vertebral column.

Page  144 144 ANVSWERS TO PRACTICAL QUESTIONS 5. Ou,,ght a child's feet to dangle from a high chair? The position is as unnatural and painful for a child as for a grown person. 6. Why can we tell whether a fowl is young by pressing on the point of the breast-bone? Because that part of the breast-bone is not ossified in a young fowl. 7. What is the use of the marrow in the bones 2 It contains the blood-vessels carrying material for the. growth of the bone, and also diffuses any shock which the bone may receive. 8. Why is the shoulder so often put out ofjoint? Because of the shallowness of the socket in the scapula. 9. How can you tie a knot in a bone? By removing the mineral matter and thus softening a rib-bone, a knot can be easily tied in it. Io. Why are hiqgh pillows injurious? They elevate the head, and so give an unnatural position to the spine. For the pads between the vertebrae to assume their proper shape during the night they should be relieved of all pressure. i I. Is the " Grecian bend " a healthy position? The natural position is the only healthy one. The distortion known as the "Grecian bend" contracts the chest, chances the outline of the spine, and diminishes the vitality of the system.

Page  145 IN HUMAN PIIYSIOLO Y 14Y I2. Oght a boot to have a heel-piece A low and broad heel-piece probably aids in walking' a narrow or high one weakens and enlarges the ankle, produces bunions, corns, etc., by throwing the weight forward upon the toes, and makes the gait exceedingly ungraceful. 13. Why should one always sit and walk erect? Because then all the organs are in their natural position. 14. Why does a youzng child creep rather than walk? (See Physiology, page 50.) Its bones not yet being fully ossified, nature teaches it not to bear its weight upon them. Besides, it has not yet learned the difficult art of balancing itself. 56.-I. What class of lever is the foot when we slf r a weight on the toes? The third class. The ankle-joint is the fulcrum, the weight is at the toes, and the power is in front of the ankle, where the muscle which lifts the toes (the extensor digitorium) is attached to the foot. 2. Explain the movement of the body backward and forward, when resting zpon the thigh-bone as afulcrurz. The weight is at the center of gravity of the head and trunk, high above the hip joints, where the fulcrum is situated. The flexor muscles of the thigh are the powrer, and act close to the fulcrum. Thie weight is sometimes directly over the fulcrum, and may be on any side of it.

Page  146 I46 ANSWERS TO PRACTICAL QUESTIONS This seems to the author to be an example of the first or second class of lever. Huxley gives it as an illustration of the third class. 3. What class of lever do we use when we lift the foot while sitting down? The third class. The fulcrum is the knee-joint; the weight is at the center of gravity of the foot and leg, and the power is applied by the ligament which passes over the patella. 4. Explain the swing of the amn from the shoulder. (Sec Physiology, page 48.) The third class. The fulcrum is the shoulder-joint; the weight is at the center of gravity of the arm and hand, and the power is applied by the biceps or triceps muscle at its attachment near the elbow. 5. What class of lever is used in bending ourfingers? The fulcrum is at the junction of the finger with the palm; the weight is at the center of gravity of the finger, and may play about the fulcrum as stated in second question. It is the third class of lever, especially when force is exerted at the extremity of the fingers. 6. What class of lever is our fi9ot when we tap the ground with our toes? (See Physiology, Fig. I4, k.) The first class. The weight is at the toe when the force is exerted; the fulcrum is at the ankle; and the power is applied by the gastrocnemius muscle at its attachment to the heel.

Page  147 1.7 HUMAIN' PHYSIOLOG 4 e47 7. What class of lever do we use whien we raise ourselves from a stoopingposition? The third class. See second question. If we are attempting to lift a heavy burden, the bones act on the principle of the toggle-joint. "When one stoops to take a heavy weight upon his back or shoulder, lie puts both the knee and the hip-joints into the condition that the toggle-joint is when it is bent; and then as he straightens up, the weight is raised by an action of the joints precisely similar to that of the toggle-joint in machinery. In the case of the knee, the straightening of the joints is done by the muscles on the front part of the thigh, that draw up the knee-pan with the tendon attached to it. This is using the principle of the toggle-joint in pressing upward. It is also sometimes used in pressing downwlard. In crushing anything with the heel, we give great force to the blow on the principle of the toggle-joint, by flexing the knee and straightening the limb as we bring down the heel upon the thing to be crushed. In pushing anything before us, we bend the elbow as preparatory to the act,.and then thrust the arm out straight, thus exemplifying the toggle-joint. The horse gives great force to his kick in the same way. The great power exerted by beasts of draught and burden is to be referred very much to the principle of the toggle-joint. When a horse is to draw a heavy load, he bends all his limbs, especially the hinder ones, and then as he straightens them, he starts the load. In this case the ground is the fixed block of the mechanism, the body of the horse to which the load is attached is the movable one, and his limbs are so many togglejoints. By this application of the principle, we see draught horses move very heavy loads."-HOOKER's Physi

Page  148 148 ANSWERS TO PRACTICAL QUESTIONS ology. "So (admitting fable to be fact), when the farmer, in answer to his petition for assistance, was commanded by Hercules to exert himself to raise his wagon from the pit, he placed his shoulder against the wheel, and drawing his body up into a crouching attitude, whereby all his joints were flexed, and making his feet the fixed points, by a powerful muscular effort, he straightened the togglejoints of his limbs, and the wheel was raised from its bed of miry clay. His horses at the same moment extending their joints, the heavily laden wagon was carried beyond the reach of further detention."-GRISCOM. 8. What class of lever is thefoot when we walk? In the first stage it is clearly the second class. (See Physiology, page 47, Fig. i8.) The fulcrum is the ground on which the toes rest; the power is applied by the gastrocnemius muscle (see Fig. I4, k) to the heel; the resistance is so much of the weight of the body as is borne by the ankle-joint of the foot, which of course lies between the heel and the toes. 9. Why can we raise a heavier weight with our hand when lifting with the elbow than from the shoulder? Because we bring the fulcrum nearer the power. In the former case it is at the elbow; in the latter, at the shoulder. 10. What class of lever do we employ when we are hopping, the thigh-bone being bend tu toward the body and not used? In this case the fulcrum is at the hip-joint. The power (which may be assumed to be furnished by the rectus

Page  149 IN HUMAN PH YSIOLOGY. I49 muscle* of the front of the thigh) acts upon the kneecap; and the position of the weight is represented by that of the center of gravity of the thigh and leg, which will lie somewhere between the end of the knee and the hip. -HUXLEY. I I. Describe the motions of the bones when we are using a gimlet. The radius rolls on the ulna at the elbow, while the ulna rolls on the radius at the wrist. The two combined produce a free, rotary motion. I2. Why do we tire when we stand erect? (See Physiology, page 49.) Because so large a number of muscles must be in constant action to maintain this position. 13. Why does it rest us to change our work? We thereby bring into use a new set of muscles. I14. Why and when is dancing a beneficial exercise? When dancing is performed out-of-doors, or in a wellventilated room and at proper hours, it is doubtless a beneficial exercise, since it employs the muscles and pleasantly occupies the mind. Late at night, in a heated room, with thin clothing and exciting surroundings, it is simply a dangerous dissipation, ruinous to the health, alike of body and soul. * This muscle is attached above to the haunch-bone or ileum, and below to the knee-cap. The latter bone is connected by a strong ligament with the tibia.

Page  150 150 ANSWERS TO PI'RACTCAL QUESTIONS 15. Why can we exert greater for-ce wit/h the back teeth than with the front ones? (See Physiology, page 49.) The lower jaw is a lever of the second class. In the formner case the resistance to be overcome, i. e., the weight, is situated much nearer the power. 6. IWhy do we lean forward when zweC wish to rise from a chair? (See Philosoihhy, pages 57-8.) In order to bring the center of gravity over the feet. 17. Why, does theprojection of the heel-bone make walking easier? (See Frontispiece, and also Fig. i8 in Physiology.) It brings the power further from the fulcrum or weight. I8. Does a horse travel easier over a fat tlhan a hilly couintiy? No. The variety of travel in a hilly country, other things being equal, tends to rest the horse, and enable him to better endure the fatigue of the journey. 19. Can youze ove your zipper jaw? All the bones of the face, except the lower jaw, are firmly and immovably articulated with one another and with the cranium.-LEIDY. 20. Are people naturally right or left-handed? Many persons are naturally either right or left-handed; but most can and should learn to use either hand with equal facility.

Page  151 IN HJUMllAN PHYSIOLOGY. 151 2 I. TVhy can so f:wre persons move their cars by the muscles? Perhaps, because of lack of practice; more probably, however, the muscles (see Physiology, p. 65 and Fig. 14) are developed in few persons. 22. Is the blacksmith's right arm healthier than the left? By no means. Strength is not essential to health. The right arm may be stronger, but the functions of the left lmay be as active and well-performed. 23. Boy's often, though foolishly, thrust a pin into the flesh just above the knee. /i~y is il not pairnf? The muscles of the leg there end in tendons, which are insensible. 24. [Vill ten minufcs pr(actice in a gymnnrsizum answer- for a day's exercise? Spasmodic or violent exercise is not beneficial. It should be comparatively quiet, gentle, and continuous to produce the best effect. Moreover, the vitalizing influences of the sun and pure air demand that we should exercise out-of-doors. 25. Why zwould an elastic tendon Abe uniftled to transmait the motion of a muscle? Force would be lost by its transmission through an elastic medium. 26. When one is struck violently on the head, why does he instantly fall? The body is kept erect only by the constant exercise

Page  152 1 5 2 ANSWERS TO PRACTICAL QUESTIONS of many muscles. These perform their functions through the unconscious action of the brain and spinal cord.. A blow paralyzes the nervous system, the muscles at once cease to act, and the body falls by its weight. 27. What is the cause rf the dizference between iight and da-k neat in a fcwl! The amount of blood which circulates through different parts of the body. The organs of a fowl which are used the most become the darkest. 79. I. If a hair be plucked out, will it grow again? Yes. A new hair will always grow out so long as the papilla at the bottom of the follicle remains uninjured. 2. Wh a t causes the hair to " stand on end" when we are frighztened? (See Physiology, page 65.) "Many of the unstriated muscular fibres from the true skin pass obliquely down from the surface of the dermis to the under side of the slanting hair-follicles. The contraction of these fibres erects the hairs, and by drawing the follicles to the surface and drawing in a little point of the skin, produces that roughness of the integument called "goose-skin," or Cutis Anserina. The standing on end of the hair of the head, as the result of extreme fright, may be partly due to the contraction of such fibres, as well as to the action of the occipito-frontalis muscle."-CUTTER. 3. W17hy is the skin roughened by ridinfg in the cold? (See Physiology, page 65; also Answer to Question 2.)

Page  153 IN HUMAN PHYSIOLOGY I53 4. Why is the back of a washer-woman's hand less water-soaked than thepalm? The difference depends upon the relative abundance of the oil-glands in different parts of the body. 5. What would be the length of the perspiratory tubes in a single square inch of the palm, if placed end to end? (See Physiology, page 72. 2,800X To in. = o1P9 in.= 4 ft. 7 in. —Answer.) 6. What colored clothing is best adapted to all seasons? Light-colored clothing is cooler in summer and warmer in winter. (See Physiology, page 77; Natural Philosoakhzy, page 246.) 7. What is tkhe effect of paint and powder on the skin? They fill the pores of the skin, and thus prevent the passage of the perspiration. Moreover, they often contain substances which are poisonous, and being carried in by the absorbents cause disease. (See Physiology, page 73.) 8. Is water-proof clothing healthful for constant wear? No. It retains the insensible perspiration by which waste matter is being constantly thrown off from the system. 9. Why are rubbers cold to the feet? They retain the insensible perspiration. The moisture which gathers absorbs the heat of the feet, and readily conducts it from the body.

Page  154 I 54 ANSWEERS TO PRACTICAL QUESTIONS i o. Why does the heat seem otp/ressize when the air is moist In the moisture-laden atmosphere, the evaporation of the insensible perspiration from the surface of the body goes on slowly. The heat, which would otherwise pass off through the pores, is retained in the system. I T. Why is friction of the skin invigvoraling after a cold bath? The friction produces heat, expands the veins, etc., on the surface, and, calling the blood in that direction, produces a vigorous circulation. In other words, it causes a reaction.* (See Phzysiology, page 75.) 12. thy does the hair of domestic animals become rouzghe;zed in winter? (See Question 2.) The effect is beneficial, since more air-a non-conductor of heat-is retained by the hair, and thus the rough * " Strength in the living body is maintained by the full but natural exercise of each organ; and as we have seen, the actions of these portions of the nervous system is made dependent upon influences conveyed to them by the sensitive nerves distributed over the various parts of the body. And among these the nerves passing to the skin are the chief. The full access of all healthful stimuli to the surface, and its freedom from all that irritates or impedes its functions, are the first external conditions of the normal vigor of this nervous circle. Among these stimuli, fresh air and pure water hold the first place. Sufficient warmth is second. The great, and even wonderful advantages of cleanliness are partly referable to the direct influence of a skin healthily active, open to all the natural stimuli, and free from morbid irritation, upon the nerve-centres of which it is the appointed excitant. This influence is altogether distinct from those cleansing functions which the healthy skin performs for the blood; and in any just estimate of its value is far too important to be overlooked.'-HINTroN.

Page  155 iL HUMAN PHYSIOLOGY. 155 winter-coat of an animal is warmer than its smooth summer-coat. 13. Why do fowls shake out their feathers erect before they perch for the night? (See Question I2.) This is a wise provision of Nature to protect the fowl against the chilliness of the night. More air is confined by the roughened feathers, and thus the internal heat of the bird is prevented from radiating. I4. fHow can an extensive burn cause dealh by congestion of thze lungs? The insensible perspiration is stopped upon the burned surface, and the excretions are sent to the lungs, which are overworked and overloaded by the excess. (See Phzysiology, page 74.) 5. Why do we perspire so profusely aftcr drinking cold water? The vital organs being chilled for an instant, the blood is sent to the surface, a reaction is produced, the skin acts more vigorously as an excretory organ, and the insensible perspiration is thrown off more rapidly. 16. Whhat are the best means of preventingZ skin diseases, colds, and rheumatism? The skin should be kept in a healthy state by bathing, rubbing, etc. Exposure to sudden changes of temperature should be avoided as far as possible. Flannel

Page  156 I56 ANSIVERS TO PRACTICAL QUESTIONS worn next the skin, in all seasons of the year, is an excellent precaution against unavoidable exposure. 17. Vf/iat causes the difference between the hard hand of a blacksmzit anld the soft hand of a woman? The varying thickness of the cuticle. (See Physzology, page 62.) i8. ThVzy shorzd a painter azoid gettinzgpaint on the pamn of his hand? (See Physzoaogy, page 73.) 19. Whly should wz nSPot use the soap or soiled towel at a Because of the danger of contracting disease through the absorbents a the skin. (See Physiology, p. 73.) There is a similar danger in using a hair-brush or a comb at a barber shop. 20. TVhicih teeth cLt hike a pazir of scissors? The "back-teeth," as we commonly call them, when moved laterally, cut somewhat in this way. In chewing the food all the "Front teeth" act like scissors, as may be readily seen by noticing their movements. 2. WhichC like a cihisel? The incisors, or four front teeth of each jaw, have knife edges; the canine teeth have wedge-shaped edges; the bicuspids and molars have broader crowns. We can work the jaws so as to make the front-teeth either pierce like wedges or cut like scissors.

Page  157 I1Y HIIeAN PHYSIOLOGAY I57 22. Which should be clothed the warmer, a merchant or a farmer? The merchant is liable to more sudden and violent changes of temperature, and his body is less likely to be hardened by exposure and habit to resist them. 23. Why should we not crack nuts with our teeth? The brittle enamel is very liable to crack, and once broken can never be restored. 24. Do the edges of the upper and lower teeth meet? (See Question 21.) 25 W/hen fatiguet/, would you take a cold bath? Certainly not. The system is not vigorous enough to produce a reaction, and the effect might be dangerous. 26. Wthy is the oufter surface of a kid glovefiner than the izzner? This illustrates the difference in texture between the cutis and cuticle; the dermis and epidermis. 27. 7'Vhy will a brunette endure the sun's rays better than a blonde? (See Physiology, page 63.) The skia is perhaps of a coarser texture, and not so sensitive to heat. May it not be also that the black pigment absorbs the heat and radiates it again rather than transmits it directly to the internal organs? It has also been suggested that there is an increased flow of blood in the darker skin, and hence increased perspiration.

Page  158 158 ANSWERS TO P.RACTICAL QUESTIONS 28. Does patent-leather form a healthful coveringfor the feet? No. The pores of the leather are partly filled, and hence the insensible perspiration is largely restrained. 29. Why are men more frequently bald than women Z This is the effect of the close, unventilated head-covering commonly worn by men. 30. On what part of the head does balidness cvmmonly ocClur? On that part most fully covered by the hat or cap. 3I. What does the combination in our teeth of canines andgrinders suggest as to the character of our food? That we are to eat a mixed diet of vegetable and animal food? * " The question of the use of animal or vegetable food may well be remitted to the arbitrament of nature, as expressed in the desires; by which it would be victoriously decided, in all such climates as ours, in favor of the flesh-eater. But the sufficiency of vegetable food, if widely varied, to maintain health and even strength, is not to be questioned, for those who like it. When we hear that the ancient Persians lived a good deal on water-cress, we naturally connect in our minds their physical inferiority with the poverty of their diet; but finding, on the other hand, that the Romans, in the best period of the Republic, largely sustained themselves on turnips, and that degeneracy came in as turnips went out, we are compelled to reconsider our opinion. In brief, an exclusively vegetable food may be best suited to those by whom it really is preferred. Children in this respect exhibit the greatest difference; some, with manifest advantage, eat meat in large quantity-others can hardly be prevailed on to taste it, and yet retain perfect vigor. Similar differences, in all probability, exist among adults; but a vegetarianism self-imposed against the promp:ings of desire would t-nd, as a vigorous writer says, to make us'not the children, but the abortions of Paradise.' "-HINTON.

Page  159 IN- I IUMAN PHYSI OLOv Y. 159 32. Is a staid, formalpromenade suitable exercise? No. There is an intimate relation between the brain and the muscles. The mind should be pleasantly emp'oyed to obtain the full effect of any exercise. The sports of children are often the very perfection of healthful;ymnastic exercises? * 33. Is there any danger in changing the warm clothing of pur Jaily wear for the thin one of a party? Very great. The body is not as well protected as usuai against a sudden change of temperature, as in going from a heated-room to the carriage, and a cold is often the consequence. This may lay the foundation of, or prepare the way for, fatal disease. 34. Should we retain our overcoat, shawl, orJfurs, whern we comze into a warm room? No. The body will become over-heated, the pores be opened, and the skin be rendered susceptible to the change of temperature when we return into the open air. 35. EWhich should bathe the oftener, students or out-door laborers? "The mental operations, like all others, are connected with changes in the material of the body. In all our consciousness the chemical tendencies of the substance of the brain come into play, and thus a chain of action is set up which extends throughout the system. The influence of these brainchanges is felt wherever a nerve travels, and modifies, invigorates, or depraves the action of every part. Experience gives ample proof of this fact to every one, as in the sudden loss of appetite a piece of bad news will cause, or in the watering of the mouth excited by the thought of food. And the history of disease abounds in evidence of a similar kind: hair becoming gray in a single night from sorrow, milk poisoning an infant from an attack of passion in the nurse, permanent discoloration of the skin from terror, are among the instances on record."-HINTON.

Page  160 I60o ANSWERS TO PRA CTICAL QUESTIONS This depends entirely on circumstances-the amount of exercise, freedom and character of perspiration, state of the system, etc. Each case must be decided by it self. 36. Is abundantperspiration injurious No. It removes impure matter from the system, and hence may be beneficial. It may, however, weaken the body, and frequent hot baths should therefore be taken only on suitable medical advice. 99.-I. IV/ht is the philosophy of the " chlange of voice" ill a boy? Up to the age of fourteen or fifteen, there is little or no difference in point of size between the larynx of a boy and that of a girl; but subsequently the former grows proportionately larger, so that at last, in the adult male, the vibrating parts or vocal cords are necessarily longer than in the female. They are ilso undoubtedly thicker, perhaps even coarser in structure. From all these circumstances the adult male voice is stronger, louder, and of lower pitch than the weaker and higher vocal range accomplished by the female larynx. The cause of the difference in quality of the voice, known as its timbre, is not well known; but it must undoubtedly be dependent on physical, that is to say, structural peculiarities in some part of the laryngeal apparatus. The production of the different notes within the compass of any one individual depends upon alterations in the length and state of tension of the vocal cords, and or their degree of proximity or separation from one another

Page  161 IN HUMAN PHYSIOLOGY. I 6 The higher notes require the vocal cords to be comparatively shorter, tighter, and more closely approximated together; whilst the lower notes demand opposite conditions. A high note, furthermore, implies greater rapidity in the movement of the air through the glottis; but the quantity of air passing is larger during the production of a low note. The volume or loudness of the voice depends mainly on the combination of quantity of air with greater force of expulsion. Loudness, with clearness, also demands a peculiar resonance up in the nasal cavities and sinuses. Lastly, the unnatural or falsetto voice seems also to be produced by some tensive change effected in the upper part of the pharynx at the back of the nose: hence it is called by singers the head voice, in contradistinction to the ordinary, or chest voice. —-MARSHALL. 2. Why can we see our breath on a frosty mornzing? The vapor of the breath is condensed by the cold air. 3. When a law of hcalth and a law of fashion conjfict, which should we obey? It depends, of course, whether we prefer to be fashionable or to be healthy, to obey man or God. With too many people the former is of far greater importance, and in selecting an article of dress, few ask or think about the latter. The consequence is seen in the weakened frame, the prevalence of disease, and the shortened life. God's laws written in our bodies cannot be violated with impunity. 4. If we use a "bunk " bed, should we pack away the clothes when wefirst rise in the morninh? No. They should first be thoroughly aired.

Page  162 I62 ANSWERS TO PRACTICAL QUESTIONS 5. W~hy should a clothes-press be well ventilated? The clothes naturally contain the products of the insensible perspiration, which passing off, pollute the air of the closet. 6. Should the weight of our clothing hangfrom the waist or the shoulder? From the shoulder, so as to avoid the constriction of the compressible organs in the abdomen. 7. Describe the efects of living in an over-heated room. (I). The body becomes more sensitive to change, and the susceptibility to colds is greatly increased: (2) the dry, heated air abstracts the moisture from the skin, rendering it dry, hard, and incapable of performing its normal functions. 8. Wghat habits impair the power of the lungs? Above all others, those of a leaning posture, tightlacing, and ill-ventilation. 9. For fill, easy breathing in singing, should we use the diaphragm and lower ribs or the upper ribs alone? Nearly all the inspirations are effected by the movements of the diaphragm and the inferior ribs only.' From time to time a deeper and more complete inspiration causes the thorax to rise, not simultaneously, but successively at the base, then at the apex. In the first case the respiration is diaphragmnatic; when the lower and middle ribs are raised, it is termed lateral; and lastly, when the first rib and clavicle take part in the movement, it is

Page  163 IN HUMAN PHYSIOLOGY. 163 costo-superior or clavicular. In diaphragmatic respiration, as M. Mandl has observed, the larynx is immovable, the inspiration is easy, without effort, and permits exertion in singing or in gymnastics for a long time and without fatigue. On the contrary, persons who respire principally by the upper ribs are easily fatiguedl, and very soon out of breath. This is seen in women when. the corset compresses the base of the chest, and in singers who adopt, on erroneous principles, the bad habit of clavicular respiration. In this last method of inspiration the larynx is drawn down by the contraction of the external muscles, and its action becomes painful. The effort of the inspiratory muscles rapidly induces fatigue, and the inspiration, always incomplete, becomes also more frequent. Diaphragmatic respiration is practised by mountaineers, gymnasts, and skilful singers-a habit induced either by instinct, or a well-directed education.Wtonders of the HDman Body. I o. Wahy is it better to breathe throaugh the nose than tlhe mouth? The air passing through the nostrils becomes filtered of its coarse impurities, and the chill is taken off before it strikes against the tender, mucous surfaces of the larynx. I I. [hky shouMZd not a speaker talkZ while returnin~g home on a cold nigzht after a lectlure? The cold air will strike against the vocal apparatus when inflamed and peculiarly sensitive. I 2. What part of the boaty needs the loosest clothing? The abdomen; because of the delicate organs within, unprotected by a bony covering.

Page  164 164 ANSWERS TO PRACTICAL QUESTIONS 13. What part needs the warmest? The feet, because they are furthest from the center of heat and motion and most exposed to cold and wet: and the neck and shoulders, since here are located the delicate organs of voice and respiration. 14. Why is a " spare bed " generally unhealthy? Because it is apt to be damp and unventilated. I 5. Is there any good in sighing? (See Physiology, page 9I.) It probably brings up the "arrears " of respiration. I 6. Ought a hat to be thoroughly ventilated? How? Certainly, as the heated, foul air is injurious. A single hole at the top is quite insufficient for ventilation. Several openings should be made on the sides near the band. I 7. Why do the lungs ofpeople who live in cities become of a gray color. Probably because of the deposition of carbonaceous particles which penetrate the substance of the tissues. The coloring is permanent, like tattooing, where indiaink is pricked beneath the skin. i8. Hrow wouldyou convince a person that a bed-room should be aired? Take him from the fresh, pure, invigorating out-door atmosphere into the close, depressing air of the bed-room, when first vacated in the morning, and his sense of smell will satisfy him of the need of ventilation.

Page  165 IN HUMAN PHYSIOLOGY. 165 19. What persons are most liable to scrofula, consumption, etc. (See Physiology, pages 94-98.) The victims of lung-starvation. 20. If a person is plunged under water, will any enter his lungs? No. The epiglottis will close involuntarily and prevent the admission of water. 2 I. Are bed-curtains healthy? No. They prevent the free circulation of the air and confine the waste products thrown off from the body. 22. Wh4y do some persons take "short breaths " after a meal? The distention of the stomach prevents the free action of the lungs. If such persons are not given to gluttony, the lungs are small or the other organs misplaced. 23. What is the special value of public parts? They bring fresh air, sunshine, green grass and trees within the reach'of all. They are truly the "breathingholes of a city." They are thus of incalculable benefit both on account of their sanitary and moral influence. 24 Can a person become used to bad air, so that it will not injure him? The system may come to endure without complaint, but never fails to inflict full punishment for the infraction of nature's laws.

Page  166 i66 A.NSW.ERS TO PRA C7'CAL QUESTIONS 25. Why do we gape when we are sleepy? (See Question I5.) The stretching of the nerves may perhaps serve to restore the equilibrium of the nervous influence, disturbed by the attention being fixed during the day upon some absorbing occupation. 26. as a ftshionable waist a model of art in sculpture or painting? The Venus of Milo, in the Louvre at Paris, is the beauideal of symmetry and beauty, yet the form indicates not a "wasp-waist," but the full, free, flowing outlines of nature. The sculptor and painter in copying the human figure can make no improvement on its Divine maker. 27. Shouldi a fire-lace be closed? (See Physiology, page Ioo.) No. It is a most efficient means of ventilation. 28. Why does embarrassment orfriht cause a stammerer to stutter still more painfulltf? Stuttering is mainly a nervous disorder, and hence any excitement tends to increase the impediment of the speech. 29. Ian the organs of voice, what parts have somewhat the same office as the case of a violin and the sounding-board of a piano? (See Pl/ilosop/zy, page I76.) The pharynx, the mouth, and the nasal passages all act by resonance to modify the voice.

Page  167 N U. MUAN. PIIYSIOLOG F. I67 I 29. —I. Why does a dry, cold atmosphere favorably affect caarrh? It tends to diminish inflammation in the mucous membrane lining the nose and nasal passages. 2. Why shoutld we putt on extra covering when we lie down to sleep? The respiration and the circulation are then less active. The fire in our corporeal stoves being low, we need exti-a covering to preserve the warmth of the body. 3. Is it well to throw off oulr coats or shazwls whenl we come in heatedfrom a lonzg walk? No. We rather need to put on extra clothing at such times to keep the body from cooling too rapidly. The best hygienic teachers commend the throwing of a shawl about the shoulders whenever we sit down to rest after fatiguing labor. 4. Why are close-fitting collars or neck-ties injurious? They impede both respiration and circulation. 5. WlZhich side of the heart is the more iable to liftam. zealion? The left; since that contains the red blood just oxygen ated in the lungs. 6. What gives the toper his red nose? (See Physiology, pages I25 and I73.) The congested state of the capillaries.

Page  168 68 A.NSWERS TO PRACTICAL QUESTIONS 7. Why does not the arm die whene the surgeon ties the prindcpal artery leading to it? The anastomoses of the arteries enable a collateral circulation to be established, whereby blood is supplied to the arm. 8. When a fowl is angry, why does its comb redden? Because an extra quantity of blood is thrown into that part of the body. 9. Why does a fat man endure cold better than a lean one? Fat is a good non-conductor of heat, and helps to preserve the uniform temperature of the body. Io. Why does one become thin duringfZ a lonZg sickness? By absorption, the fat of the body is taken up and used to supply the wants of the system. The old flesh being renewed with new, vigorous material, after such a wasting sickness, a person often has better health than previous to it. i i. What would tyou do f you should come home " wet to the skin?" One should (I) go into a warm room; (2) remove all wet garments; (3) if chilled, take a hot, full- or foot-bath, and by gentle friction restore the circulation; (4) put on dry clothing. 1 2. When the cold air strikes th fjace, why does it first blanch and then flush?

Page  169 IN HUMAN PHYSIOLOGY. 169 The muscles and blood-vessels of the surface are contracted by the cold, and the blood is driven back toward the heart. yThe reaction which ensues forces the blood again toward the skin, and this flushes with the incoming tide. The face is therefore first whitened and then reddened. 1 3. What mus' be J'he ejct of tight lacing ulpon the circulation of the bloodz It must, by contracting the blood-vessels, impede the flow of the blood, and by decreasing the quantity furnished the various organs, injure their action. Thus, finally, it will impair the quality of the blood. I 4. Do you khozot fhe position of the large arteries inz the limbs, so that in case of accizent you couldr stop the flow of blood? These can be located by examining the cut in Physiology, page 104, or any good chart of the circulation. 15. WIhen a person is said to be "good-hearted," is it a physical truth Z The expressions, large-hearted, good-hearted, etc., are remains of the old idea that the affections are located in the heart rather than in the brain-the seat of the mind and all its attributes. i6. Why does a hotfoot-bath often relieve the headache? (See Physiology, pages 127-8,) It withdraws blood from the head, and so relieves the congested state of that organ.

Page  170 170 ANSWERS TO PRACTICAL QUESTIONS I 7. Why does the body of a drowned or strangled person tlrn blue? rThe blood is not purified in the lungs, and so blue or venous blood fills the vessels. I 8. WYlhat are the little " kernels " in the arm-pits? (See Physiology, page I23.) They are the lymphatic glands which sometimes become swollen. Ig. When we are excessively warm, would the thermometer show any rise of temperature in the body? (See Physiology, page I i9, note.) Probably not. In health, the average temperature of the body does not vary more than 2~. 20. WVhat forces besides that of the heari aid in propelling the blood? (See Flint's Physiology-The Circulation; Cutler's A nolvtic A natorny, etc.. page i66, et seq.) The elasticity of the arteries and the veins, the force of capillary attraction in the capillaries, etc2 I. Why can the pulse befelt best in the wrist? It is, in general, a mere matter of convenience. We can feel it not only in the radial artery at the wrist, but in the carotid of the neck, the temporal of the forehead, the popliteal * in the'inner side of the knee, etc. * If the hollow of the knee of one leg be allowed to r-nt upon the knee of the other one, it may be remarked that the point of the susoended foot moves visibly up and down at each beat of the pulse.

Page  171 iNV HUMAN PIJ YSIOLOGY. 71 22. Whly are starving people exceedingly sensitive to any ar? The marrow of the bones is absorbed, and hence the shock of a jar is unbroken. The nervous system is also weakened by the general prostration., 23. Why will friction, an application qf horse-radish leaves, or a blister relieve internal congestion? They bring the blood to the surface of the body, and so relieve the internal organ.,24. Why are students very liable to coldnfeet? Because the tendency of the blood is toward the head to supply the waste in that part of the body. 25. Is the proverb that " blood is thicker than water" literally true? (See Draper's Humnan Physiology, page II2.) The specific gravity of the blood varies from I.050 to I.o59. 26. What is the effect upon the circulation of " holding the breath?" The blood is not oxygenated, the products of waste accumulate in the system, the circulation is impeded, the blood-vessels become distended and are liable to burst, while all the delicate organs, especially the brain, are oppressed by congestion. 27. Which side of the heart is the stronger? The left, which drives the blood to the extremities.

Page  172 17 2 A.STV.ERS TO PRACTICAL QUESTIONS 28. fHow is the heart itself nourished? The coronary arteries springing from the aorta just after its origin, carry blood to the muscular walls of the heart: the venous blood comes back through the coronary veins, and empties directly into the right auricle. 29. Does any venous blood reach the heart without com-:;ng through the ven? caves? (See Question 28.) I55. —I. How do clothing and shelter economize food? The force which would be converted into heat to preserve the temperature of the body, is saved. The food needed to supply this amount of force may be reserved or changed into flesh, or into other forms of force. 2. Is it well to take a long walk before breakfast? (See Physiology, page 53.) A vigorous person in good health and in a healthy region may do so, but one in ill health, or a malarious district, needs to be braced with food before taking any except very light exercise. 3. Why is warm food easier to digest than cold? Heat favors the chemical change whereby the food is prepared for assimilation. 4. Why is salt beef less nutritious than fresh? (See Physiology, page 155, note.) The salts and juices of the meat are extracted by the brine.

Page  173 I.y HU-MAN PHYSIOLOGY. 17 3 5. What should be the food of a manl recovering from a fever? It should be that which is nutritious, easily digested, and not over-stimulating. Beef-tea or essence* is generally commended. As soon as the patient will bear it, beefsteak, tender, broiled, and not over-done, is most beneficial. 6. Is a cuzp of black coffee a healthy close to a hearty dinner? The tannic acid contained in tea and coffee (see Chemistry, pp. 211, 2I5) is neutralized by the milk generally used with these beverages. In cafi noir, black or clear coffee, the tannic acid acts unfavorably on the mucous membrane lining the stomach. Besides, the coffee, like a dessert, is superfluous, the appetite being already satisfied. It therefore, both actively and negatively, tends to delay the digestion of the meal. The glass of wine sometimes taken to aid digestion merely deadens the sensibility of the stomach, so that the food is hurried, half-digested, out into the intestines.t 7. Should ice-water be used at a meal? Only a person in robust health can endure the shock * Dr. Martindale gives the following recipe for making this essence: Cut a quantity of lean beef into small pieces, put it into a strong bottle, without water, cork it loosely so that the steam can escape, and immerse the bottle to its neck in a vessel of cold water. Place on the fire and boil for two hours; then pour off the essence. t Mix some bread and meat with gastric juice; place them in a phial, and keep that phial in a sand-bath at the slow heat of 98 degrees, occasionally shaking briskly the contents to imitate tiie motion of the stomach; you will find, after six or eight hours. the whole contents blended into one pultaceous mass. If to another phial of food and gastric juice, treated in the same way, you add a glass of pale ale or a quantity of alcohol, at the end of seven or eight hours, or even some days, the food is scarcely acted upon at all.

Page  174 174 ANSWERS TO PRACTICAL QUESTIONS of drinking ice-water at a meal. Indeed, drinking of icewater under any circumstances is dangerous and hurtful. If used at all, it should be carefully and slowly sifped, a little at a time. 8. /ihy is strong tea or coffee injurious? The tannic acid acts unfavorably on the coatings of the stomach.* The nervous system is over-stimulated, and, when the reaction occurs, becomes correspondingly depressed and weakened. The constant decay of the body, so essential to its highest activity, is greatly retarded. Wakefulness is often induced, and tlus the organs are deprived of that rest which is absolutely essential. 9. Shouldfood or drink be taken hot? The pepsine of the gastric juice, in order to produce its effect, must have a moderately warm temperature, neither too hot nor too cold. The gastric juice will not act upon the food when near the freezing point of water, neither will it have any effect if raised to the neighborhood of a boiling temperature. It must be intermediate between the two; and its greatest activity is about Ioo degrees Fahrenheit, which is exactly the temperature of the interior of the living stomach.-DALToN's Physiology, p. 103. I o. Arefruit-cakes, rich pastry, and Puddin,,s healtfiu? (See BLACK's Ten Lazows of Health, p. 83, et seq.) They are too concentrated. They are not easily penetrated by the juices of the system, and hence are not quickly digested. They stimulate the appetite, and so * Tea contains from x4 to i6 per cent. of this astringent substance, and coffee not over 6 per cent.-YOUMANS.

Page  175 IV HUMAN PHYSIOLOGY. I 7 5 lead to gluttony. They supply the system with an overabundance of nutrition, for which the blood has no use, and so lead to biliousness and other diseases of the blood and cligestive organs. i t. Why are warm biscuit and bread hard of digestion They form a pasty mass, which the juices of the digestive organs penetrate very slowly. 12. Should anly stimulants be used in youth? No. The system is then vigorous, and all its functions promptly performed. If stimulants are ever used, it should be when the body needs forcing, as when recovering from disease, or languid with the decay of the natural powers in old age. 13. JVhy should bread be made A.pongy? (See Question II.) 14. TVhich should remain longer in the mouth, bread or meat? Bread, since the pepsin is essential to the conversion of starch into sugar? I5. Wh/y should cold water be used ih making soup, and hot in boiling meat? In the former case, we desire to extract the juices of the meat; in the latter, to retain this by quickly coagulating the albumen on the surface of the meat. i6. JVame the injflrious effects of over-eating. (See P/zys.o?70gy, page 151.) 17. Why, do not buckwzaheat cakes, with syrup and butater,.ts/e as well in X7Yuy as in Yanuary? In the winter, the system craves highly carbonaceous

Page  176 170 AYSWEERS TO PRA CTCAL QUESTIONS food; in the summer, it relishes cooling, acid drinks, and an unstimulating diet. 18. Why is a late suzppr injuriozs? The system is wearied with the clay's labor, and the stomach is unfitted to undertake the task of digesting a meal as much as the body is to begin a new day's task unrefreshed by sleep.' * " Being allowed for once to speak, I would take the opportunity to set forth how ill, in all respects, we stomachs are used. From the beginning to the end of life, we are either afflicted with too little or too much, or not the right thing, or things which are horribly disagreeable to us; or are otherwise thrown into a state of discomfort. I do not think it proper to take up a moment in bewailing the Too Little, for that is an evil which is never the fault of our masters, but rather the result of their misfortunes; and, indeed, we would sometimes feel as if it were a relief from other kinds of distress it we were put upon short allowance for a few days. But we conceive ourselves to have matter for serious complaint against mankind in respect of the Too Much, which is always an evil voluntarily incurred. What a pity that in the progress of discovery we cannot establish some means of a good understanding between mankind and their stomachs; for really the effects of their non-acquaintance are most vexatious. Human beings seem to be, to this day, completely in the dark as to what they ought to take at any time, and err almost as often from ignorance as from depraved appetite. Sometimes, for instance, when we of the inner house are rather weakly, they will send us down an article that we could deal with when only in a state of robust health. Sometimes, when we would require a mild vegetable diet, they will persist in the most stimulating and irritating of viands. "What sputtering we poor stomachs have when mistakes of that kind occur! What remarks we indulge in regarding our masters! "W hat's this, now?" will one of us say; " ah, detestable stuff! What a ridiculous fellow that man is! Will he never learn? Just the very thing I did not want. If he would only send down a bowl of fresh leek soup or barley broth, there would be some sense in it:" and so on. If we had only been allowed to give the slightest hint now and then, like faithful servants as we are, from how many miseries might we have saved both our masters and ourselves! " I have been a stomach for about forty years, during all of which time I have endeavored to do my duty faithfully and punctually. MSy master, horever, is so reckless, that I would defy any stomach of ordinary ability and capacity to get along pleasantly with him. The fact is, like almost all other men, he, in his eating and drinking, considers his own pleasure only, and never once reflects on the poor wretch who has to be responsible for the disposal of everything down stairs. Scarcely on any day does he fail to exceed the strict

Page  177 IV HUXll-/AX PHYIISI OLOGY. 177 I9. IThalt makes a mnan " bilious?" (See Hall's Health by Gocd Livintg, p. III, et seq.) The liver strains the bile out of the blood. This waste matter is not withdrawn when the liver is inactive, and hence the face and eyes become yellow —the cclor of bile, and the functions all become torpid. rule of temperance; nay, there is scarcely a single meal which is altogether what it ought to be. My life is therefore one of continual worry and fret; I am never allowed to rest from morning till night, and have not a moment in the four-and-twenty hours that I can safely call my own. 1Iy greatest trial takes place in the evening, when my master has dined. If you only saw what a mess this said dinner is-soup, fish, flesh, fowl, ham, rice, potatoes, tablebeer, sherry, tart, pudding, cheese, bread, all mixed up together. I am accustomed to the thing, so don't feel much shocked; but my master himself would faint at the sight. The slave of duty in all circumstances, I call in my friend Gastric Juice, and we set to work with as much good-will as if we had the most agreeable task in the world before us. But, unluckily, my master has an impression very firmly fixed upon him that our business is apt to be vastly promoted by an hour or two's drinking; so he continues at table among his friends, and pours down some bottle and a half of wine, perhaps of various sorts, that bothers Gastric Juice and me to a degree which no one can have any idea of. In fact, this said wine undoes our work almost as fast as we do it, besides blinding and poisoning us poor servants into the bargain. On many occasions I am obliged to give up my task for the time altogether; for while this vinous shower is going on I would defy the most vigorous stomach in the world to make any advance in its business worth speaking of. Sometimes things go to a much greater length than at others; and my mastcs will paralyze us in this manner for hours, not always, indeed, with wine, but occasionally with punch, one ingredient of which —the lemon-is particularly odious to us. All this time I can hear him jollifying away at a great rate, drinking healths to his neighbors, and ruining his own. "I am a lover of early hours, as are my brethren generally. To this we are very much disposed by the extremely hard work which we usually undergo during the day. About ten o'clock, having, perhaps, at that time got all our labors past, and feeling fatigued and exhausted, we like to sink into repose, not to be again disturbed till next morning at breakfast-time. Well, how it may be with others I can't tell; but so it is, that my master never scruples to rouse me up from my first sleep, and give me charge of an entirely new meal, after I thought I was to be my own master for the night. This is a hardship of the most grievous kind. Only imagine me, after having gathered in my coal, drawn on my night-cap, and gone to bed, called up and made to take charge of a quantity of stuff which I know I shall not be able to get off my hands all night! Such, O mankind, are the woes which befall our tribe is 8

Page  178 173 ANSWERS TO PRACTICAL QUESTIO.NS 20. What is the best remedy? Diet to give the organs rest, and active exercise to arouse the secretions and the circulation. 2 1. WhaZt is the practical use of hunger? To prompt us to furnish the body with sufficient food. 22. Haocw can jugglZcrs drink wzhez standing on their heads? Because water does not fall into the stomach by its own weight, but is conveyed thither from the mouth by the contraction of tile muscular bands of the cesophagus. consequence of your occasionally yielding to the temptations of " a little supper." I see turkey and tongue in grief and terror. Macaroni fills me with frantic alarm. I behold jelly and trifle follow in mute despair. 0 that I had the power of standing beside my master, and holding his unreflecting hand, as he thus prepares for my torment and his own! Here, too, the old mistaken notion about the need of something stimulating besets him, and down comes a deluge of hot spirits and water, that causes me to writhe in agony, and almost sends Gastric Juice off in the sulks to bed. Nor does the infatuated man rest here. If the company be agreeable, one glass follows another, while I am kept standing, as it were, with my sleeves tucked up, ready to begin, but unable to perform a single stroke of work. " I feel that the strength which I ought to have at my present time of life has passed from me. I am getting weak, and peevish, and evil-disposed. A comparatively small trouble sits long and sore upon me. Bile, from being my servant, is becoming my master; and a bad one he makes, as all good servants ever do. I see nothing before me but a premature old age of pains and groans, and gripes and grumblings, which will, of course, not last over long; and thus I shall be cut short in my career, when I should have been enjoying life's tranquil evening, without a single vexation of any kind to trouble me. Were I of a revengeful temper, it might be a consolation to think that my master-the cause of all my woes-must suffer and sink with me; but I don't see how this can mend my own case; and, from old acquaintance, I am rather disposed to feel sorry for him, as one who has been more ignorant and imprudent than ill-meaning. In the same spirit let me hope that this true and unaffected account of my case may prove a warning to other persons how they use their stomachs; for, they may depend upon it, whatever injustice they do to us, in their days of health and pride, will be repaid to thzemselves in the lopg-run-our friend Madame Nature being a remarkably accurate accountant, who makes no allowance for ignorance or mistakes."-CHAMBERS' [Mentoir of a Stomach.

Page  179 N HUMC1AN- ETYLrSIOL 0 Y. I 7) 23. Why do zve relish butter on bread? Butter supplies the carbonaceous element in which bread is lacking. 24. Is cheoizg tobacco more ilj/uriolls than smokin-? (See Cutler's P'hysiology, pages 242-4.) It is not only more filthy, but also more detrimental to the health, as thereby a greater proportion of the poisonons alkaloids of the tobacco is carried into the system. Among the too frequent evil effects of this powerful narcotic are an impaired nutrition, a poisoned circulation, a stupefied mind and conscience-evils which end not with the parent but are transmitted many-fold to the child. 2 5. TYliy should ham andsa sausae be th row lghOl, ooked?'Flhe trichina, which frequents pork, is only destroyed at a high temperature. 26. WVhy3 do we wish blutler o fish, egq's 7with tapioca, oii on salad, and milz with rice.? To supply the elements of food laclking in the composition of fish, tapioca, etc. 27. Explain the relationz offood o exercise. Their relation is exceedingly intimate. If we eat much we should take more exercise, and if, on the contrary, we labor more, we desire additional food. Violent exercise, directly after a hlearty meal, is injurious; but a gentle, quiet half-hour's saunter will greatly benefit the cligestion. 28. Hfow do you exaxlain the diffe;-ic in t/e manner of ea!ing between carnivorous and herbizvorous animals? Meat requires less saliva to aid in its digestion, and

Page  180 180 ANSWERS TO PRACTICAL QUESTIONS henc it is mainly digested in the stomach; while vegetable food needs to be thoroughly masticated and incorporated with the salivary mucus. 29. Why is a child's face pltmp and an old man's wrinkledi? In the child the processes of nutrition are more active thA:n those of waste. The reverse is the case in old age. 30. Show how life dLenzds on repair and waste. (See CGeitz'stry, page 34, et seq.; and Physiology, page I20.) 3I. What is the diiference between the decay of the teeti and the constant decay of the body? The particles of the teeth lost by decay are not renewed, while in the body they are replaced as fast as worn out. - 32. Shotuld bisZcuit and cake coZtai;zing _yelZow spots of soda be eaten? Certainly not. The alkali neutralizes the acids of the alimentary juices, and thus impairs their functions, while it corrodes and irritates the delicate mucous lining of the digestive organs. 33. T zell ow the body is eomnpsed of orgfans, organs are madrte zp of tissues, and tissues of cells. (See Physiology, page 154, note.) 34. 7Why do we not need to drink three pints of water pe;r cday? (See Physio,'ogy, page 133.) The amount of water one needs depends upon the

Page  181 IN HUBMAN PHYSIOLOGa. S 8 character of his food, the nature of his labor, and the activity of the three eliminating organs-the skin, the kidneys, and the lungs. One perspiring freely, or eating dry food, needs more drink than one whose skin is inactive, or whose food consists, in part, of soups or watery vegetables. 35. Why, during a pestilence, are those who use liquors as a beverage the first, and often the only victims? The nervous system becomes impaired, the digestion weakened, and the blood impoverished: hence, the functions of the body being disturbed, its ability to resist disease is greatly impaired. It is said that the alcohol hardens the albuminous matter of the brain and the membranous lining of the lungs, and hence clogs the action of these organs. 36. What two secretions seem to have the same general use? The saliva and the pancreatic juice both change starch into sugar. They have other important uses, however, in the process of digestion, The former softens the food and aids in the work of mastication, while the latter emulsifies the fats. 37. fl2ow may the digestive organs be strengthened? The digestive organs, like the other organs, are strengthened by judicious labor. The stomach is a muscle, and like muscle, generally grows strong by use and weak by disuse. The same laws should govern one in his daily exercise of every organ-brain, hand, and stomach.

Page  182 182 ANSWERS TO PRACTICAL QUESTIONS I75. —I. Why is the pain of inctiepnt zip-disense fl-c uently felt in t/ie knee? The senisation of pain is located by the mintd, at the part of the body where the injured nerve takes it rise. 2. WEhy does a crill reueztire more sleep than an age:t person? The processes of nutrition are going on rapidly, and, in youth, much rest is required to repair the losses of each day; in age, waste predominates, andl the repairs made are of a temporary character. The building is soon to be torn clown, and little effort is taken to beautify or strengthen that which is to be used for so short a time. 3. W:hen y'ozu put your finger iln the palm of a sleeping ch ild why wUill h e grasp it? The unconscious action of the near nervous centers produces a contraction of the muscles. 4. flow may we strengthien the brain? By judicious, habitual, but not exhaustive employment. The life of the brain is in change. Monotony is stagna tion, and stagnation is decay. 5. What is the object ofpain? Pain is monitory in its character. It guards against danger and warns us of the presence of disease, i. e., the want of ease. Were it not for this, we should lose the use of the more delicate organs. A child might gaze at the sun until its eyesight was ruined. The author knew of a man who had lost the sense of feeling in one let

Page  183 IN HUMAN PHYSIOLOG Y. I83 because of the sensory nerve being severed. He was constantly bruising and burning that limb until he ruined it entirely. 6. Why will a blow on the stomach sometimes stop the heart? By sympathy. The pneumogastric or tenth pair of nerves supply the stomach and the heart. 7. flow long will it take for the brain of a man six fet higzh to receive news of an iz/ury to his foot, and to reply? The nervous force has been estimated to travel at the rate of oo feet per second, although authorities vary much. Taking this figure, it would require about oneeighth of a second.* 8. fIow can we grow, beaufifd? If one is penurious, selfish, or hard-hearted, his face will betray the fact to every passer by. Purity of thought and nobleness of soul, the simple habit of cherishing high and generous purposes, refine and spiritualize the countenance, making, at last, the homeliest features to glow with a beauty that will be a true "joy forever." 9. Why do intestinal zworms ever affec-t a childs szigzt?. Through the action of the sympathetic system of nerves. IO. Is there any indication of character in physiognomy? (See Question 8; also Physiology, page I71.) * A bare-footed boy steps on a thorn. If he had to wait for news of the injury to be sent to his brain, and an order to be telegraphed back to remove the foot, much time would be lost. As it is, with the first prick, the nearer nerve-centers act and order the foot off almost before the brain has heard of the accident.

Page  184 184 A.-SWERS TO PRACTICAL QUESTIONS I I. henz one's finger is burned, where is Mte ache? All pain is in the brain. It is located, however, by the mind, at the place of the injury. 12. Is a Iarlor generally a healthy room? No. It is generally ill-ventilated, and, to preserve the furniture, kept dark, and hence damp. I3. /liy cal7 ani idle scholar read his lesson and at f/e same tine coulnt tice marbles int his pocket? The duality of the braiin may, perhaps, account for this. (See Ph'ysiolcgy, page 162, note) I4. Izn amputating a limb, what part, when divided, will cause the keenest pain? WVhen a surgical operation is performed, the most painful part of it is the incision through the skin; the muscles, cartilage, and bone being comparatively without sensation. Hence, if we could benumb the surface, certain of the lesser operations might be undergone without great inconvenience. This is, in fact, very successfully accomplished by means of the cold produced by throwing a spray of ether, or of some other rapidly evaporating liquid, upon the part to be cut. I 5. Ihat is the effect of bad air on nervous people? The nerves connect all the organs of the body. They are therefore especially sensitive to a derangement in the function of any organ. Bad air causes impure blood, deranged nutrition, and hence a disturbance of the entire economy.

Page  185 IN HUMAN PHYSIOLOGY. 185 I6. Is there any truth in the proverb that "he who sleeps, dines?" The proverb expresses the fact that the nourishment of the brain and other parts goes on actively during sleep, they being controlled by the sympathetic nerves, 17, WZhat does a high, forehZad indicate? It suggests a large brain and a high intellectual power. I8. How does indi,estion frequently cause a headache? Through the action of the sympathetic system. I9. Zhat is the cause of thefoot's being "asleep?" (See Physiology, page I76, note.) 20. When an injury to the nose has been remedied by transplanting skin from the forehead, why is a touch to the former felt in the latter? The mind refers the sensation to the place where the nerve naturally had its origin-i. e., the part over which its tiny fibres were originally distributed. 2 I. Are closely-curtained windows healthy? No. They keep out the sun and the fresh air. 22. Why, in falling from a height, do the limbs instinctively take a position to defend the imzporlant olgans? The reflex action of the spinal cord moves the limbs i lto a position of defence, the brain having no time to act.

Page  186 i86 ANSWERS TO PRACTICAL QUESTIONS 23. What causes the pylorus to open and close at the right time? The reflex action of the nerves which preside over that organ. In a similar way, a tickling in the throat excites coughing. 24. WZhy is pleasant exercise most beneficial? A chief condition of keeping the brain healthy is to keep the unconscious nervous functions in full vigor, and in natural alternations of activity and repose. Thus it is that (besides its effect in increasing the breathing and the general vigor of the vital processes) muscular exercise has so manifest a beneficial influence on a depressed or irritable state of mind. The bodily movement, by affording an outlet to the activity of the spinal cord, withdraws a source of irritation from the brain; or it may relieve excitement of that organ by carrying off its energy into a safe channel.-HINTON. 25. Why does grief cause one to lose his appetite? Through the action of the sympathetic system. 26. Whzy should weve never study directiSy afer dinner? The blood then sets toward the stomach, and the whole strength of the system is needed to properly digest the food. 27. WHhat producs the peristaltic movement rf the stomach? The presence of the food which, through the sympathetic system, acting involuntarily, sets in motion the complicated apparatus of digestion.

Page  187 IXN HUMAN PHYSIOLOGY. 187 28. Why is a healthy child so restless and full of mischief? Nature prompts it to exercise all the muscles in its body in order to their proper development. 29. Why is a slizht blow on the back of a rabbit's neck fatal? The medulla oblongata is not defended with thick muscles as in man. 30. Why can one walk and carry on a conversation at the same time? (See Question 13, page 176.) 3 I. What are the dangers of over-study? (See Hinton's Health and its Conditions, page I93, et seq., and Cutler's A nalytical A natomy, page 248.) ~ Exhaustive mental labor overstrains the delicate nervecells of the brain, and the condition of the blood-vessels of the entire body, especially of the vital organs, is regulated, moment by moment, by its changing moods. Even the supply furnished the brain is subject to the same influence. Hence results deranged nutrition, impaired circulation, and weakened brain and body. Whenever we consume vital energy faster than it can be replaced, we encroach upon the capital, and thus cause an irreparable injury. 32. What is the influence of idleness zpon the brain? If we would have healthy bodies we must *have active brains, that the streams of force may flow into every or;rganl from a full, fresh, energizing source. "The perfect

Page  188 i88 ANStWERS TO P.RACTICAL QUESTIO,5 health of a man is not that of an ox or a horse." The proper exercise of the- brain is an essential element of real life. 33. State the close relation which exists betwezen physical and mental health and disease. "A partial cultivation of the mental faculties is incompatible not only with the highest order of thought, but with the highest degree of health and efficiency. The result of professional experience fairly warrants the statement that in persons of a high grade of intellectual endowment and cultivation, other things being equal, the force of moral shocks is more easily broken, tedious and harassing exercise of particular powers more safely borne, than in those of an opposite description, and dis. ease, when it comes, is more readily controlled and cured. The kind of management which consists in awakening a new order of emotion, in exciting new trains of thought, in turning attention to some new matter of study or speculation, must be far less efficacious, because less applicable, in one whose mind has always had a limited range than in one of larger resources and capacities. In endeavoring to restore the disordered mind of the clodhopper who has scarcely an idea beyond that of his manual employment, the great difficulty is to find some available point from which conservative influences may be projected. He dislikes reading, he never learned amusements, he feels no interest in the affairs of the world; and unless the circumstances allow of some kind of bodily labor, his mind must remain in a state of solitary isolatiqn, brooding over its morbid fancies, and utterly incompetent to initiate any recuperativet move ment."-Dr. RAY.

Page  189 IN HUMIAN PIYSIOLOGY 1 3) 34. In what consists the value of the Jower of habit? It saves the " wear and tear" of our principles. We can perform an act a few times, though with difficulty, and then ever after it becomes a habit. We resist evil once, and thenceforth it is easier. We can become accustomed to do good, so that the chances will all be in favor of our well-being in any emergency. By as much as the power of habit is thus pregnant with good, by so much is it susceptible of terrible evil. 35. How many pairs of nerves szpPly the eye? (See Physiology, page I67.) Three; the motores oculi. 36. Describe the reflex actions in readint aloud. The body is kept erect, the hand holds the book, the eyes are directed to the page, the vocal organs pronounce the words, the features express the sentiments, and the other hand makes corresponding gestures-yet all the time the mind is intent only upon the thought conveyed. 37. Under what circumstances does paralysis occur? When the nerve leading to any part of the body is injured or fails to keep up communications between that portion and the mind. 38. If the eyelids of a profound sleeper were raised, and a candle b ougght near, would the iris contract? It would, by reflex action.

Page  190 Igo90 ANSWERS TO PRAlCTICAL QUESTIONS 39. How does one coZgh in his sleep.? By the reflex action of the near nervous centers. A tickling in the throat, or some other cause, acts as the stimulus to excite their action. 40. Give illustrations of the unconscious action of the brain. (See P'hysiology, page 225.) 9 4. —I. Why does a laundress test the temperature of her flat-iron by holding it near her cheek? The sense of warmth is very keen in the palms of the hand, the cheek, etc. This sensation is much less delicate in the lips and the back of the hand. 2. When we are cold, why do we spread the palms of our hands before /hefire? (See Question I.) 3. What is meant by a "fJurred tongue " In health, the tongue has hardly a discernible lining, but in disease, the epithelium, or scarf skin, accumulates, and gives a white, coated appearance. This covering is likely to be of a yellowish shade when the liver is disturbed, and brown or dark in blood diseases. One's occupation often colors it. Thus it is said the tongue of a tea-taster has a curious orange-tint. 4. Why has sand or sulphur no taste? They are insoluble in the saliva. 5. What was the origin of the word palatable The mistaken notion that the palate, or roof of the mouth, is the seat of the taste.

Page  191 iN HUMAN PHYSIOLOGY. 19 I 6. Why does a cold in the head injure the favor of our coffe? Because the sense of taste is so dependent on that of smell. 7. Name some so-called/tavors which are really sensations (f touch. Taste is not a simple sense. Certain other sensations, as those of touch, temperature, smell, and pain, are blended and confused with it; and certain so-called tastes are really sensations of another kind. Thus an astringent taste, like that of alum, is more properly an astringent feeling, and results from an impression made upon the nerves of touch, that ramify in the tongue. In like manner, the qualities known as smooth, oily, watery, and mealy tastes, are dependent upon these same nerves of touch. A burnirg or pungent taste is a sensation of pain, having its seat in the tongue and throat. A cooling taste, like that of mint, pertains to that modification of touch called the sense of temperature. — HUTCHISON'S PIhysiolofgy, p. I 9o-I. 8. What is the ob/ect of the hairs in the nostrils? They prevent the entrance of dust and other impurities. They are also exceedingly delicate in all sensations of touch. 9. What use does the nose subserve in the process of respiration? It warns us of noxious gases, sirts out impurities, and tempers the air before it enters the delicate respiratory organs.

Page  192 T92 ANSWERS TO PRACTICAL QUESTIONS Io. Why do we sometimes hold the nose when we take unpleasant medicine? (See Question 6.) i i. WU7iy is the nose placed over the mouth? As a sentinel at the gateway to the stomach and the lungs. I 2. Describe how the hand is adapted to be the instrument of touch. Its isolation at the extremity of the movable arm, the mobility of its different parts, and the delicacy of the sensation at the tips of the fingers, exquisitely adapt the hand to be the instrument of touch. I3. Besides being the organ oef taste, what use does the tongue subserve? It aids in the mastication of the food And in speech. I 4. Why is not the act of tasting complete until we swallow? Because the organ of taste is located especially in the back part of the tongue and the soft palate. I5. Why do all things have the sameflavor when one's tongue is "furred " by fever They are really tasteless. The tongue is then dry, and there is no saliva to dissolve and carry particles of the food into the cells covering the nerves of taste. i6. Which sense is the more usful —hearing or szig-ht? (See Wonders of the Human Body, page 201.) "The sight speaks more directly to the intelligence; it

Page  193 IN HUIAN EITYSIOL OG Y. 193 enlarges the field of thought, it gives birth to precise notions of light, of form, of extent; and it permits the communication of thought by conventional signs. Hearing is a necessary condition of articulate language; without it man lives alone, affection and confidence lose their most precious forms of expression, and friendship cannot exist. Auditory sensations act upon the nervous system with more force than visual sensations. We are carried away by rhythm, or it adapts itself to our ideas and our passions; music plunges us into an ideal world, and holds us by an indefinable charm; in a word, if sight speaks more especially to the intellect, hearing addresses itself to the affections. Sight is certainly more necessary to man than hearing, but still the blind are generally gay and communicative, while the deaf seem inclined to melancholy. As to the relative influence of these two senses on the development of the intellect, we know that the education of the deaf is slow, but may be complete, while that of the blind is, on the contrary, rather rapid, but is almost always very limited; many ideas cannot be acquired by them, and, as has been remarked by M. Longet, their minds rarely attai, maturity." i7. WUhich coat is the white of the eye? The sclerotic. i 8. What makes the' dif feience in the color of eyes? The varying shade of the pigment deposited in the iris of the eye. I9. Why do wre snzff the air whenr we wish to obtain a distinct smell? As muscular actions are called into play to aid the sense of taste, as in smacking the tongue and lips, so the

Page  194 194 ANSWERS TO PRACTICAL QUESTIONS act of" sniffing," which is a mixed respiratory and nm.sal muscular effort, is used to bring odorous substances more surely and extensively into contact with the upper and proper olfactory region of the nose, besides causing a larger amount of them to pass over the mucous surface in a given time.-MARSHALL. 20. Why do red-hot iron and frozen mercury (-4o~) produce the same sensation? The sensation in both cases is that of pain, not.that of touch. 2 I. WP/hy can an elderly person drink tea wh ich to a child would be unbearably hot? The sensation of touch has become impaired, and is much less delicate. 22. Why does an old man hold his paper so far from his eyes? " Far sight" is common among elderly people, and is remedied by convex glasses. In old age the power of adjusting the crystalline lens is lost. 23. WouZld y3o rather be punished on the tips of ytur fingers than on the palm of your hand? The sense of touch is much keener in the tips of the fingers than in the palm of the hand. 24. What is the object of the eyebrows? Are the hairs straight? They serve to prevent the perspiration of the forehead from running down into the eye. They act, in a measure, with the eyelashes, also to screen the eye from the dust

Page  195 IN HUMiAN PHYSIOLOG Y. I 5 and glaring light. The hairs of the eyebrows overlap each other and are set obliquely outward. 25. Wtthat is the use of winking'? It serves to wash the eyeballs, and thus keep the "windows of the soul" clean. The necessity for winking is shown by the great effort required to restrain it even for a short time. First discomfort, then congestion of the mucous membrane, and then a profuse watering of the eye follow any attempt at stopping this necessary act. It is an obscure sense of discomfort, not usually noticed by the consciousness, that excites this movement, the objects of which are periodically to cleanse the exposed part of the eyeball, to moisten and lubricate it with the secretions from the neighboring glands, and probably in this way to aid in the preservation of the polish and translucency of the epithelial layer on the transparent portion of the globe. At the same time it carries towards the inner corner all foreign bodies, and directs the residual secretions towards the lachrymal ducts. Finally it allows a brief but periodical rest to the levator muscle of the upper evelid.-MARSHALL. 26. When you wink, do the eyelids touch at once along their whole length? Why? In winking, both lids move, but the upper one much the more extensively. Moreover, they do not come in contact all along their margins at the same instant of time, but meet first at the outer corner and then rapidly inwards as far as the lachrymal papillae on which the lachrymal ducts are situated. By this sweeping movement, all foreign bodies are carried to the lachrymal lake.-MAPSHALL.

Page  196 96 ANSWERS TO PRACTICAL QUESTIONS 27. How many rows of hairs are there in the eyebrows? The eyelashes, or cilia, consist of two, and opposite the middle of the eyelid, of three rows of finely-curved hairs -those of the upper lid being more numerous, thicker, and longer than those of the lower lid. "Those of the upper lid are curved upward, those of the lower lid are curved downward; and when the lids are brought near together, these two ranges of hairs stand like so many crossed sabres, or a kind of chevaux-de-frise, guarding the entrance to the eye."-DALToN'S Physiology, p. 330. 28. Do all nations have eyes of the same shape? No. Witness the almond-shaped eyes of the Chinese. "The greater or less extent of the opening of the lids makes the eye appear larger or smaller; the conformation of the palpebral muscles and the tarsal cartilages gives to the eye an elongated and languishing form as in the East, or round and bold as among the Occidentals; but the dimensions and form of the globe are the same in all countries and in all individuals."- Wonders of the Human Body. 29. Why does snuff-taking cause a fow of tears? Because of the action of the sympathetic system. 30. Why does a fall cause one to " see stars? " * Whenever a nerve is excited in any way, it gives rise to the sensation peculiar to the organ with which it com* "On the occasion of a remarkable trial in Germany, it was claimed by a person who had been severely assaulted on a very dark night, that the flashes of light caused by repeated blows upon the head enabled him to see with sufficient distinctness to recognize his assailant. But the evidence of scientific men entirely refuted this claim, by pronouncing that the eye, under the circumstances named, was incapacitated for vision."-HurcHsoSON.

Page  197 IN HUMAN PHYSIOLOGY. I97 municates. Thus, an electric shock sent through the eye gives rise to the appearance of a flash of light; and pressure on any part of the retina produces a luminous image, which lasts as long as the pressure, and is called aphosphene. If the point of the finger be pressed upon the outer side of the ball of the eye, a luminous imagewhich, in my own case, is dark in the centre, with a bright ring at the circumference (or, as Newton described it, like the "eye " in a peacock's tail)-is seen; and this image lasts as long as the pressure is continued.-HuxLEY. 3I. W/hy can we not see with the nose, or smell wit/ the eyes? Each set of nerves is adapted to transmit' to the brain a peculiar class of sensations alone. 32. /hat causes the roughness of a cat's tongue? The sharpness and strength of the papillae upon its tongue. This is a peculiarity of the lion tribe. 33. Is the cuticle essential to touch? Yes. If the cuticle be removed, as in case of a blister, contact with the exposed surface produces pain rather than a sense of touch. 34. Can one tickle himself? It is said not; but the author has found persons who averred that they could produce this sensation upon themselves. The sense, it is noticeable, is present only in those parts where that of touch is feeble. 35. Why does a bitter taste often produce vomiting? The 5th pair of nerves, which supplies the lip and sides

Page  198 I 98 ANSWERS TO PRA CTICAL QUESTIONS of the tongue, and perceives especially sweet and sour substances, ramifies over the face, and hence an acid will " pucker" the features; while the 9th pair, at the base of the tongue, which is sensitive to salt and bitter tastes, is distributed also to the throat, and is in sympathy with the internal organs, since it seems to be "a common nerve of feeling for the mucous membrane generally." 36. Is there any danger of looking "cross - eyed" for fun? The muscles used thus in sport may become permanently distorted. 3 7. Should school-room desks face a window? No. The light should be admitted so as to fall over the shoulder upon the book. Many school-rooms are arranged to accommodate the teacher only, while a blinding flood of light pours directly into the faces of the pupils. 38. Why do we look at a person to whom we are listening attentively? One sense instinctively aids another. 39. Do we really feel with ourfingers? No. All sensation is in the mind. 40. Is the eye a peifect sphere? No. The front projects somewhat, while, at the back, the optic nerve is attached like the stem to a fruit.

Page  199 1N HUMAN PHYSIOLOG. 199 4I. How often do we wink? Five or six times a minute. 42. Why is the interior of a telescope or microscope often painted black? To absorb the scattered rays of light which would confuse the vision. For the same reason, the posterior surface of the iris, the ciliary processes and the choroid are covered with a layer of dark pigment. 43. What is " the apple of the eye?" The pupil. 44. Whatform of glasses do old people reo uire? (See Question 22.) 45. Should we eve- z wash our ears with cold water? Rarely, if ever, lest we chill this sensitive organ. 46. What is the o!ject of the winding passages in the nose? To furnish additional surface on which to expand the olfactory nerve. 47. Can a smoker tell in the dark, whether or not his cigar is hhlted? Sight often seems to be essential to perfect what we call a sensation of taste. 48. U[ill a nerve re-unile after it has been cut? Nerve-fibre seems to re-unite as readily as muscle-fibre.

Page  200 200 AXNSWVERS TO PRACTICAL QUESTIONS. 49. Will the sight give us an idea of solidity. (See Physiology, page 196, note.) 50. Why can a skillfui surgeon determine the condition of the brain and other internal organs by examinining the interior of the eye? (See Physiology, page I96, note.) 51. Is there any truth in the idea that the image of the murderer can be seen in the eye of the dead victim? When the flame of a taper is held near, and a little on one side of, a person's eye, any one looking into the eye from a proper point of view will see three images of the flame, two upright and one inverted. One upright figtuire is reflected from the front of the cornea, which acts as a convex mirror. The second proceeds from the front of the crystalline lens, which has the same effect; while the inverted image proceeds firom the posterior face of the lens, which, being convex backwards, is, of course, concave forwards, and acts as a concave mirror.-HuxLEY. The images formed upon the retina are as fleeting as light itself, from the nature of the case, and disappear as soon as the object is removed.

Page  201 ANS WE RS TO THE PRACTICAL QUESTIONS AND PROBLEMS IN THE FOURTEEN WEEKS COURSE IN PHYSICS. MOTION AND FORCE. 37.-I-37. (See pp. I5-I9 of this Key for Answers to these Questions.) 38. If a Ioo horse-power engine can propel a steamer 5 miles per hour, will one of 200 horse-power double its speed? By no means. Resistance is proportional to v?. (See Physics, p. 26.) To double the velocity would require over 4oo horse-power. (See note, p. 27.) 39. Why is a bullet flattened if fired obliquely against thie surface of water? "Because the particles of the ball which strike the water are impeded in their course by the particles of water with which they come in contact, and are driven back upon those lying next to them, before the motion of the ball can be imparted to the water "-A. B. Watkins.

Page  202 2 02 AANSWERS TO PRACTICAL QUESTIONS 40. Why are ships becalmed at sea often floated by strong currents into dangerous localities without the knowledge of tMI crew? As there are no fixed objects with which to compare their motion, the officers are not sensible of any movement, and so are often drifted far out of their course. 4T. A man in a wagon holds a 5 o-lb. weight in his hand. Suddenly the wagon falls over a precipice. Will he, while dropping, bear the strain of the weight? No. While on solid ground, his hand resisted the tendency of the weight to fall toward the earth's centre of gravity; but all are now descending freely under the influence of gravity, and he no longer feels the pressure. 42. WVhy are we not sensible of the rapid motion of the earth? Because all the objects around us are moving in the same direction with the earth, and there is nothing at hand with which to compare. 43. 4 feather is dropped from a balloon which is immersed in and swept along by a swift current of air. Will the feather be blown away, or will it appear to a person in the balloon to drop directly down? It will seem to drop directly downward, as if in a dead calm. Its fall is vertical, however, only as regards the balloon, and not as regards the earth. (See Stewart's Physics, p. I8.) 44. Suppose a bomb-shell,flying through the air at the rate of 500 feet per second, explodes into two parts of equal weight, driving oxe-half forward in the same direction as

Page  203 INV.PHYSICS. 203 before, but with double its former velocity. What would become of the other half? One half will go forward with a; double velocity (= iooo feet per sec.), and the other half will be checked and will fall directly to the ground. (See Stewart's Physics, p. 37.) 45. Which would have the greater penetrating power, a small cannon-ball with a high velocity, or a large one with a low velocity? The former would penetrate, while the latter would crush an obstacle. 46. There is a story told of a man who erected a huge pair of bellows in the stern of his pleasure-boat, that he mzight always have a fair wind. On trial, the plan failed. In which direction should he have turned the bellows? (Sc^ Key, p. 20.) 47. If a man and a boy were riding in a wagon, and, on coming to the foot of a hill, the man should tgke zup the boy in his arms, would that help the horse? No change would be produced in the weight of the entire establishment drawn by the horse, as no readjustment of the load would modify the attraction of gravity which produces the weight. Also, action - reaction; so the man would press down on the wagon an amount equal to the weight of the boy. 43. Why does a bird, as it begins to fly, always, if possible, turn toward the wind? For the same reason that a boy, wishing to raise a kite, runs against the wind. The greater the velocity of the wind. within certain limits, the greater the lifting force. (See note, p. 32.)

Page  204 204 ANSWERS TO PRACTICAL QUESTIONS 49. If we whirl a pail of water swiftly around with our hands, why will the water tend to leave the centre of the pail? This is generally attributed to the action of the centrifugal force. More correctly, the inertia of the water, i.e., its tendency to continue to move in the straight line in which it is at each moment passing, overcomes the weak force of cohesion, and the molecules fly off from the centre of motion and collect against the outside of the pail. 50. Why will the foam collect at the hollow in the centre? The foam, being lighter than the water, has less momentum, and is forced back by the heavier particles. 51. If two cannon-balls, one wezghing 8 lbs. and the other 2 lbs., be fired with the same velocity, which will go the further? The former has much less surface in proportion to its weight and consequent momentum. It will therefore go much further against the resistance of the air. 52. Resolve the force of the wind which turns a common wind-mill, and show how one part acts to push the wheel agazinst its support, and one to turn it around. (See Arnott's Physics, p. 226.) The toy-mill shown in Fig. 14, p. 32, illustrates the principle perfectly. The vanes turn in a direction contrary to that in which they are inclined. Let GH, in Fig. Io0 p. 3i, represent the face of the vane, and the description in the text will then apply.

Page  205 IN PHYSICS. 205 53. Why is a gun firing blank cartridges more quickly heated than one firing balls? In the one case, the energy of the burning powder is changed to heat; in the other, largely to the motion of the ball. 54. When an animal is jumping or falling, can any exertion made in mid-air change the motion of its centre of gravity? The centre of gravity falls steadily I6.o8 feet (see p. 54), whatever other force may act on the body. (See Second Law of Motion.) 55-60. (See Answers under Questions I to 7, on pages 5 and 6 of this Key.) 6. Why is a " runninglump " longer than a " standing lump "? This is generally spoken of as an illustration of inertia. It is really an example under the first law of motion. The momentum of the person when running (m x v) is added to the force with which he finally springs from the ground for the jump. 62. Why, after the sails of a vessel are furled, does it still continue to move? and why, after the sails are spread, does it require some time to get it under full headway? This illustrates the tendency of matter to continue in its present state, whether of rest or of motion, i. e, its inertia. For the former part of the question, apply the first law of motion, and for the latter, the first paragraph on p. 28 of the Physics. If, on starting with a heavy load, the horses leap suddenly forward, they will break

Page  206 206 ANSWERS TO PRACTICAL QUESTIONS the harness; but, by a steady,' constantly-increased draught, they will overcome the inertia of the mass. 63. Whzy can a tallow candle befired through a board? Because it pierces the board so quickly that the particles have no time to yield. Its slight cohesion, multiplied by its velocity, is greater than the cohesion of the board. COHESION. 46.I-Io-. (See Answers to these Questions under Cohesion, pp. 6 and 7 of this Key.) i i. Why can glass be welded? Because, like iron, it becomes viscous before melting. ADHESION. I. —I-I7. (See Answers to these Questions under Adhesion, pp. 7 to 9 of this Key.) i8. Why does the water in Fig. 22 stand higher inside of the tube than next the glass on the outside? There is the influence of a larger surface of glass in proportion to the quantity of water to be lifted. I9. Why will clothes-lines tighten and sometimes break during a shower? The rope absorbs water and expands transversely. This shortens it with so much force as often to break it. The shrinking of new cloth when wet illustrates the same principle.

Page  207 LV PHYSICSS. 207 20. Show that the law of the diffusion of gases aids in preserving the purity of the atmosphere. (See New Chemzistry, p. 96.) Foul gases do not remain for any length of time in one place, but tend to spread through the adjacent atmosphere. Fresh air also seeks to creep into noisome localities. 21. In casting large cannon, the gun is cooled by a stream of cold water. Why? The object of this is to cause the iron to cool more quickly and so not give the molecules time to arrange themselves in crystals. (See p. 45.) 22. Why does paint adhere to wood? Chalk to the blackboard? These are illustrations of the force of adhesion. 23. Why does a towel dry one's face after washing? The capillary pores of the cloth absorb the water on the face. 24. Why will a greased needlefloat on water? The repulsion between the grease and the water is sufficient to support the slight weight of the needle. 25. Why is the point of a pen slit? The ink rises in the capillary space of the slit, and is there held for use. When the pen is pressed on the paper, the space is widened and the ink descends. 26. Wkhy is a thin layer of glue stronger than a thick one?

Page  208 208 ANSWERS TO PRACTICAL QUESTIONS The adhesion between the glue and the wood is stronger than the cohesion between the particles of glue; hence the thinner the layer of glue the fewer the particles acted upon only by the latter or weaker force. GRAVITATION. 62.-I-41. (See the Answers to these Queries on pp. 9 to I4 of this Key.) 42. How long would it take for a pendulum one mile in length to make a vibration? (See Key, p. 13, Problerml 37.) According to the second law of pendulums (Physics, P. 59), I sec. x:: /39: /5280 x I2 in. x - 40 + sec. 43. rHow long would it take for a pendulum reaching from the earth to the moon to make a vibration? I sec.: x':: /39.I in.: 240,000 X 5280 X 12 in. x 5 hrs. 28 + minutes. 44. Required the length of a pendulum that would vibrate centuries. (I sec.)2: (Io1 X 365.25 x 24 x 60 x 60)2:: 39.I in.:x. x - 6, I45,674,53,727,272 + miles. -SOLOMON SIAS. 45. What would be the time of vibration of a pendulum 64 metres long? (i sec.)2: x9:: I metre (nearly): 64 metres. x 8 seconds (nearly).

Page  209 IN PHYSICS. 209 46. A ball is dropped from a height of 64 feet. At the same moment d second ball is thrown Upward with szuffcient velocity to reach the same point. Where will the two balls pass each other? At the end of one second. The first ball would fall 64 feet in 2 seconds; the second would rise for 2 seconds, and they would pass in i sec. 47. Two bodies.are successively dropped from the same point with an interval of } of a second. When will the distance between them be one metre? Let t - time of descent of 2d body. Then t+.2 - time of descent of ist body. Since the space passed over equals 4.9 m. (i6 ft) multiplied by the square of the time, we have 4.9 t: - space passed over by 2d body. 4.9(t +.2)2 = 4.9t2 + I.96t +. 96 - space passed over by st body. The difference between the 2 spaces being I m., we have 4.9t2 + I 96t +.I96 - 4.9t2 =I m. I.96t-=.804. o t =.4102 sec. = time of descent of 2d body..6I02 sec. = time of descent of ist body. Therefore they will be I m. apart when the ist body has fallen for.6I02 sec., or the 2d body for.4I02 sec. PROOF.-4.9 X.61022 - 4.9 X.4Io22 = I (nearly). -WM. H. TAYLOR. 48. Explain the following fact. A straight stick loaded with lead at one end, can be more easily balanced vertically

Page  210 2 IO AXSWERS TO PRACTICAL QUESTIONS on the finger when the loaded end is upward than when it is downward. When the loaded end is upward a slighter motion is needed to bring the line of direction within the base. The principle is similar to that of the balancing pole of the gymnast. 49. What effect would the fall of a heavy body to the earth have iupon the motion of the earth in its orbit? If its line of fall was exactly opposed to the direction of the earth's motion, it would, by its momentum, tend to retard the earth. If its line of fall was exactly in the direction of the earth's motion, it would increase the earth's velocity. If its line of fall was transverse to the direction of the earth's motion, it would deflect the earth from its orbit. All of these changes would, of course, be infinitesimal in amount.' 50. If a body weighing I lb. onl the earth were carried to the sun, it would weigh 27 lbs. How much would it attract the sun? Ans. 27 lbs. 5 I. Why does watery vaporfloat and rainfall? (See Physics, p. nI6, Question i3.) The vapor of water is lighter than water itself, as the particles are pushed so far apart by the repellent forceheat. 52. If a body weighs i o kilos. on the surface of the earth, what will it weigh 1,ooo km. above? x: o kilos.:: (6,366 *)2: (7.366)2 x = 7.5 kilograms. The radius, or semi-diameter of the earth, is given by French astronomers at 6,366 km.

Page  211 IN PHYSICS. 211 53. A body is thrown vertically upward with a zeocity of I oo metres. How long before it will return to its originalposition? Ans. 20.4 seconds. 54. How long will be required for a body to fall a distance of 2,000 metres.? Equation (6) - gt 2. 2,000 98t2 2. t 20.2 seconds. 55. If two bodies weighing respectively I kilo. and I demi-kilo. are connected by a rod 9 decimetres long, where is the centre of gravity? Ans. 6 dm. from one body and 3 dm. from the other. (See Key, p. Io, Question 7.) ELEMENTS OF MACHINES. 79.-I-26. (See Answers on pp. 20 to 24 of this Key.) 27. Why is the rim of a Jy-wheel maZde so heavy? The heavier the wheel, the greater its inertia; and the further the weight is from the centre of motion (or axle), the greater its inertia or centrifugal force. (See Physics, p. 78.) 28. Describe the haznmer, when used in drawing a nail, as a bent levzr, i. e., one in which the bar is not straight. If a lever is bent, or if, when it is straight, the bar is not at right angles to the lines of action of the P and the W, it is necessary to d stinguish between the arms of

Page  212 2I2 ANSWERS TO PRACTICAL QUESTIONS a lever and the arms of the P and the W, regarded as forces which have moments around the F. In the latter sense, the arms are the perpendiculars, dropped from the F to the lines of action of the P and the W. (See Everett's Text-book of Physics, p. 23; and Todhunter's Natural Philosopahyfor Beginners, Vol. I, p. 78, where there is an excellent diagram.) HYDROSTATICS. 96.-I-38. (See pp. 24-29 of this Key.) 39. Siuppose that Hiero's crown was an alloy of silver and gold, and weighed 22 oZS. in air and 204 ozs. in water. What was the proportion of each metal? "Multiply the specific gravity of each ingredient by the difference between it and the specific gravity of the compound. As the sum of the products is to the respective products, so is the specific gravity of the body to the proportions of the ingredients. Then, as the specific gravity of the compound is to the weight of the compound, so is each of the proportions to the weight of its material."-American Cyclocedia. Second method: Let A- mass of crown -- 22 " B =sp. gr. " I= 4.66 " x mass of gold " x - sp. gr. " = 19.26 " y - mass of silver " y' sp. gr. " 1o.5 then A = x+y;

Page  213 IN PHYSICS. 213 and since mass volume - specific gravity' we have A x y B x y whence we find (approximately), Gold = I3.95 Silver- 8.o5 40. Why will oil, which floats on water, sink in alcohol? The specific gravity of absolute alcohol is only.79; hence even the dilute alcohol of commerce is lighter than water. 41. A speczic-gravify bottle holds 00oo gms. of water and i8o gms. of sulphuric acid. Required the density of the acid. Ans. I.8. 42. What is the density of a body which weighs 58 gims. in air and 46 gms. in water? Ans. 46. 43. What is the density of a body which weighs 63 gins. iaI air and 35 ginms. in a liquid of a density of.85 A Ans. I.9125. HYDRAULICS OR HYDRODYNAMICS. I03. —-5. (See Key, pp. 29, 30.)

Page  214 214 ANSWERS TO PRACTICAL QUESTIONS PNEUMATICS. ii6. —-I8. (See Key, pp. 30-32.) I9. Explain the theory of "sucking cider" through a straw. The air in the straw being exhausted, the pressure of'the air on the cider in the vessel forces the liquid through the straw. 20. WIould it make any dcierence in the action of the sZphon if the arms were of unequal diameter? It would change the relative weight of the columns ot liquid in the two arms, and so increase or diminish the difference of pressure which forces the liquid through the long arm. Now, the heavier cd and the lighter 7ab, in Fig. Io5, the faster the flow. 2 T. If the receiver of an air-pump is 5 times as large a. the barrel, how many strokes of the piston will be needed to diminish the air nearly one-haf? One-fifth of the air in the receiver is removed at each stroke. After the third stroke there would remain in the receiver 64 of the original atmosphere. 22. What would be the efect of making a small hole in the top of a divig,-bell while inz use The air would escape at the top, and the water would ascend and fill the bell. ACOUSTICS. I44. —I-6. (See Key, pp. 32-34.)

Page  215 IN PHYSI CS 21 17. Why will the report of a cannon fired in a valley be heard on the top of a'i^,lhboring mountain, better than one fired on the top of a mounlain will be heard inz the va-lley A sound always hlta3 the intensity given it by the lensity of the atmosphere where it originated, and not of that where it is heard. (See Tyndail's Lectures on Sound, p. 40.) I8. Why do ourfaotsteps in unfiurnished dwellings sound so startlingly distinct? In furnished roomas, the chairs, carpets, pictures, etc. break up the echoes. Then, also, our footsteps are louder on an uncarpe-ted floor. I9. Why do the echoes of an empyO church disappear zwhen thze audnience assemble? The audience break up the echoes which interfere with tihe original sound. Wires strung across a lofty room often serve the same purpose. 20. IVhat is the object of the sounding-board of a piano? By its vibrations and those of the body of air which it encloses, it reinforces the sound of the wires. 2 I. During some experimensts, Tyndall found that a certain sound would pass through twelve folds of a dry silk handkerchief, but would be stopped by a single fold of a zve one. Explain. (See Tyndall's Lecturer on.ight, p. 325, for a series of expc:iments showing the action of moisture in propagating the sound-waves.) 22. What is the cause of the musical m.u;-mur often heard near telegraph linies

Page  216 216 ANSWERS TO PRACTICAL QUESTIONS It is produced by the vibration of the wires. These are thrown into motion by the wind and other causes. 23. lWhy will a variation in the quantity of water inl the goblet, wheni caused to sound as in the experiment described on page 123, make a difference in the tone? It changes the length of the vibrating portion of tile glass. 24. Al what rate (in metres) will sound move through air at 2 o~ C.? Sound moves at the rate of,o090o feet at oO C. The difference is nearly 2 feet for each degree C. o090o feet + 40 feet: 1130 feet. OPTICS. 77. —I-25. (See Key, pp. 35-39.) 26. What is t/e princitple of the kaleidoscope? 27. Which will be seen at the grcater distance, a yellow or a gray body? The yellow, since it is brighter. 28. Look down into the glass of water shown int Fli. I 45, and at a certain angle you w/ill see two spoons, one small and having the real handle of fhe spolon, thoulgh apparently bent, and the real spoon with nZo hanZ. Explaill. In trying the experiments here alluded to, the glass should be looked into at all possible angles, and the spoon be turned about in the goblet. The glass of water acts as a convex lens to magnify objects; the concave

Page  217 I.V PHYSlS.S 21 upper surface of the water, when one looks down into it, as a concave lens to minify objects; and the upper surface of the water, when one looks up at it, as a total reflector of the light. These facts, together with thphenomenon of refraction, as shown in the apparent breaking of the handle where it enters the water, will account for all the curious modifications which may be noticed. The experiment is worth hours of examinati(,n. 29. When a star is near the horizon, does it seem highher o' lower than its true place? It seems higher, since the rays of light are bent downward to the eye, and the object is seen in the line of the ray as it enters that organ. 30. Wlhy can we not see a rainbozw at midday? Because the sun is not in the right position. To produce the ordinary rainbow it must be toward the eastern or western horizon. 3I. What conclusion do we draw from the fact that moonlizht shows the same dark lines as sunhizht? That its light has the same source as that of the sun, and is, indeed, sunlight. 32. Why does the bottom of a ship seen under water appearflatter than it really is? Because, by refraction, the bottom of the ship is apparently elevated above its true place. 33. Of what shape does a round body appear in water? It appears to be flattened; and hence a round body lo6ks like an oval one.

Page  218 I8 ANSWERS TO PRACTICAL QUESTIONS 34. Why is rough glass translhcent while smooth glass is transparent? The minute protuberances scatter the rays of light and do not allow them to pass freely to the eye of the observer. 35-42. (See Key, pp. 38, 39; Questions 28-35.) 43. Are there rays in the sunbeam which we cannot perceive wit/z the eye? (See Physics, pp. i63, i64.) The calorific and actinic rays are invisible. 44. Why, when we press the finger on one eyeball, do we see objects tdouble? " Each retina possesses regions of symmetry with the other, and on this fact singleness of vision depends; each point of the outer portion of the retina of the right eye has its point of symmetry in an inner portion of the left, and when from a distant object rays fall on these symmetrical points, that object will be seen single; but if, by the pressure of the finger or otherwise, we compel the image in one of the eyes to fall upon another and non-symmetrical point, the object at once becomes double." (See Draper's Human Physioltoy, p. 395.) 45. Why does a distant light, in the night, seem like a star? The light radiating in every direction produces the star-like effect, and we cannot see the surrounding objects by which to correct the impression. Hence one often mistakes a fire on a distant hill for a star nsing.

Page  219 IN PHYSICS. 219 46. Why does a bright light, in the night, seem so much nearer than it is? We judge of the distance of an object by its magnitude, by its distinctness of outline, and by the size, etc., of intervening objects with which we compare it. In the night, the brightness of a light confuses us by its vividness, seeming to be near at hand. Moreover, we cannot see the neighboring objects, whose distance we know or could estimate in the daylight. Our error is therefore one of judgment. A fire jet night thus seems near at hand, and persons often run toward it for great distances, expecting every moment to reach it. (See Question 54.) 48, 49. (See Key, p. 40; Questions 47, 48.) 50. Why is the lens of a fish's eye (seen in the eye-socket of a boiledfish) so convex? The difference of density between the water and the eye is not so great as that between the air and the eye. Hence, to refract the light sufficiently to bring it to a focus on the retina requires a more convex lens. (See Dudgeon, on the Human Eye; and Physics, p. 268, note.) 51. When do the eyes of a portrait seem to follow a spectaltr to allparts of a room? This is noticed only in a full-face portrait. In that case the spectator, when he goes to either side, fails to see the side of the eyeballs, and hence the effect is that of looking directly into the eye. "A rifleman, portrayed as if taking aim directly in front of the picture, appears to every observer to be pointing at him specially." 52. Why does the dome of the sky seem/flattened?

Page  220 220 ANSWERS TO PRACTICAL QUESTIO-S. "Because the light from above, having to pass through a less amount of air, is less obstructed than that which comes horizontally. It is therefore more vivid." 53. Why do the two parallel tracks of a railroad appear to approach in the distance? This depends upon what is known in painting as the vanishingpoin/. " Suppose two long rows of pillars, Ioo feet apart, and an observer standing at one end looking down the rows. Evidently, for the same reason as the space between the top and bbttom of the pillars, that is to say their height, becomes apparently less and less as their distance from the eye increases, so will the space between each pillar and its opposite in the other row become apparently less, and the lines of pillars will, at a certain distance (viz., where 200 feet are apparently reduced to a point), seem to join. Beyond that spot, known as the vanishing point, none of the pillars can be seen." (Read Arnott's Physics, pp. 6i6-622.) 54. fWzy does afog magnify objects? The fog diminishes the intensity of the light. The visual angle, however, remains the same. "An object at two miles, subtending the same angle as an object at one mile, is twice as broad, and the conclusion is drawn that the dim object is large. Thus, a person in a fog may believe that he is approaching a great tree fifty yards distant, when the next instant throws him into a low bush that has deceived him. A boy on the stage, with a thin gauze screen before him, will look to the audience like a man in the distance." (See Arnott's Physics, p. 628.)

Page  221 It is not the refraction of the rays of light, as is commonly supposed, which makes an object seem larger when seen through a mist. It really appears to us in its proper size. The mist, however, dims the color and the outline, giving it the indistinctness belonging to a mile in distance, while it has the magnitude of half a mile. Dr. Wayland relates that, as he was sailing through Newport harbor early one morning, in a dense fog, he observed on the apparently distant wharf some very tall men. While he was remarking upon their extraordinary size, he was astonished to see them jumping about like children, and otherwise behaving in a most unaccountable manner. Presently, as the sun dispersed the fog, he found that he was close to the wharf, and that the gigantic men were really a party of small boys amusing themselves with play. The opposite mistake is made when the atmosphere is more transparent than that to which we are accustomed. Foreign travellers in Switzerland, who have started on foot to visit a glacier or a mountain-peak which seemed within easy distance, have often been surprised to find, after two or three hours of brisk walking, that the object of their desire seemed as far away as at first. So in looking across a sheet of water, where there are no intervening objects, distance is always underrated. When we throw a stone - at an object in the water we find that our eye has deceived us, and the stone falls far short of the mark. For the same reason, objects seen on the shore from the water seem much less than their natural size. The fact is, they appear of the magnitude which belongs to the distance, but we suppose the distance less than it is; and, associating this magnitude with diminished distance, they appear to us less than they really are.

Page  222 22 2 ANSWERS TO PRACTICAL QUESTIONS In order to form these judgments correctly, one of these elements must be fixed. From this we learn to institute a comparison, and thus form an accurate opinion. If we know the magnitude of an object, the change in its color and outline will teach us its distance. If we know its distance, we can judge of its magnitude. Hence, painters, in order to give us a correct idea of an object which they represent, always place in its vicinity something with whose real magnitude we are familiar. Thus, to show the size of a pyramid, an Arab with his camel may be drawn at its foot. If the pyramid were represented by itself, its intended size might be mistaken; but every one knows the size of a camel, and from this he would judge of the magnitude of a pyramid.- Wayland's fIntellectual Philosop/hy, p. 78, et seq. 55. If you sit where you cannot see another person's imna,e, why cannot that person see yours? The angle of incidence is equal to the angle of reflection under all circumstances. If a ray from the other person is not reflected at the right angle to reach your eye, then a ray from you is not reflected at the right angle to reach the other person's eye. 56. Why can we see the multiple images in a mirror better zf we look into it very obliquely? More light is then reflected to the eye. (See Physics, p. 151, 2d note.) 57. Why is an image seen in water inverted? (Examine Fig. I40, in Physics.) 58. Why is the sun's light fainter at sunset than at midday? (See Physics, p. 149, note.)

Page  223 1N PHYSICS. 223 59. Why can we not see the fence-posts when we are riding rapidly? There is not time for the rays of light to produce a distinct impression on the retina. (See Physics, p. 177, line 13.) 60. Ought a red flower to be placed in a bouquet by an orange one? A pink or blue with a violet one? (See Physics, p. I67.) These are not complementary colors, and so weaken rather than strengthen each other. 6. Why are the clouds while whilte the clear sky is blue? Prof. Tyndall has shown that the larger particles of vapor scatter light of all colors, i. e., white light; while the smallest particles, only the blue rays. In accordance with this fact the clouds are white and the sky is blue. If the air were absolutely pure and free from all foreign matter, it is thought that the azure of the sky would not be seen and the heavens would appear black: the illumination of objects would be strong and glaring on one side, and on the opposite side the shadows would be deep and unrelieved by the diffused light to which we are accustomed. The minute particles of vapor in the air serve to scatter the direct rays of the sun and to turn them around corners and into places not in the direct line of the sunlight. (See a full and interesting discussion in Tyndall's Lecture on Ligkt, page 152, et seq.) 62. Whyt does skim-milk look blue and new milk white? The fatty globules of the new milk reflect all the colors of the spectrum to the eye; but when deprived

Page  224 224 ANSWIE'RS TO PRACTICAL QUESTIONS of the cream the milk reflects the blue light in excess of the others. 63. tihat would be the egert of filling the basin, in the exjperiment shown in JF. I47, with salt ewater? The water would be made denser and its refractive power would be correspondingly increased. (Compare Physics, p. 268, note.) 64. Why is not the image of the suz in water at midday so bright as near sunset? (See Physics, p. I51, 2d note.) 65. Why is the rainbow always oplosite the sun? (See Physics, p. i66.) HEAT. 203. —I-54. (See Key, pp. 40-47.) With regard to Question 23 there is much difference of opinion. Many authorities think that temperature, and not moisture, is the chief factor in producing barometric changes. (See Milier, Komische Physik, 637.) 55. Why will "fanning" cool the face? It brings in contact with the face a current of fresh and generally cooler air. (See Physics, p. 29I.) 56. How are safes madefire-proof? By filling the space between the inner and the outer iron-plates with a non-conducting material, as plaster, etc., the safe is rendered nearly fire-proof. In one form

Page  225 I' PHYSICS. 225 of safe, pipes of water are used, which absorb the heat and render it latent. 57. Why can yaou heat water quicker in a tin than a china cup? Because the metal is a better conductor of heat than the china. 58. Why will a woollen blanket keep ice from melting? The woollen is a non-conductor of heat. 59. Does dew form under trees? The trees reflect back the heat radiated by the earth, grass, etc., and so prevent the temperature, in general, from sinking to the dew-point. 60. What is the principle of heating by steam? (See Physics, p. 206.) 61. Why is a gun firing blank cartridges more heated than onefiring balls? (See Key, p. 207, Question 53.) 62. What is the cause of " cloud-caCpped" mountains? (See Physics, p. 197.) 63. Show how the glass in a hot-house acts as a trap to catch the sunbeam. (See Physics, p. I94.) 64. Does the heat of the sun come in through our windows? (See Physics, p. I94.) 65. Does the heat of our stoves pass out in the same way? (See Phyds:c, p. z94.)

Page  226 226 ANSWERS TO PRACTICAL QUESTIONS 67. Is a dusty boot hotter to thefoot than a polished one (See Physics, p. I94.) 68. The top of a mountain is nearer the sun; why is it not warmer? (See Question 62.) 72. Can we find frost on the windows and on the stoneJiagging the same morning? It requires a much intenser cold to produce the former effect than the latter, as glass is a poorer conductor of heat than stone. We frequently find frost on the flagging early in the fall, but frost on the window is a sign of very severe winter weather. 73. Why will not snow "pack " into balls except in mild weather? The snow must be very near the melting-point for the pressure of the hand to be sufficient to melt enough of it to produce the phenomena of regelation. (Physics, p. 202, Ist note; also Tait's Recent Advances in Physical Scienlce, p. 129, and Tyndall's Forms of Water, p. I63.) This principle involves the theory of Glaciers. "The masses of snow cannot rest on the steep slopes of Alpine summits. The pressure upon the under layers is too great to allow them to remain upon their sloping beds, and they are forced to descend. This descent is accomplished in two forms: that of an avalanche, one of the most awful and imposing spectacles to witness; or of a glacier, which is really an avalanche of ice of extremely slow motion. But the glacier differs from the ordinary avalanche not only in that its motion is so slow, but in that it consists of ice, thick, firm, and hard. The principles involved in this transition of the loose, flaky

Page  227 IV PHYSICS. 227;now which first falls upon the mountain-top into the;olid ice of the glacier, are very well illustrated, as Helmaoltz has remarked, in the manufacture of the schoolboy's snow-ball or snow-man. Very cold snow is always light and flaky, and cannot be made by the pressure of the hands into a cohesive mass; in order to succeed in that operation, snow is always employed which is already at the melting-point, or only so far below this temperature that the warmth of the hand suffices to bring it to the required temperature, and then, by dint of pressure and moulding, an icy ball may be easily produced. So with the formation of the glacier ice. A process of almost simultaneous melting and freezing goes on among the under layers of snow, and under an immense and everconstant pressure from the weight of the snow above; thus solid ice is formed. That this ice conforms itself to the various windings, constrictions, and dilatations of its rocky channel during its downward march is a fact not less familiar than wonderful." 74. Whzy is the sheet of zinc under a stove so apt to become puckered? When zinc cools after expansion it does not return quite to its former dimensions, and so becomes "puckered," as it is called. 75- Why does a mist gather in the receiver of the aipump as the air becomes rarefied? "The remaining air, cooled by rarefaction, absorbs heat from the invisible vapor in combination with it, and renders the water visible. The mist may be removed by continued action of the machine, or by readmitting the normal quantity of air." (See Arnott's Phytics, p. 448.)

Page  228 228 ANSWERS TO PRACTICAL QUESTIONS 76. Why are the tops of high mountains in the tropics covered with perpetual snow? (See Question 62.) MISCELLANEOUS QUESTIONS AND PROBLEMS FOR REVIEW. I. Does a plumb-line point to the earth's centre of figure ~ ~enitre of gravity? 2. In a dark room, let the light of a candle pass through a small hole in a card, and the image of the candle on the opposite wall will be inverted. Explain. 3. Why does drift on the Missiissippi accumulate for the most part on the west bank? 4. Hrow many times heavier is the earth than an equally al-age globe of water? 5. Why does the arc of a rainbow seem a part of an ellipse instead of a circle? 6. Why does a rocket ascend into the air? 7. Is the water at the foot of Niagara Falls warmer than that in the river above? 8. What causes wheelfire-works to rotate? 9. A brass-rod covered fightly with thin paper may be held some time in a flame without the paper being scorched; while, if the rod be of wood, the paper will scorch at once. Why is this difference? Io. How would it affect the action of a siphon if it were carried up a mountain I

Page  229 IN PHYSICS.. 229 i I. If a vessel of water containing a floating body be placed under the receiver of an air-pumrp, and the air gradually exhausted, what will be the efect on the floating body? i 2. How will it change the height of the column of mercury in a barometer to incline the tube? 13. In the image of a written page seen in a mirror, why does the writing seem to slope to the left? I4. Why does a coin placed in a tumbler look Z;,rra~er when the glass is full of water than when it is empty? I5. Two bodies of diferent bulks weigh the same in water; which will weigh the more in mercury, the larger or the smaller i 6. How does the wind drift sand, snow, etc.? I7. Why does oil "still troubled waters"? i8. Why does crouching down at the highest points in a swing, and standing up at the lowest point, increase the velocity? I9. What diference would it make in the guinea-andfeather experiment to force into the tube additional air, instead of exhausting it, as ordinarily done?

Page  230

Page  231 ANSWERS TO THE PRACTICAL QUESTIONS IN THE NEW DESCRIPTIVE ASTRONOMY. 32.-I. How higzh is the North Star above your horizon? (See Astronomy, p. 2I8.) It should be remembered that the North Star revolves around the true North Pole at a distance of about I; hence it marks the exact height of the Pole above the horizon only twice in twenty-four hours. 2. Wh1at is the sun's right ascension at the autumnal equinox? At the vernal equinox? At the vernal equinox, the sun is in Aries, and its R. A.-o. At the autumnal equinox, it is in Libra, and its R. A.-8o0~. 3. What was thefirst discovery made by the telescope? (See Astronomy, p. 20: articles in Appleton's Cycloha dia on Telescope and Galileo; and, also, Routledge's History of Science, p. I07.) Galileo's telescope was constructed on the principle of an opera-glass.

Page  232 232 ANSWERS TO PRACTICAL QUESTIONS 4. How high above the horizon of any place are the equinoctialpoints when they pass the meridian? The co-latitude of the place. (See Astronomy, note, p. 27.) 5. Jupiter revolves around the sun in 12 of our years. Assuming the earth's distance from the sun to be 93,ooo,ooo miles, conmpute Jupiter's distance by applying Kepler's third "azeo. (See Astronomy, note, p. g9.) If we square the period of any planet, expressed in years, and extract the cube root of this product, the result will be the mean distance from the sun, expressed in astronomical units, i. e., in radii of the earth's orbit. Jupiter's period of 12 years will give a result of 5.2028. 93 000,000 miles x 5.2028=483,860,400 miles. 6. The latitude qf Albany is 420 39' N; what is the sun's meridian altitude at that place when it is in the celestial equator? (See Astronomy, note, p. 27.) 90o -42 39'- 47 3 I 7. What is the co-latitude of a place? The co-latitude is the complement of the latitude. (See Astronomy, note, p. 27.) 8. What is the declination of the zenith of the place in which you reside? It equals the latitude. (See Astronomy, note, p. 27.) 9., Why are the stars generally invisible by day? (See Astraxamy, p, 25.)

Page  233 IN ASTRONOMY. 233 The stars would be visible in the daytime if it were not for the atmosphere. Compare the description of a lunar sky, on page I34 of the Astronomy. o. Why is the ecliptic so called? (See Astronomy, note, p. 58.) I I. Who first taught that the earth is round? The discovery of the rotundity of the earth has been ascribed to Thales; others attribute it to Aristotle. 2. What is Astrology? A magic art that pretends to foretell events by means of the stars. 13. How can we distinguish the fixed stars from the planets? (See Astronomy, pp. 2 and 203.) 14. How long was the Ptolemaic system accepted? It was taught in the schools for about 1400 years, or until the time of Galileo-the I7th century. I5. In what respect did the Copernican System dfater from the one now received? (See Asftronomy, p. 14.) i6. For what is Astronomy indebted to Galileo? To Newton? Galileo discovered the structure of the moon; the existence of Jupiter's moons and their revolution around their primary; the stars of the milky way; and the rotation of the sun on its axis (as proved by the appearance of the spots). Newton discovered the law of gravitation,' and by means of it explained the specific gravity of the planets, the cause of the tides, the shape of the earth, the theory of precession of the equinoxes, and the paths

Page  234 234 ANSWERS TO PRACTICAL QUESTIONS of the comets. Read Brewster's Life of Newton; also, Buckley's History of NVatural Science. I 7. What is the amount of the obliquity of the ecliptic? (See A stronomy, p. 29.) i8. Define Zenith. Nadir. Azimuth. Altitude. Equinoctial. Right Ascension. Declination. Equinox. EclZiptic. Colure. Solstice. Polar distance. Zenith distance. The Zodiac. These terms are defined under the various subjects on pp. 26-30 of the Astronomy. 9. If the R. A. of the sun be 80~, state in what sign he is then located. i60o. 280~. I sign=-3o. 80~ would locate the sun in Gemini; I6o0, in Virgo; 280~, in Capricornus. (See Astronomy, table on p. 3x.) 20. Why does the angle which the ecliptic makes with the horizon vary? (See Astronomy, p. 29.) The ecliptic being oblique to the celestial equator, the angle that it makes with the axis of the heavens must differ according to the part which is above the horizon at any specified time_ 21. Why is the angle which the celestial equafor makes with the horizon constant? (See Astronomy, p. 29.) The celestial equator is perpendicular to the axis of the heavens, and hence all parts of it make the same angle with the celestial axis and with the horizon.

Page  235 IN ASTRONOMY. 235 I98. —I. Would the earth rise and set to a Lunarian? (See Astronomy, p. I34.) The earth would not rise or set, as the moon does with us, but would merely oscillate to and fro through a few degrees. A Lunarian would see the earth constantly in the sky, undergoing all the phases the moon presents to the earth, only in reverse order. Thus, when it is full moon to us, it is new earth on the moon. During the first and last quarters, the changes would occur during the daytime; during the second and third, in the night. The rapid rotation of the earth, repeated fifteen times during a lunar night, must greatly diversify the appearance of the earth. — See Olmstead's Letters on Astronomy, p. I80. 2. Could there be a transit of Jupiter? No. Jupiter is a superior planet. (See Astronomy, p. 67.) 3. Why does Mars's inner-moon rise in the West.? (See Astronomy, note on p. 153.) "This satellite performs a revolution in its orbit in less than half the time that Mars revolves on its axis. In consequence, to the inhabitants of Mars, it would seem to rise in the west and set in the east. The revolution of the moon around the earth and of the earth on its axis, are both from west to east; but the latter revolution being the more rapid, the apparent diurnal motion of the moon is from east to west. In the case of the inner satellite of Mars, however, this is reversed, and it therefore appears to move in the actual direction of its orbital motion. The rapidity of its phases is also equally remarkable. It is less than two hours from new moon

Page  236 236 AN1SWERS TO PRACTICAL QUESTIONS to first quarter." —Newcomb & Holden's Astronomy, p. 339. 4. lit what part of the sky do you always look for the planets? Within the limits of the Zodiac. A few of the asteroids only pass outside this belt of the heavens. 5. Show how it was impossible for the darkness that occurred at the time of the Craucfcxion of Christ to have been caused by an eclipse of the sun. The Feast of the Passover took place at full moon. " With the Jews, a. month began when the new moon was seen. Persons were appointed to watch, about the time it was expected, on the tops of mountains. As soon as they saw its light, they gave notice by sounding trumpets and building fires."-Nevin's Biblical Antiquities. 6. Is there any danger of a collision between the earth and a comet? (See Astronomy p. 192.) A collision between the earth and a comet must be a rare occurrence. Babinet computed that one would strike the earth, on the average, every 15,000,000 years. There are certainly, however, comets whose orbits cross the earth's path, and if we should happen to reach the crossing at the same time with one of them, there would be a collision. We should probably never know of the event unless we were watching for it. 7. How are aerolites distinguished? (See Astronomy, pp. I77, I78.) A&rolites, when found, generally have an exterior crust of fused material, presenting a glossy, pitch-like appearance. An analysis of the interior commonly presents a combination of elements that is so characteristic as to

Page  237 11V ASTRONOMY. 2 3 7 identify the body as an aSrolite even when not seen to fall. Large masses have been found in Northern Mexico which are thus known to be of meteoric origin. "The meteoric stones may be divided into two distinct groups-meteoric ir-on, and meteoric stones proper. " I. Meteoric iron is an alloy of iron and nickel, containing about io per cent. of nickel, and small quantities of cobalt, manganese, magnesium, tin, copper, and carbon. This alloy has not been found among terrestrial minerals. " 2. The meteoric stones proper are composed of minerals of volcanic origin, and such as are found abundantly in terrestrial lavas and trap-rocks, viz.: Magnetic iron, Olivine, Sphene, Anorthite, Chrome iron, Labradorite, Apatite (?), Augite, together with a varying proportion of the meteoric ironnickel alloy." —Haughton's Astronomy. 8. When do we see the old moon in the West after sunrise? (See Astrononmy, p. I27.) 9. When do we see the moon high in the eastern sky in the afternoon before the sun sets? (See Astronomy, p. i27.) During the second quarter, before she comes into opposition. o. When is a planet morning, and when evening, star? (See Astronomy,' pp. 65, 70.) II. Is the sun really hotter in summer than in winter? (See Astrononmy, p. ior.)

Page  238 233 ANVSW ERS TO PRACTICAL QUESTIONS 12. Why is a planet invisible at conjunction Z (See Astronomy, p. 65.) I3. Must an inferior planet always be in the same part of the sky as the sun? A4 superior planet? (See Astronomy, pp. 64 and 67.) I4. Why, in summer, does the sun, at rising and at setting, shine on the north side of certain houses? (See Key, p. 67, question I7.) I5. What effect does the volume of a planet have upon the force of gravity at its surface? (See Astronomy, pp. 40, 80.) I 6. In what part of the heavens do we see the new moon? The old moon? The crescent moon? (See Astronomty, p. I27 et seq.) It is a very interesting experiment to notice how soon after conjunction we can observe the new moon. Observers have detected her when twenty-three hours old, and an instance is on record of the moon's thin crescent being seen early one morning before sunrise, and after sundown the following day. I7. What is the Golden Number in the almanac? (See Astronomty, p. 145.) i8. Why do we have more lunar than solar eclzjses? (See Astronomy, p. 146.) Solar eclipses occur more frequently than lunar -eclipses, but the latter are oftener seen at any particular place, because they are visible over a larger area of territory on the earth. I9. In what direction do the horns of the moon turn? (See AStronomy, p. 127.)

Page  239 INA ASTRONOMY. 239 20. Is the "tidal wave" a progressive movement of the water? (See Astronomy, note, p. I48.) The wind raises the particles of water and gravity draws them back again. They thus vibrate up and down, but do not advance. The forward movement of the wave is an illusion. The form of the wave progresses, but not the water of which it is composed, any more than the thread of the screw which we turn in our hand, or the undulations of a rope or carpet which is shaken, or the stalks of grain which bend in billows as the wind sweeps over them. Near the shore the oscillations are shorter, and the waves, unbalanced by the deep water, are forced forward till the lower part of each one is checked by the friction on the sandy beach, the front becomes well-nigh vertical, and the upper part curls over and falls beyond. 21. [Why does the sun " cross the line" in some years on March 21, and, in others, oni March 22? (See Astronomy, p. 99.) Leap-year also throws the dates back one day. 22. Do we ever see the sun where it really is? (See Astronomy, p. II4.) Both refraction and aberration of light change the apparent place of the sun. 23. "At Edinburgh, Scotland, there are times when the sun rises at 3~ o'clock A. M. and sets at 8, o'clock P. At, and the twilZight lasts the entire night." When and why is this? (See Astronomy, p. II6.) The latitude of Edinburgh is 55~ 57'. Any place

Page  240 240 ANSWERS TO PRACTICAL QUESTIONS north of 48~ 33' will have twilight at midnight in midsummer; for 9go — 23~ 27' (the sun's declination)-i8~ (at which twilight ceases) = 48 33'. The hours named in the problem are the times for the rising and setting of the sun at Edinburgh at the summer solstice. 24. Which is the longest day qf the year.? (See Aslronomy, p. 99.) The summer solstice points out the longest day of the year. 25. Is the moon nearer to us when it is at the horizon, or at the zenith? (See Astronomry, p. 124.) The moon is nearer to us when it is at the zenith than when it is at the horizon. 26. Hlow many solar eclipses would happen each year if the orbits of the sun and the moon were in the same plane? (See Astronomy, p. 138.) In that case a solar eclipse would occur every new moon. 27. Is there ally heat in moonlight? (See Astronomy, p. i25.) 28. Can we see fthe moon during a total eclipse? (See Astronomy, p. 146.) 29. Which of the planets are repeating a portion of the earth's history? Spectrum Analysis renders it possible, perhaps probable, that Jupiter and Saturn, and, may be, Uranus and Neptune, have not yet attained that degree of density which must necessarily precede the formation of a solid surface. They are, therefore, now in a geologic age

Page  241 INV ASTIRO OM Y. 241 similar to that in which the earth existed before its crust had become solidified. (See Schellen's Spectrum Alznalysis, P. 337.) 3o. How many times does the moon turn on her axis each year? (See Astronomy, p. 123.) The moon turns on her axis once each month. 3I. Can you explain the different signs used in the almanac? (See "Astronomical Signs " in the Dictionary.) 32. Show how the moon is a prophecy of the earth's future. The moon is a worn-out globe, and presents the same appearance that the earth will probably offer ages hence. 33. Does the sun really rise and set? (See Astronomy, pp. 14, 87.) No. This is only an optical illusion, being an illustration of our tendency to transfer motion. 34. Are the bright portions of the moon mountains or plains? The lofty portions, or mountains, of the moon, reflect the light to the earth most strongly, and hence appear the brightest. The deep "alleys, lying in shadow, look dark. 35. Which of the heavenly bodies are self luminous a (See Key, page 240, Question 29; also Astronomy, note, p. x63.) Jupiter and Saturn probably emit light, at least from the brighter spots of their surface. Read Newcomb's Astronomy, p. 342.

Page  242 242 ANSWERS TO PRACTICAL QU'ESTlO.NS 36. Why is not a solar eclipse visible over the whole earth? (See Astronomy, p. 140.) 37. What is meant by the " mean distance " of a planet? The " mean distance " is the average distance. 38. What keeps the earth in motion around the sun? (See A stronomy, p. 22.) According to the First Law of Motion, "Every body continues in its state of rest or of uniform motion in a straight line, except in so far as it may be compelled by impressed forces to change that state." 39. Do we ever see the sun after it sets? (See Astronomy, p. II4.) The refraction of the atmosphere tends to raise all objects toward the zenith, and, at the horizon, this is no less than 35', or 3' more than the mean diameter of the sun (32'). 40. When does the earth move the most rapidly in its orbit? (See A stronomy, p. T8.) The earth moves most rapidly in perihelion. 4I. Have zoe conclusive evidence that any planet is izhabited? (See Astronomy, p. 6I; clso note, p. 297.) May it not be that the same lavish hand that scatters flowers and seeds in such profusion (not one in a thousand coming to the perfection and end of its being), sows space with worlds, a few only reaching the full fruition of life. 42. When is twilight the longest? The shortest? Why? (See Astronomy, p. xI6.)

Page  243 IN ASTR ONOMY. 243 "Twilight is usually reckoned to last until the sun's depression below the horizon amounts to 8~0; this, however, varies; in the tropics a depression of i6~ or 170 is sufficient to put an end to the phenomenon, but in England a depression of I7~ to 2I~ is required. The duration of twilight differs in different latitudes; it varies also in the same latitude at different seasons of the year, and depends, in some measure, on the meteorological' condition of the atmosphere. Strictly speaking, in the latitude of Greenwich there is no true night from May 22 to July 21, but constant twilight from sunset to sunrise. Twilight reaches its minimum three weeks before the vernal equinox, and three weeks after the autumnal equinox, when its duration is I hr. 50 min. At midwinter it is longer by about seventeen minutes; but the augmentation is frequently not perceptible, owing to the greater prevalence of clouds and haze at that season of the year, which intercept the light, and hinder it from reaching the earth. The duration is least at the equator (I hr. I2 min.), and increases as we approach the poles; for at the former there are two twilights every twentyfour hours, but at the latter only two in a year, each lasting about fifty days. At the north pole the sun is below the horizon for six months, but from January 29 to the vernal equinox, and from the autumnal equinox to November 12, the sun is less than i8~ below the horizon; so that there is twilight during the whole of these intervals, and thus the length of the actual night is reduced to 2 - months. The length of the day in these regions is about six months, during the whole of which time the sun is constantly above the horizon. The general rule is, that to the inhabitants of an oblique sphere the twilight is longer izn proportion as the place is nearer the elevaledpole, and the sun

Page  244 244 ANSWERS TO PRACTICAL QUESTIONS is farther from the equator on the side of the elevated pole." -Chambers's Astronomy. When the sun rises or sets most obliquely to the horizon, then the least time is required to pass through the necessary I8~, and, of course, the length of twilight is the least. When the sun rises or sets least obliquely, the most time is required to pass through i8~, and the length of twilight is greatest. If the sun's path is perpendicular to the horizon, the sun will pass over the 18' in I hr. I2 min.; for 15~Ii hr.; and hence I8~=I - hr. 43. What is a moon?,A moon is a secondary body, or satellite, revolving about a primary body, or planet. 44., To a person in the south temperate zone, where wouldl the sun be at noon? On the meridian north of the observer. 45. Is it correct to say that the moon revolves about the earth, when we know that, accoreding to the law of Physics, they must both revolve about their common center of gravity.? (See Astronomy, note, p. 200.) The earth is not stationary as regards the moon, for both it and our satellite revolve together about their common center of gravity. Again, it is not the earth alone which revolves about the sun in the elliptical orbit, but this common center of gravity. The sun, also, is not stationary, but it and the planets revolve about the common center of gravity of the whole system. 46. During a transit of Venus, do we see the body of the planet itself on the face of the sun? (See Astronomy, p. 277.) During a transit, Venus appears as "a perfectly round

Page  245 IN ASTRONOMY. 245 black spot on the disk of the sun." The planet turns its unillumined side toward us, and is, strictly speaking, invisible. 47. How many real motions has the sun? How many apparent ones? (See Key, p. 65, Questions 4, 5.) 48. H$aow many real motions has the earth? (See Key, p. 65, Question 6.) 49. Can an inferior planet have an elongation of go0? (See Key, p. 66, Question 7.) 5o. How (1o we know the intensity of the sun's light on the surface of tany of the planets? The intensity of the heat and light varies inversely as the square of the distance. 5'. Why is the Tropic of Cancer placed where it is? (See Key, p. 66, Question 12.) 52. What planets wouldfloat in water? According to Chambers's Astronomy, the density of Saturn is.68 that of water; Uranus,.99; Neptune,.96. According to Newcomb, Saturn's density is.75. 53. How must the moons of Jupiter appear during theiZ. transit across the disk of that planet? "The satellites appear on the disk of their primary as round luminous spots preceded or followed by their shadows, which show as round black or blackish spots." -CHAMBERS. 54. " The shadow of the satellite precedes the satellite itself when Jupiter is passing frowm conjunction to opposilion, butfollows it between opposition and conjunction." Explain. When actually in conjunction, the shadow is in a right line with the satellite, and the two may be superposed.

Page  246 246.ANSWERS TO PRACTICAL QUESTIONS 55. What facts point to the conclusion that Afars may, perhaps, have passed his planetary prime? The proportion of land and water, and the appearance of the seas, all point to a conclusion somewhat similar to the one stated in the following quotation: " Mars's orbit being outside the earth's, he was probably formed earlier. The mass of Mars is not much more than the earth's, and the surface about 3; if he possessed the same degree of heat as the earth, he would have only ~ the amount to radiate, and the supply would not last so long. Though having only I- the surface of the earth, he would still cool off 3 times as rapidly as the earth. Mars must, therefore, be at least three times as far on the way towards planetary decrepitude and death as our earth."-Proctor's Poetry of Astr-onomy. 56. Why may we conceive that Satlurn and Julpiter are yet in their planetaty youth? (See Astronomy, note, p. 163.) Vast planets, like Saturn and Jupiter, must have required for cooling a far longer time than the earth, and thus the various stages of development would occupy a much greater length of time. (Read Proctor's "When the Sea was Young," in Poetry of Science.) 57'. Shzow how, if the Nebular Hyfpothesis be accepted, the fashioning of a planet must require an enormous length of time. (See Astronomy, p 255.) The experiments of Bischof upon basalt show that the earth would require 350 millions of years to cool down from 2000~ C to 200~ C. This enormous period would represent only one stage in the process of the earth's development. (Read Winchell's Worid ZLfe.)

Page  247 LV ASTRONOXIY. 247 58. Do we know the cause of gravitalion? (See Astronomy, note, p. 23.) 283.-I. In what constellation is Job's Coffin? The Letter Y? The Scalene Triangle? The Dipper? The Kids? The Trianyles? Job's Coffin is in Delphinus; the Letter Y, in Aquarius; the Scalene Triangle, in Aries; the Big Dipper, in Ursa Major; the Kids, in Auriga; and the Triangles, between Almach and Arietis. 2. NVame some facts, in the solar system for which the nebular hypothesis fails to account. It is very difficult to explain, on the basis of the Nebular Hypothesis, why the axes of certain of the planets are so greatly inclined, and, especially, why the velocity of the rotation of the inner moon of Mars should so far exceed that of Mars itself. 3. Wihich is probably hotter, a yellow or a red star? ($ee Astronomy, note, p, 24I.) When we heat a piece of iron, it first becomes red-hot, then, as the temperature rises, other colors appear, until, finally, it becomes dazzling white. (See Physics, p. I83.) 4. Are any of the stars likely to colZids with each other? Nothing strikes the astronomer more forcibly than the thought of the desolateness of space. A vast gulf, more than twenty-five trillions of miles in width, separates Neptune from the nearest fixed star. Itmhas been estimated that the average distance between two of the sixty millions of fixed stars visible to our largest telescopes, is about nine millions of millions of miles. With

Page  248 248 ANSWERS TO PRA CTICAL QUESTIOYNS this amount of "elbow-room," a collision between any two such remote neighbors would be almost impossible. Yet, Sir Wm. Thomson remarks: " It is as sure that collisions must occur between great masses moving through space, unless guided in their paths, as it is that ships, steered without intelligence, could not cross and recross the Atlantic for thousands of years with immunity from collisions." 5. Is the real day Zlnger or shorter than the apparent one? (See Astronomy, p. 264.) 6. Do we ever see the stars? (See Astronomny, p. 203.) 7. What fixed star is nearest the carth? (See Astronomny, pp. 204, 24I.) 8. How often is Polaris on the meridian of a place? As Polaris revolves about the true pole in a circle, the radius of which is nearly I l, it follows that in every twenty-four hours it is once on the meridian below the pole, and, also, once, above it. The diameter of this circle is the length of Orion's Belt, the stars at the right and the left of the central one representing the distance the polar star goes to the right and left of the pole. 9. How do we know that the stars are suns? (See Astronomy, pp. 205, 26I.) Spectrum analysis proves this to be the fact. i o. Can a watch keep apparent time? (Sec Astronomy, p. 265.) I I. How could a child be eight years oal before a retzrn of its birthday? An infant born on Feb. 29, 1796, did not have a

Page  249 IN ASTRONOXY. 249 birthday proper until Feb. 29, i804, since the year I8oo, not being divisible by 400, was not a leap-year. Many other such dates may be named. 12. When will a watch and a sun-dial agree? (See Astronomy, p. 265.) I3. What star will be the Pole Star next after Polaris? (See Astronomy, p. 217.) 14. Why is the birthday of Washington celebrated on Feb. 22, when he was born Feb. i i, 1732 (0. S.)? (See Astronomy, note, p. 312.) I 5. Does the tide have any effect on the length qf the day? (See Alstronomy, notes, pp. 89, 303.) i6. Will the Big Dzipjer always look as it does now? (See Astronony, note, p. 2I7.) The following figure, taken from Proctor's Easy Star Lessons, represents the location of the seven stars comprising the Big Dipper, as they will be seen 00oo,ooo years hence. *7By, 17. How many times does the earth turn on its axis every year? (See Astronomy, p. 264.) 18. Does the spectroscope tell us anything concerning the constitution of the moon, or any of the planets? These bodies shine, in general, by reflected light; therefore, the light examined comes from the sun. By comparing this reflected light with solar light, the change

Page  250 250 ANSWERS TO PRA CTICAL QUESTIONS produced by the planet's atmosphere may be detected. The lunar spectrum exactly accords with the solar spectrum. The spectra of Venus, Mars, Jupiter, and Saturn contain absorption lines indicating aqueous vapor. Read Schellen's Spectrum Analysis, p. 333. 19. When the United States bought Alaska from Russia, the calendar used there was found to be one day ahead of our reckoning. Why was this? One going around the world westward will lose a day in his reckoning; one going eastward will gain a day. The Alaska calendar was established by those who caine from the West to this continent, and their Tuesday corresponded to our Monday. 20. Why do the dates of thze solstices and equinoxes vary a day in dilferent years? (See Astronomry, p. 99.) Leap-year advances the dates one day. 2r. Why are not forenoon and afternoon of the same day, as given in the almanac, of equal length? (See Astronomy, p. 265.) Apparent noon marks the middle of the day; but mean noon may be either before or after the apparent noon; i. e., the time when the real sun is on the meridian. 22. In what part of the heavens (in our latitude) do the stars apparently move from west to east? The northern circumpolar constellations revolve about the North Pole, and, during a part of their paths, they apparently move from west to east.

Page  251 I-V ASTRONOMY. 25I 23. Whatyear was only nine months and six days long. (See Astronomy, note, p. 312.) 24. What day will be the last day of the Nineteenth Century? December 31, I900. 25. If one should watch the sky, on a winter's evening, from 6 P. M. to 6 A. M., what portion of the celestial sphere would he be able to see? All that is ever -seen in his latitude. 26. How do we know that the moon has little, if any, atmosphere? (See Key, p. 66, Question 14; also, Astronomy, p. 302.) 27. In Greenland, at what part of the year will the msidnight sun be seen due north? At all places whose latitude is 660 30' N., the sun will be on the northern horizon at midnioht of the summer solstice. At all places north of the Arctic Circle the sun will remain above the horizon, even at midnight, for a certain portion of the summer, the number of days increasing with the latitude. Read Ball's Elements of Astronomy, p. 142. 28. Can you give any otherproof of the rotundity of the earth, besides that named in the text (p. 85)? (See Astronomy, note, p. 299.) A sphere is the only body that always presents to us the form of a circle, no matter in what direction we view it. At sea, the circular form of the horizon is even more evident than on land.

Page  252 252 ANVSVERS TO PRACTICAL QUESTIONS 29. Point out the error in the following passage from Byron's " arkness," where the poet, in describing the effect of the sun's destruction, says. "I had a dream, * * * * * * which was not all a dream, The bright sun was extinguished, and the stars Did wander darkling in the external space Rayless and pathless." The fixed stars would be unaffected by the extinction of the sun's light. 30. Explain the remark of the First Carrier in Scene I, Act i, Kinzg Henry IV.: "An't be not four by the day, I'll be hanged: Charles' wain is over the new chimney." (See Astronomy, note, p. 3II.) "Since the two great stars which mark the summit and the foot of the Cross have nearly the same right ascension, it follows that the constellation is almost perpendicular at the moment when it passes the meridian. This circumstance is known to every nation that lives beyond the tropics or in the Southern Hemisphere. It has been observed at what hour of the night, in different seasons, the Cross of the south is erect or inclined. It is a time-piece that advances very regularly near four minutes a day, and no other group of stars exhibits to the naked eye an observation of time so easily made. How often have we heard our guides exclaim in the savannas of VenezueIa, or in the desert extending from Lima to Truxillo,'Midnight is past, the Cross begins to bend!' How often those words reminded us of that affectingo scene, where Paul and Virginia, seated near the sources of the river of Lataniers, conversed together for the last time, and where the old man, at the sight of the Southern Cross, warns them that it is time to separate." -HUMBOLDT.

Page  253 IN ASTRONOMY. 253 3I. Why does not the earth move with equal velocity in all parts of its orbit? Because at perihelion it is nearer the sun than when in aphelion, and hence the attraction is stronger. 32. How many Jovian-years old are you? A Jovian year equals i i.86 earth-years. 33. Why is the sky blue? The blue light of the firmament is light reflected by solid particles — generally of aqueous vapor-in the air. It is noticeable that early in the morning and late at night, when the sun's rays fall obliquely upon the atmosphere, they are polarized by reflection. The reflected light is blue; the transmitted light of the sky is orange or red. (Read Tyndall's Lzgh/, p. 152.) 34. At what season of t/te year does Christmas occur in Australia? (See Astronomny. Art. vii., p. 98.) 35. What causes the apparent movcment of the sun north and south? (See Astronomy, p. 95.) It is caused by the fact that the axis of the earth is inclined to the plane of the ecliptic, while the earth is revolving about the sun. 36. On whatpart of the earth is the twizig/zt the longest? The shortest? (Astronomy, p. ii6; Key, p. 243.) "Where the air is unusually full of condensed vapor, as occurs in polar regions, the twilight is greatly lengthened; where the air is unusually dry, as occurs in the tropics, twilight is said sometimes to be shortened to fifteen minutes."

Page  254 254 ANSWERS TO PRACTICAL QUESTIONS 37. lVame the causes which make our summer longer than winter-. (Astronomy, p. 102.) 38. WhyI is not total darkness produced when a dense cloid passes between uzs and the sun? (See Astronomy, p. II7.) 39. Why does the time of the tide vary each day? (See Astronomy, p. 148.) 40. Why is an annular, longer than a total, eclipse? (See Astronomy, p. I40.) 4 1. /Wy is it colder in winter than in summer? (See Astronomy, pp. 97, 98.) 42. Do the solar spots affect our weather? (See Astronomy, p. 48.) 43. C-'rcn the moon be eclijpsed in the day-time? (See Astronomy, p. I I4.) 44. Why are the sidzereal days of uniform length? Because of the almost absolute uniformity of the earth's rotation. 45. Why are not the solar days of unform Iength? (See Astronomy, p. 266.) 46. What do the moon's phases prove? The moon's phases prove that she is spherical and shines by the reflected light of the sun. 47. Why do the sun and moon appear j7attened when near the hArizon? (See Astronomy, p. 1i5.) 48. How many stars can we see with the naked eye? No one sees more than 6,ooo, and few more than 4,000 stars.

Page  255 IN ASTRONOMY. 255 49. Is there ever an annular eclipse of the moon? (See Astronomy, p. 246.) 50. " While the sun rises and sets 365 times, a star rises and sets 366 tinmes." Explain. (See Astronomy, p. 264.) 5 I. ailo many moons are there in the solar system? Twenty have been discovered. 52. What causes the twinkling of the stars? (See Astronomy, p. 207.) Some attribute the twinkling of the stars to the inequality of refraction due to the constant changes in the density of the air, produced by the constant changes in the heat. 53. Name some of the uses of fthe stars. (See Astronomy, pp. 212, 285.) 54. Describe the methods by which we determine the distance of the sun from the earth. (See Astronomy, p. 275.) 55. Why do not the signs and the constellations of.the Zodiac agree? (See Astronomy, pp. io6, 2II.) 56. When we look at the North Star, how long since the bght that enters our eye has left that body? (See Astronomy, p. 218.) 57. In what direction does a comet's tail generally point? (See Astronomy, note, p. 306.) 58. What is the cause of shooting stars? (See Astronomy, p. i82.)

Page  256 256 ANSWERS TO PRACTICAL QUTESTIOVNS 59. Why does the crescent moon appear larger thzan the dark body of the moon? (See Astronomy, p. 123.) 60. What is the real path of the moon Z (See Astronomy, pp. 123, 301.) 6. What would be the result if the axis of the earth were parallel to the plane of its orbit? (See Astronomy, Article xx., p. 103.) 62. Do we see the same stars at diferent seasons of the year? (See Astronomy, pp. 92, 93.) 63. Why do we not perceive the earth's motion in space? Because all the objects around us partake of its motion. 64. Did the earth ever shine as a star? Does it now shine as a planet?. The earth, doubtless, shone as a star while it was yet a glowing mass; now, it reflects the sun's light, like the other planets. 65. What is the nebular hypothesis? (See Astronoimy, p. 255.) 66. What is the cause of the solar spots? (See Astronomy, p. 54.) 67. Would it make the new moon "drier" or "wetter" if the moon's path ran north of, instead of on, the ecliptic at the time of new moon? The moon's latitude varies from 5~ N. to 5~ S. (exactly 5~0 8' 47"' 9). If the new moon were 5~ N., this would increase the angle of 724~ (note, p. 30) to 770, and thus make the line joining the moon's cusps more nearly parallel to the horizon. It may be easily seen that when

Page  257 rN ASTRONOMY. 257 ever the plahe of the lunar orbit lies so as to carry the moon past conjunction above the sun, then the crescent is more nearly horizontal; when below, then it is more nearly vertical. 68. Under what conditions are we accustomed to transfer motion? (See Astronomy, pp. 85, 86.) 69. Why do not the planets twinkle? (See Astronomy, note, p. 207.) 70. WfVhy is the horizon a circle? (See Key, p. 25i, Question 28.) 7 1. What causes are gradually increasing the length of the day? (See Astronomzy, notes, pp. 89, 303.) 72. What distance does the moon gain iin her orbit each year? (See Astronomy,.notes, pp. 89, 302.) 73. State the general argument which renders itprobable that other worlds are inhabited. (See Astronomy, p. 63; also, note, p. 297.) 74. allustrate the uniformity of Nature. What thought does this suggest? (See Astronomy, p. 55; also, note, p. 297.) So far as we can judge, the laws of Nature, the properties of matter, etc., are uniform throughout the universe, and reveal the workmanship of one Creator. 75. At what rate are we traveling through space? How is this determined? The mean orbital velocity of the earth is 18.4 miles

Page  258 258 AvS}VIWRS TO PRACTICAL QUESTIONS per second. Knowing the circumference 1 its yearly path, the rate of motion is easily calculated. 76. Why does the length of a degree of latitude increase in going from the equator toward either pole of the earth? The length of a degree of latitude is least at the equator and greatest at the poles. This arises from the fact that the form of the earth is not perfectly spherical, but is flattened at the poles and bulged at the equator. LENGTH OF DEGREE OF LATITUDE. LENGTH OF COUNTRY. LATITUDE. LENGTH OF DEGREE. Feet. Sweden..................... 66~ 20' Io" N. 365744 Sweden.................. 66 I9 37 367086 Russia................... 58 17 37 365368 Russia....................... 56 3 55'5 36529I Prussia.............. 54 58 26 365420 Denmark............. 54 8 13'7 365087 Hanover.................... 52 32 I6 6 365300 England................. 52 35 45 36497I England. 52 2 I9'4 36495I France............... 46 52 2 364872 France............... 44 51 2'5 364572 Rome........................ 42 59 o 364262 America..................... 39 I2 o 363786 India....................... i6 8 2I'5 363044 India.............. 12 32 20'8 362956 Peru..................... I 31 0o4 S. 363626 Cape of Good Hope.......... 33 I8 30 364713 Cape of Good Hope........ 35 43 20 364060 77. How can you detect the yearly motion of the sun among- the stars? (See Astronomy, first note, p. 94.) 78. Have you actually traced the movement of any one of the planets, so as to understand its peculiar and irreg.ular wandering among the stars?

Page  259 IN ASTRONOMY. 259 Pupils should be encouraged to watch the various movements of the heavenly bodies.-Read a thoughtful and suggestive article upon Astronomy in High Schools, in Popular Science Monthly, Vol. xx., p. 300. 79. How do you explain the varied aspect of the heavens in the different seasons of the year? (See Astronomy, p. 92.) 80. How does the spinning of a top illustrate the subject of precession? (See Astronomy, p. og9.) 81. Why do solar eclipses come onfrom the west and cross to the east, while lunar eclipses come on from the east and cross to the west? The moon is moving from west to east around the earth. In a solar eclipse, her shadow first strikes the western edge of the sun; in a lunar eclipse, the eastern edge of the moon first strikes the shadow of the earth. The monthly motion of the moon from west to east should be carefully distinguished from the daily motion caused by the earth's rotation. 82. NVewcomb, in his Astronomy, says that, " If when the moon is near the meridian, an observer could in a moment jump from New York to Liverpool, keeping his eye fixed upon that body, he could see her apparently jump in the opposite direction about the same distance." Explain. This is an illustration of transferred motion. 83. When, and by whom, was the basis of the calendar we now use fully established? The Roman calendar had become involved in confusion, when Julius Caesar, who possessed no little astro

Page  260 260 ANSWERS TO PRACTICAL QUESTIONS nomical knowledge, called to his assistance a Greek astronomer named Sosigenes, and adjusted the civil year to the astronomical year. By intercalating the extra day of leap-year, he introduced what is known as the Julian calendar, which is still in use. The Persian Calendar, invented in the eleventh century as a correction of the Julian, is remarkable for its accuracy; it consists in making every fourth year bissextile seven times in succession, and making the change for the eighth time in the fifth year instead of the fourth. This is equivalent to reckoning the Tropical year as 365s8 days, which exceeds the period determined by astronomers only by o.oooI823 of a day, or only 2- of a second, so that it would require a great number of centuries to displace sensibly the commencement of the Civil year. The Gregorian Calendar usually employed is somewhat less exact, but it is more easily reduced to days, years, and centuries, which is one of the most important objects of a calendar. It consists in employing a bissextile year every fourth year, suppressing three bissextiles in three centuries, and replacing one in the fourth. Thus in every 400 years there are reckoned only 97 leap years, making the length of the year 3654r-, which exceeds the Tropical year by 0.000258I of a day, or very nearly one second. If, following the analogy of the Gregorian Calendar, our successors shall suppress a bissextile every 4000 years, so as to make 969 instead of 970 leap years in that interval, the length of the year would become 365-.9?6 days, or 365.2422500 days, instead of 365.242219 days, as determined by observation.-Haughton's Astronomy.

Page  261 IN ASTRONOMY. 261 84 Hzow much is the Russian reckoning of time behind ours? The Russian reckoning is twelve days behind us. 85. Is there any gain in having the astronomical and the calendar year agree? " It is difficult to show what practical object is attained by such coincidence. It is important that summer and winter, seed-time and harvest, shall occur at the same time of the year through several successive generations; but it is not of the slightest importance that they should occur now at the same time that they did 5,000 years ago."-Read Newcomb's Astronomy, p. 50. 86. What relzgious festival is fixed each year by the motion of the moon? Easter occurs on the Sunday after the first full moon following the spring equinox. —Read article on Easter, in Appleton's Cyclopaedia. 87. Why can we, at different times, see both poles of the planet Mars? Because the axis of the planet is so much inclined to the plane of the ecliptic. 88. lWhat famous astronomical discovery was made on the first day of this century? (See Astronomy, p. 155.) 89. Do the stars rise and set at the poles? (See Astronomy, p. 102.) "At one of the poles of the Earth, the axis of the Earth's rotation would be vertical, and pass through the zenith, and consequently all the celestial objects would appear to travel in horizontal circles, parallel to the

Page  262 262 ANSWERS TO PRACTICAL QUESTIONS horizon, traversing these horizontal circles once in 23' 56m 4'." go. Name and locate the stars of the first magiitudz which are seen in our sky. "The twenty brightest stars in the heavens, or first magnitude stars, are as follows: they are given in the order of brightness. —LocKYER. "Sirius, in the constellation Canis Major. Canopus, " Argo. Alpha, " Centaur. Arcturus, " Boates. Rigel, " Orion. Capella, " Auriga. Vega, " Lyra. Procyon, " Canis Minor. Betelgeuse, " Orion. Achernar, " Eridanus. Aldebaran, " Taurus. Beta Centauri, " Centaur. Alpha Crucis,': Crux. Antares, " Scorpio. Altair, " Aquila. Spica, " Virgo. Fomalhaut, " Piscis Australis. Beta Crucis, " Crux. Pollux, " Gemini. Regulus, " Leo." 9I. Jame three bright stars which lie near the first meridian. a Andromedae; y Pegasi; and f Cassiopeiae. 92. What events were transpiring in our history a Saturnian century ago?

Page  263 IN ASTRONOMY. 263 A Saturnian-year equals 29.45 Earth-years; a " Saturnian century ago " was, therefore, 2,945 years since, or about Io6o B. C. This was about the time of the rise of Tyre, the reign of King David, &c.-Read Barnes's General ]History, p 79. 93. What is the szun's declination at the wzinter solstice? At the autumnal equinox? (1.) 23-~ S. (2.) o. 94. Will the width of the terrestrial zones always remain exactly as now? (See Astronomy, p. III.) 95. Is it always noon at 12 o'clock? (See Key, p. 250, Question 21.) 96. When the sun's declination is 23-~ N, in what sign is he then locat4d, and what is his R. A.? This is the time of the summer solstice, and the sun is in Cancer, the fourth sign. (See Astronomy, p. 31.) 97. What is the apparent diameter of the sun? The mean apparent diameter of the sun is 32'. 98. How can a sailor find his latitude and lngitlude at sea? (See Astronomy, p. 280.) 99. H-ozw many miles on the solar disk represent a second of apparent diameter? It on the solar disk equals *50.3 miles.-YOUNG. "The spider-line used in a large telescope will cover a portion of the sun's surface I of a second in breadth, or hide a strip over ioo miles wide."

Page  264 264 ANSWERS TO PRACTICAL QUESTIONS Ioo. At wzhat latitude will there be twilighit duTrinzg the entire midsummer night? (See Key, p. 239, Question 23.) When the sun crosses the meridian at midnight, its distance below the horizon is greater than wlen the sun is at any other part of its diurnal path. If, therefore, the depression of the sun below the horizon at midnight be not greater than i8~, the sun will, during the entire night, be within i8~ of the horizon, and hence the twilight will be continuous.-It will be noticed in solving all the problems connected with twilight (as for example, Ques 23, p 239, and Ques. 27, p. 251), that the result will be slightly changed if the exact amount of the obliquity of the ecliptic (23~ 27' 15") be used, instead of the ordinary statement, 23 ~.

Page  1 EXPLAINING MIRRORS AND LENSES. The author has met with the best success in explaining mirrors and lenses to his pupils, by using the following method. A Concave Mirror.-Holding up before his eye the forefinger of each hand, he represents to the pupil how the rays of light enter his eye convergintg; how he then sees the object on diverging rays: thus the visual angle being inct-reased, the apparent size of the object is correspondingly increased. By crossing his two forefingers before his eye he represents the focus, and shows how dciverging rays then enter the eye; the object is seen on converginig rays, the visual angle is tiecreased, and the apparent size of the object correspondingly decreased. A Convex Mirror.-Using the fingers in the same way, he illustrates how diverging rays enter the eye, the object is seen on converging rays, the visual angle is dinminished, and the apparent size of the object correspondingly diminished. The rays of light are not brought to a focus, hence the second effect of a concave mirror cannot be seen. The same illustration can be used in explaining lenses, remembering that the effect of a convex lens is like that of a concave mirror, and of a concave lens that of a convex mirror. At the close of the explanation and illustration witlh the fingers, the following formula is put on the blackboard, and the pupil applies it to each class of mirrors and lenses: CONVERGING (diverging) RAYS ENTER THE EYE, THE OBJECT IS SEEN ON DIVERGING (converging) RAYS; HENCE THE VISUAL ANGLE IS INCREASED (decreased), AND THE IMAGE IS LARGER (smaller) THAN LIFE.

Page  2

Page  3 BARNES'S POPULAR HISTORY OF THE UNITED STATES. By the author of Barnes's "Brief Histories for Schools." Complete in one superb royal octavo volume of 800 pages. Illustrated with 320 wood engravings and 14 steel plates, covering the period from the Discovery of America to the Accession of President Arthur. Part I. Colonial Settlement; Exploration; Conflict; Manners; Customs; Education; Religion, &c., &c., until political differences with Great Britain threatened open rupture. Part II. Resistance to the Acts of Parliament; Resentment of British Policy, and the Succeeding War for American Independence. Part III. From the Election of President Washington to that of President Lincoln, with the expansion and growth of the Republic; its Domestic Issues and its Foreign Policy. Part IV. The Civil War and the End of Slavery. Part V. The New Era of the Restored Union; with Measures of Reconstruction; the Decade of Centennial Jubilation, and the Accession of President Arthur to Office. Appendix. Declaration of Independence; The Constitution of the United States and its Amnendments; Chronological Table and Index; Illustrated History of the Centennial Exhibition at Philadelphia. The wood and steel engravings have been expressly chosen to illustrate the customs of the periods reviewed in the text. Ancient houses of historic note, and many portraits of early colonists, are thus preserved, while the elaborate plans of the Exposition of ].876 are fully given. The political characteristics of great leaders and great parties, which had been shaped very largely by the issues which belonged to slavery and slave labor, have been dealt with in so candid and impartial a manner as to meet the approval of all sections of the American people. The progress of science, invention, literature, and art is carefully noted, as well as that of the national physical growth, thus condensing into one volume material which is distributed through several volumes in larger works. Outline maps give the successive stages of national expansion, and special attention has been given to those battles, by land and sea, which have marked the military growth of the republic. J Specially valuable for reference in schools and households. From Prof. F. F. BARROWS, Brown School, From Prof. S. T. DUTTON, Superintendent Hartford, Conx. of Schools, ANew Haven, Conn. " Barnes's Popular History has been in "It seenls to me to be one of the best our reference library for two years. Its and most attractive works of the kind I concise and interesting presentation of have ever seen, and it will be a decided historical facts causes it to be so eagerly addition to the little libraries which we read by our pupils, that we are obliged to have already started in our larger duplicate it to supply the demand for its schools." use.'I From Hon. JOHN R. BUCK. From Prof. War. MARTIN, of Beattystown, "I concur in the above." N. J. F"This volume is well adapted to the IFrom Hon. J. C. STOCKWELL. wants of the teacher. A concise, well"I heartily concur with Mr. Barrows in arranged summary of events, and just the the within commendation of'Barnes's supplement needed by every educator who Popular History,' as a very interesting and teaches American history." instructive book of reference." From A. MORSE Esq. From Prof. C. T. R. SMITH, Principal of the Lansingburgh, N. Y., Academy. "I cordially concur in the above." the spring I procured a copy of "In the spring I procured a copy of From Rev. WM. T. GAGE.'Barnes's Popular History of the United "I heartily agree with the opinions States,' and have used it daily since, in above expressed." preparing my work with my class in AmeriFrom DAvIn CRARY, Jr. can history, with constantly increasing admiration at the clearness, fairness, and "The best work for the purpose pub- vividness of its style and judicious seleclished." tion of matter." Prices. Cloth, plain edge, $5.00; cloth, richly embossed, gilt edge, $6.00; sheep, marble edge, $7.00; half calf, $8.00; half morocco, $8.00; full morocco, gilt, $10.00. 3

Page  6 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. WATSON'S INDEPENDENT READERS. This Series is designed to meet a general demand for smaller and cheaper books than the National Series proper, and to serve as well for intermediate volumes of the National Readers in large graded schools requiring more books than one ordinary series will supply. Beauty. - The most casual observer is at once impressed with the unparalleled mechanical beauty of the Independent Readers. The Publishers believe that the aesthetic tastes of children may receive no small degree of cultivation from their very earliest school-books, to say nothing of the imlportance of making study attractive by all such artificial aids that are legitimate. In accordance with this view, not less than $25,000 was expended in their preparation before publishing, with a result which entitles them to be considered( " the perfection of conlmmon-school books." Selections. -They contain, of course, none but entirely new selections. These are arranged according to a strictly progressive and novel method of developing the elementary sounds in order in the lower numbers, and in all, with a view to topics and general literary style. The mind is thus led in fixed channels to proficiency in every branch of good reading, and the evil results of "scattering," as practised by most school-book authors, avoided. The Illustrations, as may be inferred from what has been said, are elegant beyond comparison. They are profuse in every number of the series, from the lowest to the highest. This is the only series published of which this is true. The Type is semi-phonetic, the invention of Professor Watson. By it every letter having more than one sountl is clearly distinguished in all its variations without in any way mutilating or disguising the normal form of the letter. Elocution is taught by prefatory treatises of constantly advancing grade and completeness in each volume, which are illustrated by woodcuts in the lower books, and by blackboard diagranms in the higher. Professor Watson is the first to introduce practical illustrations and blackboard diagrams for teaching this branch. Foot-Notes on every page afford all the incidental instruction which the teacher is usually required to impart. Indices of words refer the pupil to the place of their first use and definition. The biographies of authors and others are in every sense excellent. Economy. - Although the number of pages in each volume is fixed at the minimum, for the purpose recited above, the utmost amount of matter available without overcrowding is obtained in the space. Tile pages are mluch wider and larger than those of any competitor and contain twenty per cent more matter than any other series of the same type and number of pages. All the Great Features. - Besides the above all the popular features of the National Readers are retained except the word-building system. The latter gives place to an entirely new method of progressive development, based upon some of the best features of the word system, phonetics, and object lessons.

Page  7 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. PARKER & WATSON'S NATIONAL READERS. The salient features of these works which have combined to render them so popular may be briefly recapitulated, as follows: - I. THE WORD-BUILDING SYSTEM. - This famous progressive method for young children ori(giatedl and was copyrighted with these books. It constitutes a process with which the beginner with wcords of one letter is gradually introduced to additional lists formed by prelixing or affixing single letters, and is thus led alnmost insensibly to the mastery of the ilore difficult constructions. This is one of the most striking modern improvements in methods of teaching. 2. TREATMENT OF PRONUNCIATION.-The wants of the youngest scholars in this delpartment are not overlooked. It may be said that from the first lesson the student by this method nleed never be at a loss for a prompt and accurate rendering of every word encountered. 3. ARTICULATION AND ORTHOEPY are considered of primary importance. 4. PUNCTUATION is inculcated by a series of interesting reading lessons, the simple perusal of which suffices to fix its principles indelibly upon the mind. 5. ELOCUTION. -Each of the higher Readers (3d, 4th, and 5th) contains elaborate, scholarly, and thoroughly practical treatises on elocution. This feature alone has secured for the series many of its warmest friends. 6. THE SELECTIONS are the crowning glory of the series. Without exception it llay be said that no volumes of the samle size and character contain a collection so diversified, judicious, and artistic as this. It embraces the choicest gems of English literature, so arranged as to afford the reader almple exercise in every department of style. So acceptable has the taste of the authors in this department proved, not only to the educational public but to the reading community at large, that thousands of copies of the Fourth and Fifth Readers have found their way into public and private libraries throughout the country, where they are in constant use as manuals of literature, for reference as well as perusal. 7. ARRANGEMENT. - The exercises are so arranged as to present constantly alternating practice in the different styles of composition, while observing a definite plan of progression or gradation throughout the whole. In the higher books the articles are placed in formal sections and classified topically, thus concentrating the interest and inculcating a principle of association likely to prove valuable in submequeut general reading. 8. NOTES AND BIOGRAPHICAL SKETCHES. —These are full and adequate to every want. The biographical sketches present in pleasing style the history of every author laid under contribution. 9. ILLUSTRATIONS. -These are plentiful, almost profuse, and of the highest character or art. They are found in every volume of the series as far as and including the Third Reader. so. THE GRADATION is perfect. Each volume overlaps its companion preceding or followings in the series, so that the scholar, in passing from one to another, is only conscious, by the presence of the new book, of the transition. II. THE PRICE is reasonable. The National Readers contain more matter than any other series in the same number of volumes published. Considering their completeness and thoroughness, they are much the cheapest in the nmarket. i2. BINDING. - By the use of a material and process known only to themselves, in commnon with all the publications of this house, the National Readers are warranted to outlast any with which they may be compared, the ratio of relative durability being in their favor as two to one. 7

Page  8 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOK&. SUPPLEMENTARY READING. Monteith's Popular Science Reader. James Monteith, author of Monteith's Geographies, has here presented a Supple' mentary Reading Book expressly for the work of instruction in reading and science at one and the same time. It presents a number of easy and interesting lessons on Natural} Science and Natural History, interspersed with appropriate selections in prose and poetry from standard authors, with blackboard drawing and written exercises. It serves to instil the noblest qualities of soul and imind, without rehearsing stories of moral and mental depravity, as is too often done in juvenile books. The book is elaborately illustrated with fine engravings, and brief notes at the foot of each page add to the value and teachableness of the volume. 12mlo, half bould, 360 pages. The Standard Supplementary Readers. The Standard Supplementary R;laders (form, rly Swinton's Supplementary Readers), edited by William Swinton and George R. Cathcart, have been received with marked favor in representative quarters from Maine to California. They comprise a series of carefully graduated reading books, designed to connect with any series of school Readers. They are attractive in appearance, are bound in cloth, and the first four books are profusely illustrated by Fredericks, White, Dielman, Church, and others. The six books, which are closely co-ordinated with the several Readers of any regular series, are: - 1. Easy Steps for Little Feet. Supplementary to First Reader. In this book the attractive is the chief aim, and the pieces have been written and chosen with special reference to the feelings and fancies of early childhood. 128 pages, bound in cloth and profusely illustrated. 2. Golden Book of Choice Reading. Supplementary to Second Reader. This book represents a great variety of pleasing and instructive reading, consisting of child-lore and poetry, noble examples and attractive object-reading, written specially for it. 192 pages, cloth, with numerous illustrations 3 Book of Tales. Being School Readings Imaginative and Emotional. Supplementary to Third Reader. In this book the youthful taste for imaginative and emotional is fed with pure and noble creations drawn from the literature of all nations. 272 pages, cloth. Fully illustrated. 4. Readings in Nature's Book. Supplementary to Fourth Reader. This book contains a varied collection of charming readings in natural history and botany, drawn from the works of the great modern naturalists and travellers. 352 pages, dloth. Fully illustrated. 5. Seven American Classics, 6. Seven British Classics. The " Classics " are suitable for reading in advanced grades, and aim to instil a taste for the higher literature, by the presentation of gems of British and American authorship 220 pages each, cloth.

Page  9 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. ORTHOGRAPHY. Smith's Series. Smith's Series supplies a Speller for every class in graded schools, and comprises the most complete and excellent treatise on English Orthography and its companion branches extant. 1. Smith's Little Speller. First round in the ladder of learning. 2. Smith's Juvenile Definer. Lessons composed of familiar words grouped with reference to similar significa tion or use, and correctly spelled, accented, and defined. 3. Smith's Grammar-School Speller. Familiar words, grouped with reference to the sameness of sound of syllables differently spelled. Also definitions, complete rules for spelling and formation of derivatives, and exercises in false orthography. 4. Smith's Speller and Definer's Manual. A complete School Dictioneary, containing 14,000 worce', with various other useful matter in the way of rules and exercises. 5. Smith's.Etymology - Small and Complete Editions. The first and only Etymology to recognize the Anglo-Saxon our mother tongue; containing also full lists of derivatives from the Latin, Greek, Gaelic, Swedish, Norman, &c., &c.; being, in fact, a complete etymology of the language for schools. Northend's Dictation Exercises. Embracing valuable information on a thousand topics, communicated in such a manner as at once to relieve the exercise of spelling of its usual tedium, and combine it with instruction of a general character calculated to profit and amuse. Phillip's Independent Writing Spellerw: 1. Primary. 2. Intermediate. 3. Advanced. Unquestionably the best results can be attained in writing spelling exercises. This series combines with written exercise a thorough and practical instruction in penmanship. Copies in capitals and small letters are set on every page. Spaces for twenty words and definitions and errors are given in each lesson. In the advanced book there is additional space for sentences. In practical life we spell only when we write. Brown's Pencil Tablet for Written Spelling. The cheapest prepared pad of ruled blanks, with stiff board back, sufficient for 64 lessons of 25 words. Pooler's Test Speller. The best collection of " hard words " yet made. The more uncommtn ones are fully defined, and the whole are arranged alphabetically for convenient reference. The book is designed for Teachers' Institutes and " Spelling Schools," and is prepared by an experienced and well-known conductor of Institutes. Wright's Analytical Orthography. This standard work is popular, because it teaches the elementary sounds in a plain and philosophical manner, and presents orthography and orthoepy in an easy, uniform system of analysis or parsing.

Page  13 7HE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. GEOGRAP HY, MONTEITH'S SYSTEM. TWO-BOOK SERIES. INDEPENDENT COURSE. Elementary Geography. Comprehensive Geography (with 103 maps).''lese volumnes are not revisions of old works, not an addition to any series, 1; atle entirely new liroductiols, - each by itself compllete, independent, conipi chensiue, yet simile, brief, cleal), and popular; or, taken together, the most adlllir.lble " si ie s" ever otelred for a colmon-sclool course. They present the followinl features, skilfut ly ilterwoven, the student learning all about one country at a tille. Always revisedi to date of i,'intin i. LOCAL GEOGRAPHY. - Or, the Use of Maps. Important features of the maps are ttle coloring of States as objects, and the ingenious system ior laying down a mauch larger nimiber of names for reference. than are iound on any other maps of samle size, andl wtitlhout ciow(liuL. PHYSICAL GEOGRAPHY.- Or, the Natural Features of the Earth; illustiltedl iiy dile orlgintil llid striking RELIEF MAPS, being bird's-eye views or photograplii: pi(tl're' of the e'arth's surlface. DESCRIPTIVE GEOGRAPHY.- Including the Physical; with some account of (;,i\etl!tll(',ts and R-lces, Aeliirals, &c. HISTORICAL GEOGRAPHY. — Or, a brief summary of the salient points of histilry, explaining the lpresent distribution of nations, origin of geographical names-q. &(c. MATHEMATICAL GEOGRAPHY. — Including Astronomical, which describes the E1" 1 Wll's positioi an cha (racter allo)ng planets; also the Zones, Parallels, &c. COMPARATIVE GEOGRAPHY. -Or, a system of analogy, connecting new lessons with the Irevious onies. Conllarative sizes anid latitudes are sliowni on the mari,!in of e(ach niap, and all eountries are Ileasured in the'' franme of Kansas." TOPICAL GEOGRAPhY. —Consisting of questions for review, and testing the studllent's genleral and, specific knowledge of the subject, with sllggestions for geographical compositions. ANCIENT GEOGRAPHY. - A section devoted to this subject, with maps, will be aplpreciated by teachers. It is seldomll taught inl our commlon schools, because it has heretoflre required thle purchase of a separate book. GRAPHIC GEOGRAPHY, or Map-Drawing by Allen's "Unit of Measuremenlt" systelll (no w almost uiliversally recognized as without a rival), is introduced throulllolit tlhe lessons, an(d not as iian appllendix. CONSTRUCTIVE GEOGRAPHY. -Or, Globe-Making. With each book a set of meali segiiiellts is fulrnislled, with which each student may make his own globe by ollhwinii tlhe (lirectiis given RAILROAD GEOGRAPHY. - With a gran(l commercial map of the United States, illulstraillng steamler alll ralilroadl routes of travel in the United States, submarine telegraph lines, &c. Also a " Practical Tour inl Eulrole.' MONTEI'TH AND McNALLY'S SYSTEM, THREE AND FIVE BOOKS. NATIONAL COURSE Monteith's First Lessons in Geography. Montelth's New Manual of Geography. McNally's System of Geography. The new edlition of M(,Nally's Geograhlly is now ready, rewritten throughout by Ja!les Molteitil allnd S. C. Frost. In its iew dress, prinlted friol new type, and illlstratedi withl 100 new engravings, it is the latest, most attractive, as well as the most thoroughly practical book on geography extant. 13

Page  14 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. GEOGRAPHY — Continued. INTERMEDIATE OR ALTERNATE VOLUMES IN THE FIVE BOOK SERIES Monteith's Introduction to Geography. Monteith's Physical and Political Geography. z. PRACTICAL OBJECT-TEACHING. - Tile infant scholar is first introduced to a pictuSre whence lie may derive notions of tile shape of the earth, the phenomena of day and night, the dis'ribution of land and water, and the great natural divisions, which nere 0words would fail entirely to convey to the untutored mind. Other pictures follow oil tlhe samne plan, and the child's mind is called upon to grasp no idea without the aid of a pictorial illustration. Carried on to the higher books, this system culminates in Physical Geography, where such matters as climates, ocean currents, the winds, peculiarities of the earth's crust, clouds and rain, are pictorially explained and rendered apparent to the most obtuse. The illustrations used for this purpose belong to the highest grade of art. 2. CLEAR, BEAUTIFUL, AND CORRECT MAPS. —In the lower numbers the Ilaps avoid unnecessary detail, while respectively progressive and affording the pupil new matter fo)r acquisition each time he approaches in the constantly enlargring circle the point of coincidence with previous lessons in the more elementary books. In the Physical and Political Geography the lnaps embrace many new and striking features. One of the most effective of these is the new plan for displaying on each map the relative sizes of countries not represented, thus obviating much confusion which has arisen from the necessity of presemnting maps in the same atlas drawn on different scales. The maps of "McNally"' have long been celebrated for their superior beauty and completeness. This is the only school-book in which the attempt to make a complete atlas also clear and distinct, has been successful. The map coloring throughoutt the series is also noticeable. Delicate and subdued tints take the place of the startling glare of inhalarmonious colors which too frequently in such treatises dazzle the eyes, distract the attention, and serve to overwhelln the nalmes of towns and the Iatural features of the lanlds(cape 3. THE VARIETY OF MAP-EXERCISE. - Starting each time from a different basis, the pupil inll malny instances approaches the salne fact no less than six times, thus indelibly impressing it llpoun his memory. At the same time, this system is not allowed to becomelll wearisome, the extent of exercise on each subject being graduated by its relative illlmortance or difficulty of acquisitioll. 4. THE CHARACTER AND ARRANGEMENT OF THE DESCRIPTIVE TEXT. —'The cream of the science has been carefully'culled, unimllportant t matter rejected, elaboration avoided, and a brief and concise manner of presentation cultivated. The orderly collsideration of topics has contributed greatly to simplicity. Due attention is paid to the facts in history and astronolmy which are inlseparably connected with and important to the proper undlerstanding of ge~ography, and such only are admitted on any termlls. In a word, the National System teaches geography as a scienlce, pure, simple, and exhaustive. 5. ALWAYS UP TO THE TIMES. - The authors of these books, editorially speaking, never sleep. No chlange occurs in the boundaries of countries or of counties, no new discovery is made, or railroad built, that is not at once noted and recorded, and the next edition of each volulmne (arries to every school-roonl the new order of thin-is. 6. FORM OF THE VOLUMES AND MECHANICAL EXECUTION. - The Imaps and text are no longer unlllnaturally divorced ill accorlalnce with the timlehonored practice of Inaking text-books on this subject as inconvenient and expensive as possible. On the contrary, all map qluestions ar;, to be found on the page opposite the map itself, and each book is conmplete in one volulle. Tile mechanical execution is unrivalled. Paper, printing, and binding are everything that could be desired. 7. MAP-DRAWING. -- III 1869 the system of imap-drawing devised by Professor Jerome Allen wilas secured e.rclusively for this series. It delives its claim to originality and usefullless fromn the introduction of a fixed unit of mealsurement applicable to every map. The principles beiing so few, simple, and comprellensive, the subject of map-drawingr is relieved of all practical difficulty. (In Nos. 2, 2*, and 3, and published separately.) 8. ANALOGOUS OUTLINES. -At the same time with niap-drawing was also introduced (in No. 2)a new and illgenious variety of Object Lessons, consisting of a comparison of the outlilegs of countries with familiar oljeWts pictorially repreezst" 14

Page  16 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. GEOGRAPHY - Continued. Monteith's Physical Geography. This is a clear, brief statement of the lphysical attributes of the earth and their relations to the heavens. The illustrations and maps are numerous and helpful. It provides full instruction in this important branch of study ill an attractive way for the youngest scholars. It contains 54 pages in quarto form. MAP-DRAWI NG. Monteith's Map-Drawing Made Easy. A neat little book of outlines and instructions, giving the "corners of States" in suitable blanks, so that maps can be drawn by ulnskilful hands from any atlas; with instructions for written exercises or compositions oni geographical subjects, and coluparative geography. Monteith's Manual of Map-Drawing (Allenl's System). The only consistent plan, by which all maps are drawn onl one scale. By its use much timle may be saved, and much interest and accurate klowledge gained. Monteith's Map-Drawing and Object Lessons. The last-named treatise, bound with Mr. Monteith's ingenious system for committing outlines to memory by umeans of pictures of living creatures and familiar objects. Thus, South America resembles a dog's head; Cuba, a lizard; Italy, a boot; France, a coffee-pot; Turkey, a turkey, &c., &c. Monteith's Colored Blanks for Map-Drawing. A new aid in teaching geography, which will )be found especially useful in recitations, reviews, and examinations. The series comprises any section of the world required. Monteith's Map-Drawing Scale. A ruler of wood, graduated to the "' Allen fixed unit of measurement." WVALL MAPS. Monteith's Pictorial Chart of Geography. The original drawing for this beautiful and instructive chart was greatly admired in the publisher's " exhibit " at the Centennial Exhibition of 1876. It is a picture of the earth's surface with every natural feature displayed, teaching also physical geography, and especially the mutations of water. The uses to which man puts the earth and its treasures and forces, as Agriculture, Mining, Manufacturing, Commerce, and Transportation, are also graphically portayed, so that the young learner gets a realistic idea of "the world we live in," which weeks of book study might fail to convey. Monteith's School Maps, 8 Numbers. The "School Series" includes the Hemispheres (2 maps), United States, No;th America, South America, Europe, Asia, Africa. Price, $2.50 each. Each map is 28 x 34 inches, beautifully colored, has the names all laid down, and is substantially mounted on canvas with rollers. Monteith's Grand Maps, 8 Numbers. The "Grand Series" includes the Hemispheres (1 map), North America, United States, South America, Europe, Asia, Africa, the World on Mercator's Projection, and Physical Map of the World. Price, $5.00 each. Size, 42 x 52 inches, names laid down, colored, mounted, &c. Monteith's Sunday-School Maps. Including a map of Paul's Travels (95.00), ome of Ancient Canaan (0.3.00), and Modern Palestine (:3.00), or Palestine and Canaan together ($5.00).

Page  17 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. MATHEMATICS. DAVIES'S COMPLETE SERIES, ARITHMETIC. Davies' Primary Arithmetic. Davies' Intellectual Arithmetic. Davies' Elements of Written Arithmetic. Davies' Practical Arithmetic. Davies' University Arithmetic. TWO-BOOK SERIES. First Book in Arithmetic, Primary and Mental. Complete Arithmetic. ALGEBRA. Davies' New Elementary Algebra. Davies' University Algebra. Davies' New Bourdon's Algebra. GEOMETRY. Davies' Elementary Geometry and Trigonometry. Davies' Legendre's Geometry. Davies' Analytical Geometry and Calculus. Davies' Descriptive Geometry. Davies' New Calculus. MENSURATION. Da-vies' Practical Mathematics and Mensuration, Davies' Elements of Surveying. Davies' Shades, Shadows, and Perspective. MATHEMATICAL SCIENCE. Davies' Grammar of Arithmetic. Davies' Outlines of Mathematical Science. Davies' Nature and Utility of Mathematics. Davies' Metric System. Davies & Peck's Dictionary of Mathematics. 17

Page  18 THE,VA TIONAL SERIES OF STADIYlAi'D SCHOOL-BOOKS. DAVIES'S NATIONAL COURSE OF MATHEMATICS. ITS RECORD. In claiming for this series the first place among American text-books, of whatever class, the l)ublishers appeal to the mlaglilicenl t record which its volulllles lhave earned during the thirt/-Jire ye-(ts of Dr. Charles Davies's llatlhemtatical labors. Thle unreitting exertions of a I1fe-time have placed the mordern series on the samle prout elillellce amolg compnetitors tlhat eachl of its predecessors had successively eiijoyed il a course of constantly inmprovexd editinons, now rounl(ed' to their perlfet:t fruition, - for it seems almost thalt this scieice is susceptible of no further demolllstration.l Durlig the period alluded to, many a aiuthors i editors in this department started ilto publi; notice, and, by borrowing ideas and prtil)ocesses originlal witil Dr. Davies, have enjoyed a briei poiularity, but are now almost unknown. o, Many of the series of to-day, built upon a similar basis, and described as " iodlern books," are destineti to a simila;r iate; wvlile the 1most far-seeing eye will tind it diiiicuit to fix tile tine, o. the basis of any datta afordletd by their p:.ast history), wilen these books will cease to Increase and prosper, anlldl,ix a still irller hold oil tile ailection of every elucaLced Aellencaln. One c,aus of thins unparalleled tpopul:ln ity is fiblund ill tile fact that thle ell telrllse of the author did inot cease with the ori'gin:ll conl!,ietioni of his books. Always a practicai teacherl,' e has incorporated ill his text-books froll timie to time tile a;ivantagesof evecry iniurovelneut in Inetlhol1s of teachilug. and every advance is sceltice. Dtullrg ail the yeaLrs in whliclh lie hlasheen lab,,ring lhe constanltly submiitted his owu theories ai tlhose of otllers to the praetical test of the ciass-roo:l, lap)roving, reJectinlg, olr lofliifyllg thenl as the exierience thus obtainedi miight sutggest. Iin this way iie has beeli aide to prodlucde an allmlost perreEt series of class-books. in which every department of niatlhelnatis has received minute andl exihaustive attentiuon. Uponll the death of Dr. Davies, which took pl;ace in 1S76, his work was immediately talell tui by his frlller pullil aut ndatllelmatical associate of mlany years, Prof. W. G. Peck, LL. D., of Columbia College. By lilin, with Prof. J. II. Van Alnrlinge, of Columbia College, the originlal series is kept carefully revised and up to tle times. DAVIES'S SYSTEMI IS THE ACKNOVWLEDGED NATIONAL STANDARD FOR THE UNITED STATES, for the followitg reasotls:1st. It is the basis of illstriuction in the great national schools at West Point and Annapolis. 2d. It lihas received the qanasi indorsement of the National Congress. 3d. It is esxclusively used in the public schools of the Nstihnal Capital. 4th. Tihe officials of the Government use it as authority in a;ll cases imnvolving mathiematilcal questions. 5th. Our great sol(diers and sailors coinmtan7ling the national a.ries and navies were educated ill this systein. So have beenl a lmajority of emhilent scientists in this counltry. All these refer to " Davies" as autlhority. 6th. A larer numnber of American citizens have received their education from this than from any other series. 7th. Tie series has a larger circtlation th rotihout the whole country tlian any other. behig exteisively used in every State im the Union.

Page  19 THE NATIONAL SERIES OF STANDARD SCHeOL-BOOKS. DAVIES AND PECK'S ARITHMETICS. OPTIONAL OR CONSECUTIVE. The best thoughts of these two illustrious mathematicians are combined in the following beautiful works, which are the natural successors of Davies's Arithluetics, sulniptuously printedl, and bound ill crilisoll, green, and gold: - Davies and Peck's Brief Arithmetic. Also called the " Elelmentary Arithlllletic. " It is tile shortest presentation of the subject, and is udtqatte for all grades in collllllmmon schools, beilg a thorough introduction to practical lite, except for the specialist. At first tlle autlors play with tilhe little learner for a few lessons, by object-teaching all( kindred alluremlents; but he soo1 lbegills to realize that study is earliest, as he becolmes falliliar with tile simpler operations, and is delighllted to lind himself master of inllortant results. The second part reviews the FunTdamental Operations on a scale proportioned tu the enilarged intelligence or the learller. It establishes the General Principles and Properties of Numbllers, ald then piroceeds to Fractions. Currelcy and the Metric System are fully treated in comiec tion with Decimlals. Componld Numbers and Reduction follow, alld lilally l'ercentage with all its varied applications. A1) Index of words and pliinciples coiicludes the 1(book, for which every scholar and most, teachers will be grate'lll. How mnuch timle has been spent in searching for a halfforgotteln definitioll or principle in a lormer lesson! Davies and Peck's Complete Arithmetic. Tlis workll; celtaiily deserves its 11ilae in the best sense. Th'lough complete, it is not, like most othlels wlhichl lear the same title, cumsbersusie. Tl:ese autlhors excel in clear, lucid delnonstrations, teaching thle science pure and simpllle, yet not ignoring convenient nietliods andi practical aIlpplicationls. F'o turnligig out a thorough business man no other work is so well adapted. He will have a (lear conmlluelelhsion of the science as a whole, alid a working acquaintance with dletai s wllichl Iiust serve hilni well in all emergencies. Distinguisllillg features of the libook are the logical progression of the subjects alid the great variety of practical Irolemls, lot iirzzezi.;, whicl are lelleath the dignity of educational science. A clearlilnlded critic hias said of Dr. Peck's work that it is fiee froml tllt juggling %with numbers wlicl ollie authors flalsely call' Anialysis." A series of Talules for converLing ordinary weights alnd measures into the Mletric:ysteml appear in the later editions. PECK'S ARITHMETICS. Peck's First Lessons in Numbers. This book lcills w ith lic(torial illllustratiolls, and unfolds gradually the science of unminbernes. It lloticeably sinillifies thle sublject by develoling the ipilntilples of addition anid sul)tiactioln simllultanleously ~ as it does, also, those of multiplication and division. Peck's Manual of Arithmetic. Tliis Ioolk is (lesignllel especially or those who seek sufficient instruction to carry thelin sllceesstullly thllrough practical life, but have nlot time for extended study. Peck's Complete Arithmetic. This collplleles tile series but is a iruch briefer hook than most of the complete arithmnetics, and is recolmmlended not oiily for what it contains, but also for what is omittedl. It mllay be said of Dr. Pecl's books more truly than of any other series published, that they are clear and silnlle in delfiition iand rule, and that superfluous matter of every kind ha1s 1)ecn f;iitltfully eliimiinated, thus magnifying the working value of the book asd saving unnecessary expense of time anld labor. 10

Page  20 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. BARNES'S NEW MATHEMATICS. In this series JOSEPH FICKLIN, Ph. D., Professor of Mathematics and Astronomy in the University of Missouri, has combined all the best and latest results of practical anti experimental teaching of arithmetic with the assistance of many distinguished mlathematical authors. Barnes's Elementary Arithmetic. Barnes's National Arithmetic. These two works constitute a complete arithmetical course in two books. They meet the demand for text-books that will help students to acquire the greatest amount of useful and practical knowledge of Arithmetic by the smallest expenditure of titme, labor, and money. Nearly every topic in Written Arithmetic is introduced, and its principles illustrated, by exercises in Oral Arithmetic. The free use of Equations; the concise method of conlbining and treating Properties of Numbers; the treatment of Multiplication and Division of Fractions in two cases, and then reduced to one; Cancellation by the use of the vertical line, especially in Fractions, Interest, and Proportion; the brief, simple, and greatly superior method of working Partial Payments by the "Time Table " and Cancellation; the substitution of formulas to a great extent for rules; the full and practical treatment of the Metric Systeum, &c., indicate their completenless. A variety of methods and processes for the samre topic, which deprive the pupil of the great benefit of doing a part of the thinki.nq and labor for himself, have been discarded. The statement of principles, definitions, rules, &c., is brief and simple. The illustrations and methods are explicit, direct, and practical. The great number and variety of Examples embody the actual business of the day. The very large amount of matter condensed in so sl-all a compass has been accomplished by economizing every line of space, by rejecting superfluous matter and obsolete terms, and by avoiding the repetition of analyses, explanations, and operations in the advanced topics which have been used in the more elementary parts of these books. AUXILIARIES. For use in district schools, and for supplying a text-book in advanced work for classes having finished the course as given in the ordinary Practical Arithmetics, the National Arithmetic has been divided and bound separately, as follows: — Barnes's Practical Arithmetic. Barnes's Advanced A rithmetic. In many schools there are classes that for various reasons never reach beyond Percentage. It is just such cases where Barnes's Practical Arithmletic will answer a good purpose, at a price to the pupil much less than to buy the complete book. On the other hand, classes having finiihed the ordinary Practical Arithmetic can proceed with the higher course by using Barnes's Advanced Arithmetic. For primary schools requiring simply a table book, anid the earliest rudiments forcibly presented throughi object-teaching and copious illustrations, we have prepared Barnes's First Lessons in Arithmetic, which begins with the most elementary notions of numbers, and proceeds, by simple steps, to develop all the fundamental principles of Arithmetic. Barnes's Elements of Algebra. This work, as its title indicates, is elementary in its character and suitable for use, (1) in such public schools as give instruction in the Elements of Algebra: (2) in institutions of learning whose courses of study do not include Higher Algebra; (3) in schools whose object is to prepare students for entrance into our colleges and universities. This book will also meet the wants of students of Physics who require scne kncllasde ot 20

Page  21 THE NA TfONAL SERIES OF STANDARD SCHOOL-BOOKS. Algebra. The student's progress in Algebra depends very largely upon the proper treatment of the four Fundamental Operations. The terms Addition, Subtraction, Multiplicatzon, and Division in Algebra have a wider meaning than in Arithmetic, and these operations have been so defined as to include their arithmetical meaning; so that the beginner is sirt)ly called upon to enlarge his views of those fundamental operations. Much attention has been given to the explanation of the negative sign, in order to remove the well-known difficulties in the use and interpretation of that sign. Special attention is here called to " A Short Method of Renloving Symbols of Aggregation," Art. 76. On account of their importance, the subjects of Factoring, Greatest CoLmmon Divisor, and Least Common M.ultiple have been treated at greater length than is usual in elementary works. In the treatment of Fractions, a method is used which is quite simple, and, at tie same time, more general than that usually employed. In connection with Badicl Quantities the roots are expressed by fractional exponents, for the principles and rules applicable to integral exponents may then be used without modification. The Equation is made the chief subject of thought in this work. It is defined near the beginning, and used extensively in every chapter. In addition to this, four chapters are devoted exclusively to the subject of- Equations. All Proportions are equations, and in their treatment as such all the difficulty commonly connected with the subject of Proportion disappears. The chapter on Logarithms will doubtless be acceptable to many teachers who do not require the student to master Higher Algebra before entering upon the study of Trigonometry. HIGHER MATHEMATICS. Peck's Manual of Algebra. Bringing the methods of Bourdon within the range of the Academic Course. Peck's Manual of Geometry. By a method purely practical, and unembarrassed by the details which rather confuse than simplify science. Peck's Practical Calculus. Peck's Analytical Geometry. Peck's Elementary Mechanics. Peck's Mechanics, with Calculus. The briefest treatises on these subjects now published. Adopted by the great Universities: Yale, Harvard, Columbia, Princeton, Cornell, &c. Macnie's Algebraical Equations. Serving as a complelent to the more advanced treatises on Algebra, giving special attention to the analysis and solution of equations with numerical coefficients. Church's Elements of Calculus. Church's Analytical Geometry. Church's Descriptive Geometry. With plates. 2 vois. These volumes constitute the "West Point Course" in their several departments. Prof. Church was long the eminent professor of mathematics at West Point Military Academy, and his works are standard in all the leading colleges. Courtenay's Elements of Calculus. A standard work of the very highest grade, presenting the most elaborate attainable survey of the subject. Hackley's Trigonometry. With, applications to Navigation and Surveysing, Nautical and Practical Geometry, and G'ffide'sy. 21

Page  22 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS, GENERAL HISTORY. Monteith's Youth's History of the United States. A History of the United States for beginners. It is arranll(ed upon tile cateclietical plan, with illustrative Inaps and engrravings, review questions, dates in plarentheses (that their study may be optjonal with thle ynrllner class of learners), and interesting biographical sktches of all persons who have been prominently idelmtified with the 0history of our (ounu1try. Willard's United States. School and University Editions. The plan of this standard work is chronologically exhibited in front of the titlepage. Tihe maps and sketches are found useful assistants to the memnory; and dates, usually so udifficult to remember, are so systematically arranged as in a great degree to obviate the difficulty. Candor, impartiality, and accuracy are the distinguishing features of the narrative portion. Willard's Universal History. New Edition. The most valuable features of the " UI:ited States" are reproduced in this. The peculiarities of the work are its great conciseness and the prominence given to the chronological ordler of events. The margin marks each successive era with great dis. tinctilets, so that the pupil retains not only the event but its time, and thus fixes the order of history firmny and usefully in his mind. Mrs. Willard's bouoks are constantly revised, anll at a4l times written up to embrace important historical events of recent d:lte. Professor Arthur Gilman has edlited the last twenty-five years to 1882. Lancaster's English History. B:. the Master of the Stoughton Granimmar School, Boston. The most practical of the " lIrief booksl;." Though short, it is not a bare and uninteresting outline, but conltailns enoulgh of explanation and detail to make intelligible the crtse atnd c:ffect of events. Their relations to the history and developmlent of the American people is made specially prolninen;. Willis's Historical Reader. Beillg Collier's Great Events of History adapted to American schools. This rare enitofe of general history. rein arkable for its cllarminlg style and judicious selection of eveluts on whvliih the destinies of nations have turned. has been skilfully manipulated by Professor Willis. with as few changes as would blring the Unlited States inlto its proper nositiuon in the historical perspective. As reader or text-book it has few equals anld no sulerior. Berard's History of England. By an authoress well known for the success of her History of the United States. Tile social life of the English people is felicitously interwoven, as in fact, with the civil amll military transn.actions of the realm. Ricord's History of Rome. Pou.sesses the lcharm of an attractive romance. The fables withll which this history aboolnds are introduicedl in su(ch a way as not to doaeive ths incxptericuced. while adding; materially to the value of the work as aL reliable iudex to the. character and institutionus as well a~ the history of tlle Rouian Ieople.

Page  23 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. HISTORY - ColtinLued. Hanna's Bible History. The only compendium of Bible inarrative which affords a connected and chronological view of the important events there recorded, divested of all superfluous detail. Summary of History; American, French, and English. A well-proportioned outline of leading events, condenlsing the substance of tile more sxtensive text-books in common use into a series ol statements so brief, tlhatt every word may be comnuitted to mnem!ory, and yet so comprehensive that it presents an accurate tlough general view of the lwhlole continuous life of nlations. Marsh's Ecclesiastical History. Affordling the History of the Churc(h in all ages, with acrcounts of the pagan world during the biblical periods, alnd tile charlacter, rise, and progress or all religions, as well as the various sects of the worshlippers of Christ. The wvork is entirely nonll-sectarian, thoughll strictly catholic. A separate volume contains carefully prepared questiouls for class nse. Mill's History of the Ancient Hebrews. With valuable Chronological Clharts, prepared by Prolessor Edwards of N. Y. This is a stccinet account of the chosen people of God to the timne of the destruction of Jerusalem. Complete in one volume. Topical History Chart Book. By Miss Ida P. Whiteollb. To be used in connection with any/ History, Ancient or iodlern, instead of the ordinary blank book for sumlmary. It embodies the names of co0t55t./)Slfy rulersc fronl the earliest to the present time, with blanks under each, in which thle pupil may write the summlary of the life of the ruler. Gilman's First Steps in General History. A "suggrestive outline " of rare compactness. Esach country is treated by itself, and the Unlited States receive special attention. Frequent mnaps, co(ltelmporary evellts in tables, references to standard works for fuller details, alnld a moinute Index constitute the " Illustrative Apparatus." From no other work thatt wve know of can so suecinct a view of the world's historly be obtained. Considerinfg the necessary limitation of space, the style is surprisingly vivid, and at times even ornate. In all respects a charming, though not the less practical, text-book. Baker's Brief History of Texas. Dimitry's History of Louisana. Alison's Napoleon First. Thle history of Europ)e froml 17S8 to 1815. By Archibald Alison. Abridged by Edward S. Gould. (One vol., 8vo, with appelndix, questions, and maps. 550 pages. Lord's Points of History. ThIe salienst points in the history of the Norld arranged catectletically for class use or for review and examination of teacher ol pupil. By John Lord, LL.D. 12nmo, 300 ipages. Carrington's Battle Maps and Charts of the American Revolution. Topographic{al Maps and Chlronological Charts of every battle, with 3 steel portraits of Waslliilgton. Svo, cloth. Condit's History of the English Bible. For thlleoloical and historical studenlts this book inls an intrinsic value. It gives the history of all the English translations down to the pr(esent time, together with a careful feview of their influence upon English literature and language. 23

Page  24 THE VA TIONAL SERIES OF STANDARD SCHOOL-BOOKS. BARNES'S ONE-TERM HISTORY SERIES. <,, m p; Z Z "v <Sal! Re A Brief History of the United States. This is probably the MOST ORIGINAL SCHOOL-BOOK pub, lished for many years, in any department. A few of its claims are the following: — i. Brevity. - The text is complete for grammar sehool _ — [ i [] or intermediate classes, in 299 121ino pages, large type. It mlay readily be completed, if desired, in one term of 2. Comprehensiveness. - Though so brief, this book'///~ / ]-/~/'~~~"/~. ~-~- ~ contains the pith of all the wearying contents of the larger -' -f / ni- misanuals, and a great deal more than the memory usually retains lroul the latter. 3. Interest has been a prime consideration. Small books have heretofore been bare, full of dry statistics, unattractive. This one is charmingly written, replete with anecdote. and brilliant with illustration. 4. Proportion of Events. -It is remarkable for the discrimination with which the different portions of our history are presented aecording to their importance. Thus the older works, being already large books when the Civil War took place, give it less space than that accorded to the Revolution. 5. Arrangement. -In six epochs, entitled respectively,'Discovery and Settlement, the Colonies, tile Revolultion, Growth of States, the Civil War, and Current Events. 6. Catch Words. - Each paragraph is preceded by its leadling thought in prominent type, standing in the student's mind for the whole paragraph. 7. Key Notes. -Analogous with this is the idea of grouping battles, &c., about some central event, which relieves the sameness so common in such descriptions, and renders each distinct by some striking peculiarity of its own. 8. Foot-Notes. -These are crowded with interesting matter that is not strictly a part of history proper. They may be learned or not, at pleasure. They are certain in any event to be read. 9. Biographies of all the leading characters are given in fill in foot-notes. Io. Maps. - Elegant and distinct maps from engravings on copper-plate, and beautifully colored, precede each epoch, and contain all the places named. ii. Questions are at the back of the book, to compel a more independent use of the text. Both text and questions are so worded that the pupil must give intelligent answers IN HIS OWN WORDS. "Yes" and "No " will not do. 24

Page  25 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. HItSTORY - Continued. I2. Historical Recreations. — These are additional questions to test the student's knowledge, in review, as: "What trees are celebrated in our history?" "When did a fog save our army?" "What Presidents died in office?" "When was the Mississipli our western boundary?" "Who said,'I would rather be right than President'? " &c. I3. Thl Illustrations, about seventy in number, are the work of our best artists and engravers, produced at great expense. They are vivid and interesting, and mostly upon sulbjects never before illustrated in a school-book. I4. Dates. — Only the leading dates are given in the text, and these are so associated as to assist the memory, but at the head of each page is the date of the event first mentioned, and at the close of each epoch a summary of events and dates. I5. The Philosophy of History is studiously exhibited, the causes and effects of events being distinctly traced and their inter-connection shown. I6. Impartiality. — All sectional, partisan, or denominational views are avoided. Facts are stated after a careful comparison of all authorities without the least prejudice or favor. 27. Index. - A verbal index at the close of the book perfects it as a work of reference. It will be observed that the above are all particulars ill which School Histories have been signally defective, or altogether wanting. Many other claims to favor it shares in common with its predecessors. TESTIMONIALS. From PROF. Wm. F. ALLEN, State [jiO- has been used for several years in the versity of Wi'vsconsin. Lewiston schools, and has proved a very "Two features that I like 1ery? much satisfactory work. I have examined the are the anecdotes at the foot of the page new edition of it." and the'HIistorical Recreations' in the Appendix. The latter, I think, is quite Fiom HON. R. K. BUCHEL,, City Superina ns-w feature, and the other is very well tendet S.hools, Lancaster, Pa. executed." " It is the best history of the kind I have From HON. NEWTON BATEMAN, Superin- ever seen." tendent Public Instruction, Illinois. From T. J. CHARLTON, S'uperintendent "Barnes's One-Term History of the Public Schools, lVinccnnes, Ind. United States is an exceedingly attrac- "We have used it here for six years, tive and spirited little 1hook. Its claim and it has given almost peri'ect satisfacto several new and valuable features seems tion.... The notes in fine print at the well founded. Under the form of six well- bottom of the pages are of especial value." defined epochs, the history of the United States is traced tersely, yet pithily, from From PROF, WM. A. MowRY, E. J- C. the earliest times to the present day. A School, Providence, R. I. good map precedes each epoch, whereby e the history and geograplhy of the period Permit me to exress my high appremay bbe studied totetller, as tl~ry ulu/s ciation of your book. I wish all textshould be. The syllabus of each paragraph for the young had equal merit." is made to stand in such bold relief, by the use of large, heavy type, as to be of From HON. A. M. KEILEY, City Attorney, mluch mnemonic value to the student. The Late MaZor, and President of the Schoot book is written in a sprightly and i- ard, City f ichmoa, Va. quant style, the interest never flaggin " I do not hesitate to volunteer to you from beginning to end, -a rare and diffi- the opinion that Barnes's History is encult achievement in works of this kind." titled to the preference in ahlost every respect that distinguishes a good schoolFroim HON. ABNER J. PHIPPS, Slperiml- book... The narrative generally exhibits tendent S.hols, L'-wistonz, laine. the temper of the judge; rarely, if ever,' Barnes's History of the United States of the advocate." 25

Page  28 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS, DRAWING. BARNES'S POPULAR DRAWING SERIES. Based upon the experience of the most successful teachers of drawing in the United states. The Primary Course, consisting of a manual, ten cards, and three primary Irawing 1)oo0s, A, B, alnd C. Intermediate Course. Four numbers and a manlal. Advanced Course. Four numllbers and a manual. Instrumental Course. Four numbers and a imanual.'lle hLelllt elOare, Alva.tced, andll Instrumlental Courses are furnished either in book or0 card orlll at the samle pricts. The books contain the usual blanks, with the unusual advanlltage of opening iolm the.ulpil, - llacing tile copy directly in front and above the blanlk, tlus occulpying hiut little desl;-room.ll The cards are ill tie endl Inote ecoilolmnica! than the books, if used in connection with the patent blalk bfolios that accotl)anyll this series. The cards are arranged to be bound (or tied) in the folios and removed at pleasure. The pupil at the end of each number has at complete book, containing only his own work, while the copies are preserved and inserted in another fol,o ready for use in the next class. Patent Blank Folios. No. 1. Adapted to Intermediate Course. No. 2. Adapted to Advanced and Iinstrumiental Courlses. ADVANTAGES OF THIS SERIES. The Plan and Arrangement. — The examples are so arranged that teachers and pupiils can see, at a glanlce, how they are to ibe treated and where they are to lie copied. Inl this system, copyilg and designingii do not rec(eive all the attention. The plani is broader in its aims, dealing with drawing as a branch of common-school instruction, arai givillg it a wide educational value. Correct Methods. - In this system the pupil is led to rely upon himself, and not upon delusive inmeihanical aids, as printed guide-mlarks, &c. One of thle prinlcipal oljects of any good course in freelland drawing is to educate the eye to estimate location, orlll, anld size. A system which weakens tIhe motive or removes tIle necessity of /hinkii. q is false in theory and ruifnous in practice. The object should he to educate, not craml; to develop the intelligence, lnot teach tricks. Artistic Effect -Tllhe beauty of the exalliles is not destroyed by crowding tile pages with useless and badly printed text. The Manuals contain all necessary instructioin. Stages of Development. - Many of the examples are accompanied by diagrarls, sliowilvg the diflerellt sta-es of developlelnt. Lithographed Examples.-Tlhe examlples are printed in imitation of pencil drawing (Il) ill hard, l)la(:lil:cs) that the plupil's work may resemble tlhem. One Term's Work. -a Each book contains what can lbe acc-ollmplished in an average term, aiid no inore. T'Ilhus a pup)il linihAes one book before beginning another. Quality - not Quantity. - Success in drawing depends uploii the amount of thought exercised by tile lupil, and uot upon the Llrge nmitmher of examdlples drawn. Designing. -Elemllletary desigln is nloie skilfully taught in this systeml than by any otherl. In addlition to tle instl c tion given in tle books, the pupil will filld riited on the insides of tile covers a v\riety of beatutiful patterns. Enlargement and Reduction. —Tlie practice of enlarging anld reducing from copies is nlot colmlllleiced undlil the p-upil is well advanced in the course and therfolre better alde to cooyle with this diflicult feature ill drawilg. Natural Forms. — This is the only (course that gives at convenient intervals easy anl lrogcessive exercises in the drawing of inatural frc]IS. Economy. - By the patent bildilng des( iibed abo e, the copies need not be thrown aside wlieii it book is filled out, but are preserv ed in pelrfec t conditioon for future use. The blank books, only, will Ihav-e to oe ipulr( ased after thle first inltroduction, thus eilectimg a saving of more tlhan hlal in tie usual cost of drawilg-books. Manuals for Teachers. - The ManIuals ac(olnlpanying this series contain practical instructions for cmllductil drawlilg in the class-room, with defi ite directions foi drawing etac of the examples in tle books, instructions for designing, model and object drawing, drawing from natural forms, &c. 28

Page  29 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. DRAWING - Continued. Chapman's American Drawing-Book. The statndalrd American text-book and authlolity in all lbrallches of art. A compilation of art principles. A manual tor the amateur, and basis of study for the professional artist. Adapted for schools and private instruction. CONTENTS. — " Any one who can Learn to Write can Learn to Draw." - Primary Instruction in Drawig.- Rudiments of Drawinl the lunlani' Head. -- Rudiments in Drawing, the Human Figure. - Rudiments of Drawing. - The Elements of Geometry.Perslpective. - Of Studying and Sketching from Nature. - Of P'aintillg. - Etching and Encgraving. - Of Modelling. - Of Composition. - Advice to the American Art-Student. The work is of course magnificently illustrated with all the original designs. Chapman's Elementary Drawing-Book. A progressive course of practical exercises, or a text-book for the training of the eye and hand. It contains the elements from the larger work, and a copy should be in the hands of every pupil; while a copy of the "American Drawing-Book," named above. should be at hand for reference by the class. Clark's Elements of Drawing. A complete course ill this graceful art, from the first rudiments of outline to the finished sketches of landscIape and scenery. Allen's Map-Drawing and Scale. This method introduces a new era in mi-ap-drawing, for the following reasons: 1. It is a system. This is its greatest merit. — 2. It is easily understood and taught. — 3. Thle eye is trained to exact imeasurement by the use of a scale. -4. By no slecial effort of the Inemiory, distance and comparative size are fixed in the mind. - 5. It discar(ls useless constructionl of lines. -6. It can be taught b)y any tetacher, even though there may lave been no previous practice in Illap-drawing. - 7. Any pupil old enough to study geography can learn by this system, in a short time. to draw accurate maps. - 8. The systeml is not the result of theory, but comes directly from the school-room. It has been thoroughly and successfully tested there, with all grades of pupils. — 9. It is economical, as it requires no mapping plates. It gives the pupil the ability of rapidly drawing accurate nlaps. FINE ARTS. Hamerton's Art Essays (Atlas Series):No. 1. The Practical Work of Painting. With portrait of Rubells. 8vo. Paper covers. No. 2. Modern Schools of Art.. Incluidimig American, English, and Continental Painting. 8vo. Paper covers. - Huntington's Manual of the Fine Arts. A careful nmanual of instruction in the history of art, up to the present time. Boyd's Kames' Elements of Criticism. The best edition of the best work on art and literary criticism ever produced in English. Benedict's Tour Through Europe. A valuable companion for any one wishing to visit the galleries and sights of the continent of Europe, as well as a charming book of travels. Dwight's Mythology. A 1knowle(lge of mythology is necessary to an appreciation of ancient art. Walker's World's Fair. The industrial and artistic display at the Centennial Exhibition 29

Page  31 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. BOOK-KEEPING TEXT. Powers's Practical Book-keeping. Powers's Blanks to Practical Book-keeping. A Treatise on Book-keeping, for Public Schools and Academies. By Millard R. Powers, M. A. This work is designed to impart instruction upon the science of accounts. as applied to mercantile business, and it is believed that more knowledge, and that, too, of a more prae(tical nature, can tie gained by the plan introduced in this work, than by any other published. Folsom's Logical Book-keeping. Folsom's Blanks to Book-keeping. This treatise embraces the ilteresting and important discoveries of Professor Folsom (of the Albanly ".Bryant & Strattol College "), the partial enunciation of which inl lectures and otherwise has attracted so mIuItcl attention in circles interested in commercial education. After studying business phenomena for many years, he has arrived at the positive laws and principles that underlie the whole subject of accounts; linds that the science is based in value as a generic term; that value divides inlto two classes with varied species: that all the exchanges of values are reduc:ible to nine equations; and that all the results of all these exchanges are limited to thirteen in number. As accounts have been universally taught hitherto, without setting out from a radical analysis or definition of values, the science has been kept in great obscurity, and been made as difficult to impart as to acquire. On the new theory, however, these obstacles are chiefly removed. In reading over the first part of it, in which the governing laws and principles arc discussed, a person with ordinary intelligence will obtain a fair conception of the double-entry process of accounts. But when he comes to study thoroughly these laws and principles as there enunciated, and works out the examples and melloranda which elucidate the thirteen results of business, the student will neither fail in readily acquiring the science as it is, nor in becoming able intelligently to apply it in the interpretation of business Smith and Martin's Book-keeping. Smith and Martin's Blanks. This work is by a practical teacher and a ipractical book-keeper. It is of a thoroughly popular class, and will be welconled by every one who loves to see theory and practice combined in an easy, concise, and methodical form. The single-entry portion is well adapted to supply a want felt in nearly all other treatises, which seem to be prepared mainly for the use of wholesale merchants; leaving retailers, mechanics, farlners, &c., who transact the greater portion of the business of the country, without a guide. The work is also commended, on this account, for general use in young ladies' seminaries, where a thorough grounding in the simpler form of accounts will be invaluable to the future housekeepers of the nation.. The treatise on double-entry book-keeping combines all the advantages of the Iost recent methods with the utmost simplicity of application, thus affording tile pupil all the advantages of actual experience in the countilg-house, and giving a clear comprehension of the entire subject through a judicious course of mercantile transactions. PRACTICAL BOOK-KEEPING. Stone's Post-Office Account Book. By Micah H. Stone. For record of Box Rents and Postages Three sizes always in stock. 64, 108, and 204 pages. INTEREST TABLES. Brooks's Circular Interest Tables. To calculate simple and compound interest for any amount, from 1 cent to $1,000, at aurrent rates from 1 day to 7 years. 31

Page  32 TItE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. DR. STEELE'S ONE-TERM SERIES, IN ALL THE SCIENCES. Steele's I4-Weeks Course in Chemistry. Steele's I4-Weeks Course in Astronomy. Steele's I4-Weeks Course in Physics. Steele's I4-Weeks Course in Geology. Steele's I4-Weeks Course in Physiology. Steele's I4-Weeks Course in Zoology. Steele's I4-Weeks Course in Botany. Our text-books in these studies are, as a general thing, dull and uninteresting. They contain from 400 to 600 pages of dry facts and unconnected details. They abound in that which the student cannot learn, much less remember. The pupil commences the study, is confused by the tile print and coarse print, and neither knowing exactly what to learn nor what to hasten over, is crowded through the single term generally assigned to each branch, and frequently comes to the close without a definite and exact idea of a single scientific principle. Steele's " Fourteenl-Weeks Coulses " contain only that which every well-informed person should know, while all that which concerns only the professional scientist is omitted. The language is clear, simple, and interesting, and the illustrations bring the subject within the range of home life and daily experience. They give such of the general principles and the prominent facts as a pupil can make familiar as household words within a single term. The type is large and open; there is no fine print to annoy; the cuts are copies of genuine experiments or natural phenomena, and are of fine execution. In fine, by a system of condensation peculiarly his own, the author reduces each branch to the limits of a single term of study, while sacrificing nothing that is essential, and nothing that is usually retained from the study of the larger manuals in common use. Thus the student has rare opportunity to economize /his time, or rather to employ that which he has to the best advantage. A notable feature is the author's charming "style,"'frtified by an enthusiasm over his subject in which the student will not fail to partake. Believing that Natural Science is full of fascination, he has moulded it into a form that attracts the attention and kindles the enthusiasm of the pupil. The recent editions contain the author's "'Practical Questions" on a plan never'before attempted in scientific text-books. These are questions as to the nature and cause of common phenomena, and are not directly answered in the text, the design being to test and promote an intelligent use of the student's knowledge of the foregoing principles. Steele's Key to all His Works. This work is mainly composed of answers to the PracticalQuestions, and solutions of the problems, ill the author's celebrated "'Fourteen-Weeks Courses " in the several sciences, with many hints to teachers, minor talf)es, &c. Should be on every teacher's desk. Prof. J. Dorman Steele is an indefatigable student, as well as author, and his books have reached a fabulous circulnation. It is safe to say of his books that they have accomplisbed more tangible and better results in the class-room than any other ever offered to American schools, and have been translated into more languages for foreign schools. They are even produced in raised type for the blind. 32

Page  34 THE NATIONAL SERIES OF STANDARO SCHOOL-BOOKS. THE NEW GANOT. Introductory Course of Natural Philosophy. This book -was originally edited froml Gallot's " Popular Physics," by William G. Peck, LL.D., Professor of Mathemllatics alld Astronloly, Co'lilnia College, anld of Mec.hanics in the School of Mines. It has recently beenl revised by Levi S. Burbank, A. M., late Principal of Warren Academy, Woburn, Mass., and James I. Hanson, A.M., Princ(ipal of the High School, Woblurn, Mass. Of elementary works those of M. Ganot stand pre-eminenlt, not only as popular treatises, but as thoroughly scientific expositions of the rilnicilles of Physics. His "Trait6 de Physique " has not only met with unprecedenlted success in France, but has been extensively used in the preparation of the best woriks oni Physics that have beent issued froml the American press. In addition to the "Traite de Physique," which is intended for the use of colleges and higher institutions of learning, M. Ganot published this more elementiary work, adapted to the use of schools and academies, in which he fitllhfully prleselved the prominent features and all the scientific accuracy of the larger vnork. It is clharcterize(l by a well-balanced distribution of subljects, a logical d'evelopment of s(ientific principles, and a remarkable clearness of delinition and explantaition. In addition, it is profusely illustratedl with beautifully executed enllraviigs, admlirably cailculated to convey to tlme miind of the student a clear conception ot tlc ltrincilles. unfolded Their completeness and accuracy are such as to enabtle the len'lher to dispense witlh miuchl of the apparatus usually employed in teach;ling the elemnelnts of Physi(al Science. After several years of great,ojmlarity tile Amlericanl 1Ilublishlers have brought this.mportanlt bliok thoroughly up to tile tilses. The dleatllh or' the a.lomlislhed educttor, Professor Burbank, took place bsefore lie he lad comlleted his work, and it was 11he taken in haind by liis friend, Professor Hansols, who was falmiliar with his plains, anid ilas ably and satisfactorily brought tile work to compllletion. The essential characteristics and general plan of the book have, so far as possible, been retained, but at the sar-e time illany alrts Ilave been entirely rewritten, much new matter added, a large illllnber of new cuts introduceld, an(d the whole treatise thoroughly revised and brought into harmony with the present advanced stage of scientific discovery. Among the nlew features designed to aid in teaching the subject-matter are the sulnmaries of topics, whlicll, it is thought, will be found very convenient in short reviews. As nlany teachers prefer to pirepare their own questions on the text, and many do not have time to spend in the solution of plroblems, it has beenl deemed expedient to insert both the review questions rand problemrns at the end of the volumne, to be used or not at the discretioni of the instructor. Fronm the Churchmnsan. jects of which it treats. That work was intendled for higher institutions of learn" No department of science has uinder- ing, and Mr. Gaiiot prepaler' a nmore gone so many ilnprovements and clhanges elelmentary worik or schools and acadein the last quarter of a century as that of mIes. It is as scientifically accurate as natural philosophy. So many and so ilu- the larger work, and is chaiacterized by portant have been the discoveries aiid a logical development of sciintific princiinventions in every branch of it thllat les, by clearness of definitin and explaeverything seems changed Lbut its fnnda- nation, by a proper distribu:tion of submental principles. Ganot has chapter jeets, and by its admirable engravings. upon chapter upon subjects that were not We here have Ganot's work enhanced in so much as known by nalne to Olmsted; value bythe labors o.f Professor Peck and of and here we have Ganot, first edlited by Messrs. Biurbuk anknd Hanson, and b)rollght Professor Peek, and afterward revised Isy up to our own times. The essential charthe lal.te Mr. Bilrii!ank and Mr. Halisoii. No acteristies of Ganot's work have been reelementary works upon pshilosophmy have tained, but much of the book has been been superior to those of Ganot, either as rewritten, andi many new cuts Ihave beens popular treatises or as scientific exposi- introduced, ma(le necessary by the jpro(gtions of the principles sf physics, and ress of scientific discovery. The short his'Trait6 (le Physique' has not only had reviews, the questions on the text, and a great success in France, but has been the Iprohleums given for solutionl are desirfreely used in this country in thle prepa- able additions to a work of this kind, and ration of American books upon the sub- will give tile book increased popularity." 31

Page  36 THE NATIONAL SERIES OF STANDARD JnOHCOL-BOOKS. FAMILIAR SCIENCE. Norton & Porter's First Book of Science. Sets f)rth the principles of Natural Philosophy, Astroloiny, Clhemistry, Physic:o y. andl Geology, on the catechletical plan for plimary classes an I beginnlers. Chambers's Treasury of Knowledge. Progressive lessons upon — irst, colmmon things which lie most immediately around us, and first attract the attention of the young mind; secontd, corlnmon objects froln ilhe mineral, animal, and vegetable kingdoms, manufactured articles, and miscellaneous substances; third, a systelnatic view of nature under the various sciences. May be used as a reader or text-book. Monteith's Easy Lessons in Popular Science. This book combines within its covers nlore attractive features for the study of science by children than any other book published. It is a reading book, spelling book, colmposition book, drawing book, geography, history, book on blotany, zoology, agriculture, manufactures, comrlmerce, and natural philosoplly. All these subjects are presented in a simple and effective style, such as would be adopted by a good teacher on an excursion with a class. The class are supposed to be taking excursions, with the help of a large pictorial chart of geography, which can be suspended before theml in the school-room. A key of the chart is inserted in every copy of the book. With this book the science of common or familiar things canl be taurllt to beginners. NATURAL PHILOSOPHY. Norton's First Book in Natural Philosophy. Peck's Elements of Mechanics. A suitable introduction to Bartlett's higher treatises on Mechanical Philosophy, and adequate in itself for a complete academical course. Bartlett's Analytical Mechanics. Bartlett's Acoustics and Optics. A complete systeml of Collegiate Philosophy, by Prof. W. H. C. Bartlett, of West Point Military Academy. Steele's Physics. Peck's Ganot. GEOLOGY. Page's Elements of Geology. A volume of Chambers's Educational Course. Practical, simple, and eminently calculated to make the study interesting. Steele's Geology. CHEMISTRY. Porter's First Book of Chemistry. Porter's Principles of Chemistry. The above are widely known as the productionls of one of the most eminent scientif., men of America. The extreme simplicity in the method of presentimng the science, wi'i exhaustively treated, has excited( universal c(ommendation. Gregory's Chemistry (Organic and Inorganic). 2 vols, Tihe sc(ience exhaustively treated. For colleges and medical students. Steele's Chemistry. 36

Page  37 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. NATURAL SCIENCE —Continued. BOTANY. Wood's Object-Lessons in Botany. Wood's American Botanist and Florist. Wood's New Class-Book of Botany. The standard text-looks of the United States in this department. In style they are simple, popular, and lively; in arralgement, easy and natural; in description, graphic and scietiic. The Ta'l'bles for Analysis are reduced to a perfect system. They include the flora of the whole Unital States east of the Rocky Mountains, and are well adapted to the regions west. Wood's Descriptive Botany. A complete flora of all plants growing east of the Mississippi River. Wood's Illustrated Plant Record. A simple form of blanks for recording observations in the field. Wood's Botanical Apparatus. A portable trunk, containing drying pre:ss, knife, trowel, microscope, and tweezers, and a copy of Wood's " Plant Record," - thle collector's complete outfit. Willis's Flora of New Jersey. The most useful book of reference e cer published for collectors in all parts of the country. It contains also a Bot-anical Directory, with addresses of livingl Amllerican botanists. Young's Familiar Lessons in Botany. Colnbinlng simplicity of diction with some degree of technical and scientific knowledge,,or intermediate classes. Specially adapted lor the Southwest. Wood & Steele's Botany. See page 33. AGRICULTURE. Pendleton's Scientific Agriculture. A text-book for colleges and schlools; treats of the following topics: Anatomy and Pllysiology of' Plaiits; Agricultural Meteorology; Soils as related to Physics; Chemistry of tile Atmlospllere; of Plants; of Soils; Fertilizers and Natural Manures; Animal Nutrition, &c. By E. M. Pendleton, M. D., Professor of Agriculture ill the Unliversity of Georgia. From PRESIDENT A. D. WHITE, Cornell From PRESIDENT ROBINSON, of Brown University. University. " Dear Sir: I have'examined your "It is scientific in method as well as in'Text-hlook of Agricultural Science,' and it matter, comprehensive in plan, natural seems to me excellent in view of the pur- and logical in order, compact and lucid in pose it is intended to serve. Many of its statements, and must be u.efnl both as your chalItcrs inlterested me especially, a text-book in agricultural colleges, and and all parts of the work seem to combine as a hand-book for intelligent planters and scienltific, instruction with practical iltfor- farmers." mation in proportions dictated by sound common sense." 37

Page  40 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. JESTHETICS. Huntington's Manual of the Fine Artso A view of the rise and progress of art in differeut countries, p brief account of the most emilnent masters of art. and an analysis of the principles o, art. It is complete in itself, or may precede to a(tvantage the critical work of Lord Kames. Boyd's Kames's Elements of Criticism. The best edition of this standard work; without the study of which none may be considered proficient in the science of the perceptions. No other study can be pursued with so marked an effect upon the taste and refinement of the pupil. ELOCUTION. Watson's Practical Elocution. A scientific presentment of accepted principles of elocutionary drill, with blackboard diagrams and lull collection of examples for class drill. Cloth. 90 pages, 121zo. Taverner Graham's Reasonable Elocution. Based upon the belief that true elocution is the right interpretation of thought, and guiding the student to an intelligent appreciation, instead of a ilerely mechanical knowledge, of its rules. Zachos's Analytic Elocution. All departments of elocution —such as the analysis of the voice and the sentence, phonology, rhythm, expression, gesture, &c. —are here arranged for instruction in classes, illustrated by copious examples. SPEAKERSS Northend's Little Orator. Northend's Child's Speaker. Two little works of the same grade but different selections, containing simple and attractive pieces for children under twelve years of age. Northend's Young Declaimer. Northend's National Orator. Two volumes of prose, poetry, and dialogue, adapted to intermediate and grammar classes resplectively. Northend's Entertaining Dialogues. Extracts eminently adapted to cultivate the dramatic faculties, as well as entertain. Oakey's Dialogues and Conversations. For school exercises and exhibitions, combining useful instruction. James's Southern Selections, for Reading and Oratory. Embracing exclusively Southern literature. Swett's Common Schcol Speaker. Raymond's Patriotic Speaker. A superb compilation of modern eloquence and poetry, with original dramatic exercises. Nearly every eminent modern orator is represented. 40

Page  43 THE NATIONAL 8ERIES OF STANDARD SCHOOL-BOUK$. MODERN LANGUAGES. A COMPLETE COURSE IN THE GERMAN. By James H. Worman, A.M., Professor of Modern Languages in the Adelphi Acad. amy, Brooklyn,\ L. I. Worman's First German Book. Worman's Second German Book. Worman's Elementary German Grammar. Worman's Complete German Grammar. These volumes are designled for intermlediate and advanced classes respectively. Though following the same general method with " Otto " (that of "Gaspey "), our author differs essentially in its application. He is more practical, more systematic more accurate, and besides introduces a number of invaluable features which have never before been combined in a Germlan gramlnmar. Among other things, it may be claimed for Professor Worman that he has been the first to introduce, in an American text-book for learning German, a system of analogy and comparison with other languages. Our best teachers are also enthusiastic about his methods of inculcating the art of speaking, of understanding the spoken language, of correct pronunciation; the sensible and convenient original classification of nouns (in four declensions), and of irregular verbs, also deserves much praise. We also note the use of heavy type to indicate etymological changes in the paradigms and, in the exercises, the parts which specially illustrate preceding rules. Worman's Elementary German Reader. Worman's Collegiate German Reader. The finest and most judicious compilation of classical and standard German literature. These works embrace, progressively arranged, selections from the nlasterpieces of Goethe, Schiller, Korner, Seumie, Uhland, Freiligrath, Heine, Schlegel, Holty, Lenau, Wieland, Herder, Lessing, Kant, Fichte, Schelling, Winkelmann, Humboldt, Ranke, Raumer, Menzel, Gervinus, &c., and contain complete Goethe's "Iphigenie," Schiller's "Jungfrau;" also, for instruction in modern conversational German, Benedix's " Eigensinn." There are, besides, biographical sketches of each author contributing, notes, explanatory and philological (after the text), grammatical re:erences to all leading grammars, as well as the editor's own, and all adequate Vocabulary. Worman's German Echo. Worman's German Copy-Books, 3 Numbers. On the same plan as the most approved systems for English penmanship, with progressive copies. CH UTAUQUA SERIES. First and Second Books in German. By the natural or Pestalozzian System, for teaching the language without the help of the Learner's Vernacular. By Janles 1H. Worlman, A. M. These books belong to the new Chautauqua German Language Series, and are intended for beginners learning to speak German. The peculiar features of its method are:1. It teaches the language by direct appeal to illustrations of the objects referred to, and does not allow the student to guess what is said. lie speaks from the first hour sucderstandingl? anl acccuratelcl. Therefore, 2. Grammar is taught both analytically and synthetically throughout the course. The beginning is made with the auxiliaries of tense andl mood, because their kinship with the English makes them easily intelligible; then follow tile declensions off nouns, articles, and other parts of speech, always systematically arranged. It is easy to confuse the pupil by giving himn one person or one case at a tinme. This pernicious practice is discarded. Books that beget unsystematic habits of thought are worse than worthless. 43

Page  44 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS, MODERN LANGUAGES - Conltinued. 3. The rutzs are introduced after the examples; the purpose being to employ first the lower or sense faculty of the mind. 4. Everything is taught by contrast and association, to avoid overtaxing the memory at tile expense of liti reason. 5. The lessons convey much practical varied information, and engage the observing as well as tile thinking faculties of the learner's mind. In short, this brief series contains within its few pages all the essentials of German Grammar so presented that their mastery is easy, and the student prepared upon its completion to enter upon the study of the more recondite, complicated, and irregular principles of the language. From PROF. SCHELE DE VERE, autlhor of a little books for beginners in German and French Grammar, Studies in E'nglish, ic., French prepared by Professor Worman. dc., University of Virginia, Va. The Professor is taking his pupils alangr the right road rapidly and delightPROF. JAMES H. WORMAN. full MY DEAR Sin,-r Your very liberal pub- Whatever may be said of the tediouslishers (Messrs. A. S. Barnes & Co.) have ness of learning the grammar of a new done me the honor to send me a copy of a new done me tahe honor to send me a copy of language, I think all will agree that the your excellent works, The First French and'reat labor is mastering tie vocabulary. the Second. German Book. It needed r And it is just at this point that 1 think no introductioll ill the shape of colnpli- these books are of great use. The exercises mentary notices sans nohmbres to carll mly are so developed out of pictured objects and attention to the eminent merits of these actions, and are so well graduated that valuable publications. But I was sinvaluablate publiacations. Bt I was sin-r almlost fronm the very outset they go alone. cerely glad that the public at large, as A befiner would lave little use for well as me, confreres litteraires damns ce a dictionary in reading the' First French departement de la Linguistique, have at v departent d la inguitiue, ave t Book;" and yet the words are so introduced length discerned the great advantages of ad often used, tat the meaning is and so often used, that the meaning is your Imnethod, and enabled you and your kept constantly before the mind, without publishers to bringh out your works ill a the intervention of a translation. By this style so truly in sympathy with the in- means the pupil soon makes them his trinsic value of the different volumes. permanent possession Most unllfort lunlately - for how I sholld A dozen volumes as well graduated as delight to wield such exquisitely shaped these would do much to give the student and sharpened instruisneiets to make niy an extended vocabulary. I trust Professor way into thick crania and dense brains! Worlxan will continue his good work. — our university way of teaching does Yours very truly, not admit of the admirable method prescribed in your volumes. The laws of the Medes arel as Irreversible here as the Decrees of Mr. Jeferson, and whllell I fan- From MR. R. T. TAYLOR, of Beaver, Pa.. cied I had obtained the victory, I found esrs. A S. BARNES & CO. myself faced by a stern decree. All I call EAR SIR, - Your kindness in sending do, therefore, is to recomlnnend your works books appreciated. I hae exaisined ProInost earnestly and niost urgently, ia the fessor Wolrlnan's "Filrst French Book "and point of econoiiiy, to my young graduates, I think it the best thing of the kind I have hundreds of whomiu leave us every harvest ever seell. There is just enough of the time, to scatter their seeds broadcast over grammar combined to make the natural the vast tields of the South, and to profess practicable I shall introduce boldly their adherence to the confessions the work into my school this fall. ie lave ~of their teachers.been using Prolessor Wornlaln's CGerman Wishing you. heartily the best success, WishingR youheatilythe lest success, books and are velry much pleased with and hoping that I shall be able hereafter The Echo," in particular dealso modestly to assist you, I remain, very lights pupils. They make nlpre atlancesincerely yours, SCHELE DE VEREl. mernt in one year by this method than in two by the old manner of teaching. From Head AMaster, Boston (Mass.) Nornal Wishing you success in your business, School. I am MESSRS. A. S. BARNES & CO -I want to Yours very truly, thank you for the copies of those beautiful R. T. TAYLOR. 44

Page  49 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. SCHOOL MUSIC. The National School Singer. Bright, new music for the day school, embracing Song Lessons, Exercise Songs, Songs of Study, Order, Promptness, and Obedience, of Industry and Nature, Patriotic and Temperance Songs, Opening and Closing Songs; in fact, everything needed in the school-room. By an eminent musician and composer. Jepson's Music Readers. 3 vols. These are not books from which children simply learn songs, parrot-like, but teach the subject progressively, the scholar learning to read music bymethods similar to those employed in teaching him to read printed language. Any teacher, however ignorant of music, provided he can, upon trial, simply sotlld the scale, may teach it without assistance, and will end by being a good singer himself. The "Elementary Music Reader," or first volume, fully develops the system. The two companion volumes carry the same method into the higher grades, but their use is not essential. The First Reader is also published in three parts, at thirty cents each, for those who prefer themi in that forln. Nash and Bristow's Cantara. The first volume is a complete musical text-book for schools of every grade. No. 2 is a choice selection of solos and part songs. The authors are Directors of Music in the public schools of New York City, in which these books are the standard of instruction. The Polytechnic. Collection of Part Songs for High and Normal Schools and Clubs. This work contains a quantity of exceedingly valuable material, heretofore accessible only in sheet form or scattered in numerous and costly works. The collection of "College Songs" is a very attractive feature. Curtis's Little Singer, -School Vocalist. Kingsley's School-Room Choir, - Young Ladies' Harp. Hager's Echo (A Cantata). SCHOOL DEVOTIONAL EXERCISE. Brooks's School Manual of Devotion. This volume contains daily devotional exercises, consisting of a hymn, selections of Scripture for alternate reading by teacher and pupils, and a prayer. Its value for opening and closing school is apparent. Brooks's School Harmonist. Contains appropriate tulles for each hymnil in the " Manual of Devotion" described above. Bartley's Songs for the School. A selection of appropriate hymns of an unsectarian character, carefully classifi.d and set to popular and "' singable " tunes, for opelillng and closing exercises. The Secutar Department is full of bright and well-selected music. 49

Page  50 THE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. TEACHERS' AIDS AND SCHOOL REQUISITES. CHARTS AND MAPS. Baade's Reading Case. This remarkable piece of school-room furniture is a receptacle containing a numbei of primary cards. By an arrangement of slides on the front, one sentence at a time is shown to the class. Twenty-eight thousand transpositions nay be made, affording a Variety of progressive exercises whicl no other piece of apparatus offers. One of its best features is, that it is so exceedingly simple as not to get out of order, while it may be operated with one finger. Clark's Grammatical Chart. Exhibits the whole science of language in one comprehensive diagram. Davies's Mathematical Chart. Elementary mathematics clearly taught to a full class at a glance. De Rupert's Philological and Historical Chart. This very comprehensive chart shows the birth, development, and progress of the literatures of the world; their importance, their influence on each other, and the century in which such influence was experienced; with a list for each country of standard authors antl their best works. Illustrating also the division of languages into classes, families, and groups. Giving date of settlement, discovery, or conquest of all countries, with their government, religion, area, p)opulation, and the percentage of enrolment for 1872, in the primary schools of Europe and Anlerica. Eastman's Chirographic Chart. Family Record. Giffins's Number Chart. Teaches addition, sultraction, mnllltiplication, and division. Size, 23 x31 inches. Marcy's Eureka Tablet. A new system for tle allhabet, by which it may be taught without fail in nine lessons. McKenzie's Elocutionary Chart. Monteith's Pictorial Chart of Geography. A crayon picture illustrating all the divisions of the earth's surface commonly taught in geography. WaI. L. DICKINSON,,1S7erinteedeint of in all good geographies. I think the School.s, Jersey! City, scays. chart would beh a grnat help in any pri" I is an admirable amnilification of the mnar department." systemn of pictorial illuistration adopted Monteith's Reference Maps. School and (rand Series. Names all ai(l down in simall type so that to tie pupil at a short distance they are outline maps, while they serve as their oevn key to the teacher. Page's Normal Chart. The whole science of elementarv sounds tabulated. Scofield's School Tablets. On five cards, exhibiting ten surfaces. These tablets teach orthography, reading, object-lessons, color, fo)rm, &(c. Watson's Phonetic Tablets. Four cards and eight surfaces; teaching pronunciation and elocution phonetically. For class exercises. Whitcomb's Historical Chart. A student's topical historical chart, fromii the cireation to the present time, including results of the latest chronological research. Arranged with spaces for summary, that pupils may prepare and review their own chart in connection with anly text-book. Willard's Chronographers. Historical. Four mllmllers: Ancient chronlographer, English chronographer, Americanl chronographer, temple of time (general). Dates and events represented to the eye. 50

Page  51 THE NATIONAL,.ER/IE. OF GTI/NtADD JCHOOL-BOOKJ. APPARATUS. Bock's Physiological Apparatus. A collection of twenty-seven analtoilical molels. Harrington's Fractional Blocks. Harrington's Geometrical Blocks. These patent blocks are hinged, so that each forlll can be dissected. Kendall's Lunar Telluric Globe. Moon, globe, and tellurian combined. Steele's Chemical Apparatus. Steele's Geological Cabinet. Steele's Philosophical Apparatus. Wood's Botanical Apparatus. RECORDS. Cole's Self-Reporting Class Book. For saving the teacher's labor in averaging. At each opening are a full set of tables showihg any scholar's standing at a glance, and entirely obviating the necessity of computation. Tracy's School Record. {Dek dit}on } For keeping a simplle but exact record of attendance, deportment, and scholarship. The larger edition contains also a calendar, an extensive list of topics for compositions and colloquies, themles for short lectures, suggestions to young teachers, &c. Benet's Individual Records. Brooks's Teacher's Register. Presents at one view a record of attendance, recitations, and deportment for the whole term. Carter's Record and Roll-Book. This is the most complete and convenient record offered to the pullic. Besides the usual spaces for general scholarship, deportlllent, attendance, &c., for each name and day, there is a space in red lines enclosing six minor spaces in blue for recording recitations. National School Diary. A little book of blank formsn for weekly report of the standing of each scholar, from teacher to parent. A great convenience. REWARDS. National School Currency. A little box containing certificates in the form of money. The most entertaining and stimulating system of school rewards. The scholar is paid for his mlerits and lined for his short-comings. Of course the most faithful are the most successful in business. In this way the use and value of money and the methodu of keeping accounts are also taught. One box of currency will supply a school of fifty pupils. 51

Page  52 TIlHE NATIONAL SERIES OF STANDARD SCHOOL-BOOKS. PENMANSHIP, PENS, &c. Beers's System of Progressive Penmanship. Per dozen. This " roun l hand" system of Penmanship, in twelve numbers, comnmends itself by fits simplicity and thoroughness. The first four numbers are primary books. Nos. 5 to 7, advanced books for boys. Nos. 8 to 10, advanced books for girls. Nos. 11 and 12, ornamental penmlanship. These books are printed fronm steel plates (engraved by McLees), and are unexcelled in mechanical execution. Large quantities are annually sold. Beers's Slated Copy Slips. Per set. All beginners should practise, for a few weeks, slate exercises, familiarizing them with the formr of the letters, the motions of the hand and arm, &c., &c. These copy slips, 32 in numnber, supply all the copies found in a complete series of writing-books, at a trifling cost. Payson, Dunton, & Scribner's Copy-Books. Per dozen. The National System of Penmnanship, in three distinct series: (I) Common School Series, comprising the first six numbers; (2) Business Series, Nos. 8, 11, and 12; (3) Ladies' Series, Nos. 7, 9, and 10. Fulton & Eastman's Chirographic Charts To embellish the school-room walls, and furnish class exercise in the elements of Penmanship. Payson's Copy-Book Cover. Per hundred Protects every page except the one in use, and furnishes "lines" with proper slope for the penmnan, under. Patented. National Steel Pens. Card with all kinds... Pronounced by competent judges the perfection of American-mlade pens, and superior to any foreign article. SCHOOL SERIES. Index Pen, per gross.$... $0.75 School Pen, per gross... $0.60 Academic Pen do..63 BUSINESS SERIES. Fine Pointed Pen, per gross....70 Albata Pen, per gross..... $0.40 POPULAR SERIES. Bank Pen, do..70 _POPULAR S ERIES. Empire Pen do..70 Capitol Pen, per gross.$1 00 Commercial Pemn, per gross..60 do. do. per box of 2 doz..25 Express Pen, do..75 Bullion Pen (imit. gold) per gross.75 Falcon Pen, do....70 Ladies' Pen..... do....6.3 Elastic Pen, do.....75 Stimpson's Scientific Steel Pen. Per gross.. $1.50 One forward and two backward arches, ensuring great strength, well-balanced elasticity, evenness of point, alnd smoothness oi execlutiion. One gross in twelve contains a Scientific Gold Pen. Stimpson's Ink-Retaining Holder. Per dozen. $1.50 A simple apparatus, which does not get out of order, withholds at a single dip as much ink as the pen would otherwise realize front a dozen trips to the inkstarnd, which it supplies with moderate and easy flow. Stimpson's Gold Pen, $3.00; with Ink Retainer. $4.50 Stimpson's Penman's Card.25 One dozen Steel Pens (assorted points) and Patent Ink-retaining, Pen-holder. 52

Page  53 THE lNATIONAL SERIES OF STANDARD MISCELLANY. LIBRARY AND MISCELLANEOUS PUBLICATIONS. TEACHERS' WORKING LIBRARY. Object Lessons. Welch. This is a complete exposition of the 1)popular modern system of "object-teaching," for teachers of primary classes. Theory and Practice of Teaching. Page. This volume has, without doubt, been read by two hundred thousand teachers, and its popularity remains undiminished, large editions beinl exhausted yearly. It was the pioneer, as it is now the patriarch, of pr,)fessional works for teachers. The Graded School. Wells. Thle proper way to organize grade(d schools is hlee illustrated. The author has availed himself of the best elements of the several systems prevalent in Boston, New York, Philadelphia, Cincininati, St. Louis, and other cities. The Normal. Holbrook. Carries a working school on its visit to teachers, showing the most approved methods of teachingr all the crommon branclhes, including the technicalities, explanations, deimcnstrations, and definitions introductory and peculiar to each branch. School Management. Holbrook. Treating of the teacher's qualifications; how to overcome difficulties in self and others; organization; discipline; methods of inciting diligence and order; strategy in lnanagenent; oibject-teaching. The Teachers' Institute. Fowle. This is a volume of suggestions inspired by the author's experience at institutes, in the instruction of yolng teachers. A thousand points of interest to this class are most satisfactorily dealt with. Schools and Schoolmasters. Dickens. Appropriate selections from the writings of the great novelist, The Metric System. Davies. Considered with reference to its enrer'll inroduction, and embracing the views of John Quincy Adaims and Sir John I-erschel. The Student; The Educator. Phelps. 2 vols. The Discipline of Life. Phelps. The authoress of these works is one of the Iiost distinguished writers on education, and they canlnot fail to prove a valuable addition to the School and Teachers' Libraries, being in a ligh degree both interestinig and instructive. Law of Public Schools. Burke. By Finley Burke, Counsellor-at-Law. A new volume in "Barnes's Teachers' Libralry Series." 12mo, cloth. "Mr. Burke has given us the latest Law of Public Schools.' by Finley Burke, expositions of the law on this highly im- Esq., of Council Bluffs. In my opinion, plortant subject. I shall cordially com- the work will be of great value to school mend his treatise." - TiHEODORE DWIGHT, teachers and school officers, and to lawLL.D. yers. The subjects treated of are thoughtFromL the HON. JOSF.PH M. BECK, Judge of fully considered and thoroughly examined, Suspre'me Court, lowua. and correctly and systematically arranged. " I have exanmined with considerable The style is perspicuous. The legal doeare the manuscript,of'A Treatise on tle trilcs of the work, so xar aS I have, been 53

Page  54 THE NATIONAL SERIES OF STANDARD M/SCELLANY. MISCELLANEOUS PUBLICATIONS - Continued. able to consider them, are sound. I have valuable and important information conexamined quite a numlber of the authori- cerning school law, which has lnev\er before ties cited; they sustain the rules an- been accessible to either teacher or school nounced in the text. Mr. Burke is an able officer. A. ARMSTRONG, and industrious member of the bar of the Supt. Schools, Sioux City, Iowa. Supreme Court of this State, and has a high standing in the profession of the DES MOINES, May 15, 1880. law." The examination of " A Treatise oii the "I fully concur in the opinion of Judge Law of Public Schools,' prepared by FinBeck, above expressed." -JOHN F. DIL- ley Burke, Esq., of Council Blufts, has LOBNe. Nab Yoerk, Mays, 1880). given me much pleasure. So far as J know, there is no work of similar characSIoux CITY, IOWA, May, 1880. ternowin existence. I think such a work I have examined the manuscript of will be exceedingly useful to lawyers, Finley Burke, Esq., anld ind a full citation school officers, and teachers, and I hope, of all the cases and decisions pertaining to that it may find its way into their hands. the school law, occurring in the courts of G. W. VON COELLN, the United States. This volume contains Supt. l'ublic lust. for Iowa. Teachers' Handbook. Phelps. By William F. Phelps, Principal of Minnesota State Normal School. Embracing the objects, history, organization, and managrelment oi teachers' institutes, followed by methods of teaching, in detail, for all the fundamental branlches. ELvery young teacher, every practical teacher, every experienced teacher even, needs this book. From thke New Fork- Tribune. This is the key-note of the present excellent volume. In view of the supreme "The discipline of the school shoull ilmportance of the teacher's calling, Mr. prepare the child for the discipline of life. Phelps has presented an elaborate systeln The country schoolmaster, accordingly, of instruction in the elements of learning, holds a position of vital interest to the with a complete detail of methods and destiny of the republic, and should neg- processes, illustrated with an abundance lect no means for the wise and efficient of practical examples and enforced by discharge of his significant functions. judicious councils." Topical Course of Study. Stone. This volume is a compilation from the courses of study of our most successful public schools, and the best thought of leading educators. The pupil is enabled to make full use of any and all text-books bearing on the given topics, and is incited to use all other information within his reach. American Education. Mansfield. A treatise on the principles and elements of education, as practised in this tountry, with ideas towards distinctive republican and Christian education. American Institutions. De Tocqueville. A valuable index to the genius of our Government. Universal Education. Mayhew. The subject is approached with the clear, keen perception of one who has observed its necessity, and realized its feasibility and expediency alike. The redeeming and elevating power of improved colmmon schools constitutes the inspiration of the volume. Oral Training Lessons. Barnard. The object of this very useful work is to furnish material for instructors to impart orally to their classes, in branches not usually taught in common schcols, embracing a' departments of natural science and much general knowledge. Lectures on Natural History. Chadbourne. Affording, many themes for oral instruction in this interesting science, espeolally in schools where it is not pursued as a class exercise. 54

Page  56 THE NATIONAL SERIES OF S TANDARD'ISCELLANr, MISCELLANEOUS PUBLICATrlON6' - Conlti, cia. School Amusements. Root. To assist teachers inr making the school interesting, with hints upon the management of the school-room. Rules for military and gymnllastic exercises are included. Illustlrated by diagrams. Institute Lectures. Bates. These lectures, originally delivered before institutes, are based upon various topics in the departments of mllental and mIoral culture. The voltune is calculated to prepare the will, awaken the inquiry, and stimulate the thought of the zealous teacher. Method of Teachers' Institutes. Bates. Sets forth the best mIrethod of conducting institutes, with a detailed account of the object, organization, plan of instruction, and true theory of education on which such instruction should be based. History and Progress of Education. The systems of education prevailing in all nations and ages, the gradual advance to the present time, and the bearing of the past upon the present, in this regard, are worthy of the careful investigationl of all concerned ill education. Higher Education. Atlas Series. A collection of valuable essays. CONTENTS. International Communication by Language, by Philip Gilbert Hairlerton; Reform in Higher Education; Upper Schools, by President James McCosh; Study of Greek and Latin Classics, by Prof. Charles Elliott; The University System in Italy, by Prof. Angelo de Gubernatis, of the University of Florence; Universal Education, by Ray Palmer; Industrial Art Education, by Eaton S. Drone. LIBRARY OF LITERATURE. Milton's Paradise Lost. (Boyd's Illustrated Edition.) Young's Night Thoughts. do. Cowper's Task, Table Talk, &c. do. Thomson's Seasons. do. Pollok's Course of Time. do. These works, models of the best and purest literature, are beautifully illustrated, and notes explain all doubtful meanings. Lord Bacon's Essays. (Boyd's Edition.) Another grand English classic, affording the highest example of purity in language and style. The Iliad of Homer. (Translated by Pope.) Those who are unable to read this greatest of ancient writers in the original should not fail to avail themselves of this standard metrical version. Pope's Essay on Man. This is a model of pure classical English, which should be read, also, by every teacher and scholar for the sound thougllt it contains. Improvement of the Mind. Isaac Watts. No mental philosophy was ever written which is so comlrelhensive and practically useful to the unlearned as well as learned reader as this well-known book of Watts. Milton's Political Works. Cleveland. This is the very best edition of the great poet. It includes a life of the author, notes, dissertations on eachl poem, a faultless text, and is the only edition of Milton with a complete verbal index. 56

Page  59 THE NATIONAL SERIES OF STANDARD MISCELLANY, MISCELLANEOUS PUBLICATIONS - Contilued. LIBRARY OF HISTORY. Ancient and Mediaeval Republics. Mann. A review of their institutions, and of the causes of their decline and fall. LYj llenry Maln. 8vo. 584 pages. cloth. Outlines of General History. Gilman. The number of facts which the author has comlpressed into these outline sketches is really surprising; the chapters on the Mliddle Ages and feudalisn- afford striking exSr)lies of his power of succinct but comprehensive statement. In his choice of el), esentative periods and events in the histories of nations he shows very sound judgmnent, and his characterization of conspicuous historical figures is accurate and impartial. Great Events of History. Collier. This celebrated work, edited for American reader, by Prof. 0. R. Willis, gives, in a series of pictures, a pleasantly readable and easily remenlbered view of the Christian era. Each chapter is headed by its central point of interest to afford association for the mind. Delineations of life and manners at diflerent periods are interwoven. A geographlical appendix of great value is added. History of England. Lancaster. Au arrarngement of the essential facts of English history in the briefest manner consistent with clearness. Witb a fine map. A Critical History of the Civil War. Mahan. By Asa Mahan, LL.D., author of " Intellectual Philosophyl," " Elements of Logic," &e. First president of Oberlin College, Ohio. With an introductory letter by LieutCen. M. W. Smith of the British army. 8vo. 450 pages. Cloth. The plan of this work is to present, not the causes and details of facts which led to the war, but the conduct and managenment of the war oln the lpart of those concerned. It is a matter of present aid future importance to Americans to know not only how the war was conducted, but also how it might have been more successflllly carried on. T'he author has made the science of war a subject of careful and protracted study, and his views are pronounced and scientific. He takes strong ground, writes with vigor, and the interest of the reader is fully sustained from the beginning to the close of the book. His conclusions have already passed into history, and this worlk will be regarded as one of the most important contributions to the literature of the subject. Europe under Napoleon First. Alison. A history of Europe froml 17S9 to 1815. By Archibald Alison. Abridged by Edward S. Goultd. 1 vol. Svo, with appendix, questions, and naps. 550 pages.''One of the best abridgments I ever "It seems to me an excellent abridgsaw. The material facts are all retained, ment. Written in clear and chaste atlld Mr. Gould l has displayed great indus- style, presenting the narrative in exact try and skill in preserving the substance form for the general reader.... "JUDGF. of so great a history." —CHANCELLOPR JOSEPH STORY. JAMES KENT. History of Rome. Ricord. An elltertainilig narrative for the young. Illustrated. Embracing successively, The Kings, The Republic, The Emipire. History of the Ancient Hebrews. Mills. The record of "God's people" from the call of Abraham to the destruction of Jerusalemll; gathered from sources sacred and profane. The Mexican War. Mansfield. A history of its origin, anld a detailed acco'mit of its victories; with offlicial despatches, the treaty of peace, and valuable tables. Illustrated. 59

Page  60 THE NA TIONAL SERIES OF STANDARD MISCELLANr, MISCELLANEOUS PUBLICATIONS — Conltinued. Early History of Michigan. Sheldon. A world of value and deep interest to tile people of the West. Compiled undcer the supervision of Hion. Lewis Cass. Portraits. History of Texas. Baker. A pithy and interesting rhsuml. Copiously illustrated. The State constitution and extracts from the speeches and writings of eminent Texans are appended. Magazine of American History. 8 volumes. Illustrated. A collectiom of valuable data relating to American History. Points of History. For schools and colleges. By John Lord, LL.D., author of "Old Roman World," M" Modern History," &c. Barnes's Popular History of the United States. 1 vol. This superbly illustrated w(orik is bly the author of "Barnles's Brief Histories " (for schools). The leading idlea is to msake Amlericasn history popular for the masses, and eslecially with the young. The style is therefore life-like and vivid, carrying the reader along by the sweetp of the story as iii a novel, so that when he begils an account of an inmportant event he ca lllt very well lay downl the book until he finishes. It is complete from the earliest tillle to date. " Barnes's Popular History or the Unlited States " was undertaken at the close of the first hundred years of Amlerican Iude.pedence. The author proposed to give to the whole people of the United States and the world a thoroughly imlartial history of America, from the nlound-buil(lers to the present time. As such it was nec(essary to steer free froii whatever in recent history would arouse sectional animlosity or party bitterness. Ile determined to iiieet all questions of burning momlnet in the judicial rather than controversial spirit, and while giving to every event its due importance, he would seek to avoid controversy by the gentle word "'that turueth away wrath." Thle work is now finished downi to President Arthur's admiinistration. In it the truth of American history is impartially given in true historic forli, without fear or favor. It is a work that all sections of the country can read and enjoy. Although thle author is a Northern man and sollier, his workl is popular and widely used as a text-b)ook East, West, North, and South. An Allbalnma teacher lately wrote a.s follows:' We are using your history and like it, though it loes n,'t favor us rebels. " Anld so it is liked throughout the country, because it does m't favor anly side at the expense of truth and justice. Inistead of beinig spread out inll iany volumies, more or less didactic, statistical. or dry, the book is comllplete in one royal Svo volumlle of 850 pages, with 14 full-page steel engravings and 320 text illustrations on wood, engraved by elninenlt artists. It is fully up to the tiles and ilncludes an account tof Presideslt G(arlield's brief adminisistration and tragic death. Mrs. Martha J. Lamb's Histcry of New York City. 2 vols., Clotlh. This is a coiilhicte survey of the history o" New Yuorl fron( early settlement to the present tinie. It,lesns with a brief outline of tlle ( on!litioni or the Oll World psior to the settlement of.tle New, and proceeds to give a carleful lanalysis of the two great Dutch Colnmercial C'orsporationls to which New York owes its origin. It sketches the rise amid growth of thle little colony on Manhiattan Island; describes the Indian wars with which it was afflicted; gives color and life to its Dutch rulers; paints its subjugation Iby the English, its after vicissitsudes, the Revolution of 1689 in short, it leads thle reader through one contillnuous chain of events downs to the Ameerican Revolution. Then, gathering iup thle threads, the author gives an artistic and comlprehensive account of the progress of thle city, in extent, education, culture, literature, art, and political anid coiamsercial imrlpor-taii tle duriiig thle last (entury. Prominent ipersons are introduced ill all the differenlt periods, with choice bits of family history, and glimpses of social life. The work contal Is maps o, thie city in the.diferent decades, and several sre 60

Page  61 THE NA ATIONAL SERIES OF STANDARD M/SCELLANY, MISCELLANEOUS PUBLICATIONS- Continued. portraits from original paintings, which have never before been engraved. The illustrations, about 320 in number, are all of an interesting and highly artistic character. "Widely welcomed both for its abun- "There is warmth and color and life in dant stores of information and the attrac- every passage." - New York Sun. tions of the narrative." —New York "The work has been done faithfully Tribune. and picturesquely." - The Nation. Carrington's Battles of the Revolution. A careful description and analysis of every engagement of the War for Independence, with topographical charts prepared from personal surveys by the author, a veteran officer of the United States army, and Professor of Military Science in Wabash College. Baker's Texas Scrap-Book. Comprising the history, biography, literature, and miscellany of Texas and its people. A valuable collection of material, anecdotical and statistical, which is not to be found in any other form. The work is hand(somely illustrated. DICTIONARIES AND ENCYCLOPAIDIAS. Home Cyclopaedia of Literature and Fine Arts. Index to terms employed in belles-lettres, philosophy, theology, law, mlythology, painting, music, sculpture, architecture, and all kindred arts. By Geo. Illley and Chas. A. Dana. The Rhyming Dictionary. Walker. A serviceable manual to composers, beilng a complete index of allowable rhymes. Dictionary of Synonymes; or, The Topical Lexicon. Williams. Terms of the English language closiifie;l by subjects and arranged according to their affinities of meaning, with etynlologies, definitions, and illustrations. A very entert'aining and instructive work. Hawaiian Dictionary. Mathematical Dictionary. Davies and Peck. A thorough compendium of the science, with illustrations and definitions. Kwong's Dictionary. A dictionary of English phrases. With illustrative sentences. With collections of English and Chinese proverbs, translations of Latin and French phrases, historical sketch of the Chinese Empire, a chronological list of the Chinese dynasties, brief biographical sketches of Confucius and of Jesus, and complete index. By Kwong Ki Chiu, late member of the Chinese Educational Mission in the UnIited States, and formerly principal teacher of English in the Government School at Shanghai, China. 900 pages, 8vo, cloth. From the Hartford Courant. From the New York Nation. "The volume shows great industry and "It will amaze the sand-lot gentry to be apprehension of our language, and is one informed that this remarkable work will of the most curious and interesting of supplemllent our English dictionaries even linguistic works." for native Americans." BARNES'S LIBRARY OF BIOGRAPHY. The Life of President Garfield, From Birth to Presidelcy, by Matjor J. M. Bundy, editor New York " Evening MailExpress." Froim Mentor to Elberon, by Col. A. F. Rockwell. Oration and Eulogy, by Hon. James G. Blaine. This life of our martyred President, by Major Bundy, Mr. Blaine, and Colonel Rockwell. 81

Page  63 (HE NA TIONAL SERIES OF STANDARD MISCELLANY. MISCELLANEOUS PUBLICATIONS — C'oltinued. Prison Life. Interesting biographies of celebrated prisoners and martyrs, designed especially for the instruction and cultivation of youth. Men of Mark. Bryant, Longfellow, Poe, Charles Tennyson Turner, Macaulay, Freeman, Curtius, George Ticknor, Sumnler, John Stuart Mill. By Edwin P. Whipple, Edward A. Freeman, and others. 275 pages, 8vo, paper covers. The Hero of Cowpens. This book presents a complete history of the lives of heroic Daniel Morgan an(l of Benedict Arnold. These Revolutionary characters are viewed in -varied ]ighllts, al(l the author Ires produced a imost captivating historical sketch, a.s illnterestillng as a romance. Autobiography of Havilah Mowry, Jr. A City missionary. BARNES'S LIBRARY OF TRAVEL. Silliman's Gallop among American Scenery; Or, Sketches of American Scenes and Military Adventure. By Augustus E. Sillimnan. 338 pagres, 8vo, illustrated. It is a moAt agreeabile volume, and we comnmend it to the lovers of the " sparkling" style of literature. It carries the rea(ler through and past many of the spots, North and South, made memoral)le by events of the Revolution and the War of 1812. Texas: the Coming Empire. McDaniel and Taylor. Narrative of a two-thousand-mile tilj) (, lhorseback through the Lone Star State; with lively descriptions of people, scencry, and resources. Life in the Sandwich Islands. Cheever. The "' heart of the Pacific, as it was and is," slhows miiost vividly the contrast between the depth of degradation and b)arbarisni anl the light and liberty of civilization, so rapidly realized in these islands un(.ler the hli.nlanizing influence of the Clhristian religion. Illustrated. The Republic of Liberia. Stockwell. This volume treats of tile geographyll, climate, soil, anid productions of this interesting country on the coast of Africa, witli a history of its early settlemieiit. Our colorcd citizens especially, from whomll the founllers ot the new State went fortll, should read Mr. Stockwe]l's account of it. It is so arranged as to be availablle for a school reader, and inl colored schools is peculiarly apipropriate as anl inst'unmellt of education for the young. Liberia is likely to bear an imnlportanlt p)art inl the future of tlheir race. Discoveries among the Ruins of Nineveh and Babylon. With 20 illustrations and a complete index. By Austen II. Layardl, 11. P. Abrldgcd edition. 550 pages, 12mo, c(loth. Monasteries of the East. Embracing descriptions from personal observation of Egypt in 1833; the Natron Lakes, the Convent of the Pulley, the Ruined Monastery at Thebes, the White lMonastery, the Island of Philoe, &c., Jerusalem, tl:e Monastery of St. Sabbla, aind the Molnasteries of Metesra, Saint Athos. By Robert Curzoin, Jr. 400 pages, 12ino, cloth. A Run through Europe. By Hon. Eristus C. Benedict, late Chancellorr of the University of New York. A six monthls' tour through the galleries and capitals of'Eurole, by a most inltelligemnt observer, in the year 1867. 12mo, cloth. 63

Page  64 THE NA TIONAL SERIES OF STANDARD MISCELLANY. MISCELLANEOUS PUBLICATIONS - Continued. Eighteen Months on a Greenland Whaler. By Joseph P. Faulkner, an " ex-assistant whale-catcliher in an American schooner," ar, author of other recollectlins of the sea. 318 pages, i6n.o, cl(0th. The Polar Regions; Or, The First Searlch After,Sir John Franklin's Expedition. By Lieut. Sherard Osborn, commanding H. 1M. S. Pioneer (tile first steam vessel that ever penetrated the Northern sea). 212 pages, 12mmo, cloth. St. Petersburg. Jcrmann. Americans are less famliliar with tile history and social customs of the Russian people than those of any otllher m(derin civilized nation. Opportunities such as this book affords are not, thelietre, to ble neglec(ted. Thirteen Months in the Confederate Army. The author, a Northern man consc'ripted into the Confederate service, and rising from the ranks bhy soldierly c onduct to positions of resplousilbility, had remarkable opportunoities tor the aclquisition of facts respecting the conduct of the Southern arimmies, and the policy and (l eeds of their leaders. He particilpated in mlany engagemnents, an(l his b,,ok is one of the most exciting narratives of adventure ever published. Mr. Stevenson takes no ground as a partisan, but views the whole subject as with tile eye of a neutral, only interested in subserving the en(ls of hllistory by tlhe contribution of impartial facts. Illustratedl. The Isthmus of Tehauntepec. Anderson. 8vo, cloth. A history of the Isthmus from earliest times to the present, wti',h an aceoant of;ailroad enterprises andl valuable lnaps and charts. BARNES'S RELIGIOUS LIBRARY. Ray Palmer's Poetical Works. An exquisite edition of the complete hymns and other poeticam writings of the most eminent of American sacred l)o()s, arlthor of " My Faith Looks up to Thee." Formation of Religious Opinions. Palmer. Hints for the benefit ofr young peolde who have found themselves disturbed by inward cquestionings or doubts conelrning the Christian faith. Nine Lectures on Preaching. Dale. By Rev. R. W. Dale, of Englalnl. Deliverled at Yale College. Contents: Perils of Young Preachers; The Intellect il Relation to Preachinll; Reading; Preparation of Sermons; Extemporaneous Preaching; Evangelistic'lreaclhing; Pastoral Preaching; Conduct of Public Worship. Dale on the Atonement. The theory and fact of Christ's atonement profoundly considered. The Service of Song. Stacy. A treatise oli singing, ini public and privite devotion. Its history, office, and inlportance consirlered. "Remember Me." Palmer. Preparation for the Holy Conmmunlion. Bible Lands Illustrated. A pictorial halld-hook of the antiquities and modern life of all the sacred countries. By Henry C. Fish, T).D. With six hundred engravings and maps, one thousand elucidated Scripture texts, and two th;ousand indexed subjects. 8vo, cloth, 900 pages. 64

Page  66 'THE NATIONAL SERIES OF STANDARD MICtCELLtAN.. MISCELLANEOUS PUBLICATIONS - Continued. Froude's Theological Unrest. (Atlas Series.) The History of the English Bible, Extending from the earliest Saxon translations to the present Anglo-American Revision, With special reference to the Protestant religion and the English language. By Blatcford Condit. With steel portrait of Wycliffe. 400 pages. 12mo, cloth. This is a consecutive history of all the English versions of the Scriptures and their translators, inclllding also the history of Protestantisnl in England and the growt.h ami changes of the English langtuage. BARNES'S YOUTH'S LIBRARY. Earnest Words on True Success in Life. Addressed to young men and women. By R.ty Palmner. 290 pages, 12mno, clot,,. Ida Norman. Two vols. ill one. A novel With illustrations. By Mrs. Lincoln Phelps. 432 pages, 12t1o, cloth. The Educator; or, Hours with my Pupils. A series of practical hiiits to young ladies on questions of behavior and education. By Mrs. Lincoln l'llell)s. 364 plages, 121too, cloth. The Student; or, the Firesidc Friend. A series of lectures to yount, ladies, in which the author gives a course of practical instruction for hlome study, ittcluding physical, intellectual, social, domestic, and religiotus trainingr. Intended to awaken ill the minllds of the young an idea of the importanlce and value of education, and to provide the means of self-instruction. With an index. 380 pages, 12tlio, cloth. Monasteries of the East. Emlbtracinlg visits to monasteries inl the Levant. By the Hon. Robert Curzon, Jr. 416 pages, 12tno, cloth. Life in the Sandwich Islands. By Rev. Henry T. Cheever. 356 pages, 12mno, cloth. Lives of the Signers. Carefully prepare(l sletches of the lives and careers of the signers of the document declarinlg the intdependellce of the States of Atmerica. By N. Dwight. 374 ptages, 12nmo, cloth. Discoveries among the Ruins of Nineveh and Babylon. Witht travels in Anrmenia, Kutrdistan, and the Desert. Being the result of the second expedlitiont unlldertaken for the trustees of the Britishl Mttseun. Anl abridgmlent. By Austen H. Layard, M. P. 550 pages, 12tno, clotth. The History of the Jews. From the flood to their dispersement. Froin sources sacred and profane. A most excellent work in colnnection, with the study of the Scriptures. Giving a connected account of the histoty and acts of this elcosen people. By Abraham Mills, with colored charts, mlaps, atnd illustrations. 444 pages, 12tto. Johnny Morrow, the Newsboy. Ail altobiograplly written by the hero whell sixteen years of age. 16mo, cloth. A plain story of one who represents a class. The writer, although a newsboy and pedler of trinkets, is well remembered in New Haven, Contr., and possesses a power and maturity of expression quite remarkable. 66

Page  67 THE NA TIONAL SERIES OF STANDARD MISCELLANY. MISCELLAN EOUS PUBLICATIONS - Continued. Stories of Prison Life. Cloth, 16mo. Biographies of noted political prisoners, as Picciola, the heroine ot Siberia; Silvio Pellico, and Baron Trenck. The Son of a Genius. A tale. By Mrs. Hofialld. Cloth, 16mno. St. Chrysostom; or, the Mouth of Gold. By Rev. Edwin Johnson. Cloth, 16lno. An original dramatic poem, in six canto With explanatory notes. VALUABLE SPECIAL BOOKS. Opium Habit and Drunkenness. T'he extent, terrible effects, and radical cure. Read Dr. Hubbard's " Opiumania and Dipsomania." "To many victims and their friends, this book will come like a prophet of God." - Christia I nion. Grecian and Roman Mythology. Dwight. The presentation ii, systemlatic form of the fables of antiquity affords most entertainin reading, and:J valuable to all as an index to the lythlological allusions so Irequent in literature, as well as to students of the classics who would peruse intelligently the classical authors. Illustrated. General View of the Fine Arts. Huntington. The preparation of this work was suggested by the interested inquiries of a group of young people concerning the productions and styles of the great masters of art, whose names only were familiar. This statement is suflicient index of its character. The Poets of Connecticut. Everest. With the biographical sketches, this volume forms a complete history of the poetical literature of the State. BARNES'S CHOICE STANDARD ENGLISH LIBRARY. Fifty-Nine Essays. By Lord Balcon. With notes, critical and biographical, by IIallam, Macaulay, and others. Edited by James R. Boyd. 426 pages, 12nio, cloth. Paradise Lost. By John Milton. With five filll-page engravings, explanatory and critical notes, index, &c., &c. Edited by James R. Boyd. 560 pages, l2mo, cloth. The Task, Table Talk, and other Poems. By William Cowper. With notes, critical and explanatory, complete index, and five full-page engravings. Edited by James R. Boyd. 436 pages, 121lo, cloth. Night Thoughts. By Edward Young. With sketch of life and works of the author, and explanatory notes. By James R. Boyd. With steel-plate illustrations. 516 pages, 12mo, cloth. The Course of Time. By Robert Pollok. With two steel-plate engravings: portrait at age of 28, and early home; critical observations of various authors, with notes by Dr. Boyd. 67

Page  68 THE NA TIONAL SERIES OF STANDARD MISCELLANY. MISCELLANEOUS PUBLICATIONS —Continued. The Seasons. By James Thomson. With four steel-plate illustrations, opinions of distinguished critics on the genius and character of the work, explanatory notes by the editor, and a complete index. Edited by James R. Boyd. 336 pages, 121no, cloth. The Poetical Works of John Milton. With a life of the author, prelimlinary dissertation on each poem, notes, critical and explanatory, an index to the subjects of Paradise Lost, and an extra index to all the poems. Complete in one volume. By Charles Dexter Cleveland. 690 pages, 12m11o, half roan. Elements of Criticism. By Henry Home, of Kanies, one of the Lords Conmmissioners of Judiciary in Scotland. Edited, with explanatory notes, by Jamles It. Boyd. 486 pages, l121lo, cloth. The Plays of Philip Massinger. With an introduction and notes, critical and explanatory. By William Gifford. Colnplete in one volume. 540 pages, large 8vo, cloth. The Life of Samuel Johnson, LL.D. By James Boswell. With copious notes and biographical illustrations. By Ed. Malone. Complete in one volume. 600 pages, 8vo, cloth. An Essay on Man. By Alexander Pope. With notes. Edited by a teacher. 44 pages, 12mo. The Iliad of Homer. Translated ill verse. By Alexander Pope. 568 pages, 32mno, roan. Improvement of the Mind. By Isaac Watts, D.D. With Denman's Questions. 304 pages, 12mo, half bound. BARNES'S LIBRARY OF POLITICS. The Young Citizen's Catechism. 192 pages, 16tmo, cloth. A most comprehensive little work for beginners; explaining the duties of district, town, city, county, State, and United States offlcers, and giving practical rules for Parliamentary prlactice, legal and connmmercial business. By Elisha P. Howe. First Lessons in Civil Government. 280 pages, 12mlo, cloth. Based uponl the laws of New York State but adapted to the requiremlents of the student in any State. Revised in 1877. By Andrew W. Young. Civil Government in the United States. 330 pages, 1'2mo, cloth. Containing a full statement of general principles on a comnlprehensive plan, embracing State, county, city, town, and federal organizations. This work traces the development of free institutions from gernns in the early English constitution, through colonial and revolutionary history, down to date. It is arranged topically to assist in fixing details in the student's mind. It omits unnecessary statistics and fulfils the highest requirements of a citizen's ilmanual. By George H. Martin, Teacher of Ilistory and Civil Politics in the Mass. State Normal College. The Political Manual. 350 pages, 12tlo, cloth. A complete record of the theory and practice of the general and State governments of tile United States. By Edwin D. Mansfield, LL.D., Professor of Constitutional Law. 68

Page  69 THE NATIONAL SERIES OF S$TANDARD MISCELLANY. MISCELLANEOUS PUBLICATIONS — Continued. Lessons on Political Economy. 2z0 pCales, 12too, clotl. Treating the science famliliarly so as to bring it to the practieal knlowleige of all classes of society. If the principles herein presented are thor. oughlly mastered, the student will have a competent knowledge of the science for all oidinlary purloses. By J. T. Champlin, LL.D., President of Colby University. A Manual of International Law. 322 pages, 12nmo, cloth. This work presents within moderate compass the principles of international law as recognized in the world at the present time. It is the first notable attempt to popularize this important branch of polilical knowledge, and gives an interestilg view of the influence of the United States on the diplomacy of the world. By E1dward iM. Gallaudet, Ph. D., LL.D. Professor of Moral and Political Science, and President of the College of Deaf Mutes, Washington, D. C. De Tocqueville's Democracy in America. American Institutions and their Influence. (Abridged.) By Alexis de Tocqueville. 4t0 pages, 12mo, cloth. Being part second of the "Delmocracy in America," by the same writer. Arranged, with notes, introduction, and appendix, by Hon. John C. Spencer. The Republic of the United States of America, and its Political Institutions Reviewed and Examined. (Complete.) By Alexis de Tocqueville, Member of the Institute of France and of the Chamber of Deputies. 876 pages, 8vo, cloth. Translated by Henry Reeves, Esq., with pretac:e and notes by Hoi. John C. Spencer. Two volumes in one. Principles and Acts of the Revolution in America. By Hezekiah Niles, editor of the " Weekly Register. " 522 pages, 12nmo, cloth. A grand storehouse of the patriotic and soul-stirring speeches and orations delivered during the Revolution, and embodying the opinions and immortalizing the conduct of the leaders and actors in the events of that period. The collection embraces nearly if not all the important impassioned addresses that contributed to fire the ptublic sentiment and sustain the enthusiasm which ended in victory. While the chief obQject of the volume is to stir the feelings of the period, it is also an historical volume. In a word, this volume contains all the great speeches and orations, extracts from the proceedings of the greatest meetings and fromt important writings of all the States at the time of the Revolution. Constitutions of the American States and of the United States in I86; Or, PRIOR to THE WAR OF THE REBELLION. With an essay on the character of the changes in these constitutions prior to the year 1879. By Wilmot L. Warren. 602 pages, 8vo, cloth. Political Essays. Paper; cloth. Labor, Granger, Indian, Chinese, and constitutional questions. (Atlas series, No. 3 ) By Thomlas Hughes, Thomas Brassey, Judge Cooley, E. A. Freeman, LL.D., Francis A. Walker, and others. The Commonwealth Reconstkucted. By Charles C. P. Clark, M.D. 216 pages, 8vo, cloth. A sketch of the condition of political affairs, town, State, and federal, in 1878. With a new plan for the complete reconstruction of the body politic. 69

Page  70 THE NA TIONAL SERIES OF STANDARD MISCELLANY. MISCELLANEOUS PUBLICATIONS - Continued. THE ATLAS SERIES OF ESSAYS. PAPER BINDING. No. I. The Currency Question. The nature of the discussion prior to resumpntion; with a view of the future and permanent financial wants of the United States. By Hon. Amasa Walker, LL.D. Contents: Our National Currency; The Money Probleml. No. 2. Men of Mark. BIoraphical and Critical Essays. Contents: Lord Macaulay, by Edward A. Freemali, D.C.L.; George Ticknor, by Edwin P. Whipple; Ernst Curtius, by R. P. Keep, Ph. D.; Philip Gilbert Hamerton; Henry Wadsworth Longfellow, by Ray Palmer; To John Lothrop Motley, a poem, by William Cullen Bryant; Edgar Allan Poe, by John II. Ingram; Charles Tennyson Turner, by A. J. Sylington, M.A.; Edward A. Freemlan, by Henry Copp6e, LL. D.; Charles Sumner, by President Magoun, of Iowa; J ohn Stuart Mill, Nos. 1 and 2, by President Porter, of Yale College. No. 3. The Labor Question. Political Essays. Contents: Co-operative Stores in England, by Thomas Hughes, M.P.; Wages in England, by Thomlas Brassey, M.P.; The Sea-Shell and the Sonneteer, a poem, by Charles Tennyson Turner; Grangerism, by Dr. Francis Wharton; The Grange and the Potter Law, by a Granger; The American Republic, by Gen. Franz Sigel; Indian Citizenship, by Gen. Francis A. Walker; The Chinese Question, by Dr. E. D. Mansfield; The Guarantee of Order and Republican Government in the States, by Judge T. M. Cooley; Some Checks and Balances in Government, by Judge T. M. Cooley; The Difficulties of Republicanism in Europe, by Edward A. Freeman, D.C.L. No. 4. The Centennial Exhibition, Philadelphia, 1876. A critical account. By Gen. Francis A. Walker, Chief of the Bureau of Awards. No. 5. European International Exhibitions. Paris, 1878, and Vietina, 1873. Contents: The Paris Exhibition, by Charles Gindriez, a Paris architect; Vienna and the Centennial, by Prof. James Morgan Hart. No. 6. A Shocking Story. By Wilkie Collins. No. 7. Buried Treasures. Where the Precious Metals Go, by Honl. J. V. C. Smith, ex-mayor of Boston. No. 8. The Gold Room. By Kinahan Cornwallis. Contents: The New York Gold-Room; The New York Stock Exchange; The New York Clearing-House. No. 9. Higher Education. No. 1. Contents: International Comrlunication by Language, by Philip Gilbert Hamerton; Reform in Higher Education; Upper Schools, by Pres. Jalmes McCook; Study of Greek and Latin Classics, by Prof. Charles Elliott; The University System in Italy, by Prof. Anrelo de Gubernatis, of the University of Florence; Universal Education, by Ray Palmer; Industrial Art Education, by Eaton S. Drone. No. Io. England and the Government. IBy the Rt. Hon. WV. E. Gladstone, Premier. Contents: A Caustic Review of Beaconstield's Policy; A Model Political Documlent. No. ii. Theological Unrest. Contents: Science and( Theology, Ancient and Modern, by James Anthony Fronde; The Conflict of Science and Religion, by Rev. E. A. Washburn, D.D.; Does Humanity Require a New Revelation - a Reply to Mr. Froode, by Prof. P. G. Tait, University of Edinburgh. 70

Page  71 THE NA TIONAL SERIES OF STANDARD MISCELLANY. MISCELLANEOUS PUBLICATIONS - Continued. No. I2. Higher Education. No. 2. (In press.) Contents: Learned Women at the Bologna University, by Madamle Villari, of Florence, Italy; Russian Universities, by C. K. Adamls; Study and Practice of Medicine by Women, by Jalmes R. Chadwick; Technical Education and Free Trade, by Lyon Playfair. The Smithsonian llnstitute, by Henry W. Elliott; The Service of Frarcis Lieber, I y Dr. J. C. Blllntschli; The Concord School of Philosophy, by Dr. Julius H. Ward; The University of Texas, by Prof. Oscar H. Cooper. No. I4. Practical Work of Painting and Etching. With portrait of Rubenls. By Philip Gilbert Hamerton. No. 21. Modern Schools of Art. By Philip Gilbert HIamerton. CHRISTIAN WORSHIP. MUSIC. Worship in Song. A selection (of hymns and tunes for the service of the sanctuary. By Jos. P. Holbrook, Mus. Doc., musical editor of " Songs of the Church," " Songs for the Sanctuary," "Baptist Praise Book," " Methodist Hymnal," author of " Quartet and Chorus Choir," &c., &c. In this work Dr. Holbrook has put the mature results of long, patient, and careful study. Iis excellent judgment and taste and the great attractiveness of his compositions, and especially his admirable adaptations, have already been noted and appreciated by all who are fanmiliar with the former works edited by him. In addition to his own umore familiar compositions, as well as new tulles which now appear for the first time, the author has drawn upon the store of English and German tunes, such as have alleady become dear to American congregations. Where entirely new tunes appear, or such as are not generally known, tile chorister will always find an old " standby" upon the same or opposite page. The book is thus adapted to both the precentor and choir. In the selection and arrangement of hymns, he has been efficiently assisted by Rev. Dr. J. Glentworth Butler, who has been a life-long student of English hymnology. The work contains 450 pages, in full cloth and burnished edges. The Evangelical Hymnal. By the Rev. Charles Cuthbert Hall, pastor of the First Presbyterian Church, Brooklyn, N. Y., and Sigismond Lasar, editor of "The Hymlnary."'Il his Look contains approved versions of (00 excellent llhymns, with tunes by the most celebrlated composers of ancient and modern times. The adaptations of tullnes to hymns have been made with special reference to a higher standard of ecclesiastical music than may be found in ally other American hymllal. Thile biographical index contains brief but comprehensive notices of authors, translators, and composers; land much valual)le biographical information is printed at the headineg of each hymln, and in frequent footnotes. Baptist Praise Book. By Rev. Drs. Fuller, Levy, Phelps, Fish, Arnitage, Winkler, Evarts, Lorimer, and Manly, and J. P. Holbrook, Esq. 1,311 hyllns, with tunes. Edition without tunes. Chapel edition, 550 hymns, with tunes. Plymouth Collection. (Congregational.) By Rev. Henry Ward Beecher. 1,374 hymns, with tunes. Separate'dition for Baptist churches. Editions without tunes. Hymns of the Church. (Undenominational.) By Rev. Drs. Thompson, Vermilye, and Eddy. 1,007 hymns, with tunes. The use of this book is required in all congregations of the Reformed Church in America. Edition without tunes. Chapel edition (" Hymns of Prayer and Praise" ), 320 hymns, with tunes. 71

Page  72 THE NATIONAL SERIES OF STANDARD CHURCh-dOOKS. CHRISTIAN WORSHIP - Continued. Episcopal Common Praise. The service set to appropriate mllusic, with tunes for all the hymns in the book of Common Prayer. Hymnal, with Tunes. (Episcopal.) By Hall & Whiteley. The New Hymnal. set to music. Edition, with chants. Edition of hymns only ( Companion " Hymnal). Quartet and Chorus Choir. By J. P. Ilolbrook, Mus. Doc. An admirable collection of approved hymns and tunes suitable for choirs. Pilgrim Melodies. By J. E. Sweetser. Hymniis and tunes. Christian Melodies. By Geo. BI. Cheever. IlynllllS and tunes. Mount Zion Collection. By T. E. Perkins. For the choir. Selah. By Thos. Hastings. For the choir. LITURGICAL. Public Worship. Containing complete services (not Episcopal) for five Sabbaths; for use in schools, public institutions, suniller resorts, churches without a settled pastor; in short, wherever Christians desire to worship, no clerg'yman being present. The Union Prayer-Book. A manual for public and plrivate worship. With those features which are olbjectionable to other denominationls of Christians than Episcopal eliminated or modified. Contains a service for Sunday-schools and family prayers. The New Psalter. Selections fiom the Psalms, Isaiah, and New Testament, for responsive reading. Founded on the Revised Version. Prepared by the Rev. R. S. Storrs, D.D. Precept and Praise. A manual of worship and study for Sunday-schools. A General Liturgy and Book of Common Prayer. By Prof. Hopkins of Aulurn Theological Seminary. This is a complete liturgy anld prayer book for non-episcopal churches. Stacy's Service of Song. A treatise on singing in private devotion, in the family, in the school, and in the worshipping congregation. By Rev. A. G. Stacv. With introduction and indorsemeni of Rev. Thomas O. Summers, D.D. In this hlnolo the author reviews the history oi music inl churches and gives aln interesting accm)unt of the quality, character, and fornls thereof at the present time.

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