The works of the Honourable Robert Boyle, Esq., epitomiz'd by Richard Boulton ... ; illustrated with copper plates.

THE WORKS Of the HONOURABLE ROBERT BOYLE, Esq EPITOMIZED.

BOOK V. PART I.

CHAP. I. New Experiments of the Positive or Relative Levity of Bodies under Water.

WHEN any Body that is lighter in Specie than Water is immersed in it, and upon the removal of that force which depressed it, it rises a∣gain, it is usually attributed to the Positive Le∣vity of that Body; but since the instance of Wood emerging is that which is usually offe∣red as an Argument, to it I shall answer, That Wood being a Body full of Pores (except some which will not swim in Water) and upon that

account specifically lighter than Water, the Water by the Pressure of that which is incumbent, get∣ting betwixt the Superficies of the Vessel, and the Body immersed, causes it to rise, the Water which succeeds it in its place making a more powerful Pressure against it, than its Specifick Gravity enables it to resist. And that Bodies Specifically lighter than Water will be thus buoyed up by it, will appear from the Hydro∣statical Paradoxes hereafter to be laid down.

And tho' it be usually urged, that the Bodies im∣immersed are too closely contiguous to the bot∣tom of the Vessel for the Water to insinuate them∣selves betwixt; yet from the following Experiment it will appear, that were the contiguous Surfaces so close, the positive Levity of the Wood would not be able to raise it; for two black Marbles, being so exactly polished as to be as contiguous as possibly they might, we tyed a Bladder full of Air to the uppermost, and then causing them both to be immersed in Water, the positive Levity of the Bladder, would not cause the Bladder to rise; but as soon as by a servant the uppermost Marble was gradually slipped half off the Polished Surface of the lowest, the Water which before was not able to insinuate it self betwixt the Surfaces of the contiguous Mar∣bles, and to separate them, presently caused the Bladder to rise with a considerable swift∣ness and force, above the Surface of the Water: Which Event, that it did not depend on Na∣ture's abhorrency of a Vacuum is evident, since that would have an equal force when the Polish∣ed Surfaces were wholly contiguous, the Pow∣er of Nature's abhorrency of a Vacuum being

held by its Assertors to be unlimited. And that it was not the heaviness of the upper Marble, nor want of lightness in the included, appeared, since when the Surfaces of the polish∣ed Marbles were not contiguous, the Bladder was able to lift up a weight of six or seven pound, besides the Marble.

And to shew, that the Bladder might be raised by the Pressure of the Water, accord∣ing to the laws of Hydrostaticks usually buoy∣ing up Bodies Specifically lighter than it self, having pressed out the greatest part of the Air contained in a Bladder, I tyed a piece of Iron to it, and immersed it in a wide-mouth'd Glass, which was so deep that the Bladder was total∣ly immersed, and yet not far below the Surface of the Water, and this being convey'd into our Pneumatick Engine, when by exhausting the Air part of the Pressure was taken off, the Air in the Bladder expanding it self, and take∣ing up more Room in the Water, and conse∣quently becoming so much more Specifically lighter, and the resistance of the Water which endeavours to buoy it up becoming respective∣ly greater, it was together with the suspended weight, raised to the Surface of the Water, and continued there till the outward Air was let in again; and then the Air being contracted into its former dimensions, it subsided again. In which Experiment the positive Levity of the Air was not varyed, but only its relative and respective weight in reference to its proportion of Water.

And that Rarefaction alters not the positive Levity of Bodies, may appear from the follow∣ing

Experiment; for having oyled a Bladder, and when the Air was expressed, tyed it to the neck of a Vial, I found, that in the exhausted Receiver, tho' the Air in the Vial was so far ex∣panded as to fill the whole capacity of the Blad∣der, yet the Vial neither rose higher; nor sub∣sideded lower when the Air was drawn out, or let in again.

CHAP. II. New Experiments about the Pressure of the Air's Spring on Bodies under Water.

TO shew that the Spring and Weight of the Air hath manifest effects on Bodies sepa∣rated from an immediate contact by the Inter∣position of Water, I shall subjoyn the following Experiments.

EXPERIMENT II.

We luted the neck of a Vial, which was ca∣pable of containing above a point of Water, upon that pipe which conveys Air out of the Receiver into the Pump, which being done, we whelmed over this Receiver our large one, and having poured in a sufficient quantity of Wa∣ter, we closed it up with the Turn-key, that no Air might get out that way, and then the Air being exhausted out of the Vial, if flew in∣to a great many peices, the sides of the Glass being not able to resist the Pressure of the Air,

that lay upon the Surface of the Water in the large Receiver.

EXPERIMENT II.

The greatest part of the Air being squeezed out of a Bladder, and the Bladder tyed to a weight, which kept it something below the Sur∣face of Water contained in a wide-mouth'd Glass; this being convey'd into a Receiver, the Air in the Bladder expanded, as the Air on the Superficies of the Water was extracted.

EXPERIMENT III.

A Brass Plug being fitted to a Cylinder which was closed with a Plate of the same Me∣tal at one end; we put a Bladder half blown into the Cylinder, and placing the Plug upon it, with a weight of a Conical figure upon that; we poured so much Water into the Receiver in which it was placed, as covered the top of the Conical weight, but left the Ring which was fixed to the top of it, and which was fastned to the Turn-key by the help of a string; and things being thus ordered, when the Air above the water was considerably exhausted, the Spring of the Air in the Cylinder rais∣ed the Plugg and Weights a considerable height, tho' the whole weight amounted to twenty eight pounds.

EXPERIMENT IV.

A Glass Vial being closed with Cement, and immersed in a deep Brass Cylinder of Water, this was convey'd into our Receiver, and when the Air which pressed upon the Water was drawn off, the Vial in the bottom of the Water was violently shattered in pieces by the Spring of the included Air, for want of a sufficient Pressure of the Air incumbent on the Water, to resist the force of that Spring.

EXPERIMENT V.

To shew that the Expansion or Rarefaction of Air increases not the positive Levity of Air, we suspended a Bladder half full of Air, with a Counterpoise, at a ballance in our Receiver, and tho' when the Air was ex∣hausted, the Bladder was sufficiently distended; yet it seemed to retain the same weight, whe∣ther dilated or contracted.

CHAP. III. New Experiments concerning an effect of the varying weight of the Atmosphere upon some Bodies in the Water. Communicated in the Transactions of Feb. 24.1672/3.

COnsidering that the Pores of most Liquors are plentifully stocked with Aery Parti∣cles, and that upon that account the Atmo∣sphere may according to its several degrees of weight have considerable Effects on them, I caused three small Glass-Bubbles with slender Stems to be blown, which were so equally pois∣ed in Water by their weight, that a little thing would make them emerge or sink. And I ob∣serv'd, that these being put into Water con∣tained in a wide-mouth'd Glass, sometimes they would emerge and sometimes subside, and sometimes emerge again, as the Atmosphere va∣ryed in weight or degrees of Heat and Cold.

And it was easie to observe, that when the Heat of the Air raised one of these Bubbles, the heat of the Sun-Beams would so rarisie the Water included in them, as to cause some of it to get out, upon which the Bubbles emerged, but when those Beams were intercepted, the Water being condensed, and getting into the Bubble again, it would subside. But when their subsiding depended on the weight of the At∣mosphere, if the Mercury in the Baroscope stood high, the Heat of the Sun would not raise the Bubbles.

N. B. 1. That the Bubbles not being all e∣qually poised, sometimes one and sometimes two would rise, as the Air was heavier or lighter, and consequently capable of affecting the lightest only, or all.

2. The Success did not always answer, for when the subsiding depended on some occult cause, they would continue there, as if some airy Parts had insinuated themselves into the Water.

3. The fittest time for these Experiments, and in which they best succeed, is in the Spring, the Air being more subject to vary in its Weight, as well as other things.

CHAP. IV. New Experiments about the differing Pres∣sure of heavy Solids and Fluids.

ONE great reason why some Learned Men believe that the Air hath no such a consi∣derable Pressure on subjacent Bodies as we teach, is, because they think it would be too heavy for Animal Bodies to live or move under it; but since we have positive proof of it, we may as well doubt whether the Load-stone be en∣dewed with an attracting and other Virtues, because we cannot understand how they are perform'd. Besides, Men being born under such a Pressure, their Bodies seem not only ac∣custom'd to it, but proportionably strong. But could we suppose a Man born somewhere,

without the incumbent weight of an Atmo∣sphere, doubtless such Bodies would not be so able as ours to resist its Pressure.

But it is urged by some, that were there such a Pressure of the Atmosphere, it would cause Pain; but to this it may likewise be answered, that our Bodies being from the Birth accustom∣ed to it, we only feel Pain upon some new unaccustomed and additional Pressure; so when we are accustomed to wear heavy Cloaths, we are not sensible of their weight, nor are we sensible of the Heat of the Blood in our Heart, because it's habitual to those Parts, whereas if our finger be put into the Heart of a newly dissected Animal, we shall find it sensibly hot.

But further, from what I have elsewhere laid down, it appears, that a Cubick Inch of Air will be able to resist the weight of the whole incumbent Atmosphere, and that a little quan∣tity of Air resists a further compression as well as a greater; and I have likewise shewn, that the Pores of the Parts of Animals whether fluid or consistent, are plentifully stocked with numerous Aerial Bubbles, which cause those Bodies to swell or expand in our exhausted Re∣ceiver. And as for those membranous and fibrous Parts which are not altogether so po∣rous, they are of so strong and firm a Texture, as to resist external Pressure upon that account. Besides, there is a great deal of difference be∣twixt the partial Pressure of a solid Body, and the Pressure of an Ambient Fluid, which pres∣ses uniformly, and is resisted either by the so∣lidity of the Parts, or the Spring of those Airy

Particles contained within their Pores. And that the uniformness of the Pressure makes it less sensible, is evident, since it hath been ob∣served, that tho' the Atmosphere is so much lighter upon the tops of some high Mountains, as not to elevate Mercury so high in a Baro∣scope by three Inches, as at the bottom, yet those that have been upon those Mountains tell us, that they perceived no considerable diffe∣rence in the Pressure of the Atmosphere above and below; nor are Miners sensible of any great weight upon them, tho' in deep Mines in Mountainous Countrys; nor are Divers sensible of any Pressure when under Water; but that Air weighs in Air, and that Water weighs in Water, I have elsewhere made it evident; yet I don't think that a Diver is violently depressed by the weight of the incumbent Water, since from what we have elsewhere delivered it ap∣pears, that if a Man's Body were of an equal specifick Gravity with the Water, the subjacent Water would sustain him, but his Body being heavier than an equal bulk of Water, the Sur∣plusage of weight depresses it; for which Reason, in some Sea-Water, which is near of the same specifick Gravity with their Bodies, Divers find it very difficult to dive. However it is not a little strange, that at so great a depth as one hundred fathom Divers should not perceive a sensible Pressure, especially upon their Thorax and Abdomen: But I am apt to believe that the inadvertency of some of them, rather than any thing else makes them not take notice of it; or else the haste which they rise and sink in; since I have been told by some,

that they have perceived a manifest Pressure when they sunk leisurely. And I was likewise told by another, that when he descended a great depth under Water, the Blood was squeez∣ed out of his Nose and Eyes; and another who dived in a Leathern-case told me, that it was so much pressed against his Thorax and Belly, that he was forced suddenly to come up a∣gain.

But since these Relations are not altogether to be relied on, I shall endeavour to give a Reason why the Pressure is no more sensible; which I take to be the strong Texture of a Hu∣man Body, and the uniformity of the Pressure. As to the first, to what I have said of the Re∣sistance made by our Bodies to external Pres∣sure, I shall only add, that a Bladder being ty∣ed upon the end of a Cylinder, about an Inch in Diameter, when the Air was exhausted, the in∣cumbent Pressure of the Atmosphere was not able to break it, tho' when a Man's hand was placed there, he was not able to raise it till some of the Air was let in again, the Pressure which held his hand down being equivalent to a Cylinder of Water thirty foot high. But to shew the effects of an uniform Pressure of Liquids upon Solids contained in them, I shall subjoyn the following Tryals.

EXPERIMENT I, II, and III.

Having placed an Egg betwixt two Bladders half blown, in a Brass Cylinder, and cautiously put a Plug upon them, with as much weight upon it as amounted to thirty pound, I placed

them all in a Receiver, and when the Air was exhausted, tho' the expanding Bladders must needs press equally against the Egg and the Plug, yet the incumbent weight was raised, and the Egg when taken out as whole as before; the weight it sustained in the Cylinder being not quite so much as the weight of the Atmosphere. But tho' the Egg was able to sustain so much weight when pressed upon uniformly; yet Weights being successively laid upon the same Egg exposed to the open Air, four Pound weight crushed it in pieces. And by further Tryals we found, that an Egg-shell, which had all the Yelk and White taken out, as also a thin Glass Bubble, being placed betwixt two Bladders, as in the first Experiment, neither of them was in the least cracked.

EXPERIMENT IV.

To shew that what we have taught of the Na∣ture of Fluids, will hold in Water as well as Air, if the Pressure be uniform, we enclosed an Egg in a Bladder almost full of Water, and put∣ting it into the Brass Cylinder, we heaped up∣on the Plug as many Weights as amounted to seventy five pound, yet the Egg being taken out, was as found as when first put in. In which In∣stance it cannot be pretended, that the Egg bore no weight, by those that allow not Water to gravitate in Water, since there was a consi∣derable Pressure made by Metalline Weights, which every body allows to weigh in Water. From this Experiment, and the other before mention'd, of an Egg being broke by a partial

Pressure, it appears, that the Strength of the Texture of a Humane Body, together with the Uniformity of the Pressure of ambient Water, may be the reasons why Divers feel no greater Inconveniency under Water; for tho' their Thorax may be a little more compressed than other Parts, yet that Part being naturally dila∣ted and contracted, a little Pressure may make no sensible Alteration: But I have been told by a Diver, that at a consicerable Depth, he per∣ceived a painful Pressure upon the Drums of his Ears, 'till he contriv'd a way to guard them from that Inconveniency; the reason of which Phaenomenon seemed to be no other, than that in that Part there was not an equal internal Pressure, to resist and counterballance the ex∣ternal Pressure of the Water.

CHAP. V. An Invention for estimating the Weight of Water in Water, with ordinary Ballances or Weights. Communicated in the Pub. Transact. of Aug. 16. 1669.

A Bubble about the bigness of a Pullet's Egg, with a long Stem turned upo at the end, was heated; and, when the Air was most of it expelled, sealed up; and then being by a con∣venient weight of Lead immersed under Water, it was suspended at the end of a Ballance, and counterpoised; and then the Apex of the Stem being broke off with a Forceps, so much

Water got into the Cavity of the Bubble, as required four drachms and thirty eight grains to reduce the Ballance to an Aequilibrium. Which being done, we drove out the Water by the help of a Flame of a Candle into another Glass, which was counterposed, and we found that it weighed four drachms and thirty grains, which together with what was evaporated and lost, and the weight of the Apex, amounted to the weight first mention'd. So that from hence it appears, that Water weights as much in Water, as it does in the open Air; which according to the best Computation we could make, succeed∣ed a second time in a larger Bubble.

As for the Objections which Mr. George Sin∣clair hath made to this Experiment, since it is the Opinion of our Author, that he only dif∣fers from him in Expressions, I shall wave what he there says, as not at all requisite in this Place; and shall only add what our Author hath said, to explain what he means by Water weigh∣ing in Water, viz. That it gravitates or weighs, in as much as it tends downwards, upon the account of its specifick Weight, tho' it does not preponderate, that is, the Parcel of Water weighed hath but an equal Tendency down∣wards with the Ambient Water, but upon an additional Weight it preponderates as much as the additional weight increases its Tendency towards the Center.

CHAP. VI. Hydrostatical Paradoxes made out by new Experiments.

BEfore I procced to the Hydrostatical Para∣doxes, I shall briefly intimate, that tho' I can readily assent to the Hydrostatical Conclusi∣ons laid down in Monsieur Paschall's Discourse; yet as for the Experiments he makes use of to prove them by, I must own, I am not satisfy'd with them; since he makes use of such as require that a Man should sit under Water fifteen or twenty Foot, with the end of a Tube leaning upon his Thigh. But he neither acquaints us how a Man shall be able to continue there, or how he shall discern the alterations in the Mer∣cury or other Bodies, at the bottom. Besides, such Experiments as he proposes require Tubes twenty foot long, and Vessels as many foot deep, which are hard to be got in England; nor is it possible to obtain from a Tradesman, Brass Cylinders or Pluggs, made with so much Mathematical Exactness as he proposes.

Having therefore contriv'd a more easy way to demonstrate the Truths contain'd in the foregoing Paradoxes; before I proceed to ex∣amine them, I shall premise a word or two by way of Postulatum or a Lemma; which consists of three Parts: The first of which is, That if a Pipe open at both ends, and held perpendicu∣lar to the Horizon, have the lower of them un∣der Water, there passes an imaginary Plain, which touching the Orifice of the Pipe, is pa∣rallel

to the Horizon, and likewise, as to sense, to the upper Surface of the Water. To which it will be consonant, secondly, that as long as the Surface of the Water is even, the Water incumbent on this Plain will equally press on all the parts of it. But, thirdly, if there be a greater Pressure on one part of this Plain than another, as when a Stone presses upon it, the Water which lyes under that Stone will be dis∣placed, as the Stone subsides successively, 'till it come to the Bottom. But on the contrary, if there be less Pressure on one part of that Plain than on another, the Liquor will be raised on that part so high, 'till the Liquor on that part of the Plain gravitates equally as the Water in∣cumbent on the other parts of it; which will appear from the following Experiments.

And first, If a Cylindrical Pipe open at both ends, be held in a perpendicular Posture, and the lower end be immersed three Inches in Water, the Liquid within the Tube having a free Communication, will be of an equal height with the external Water, and in thin Tubes, a little higher. But if Oyl be gradually poured upon the Water without the Pipe, the superfi∣cial Plain will have a greater Pressure upon it without than within, and consequently the Water under the Tube, finding not so great a Pressure within the Pipe as without, it gradually rises, 'till the external and internal Pressure upon the imaginary Plain be equal.

But since this will be further evident from what is contain'd in the following Paradoxes, I shall proceed to them, as soon as I have laid down the following Experiments, to shew Air

is not a Body devoid of Weight, as some Peri∣pateticks suppose. The first is, that a Glass Bubble being blown, whose Capacity was short of two cubical Inches, it was instantly herme∣tically sealed, whilst hot; and when it was cool, being placed in a nice pair of Scales, and then the Apex of the Stem being broke off, the Air rushing in with a noise, caused the Bubble to preponderate half a Grain, tho' by breaking of the Stem under Water, it appear'd that the rarify'd Air remaining in the sealed Glass, pos∣sess'd one fourth of its Capacity. Another time the same Experiment being tryed, the Air contain'd seem'd to weigh near three quarters of a Grain; and the Capacity of the Receiver being filled with common Water, it weighed 905 Grains: So that allowing the Air contain'd to take up one fourth, and that the weight of the remaining Part was ¼, probably the weight of the whole was about a Grain; and conse∣quently the Water weighed little more than nine hundred times as much as an equal Bulk of Air.

PARADOX I. [paradox 1] That in Water, and other Fluids, the lower Parts are pressed by the upper.

If in a Glass of Water, A B C D (see Plate the second, Fig. the first) a Cylindrical Tube be immersed, which contains Oyl of Turpen∣tine; and that Oyl be suspended there, (by keep∣ing the upper Orifice close, after it hath been suck'd up to a convenient height) 'till the Pipe

is depress'd to a convenient Depth in the Wa∣ter; if the lower end of the Pipe B Q be im∣mersed 'till it reaches to the imaginary Surface G H, and the Oyl X Q presses no more upon that imaginary Surface, than the Water with∣out the Tube, then the Oyl will be suspended there, and not be able to depress the Surface of the Water below it; but if the Surface of the Oyl in the Tube be much above the Water, and it presses more upon the imaginary Surface G H than the Water without, then it will make its way through that Surface, 'till the Oyl within and the Water without are brought to an Ae∣quilibrium again, so that they both equally press upon the Surface G H; and the like will hap∣pen, if the Tube be raised to the Surface D S, and gradually on to the Surface L M; for as the Pressure of the external Water grows less and less, as the imaginary Surface is nearer the top of the Glass, so the Oyl in the Tube grow∣ing preponderant, falls out at the lower end of the Tube, 'till the Tube T V being almost raised to the Surface L M, but a little Water pressing upon that Surface, the Oyl is almost wholly fallen out of the Cylindrical Cavity of it. But if instead of raising the Pipe P Q, it be depressed to the Position N O, the Water incumbent on the Surface E F on the outside the Pipe, being more powerful than the Cylin∣der or Oyl W AE, which is only aequiponderant to a Cylinder of Water leaning on the Surface G H, the Oyl must be buoyed up by the Pres∣sure of the external Water, and the Space O AE filled with Water, so that the Oyl betwixt W AE, and AE O, being both aequiponderant to a Cy∣linder

of Water, they may equally press upon the Surface E F with the Water on the outside. And agreeable to what hath been said it is, that the Cylinder of Oyl X Q will be something above the Surface L M, when the Tube is only immersed to the Surface Q. Since Oyl of Tur∣pentine being specifically lighter than Water, the Cylinder must be longer, to press upon the Surface G H, equally with a Cylinder of Wa∣ter, no longer than from the Surface L M to G H. And if a heavier Liquor than Water were made use of, the Surface X must be more above L M than in Water, otherwise it would not press equally upon the subjacent Surface. From whence appears the Truth of the Propo∣sition, for if the Oyl be kept suspended at a different Height as the external Water is deep∣er, to countervail it; and if as it is raised from G H to I K, the Oyl in the bottom of the Pipe is pressed out, it must needs follow, that it is pressed down by the weight of the incumbent Oyl, since then the surface of the Water I K, being not equally pressed upon from without, as by the Oyl, it is able to break that Surface and make its way out.

But before I proceed to the following Pro∣positions, I shall subjoin the following Adver∣tisements.

• First, What we say of the Pressure of Fluids upon one another, is to be attributed to heavy Fluids in general, except some reason appears for a particular exception in some Pla∣ces.
• Secondly, That in slender Pipes the Sur∣face of the Liquor within, is generally above the Surface of the external,
• Thirdly, Small Pipes are the fittest for these Experiments, be∣cause

• in larger the emerging Oyl passing through the Water obscures the Light of what is design'd to be visible.
• Fourthly, We make use of Oyl of Turpentine, rather than any other Liquor, because clear and colourless, and not apt to stain ones Cloaths; and as for the offensive Smell, that may be corrected with Oyl of Rhodium, or any other odoriferous Oyl, tho' any other Liquor may be made use of, that will not mix with Water.
• Fifthly, Oyl of Turpentine may be tinged with Copper, to render the Phaenomena within more visible; for which reason we often employ a Decoction of Brasil instead of clear Water, or of Log-wood, or red Ink it self.
• Sixthly, the Figure of the Glasses may be what you please, but the Pipes must be broader or longer as occasion requires.
• Seventhly, The Pipes are to be filled by sucking up the Air to a convenient Height, and then stopping the Orifice above with ones Finger; but if it be too high, the Experimenter may let it out as he pleases, by admitting a convenient quanti∣ty of Air in at the Top, by gradually remov∣ing his Finger.
• Lastly, In such Experiments as require a considerable disparity betwixt the two mingled Liquors, we may make use of Oyl of Tartar per Deliquium instead of Water, and Spirit of Wine instead of Oyl of Turpen∣tine; these Liquors being not disposed to min∣gle with one another; and instead of fair Wa∣ter 06 we may make use of a filtred Solution of Sea-Salt, when the other is not easily got.

And when we have a mind to vary the Experiment, we may make use of Oyl of Turpentine along with the other two; and by depressing a Tube

into them with Water in the bottom, exhibit very pleasing Phaenomena.

PARADOX II. That a lighter fluid may gravitate or weigh upon a heavier. [paradox 2]

The truth of this is evident, since all Bodies have a tendency towards the Center; by which they are always disposed to press downwards, tho' sometimes they have a respective Levity, as when a piece of Wood emerges in Water, yet nevertheless that relative Levity argues not that it hath no weight at all, since tho' when a Man stands in a pair of Scales and lifts up a weight, notwithstaning the Ascent of the weight he will perceive a manifest tendency of it down∣wards.

But to make it more plain (See Plate 2d. Fig. 2.) where supposing a Cylinder of Water I G, to be immersed in Oyl of Turpentine to the immaginary Surface E F; the Water in the Pipe I H being heavier in Specie than the Oyl, it will equally ponderate upon the Surface E F as the lighter Oyl K E L I, and if the Pipe be immersed deeper, the Cylinder of Water be∣ing not equiponderant with the extenal Oyl, the Oyl will, tho' a lighter Body in Specie, rise in the bottom of the Tube and buoy up the Water.

Again the Bubble X which consists of a Glass heavier than Water and Air which is lighter; or partly of Water it self which is specifically as heavy, as long as the whole aggregate is

lighter than Water of an equal bulk it will float, but if it grows heavier it will sink, and if any heavy Body presses upon it, which is specifically heavier than Water, by which the included Air may be compressed, the Bubble will subside, but when that Pressure is taken off, and the Air ex∣pands it self again, it will as soon emerge, the Water that was before sucked in being by that means expelled.

But for a further Confirmation of this second Paradox, I shall add the following Experiment, viz. That having put a Glass-Bubble pretty well poised, into a Tube filled within a foot of the top with Water, it swam there, till a good deal of Oyl of Turpentine was poured upon the Water, but then more Water being forced into the Bubble by the weight of the incumbent Oyl, it presently subsided; but when part of that Oyl was taken off, the spring of the Inter∣nal Air forcing the impressed Water out a∣gain, the Bubble presently immerged. And,

For a further Confimation of this Paradox as well as the first, I shall add, that a Bubble swimming in a Tube, as in the former Experi∣ment, tho' depressed to the bottom by a Wier, yet when that Pressure is taken off again it will rise up as before; but if it be held under Water till more is poured in, and till it rises about a foot above it in the Tube, the weight of the incumbent Water will depress it, but if that Water be gradually taken off, the Bubble will presently emerge.

If it should be asked why in these Tryals I did not make use of Oyl of Tartar per Deliquium, instead of Water? I shall answer, That in such

slender Pipes as the first Experiment was made in, as the Oyl of Tartar flowed down one side, the Oyl of Turpentine would rise on the other; which makes me wonder that Monsieur Paschall should teach, that if a Tube filled with Mercu∣ry be immersed fourteen foot under Water, if the Tube be fourteen foot long, the Mercury will not wholly run out, but continue to the height of a foot in the bottom of it; and I the more wonder at it, since probably the Impetus would make it descend; and since the like would not succeed with much more favourable circumstances, betwixt Oyl of Turpentine and Oyl of Tartar.

PARADOX III. [paradox 3] That if a Body contiguous to the Water be alto∣gether or in Part lower than the highest level of the said Water, the lower part of the Body will be pressed upward by the Water that touches it beneath.

This may be proved from what hath been delivered under the first Paradox, for where∣ever an imaginary Surface is beneath the real one, the weight of the Water being incumbent on all other Parts of the same Superficies, that part on which the immersed Body chances to lean must have a Proportionable endeavour up∣wards; and if that endeavour be greater than the specifick Gravity of the immersed Body is able to resist, then it is buoyed up; and tho' the Gravity of the immersed Body is so great, as to over-power the tendency of the Water

upwards, yet the tendency of that Water is not therefore to be denyed, for as much as it in some measure resists the subsiding of that Body. And this may be confirmed by the Ex∣periment tryed in the second figure, for as more Oyl is externaly poured on, the Water is impelled and buoyed up in the Pipe by the subjacent Oyl, which could not be, if the Oyl did not press against it beneath; and even when the Water and Oyl are in an Aequilibrium, the latter presses upwards, in as much as it resists the descent of the Water out of the Tube. And the truth of this Proposition is equally true, whether we suspend Oyl in Water or Water in Oyl.

And that the Water makes a resistance to Bo∣dies that descend in it, will appear from the following Scheme; for supposing the Pipe E F to contain Oyl specifically heavier than Water, and when the Oyl and Water without were in an Aequilibrium, the Pipe be raised, drops of Oyl will fall out, but much more slow∣ly than in the open Air, where if the drop G were not specifically heavier than the Water, it would not break the imaginary Surface of the Water H I. But further, it not only from hence appears, that since as long as the two Liquors are in Aequilibrium they are not able to remove each other out of their places; but from hence we may infer, that a Liquor of an equal specifick Gravity with Water, being placed in any part of that Liquor, would re∣main in the place assigned.

But to illustrate what we have said, of Wa∣ter obstructing the descent of Bodies heavier than it self, I shall add, that if twelve ounces of Lead be counterpoised in the Air, when the Lead is let down below the Surface of the Wa∣ter, the Scale in the Air will manifestly pre∣ponderate; which shews that the Water hinders the descent of the other. And the resistance of Fluids to the lower superficies of Bodies may be further confirmed by observing, that Bodies specifically lighter than Water are raised by it, as Wood and drops of Oyl; the Reason of which seems to be this, that there is a greater Pressure upon the lowest part N, than upon the upper part of the drop M, because that upon all the Surface K L there is an uniform Pressure of the Water A K. B L, and upon all the Parts of the Surface H I there is a greater weight of Water A H. B I, except at the part N, for there the Oyl G, being not so heavy as so much Water, it is consequently unable to resist the ascent of the Water beneath it, for which Reason it is buoyed up; and the case being the same with that and any other Parallel Plain, where∣ever it is in its ascent, it must be by the same Reason gradually raised up, for the Oyl being pressed against by two Pillars of Water, the one above and the other below, and the low∣er being longer by the thickness of the rising Body, than that which lyes upon it, it must consequently be buoyed up, and more or less swiftly as the lower Basis presses more or less on the subjacent superficies.

And for the like Reason when two pieces of stick of a different length are immersed in Water; the longest rises the fastest, for if O P were two foot high, and Q R but one, and both rested upon the same imaginary Plain, the one hath a Pillar of Water a foot longer to resist its rising than the other, and as the e∣merging Body rises slower, as the proportion be∣twixt the upper and the lower Pillar of Wa∣ter is less; so thence may be deduced a Reason why in some Liquors, whose whiteness depends on the intermixture of drops, are so long a rising, the minuteness of them rendering the difference of the upper and lower Pillar of Air inconsi∣derable, but as these drops by moving up and down unite into larger, the difference grow∣ing more considerable, they are accordingly buoyed up in less time, and swim upon the top of the Water.

And for the same Reason, that these Bodies float upon Water, a Cubick Inch of Wood is by its specifie Gravity only so far depressed into the Water contained in the Vial A B. C D, till the Water about it makes an equal Pressure upon the imaginary Surface X W, and because the Wood is not so heavy in Specie as Water, therefore part is kept emerging above the su∣perficies of it.

But to shew further, that the weight of a floating Body is equal to as much Water, as its immersed Port takes up the Room of, I shall subjoyn, that having placed several Marks upon the Surface of a floating Glass, and, when it was taken off the Water, put just so much Water into it as filled it up to those Marks, by that

means I found, that the weight of the Water which was sufficient to fill the space possessed by the floating Vessel, below the Surface of the Water, was equal to the weight of the whole floating Vessel, and all that was contained in it. And the same end may be obtained another way, viz. By first filling a Cistern or Pond with Water, by a Vessel of a known capacity, and then having emptyed it again; for if the Vessel be placed in that Cistern or Pond, and Water put into the Cistern again till it floats the Ves∣sel, and fills the Cistern or Pond full, as much as it falls short of the weight of Water first contained in the Cistern, so much is the weight of the floating Body.

PARADOX IV. That in the ascension of Water in Pumps, &c. There needs nothing to raise the Water, but a competent weight of an external fluid.

The truth of this Paradox sufficiently appears from what hath been before delivered; how∣ever to make it plainer, if possible, I shall add, that if a tinged Liquor be sucked up about an Inch into a Tube, and whilst the upper Orifice is covered with ones Thumb, it be depressed in Water till the superficies of the external Water is above the Surface of the internal, and then a considerable quantity of Oyl be pour∣ed upon that, and when ones Thumb is taken off the upper Orifice of the Pipe, the external Flu∣ids will by their Pressure, raise the tinged Li∣quor above the Surface of the Water, tho' not

quite so high as the Oyl: From whence it ap∣pears, that a Liquor may be raised in a Tube by the Pressure of an external fluid, and that lighter than it self in Specie, which may illustrate what we have said of the rising of Water in Pumps, where by the Pressure of the Atmo∣sphere the Water is buoyed up, when the Pres∣sure of the incumbent Atmosphere is taken off the internal superficies by the rising sucker, and makes way for the Water to ascend with∣in the Pipe.

I took likewise a small Tube, whose Diame∣ter was the sixth part of an Inch, and having im∣mersed it an Inch in Quick-silver, I put my Thumb upon the upper Orifice, and kept it there till I had immersed the Tube eighteen Inch∣es in Oyl, by the weight of which pressing against the Quick-silver, it was not only kept from fall∣ing out of the Pipe, but raised a little, and as when the Tube was raised some of the Mercury would fall out, so when it was depressed the Mercury would be buoyed up, by the greater weight of the external Liquor upon it. And indeed that the Water in a Pump may be raised by the Pressure of an external fluid, will appear more fully to him that shall consider, that in the Torrecellian Experiment the Pressure of the external Air is able to raise Mercury in a Tube twenty nine or thirty Digits, which is equipon∣derant to a Cylinder of Water thirty three or thirty four foot high.

[paradox V] PARADOX V. That the Pressure of an external fluid, is able to keep an Heterogeneous Liquor suspended at the same height in several Pipes, tho' those Pipes be of very different Diameters.

This is evident from what is represented in Fig. 6. Plate the second, for if the Orifice of that Vessel A B C D be closed up with a Cork, and that Cork have four holes, in three of which the Pipes are fixed, and in the fourth the Tun∣nel, and if, when so much Water hath been poured in as reaches to the Surface E F, Oyl be poured through the Tunnel till it reaches to the Surface G H it will depress the Surface of the Water down lower, and the Oyl not being able to get into the Pipes L. M. N. by its weight, it will cause the Water to rise to O P Q, the Surface of the Water, which before rested at E F, being depressed down to I K, upon which imaginary Surface the Water contained in the Tubes, answerable to their Bulk, making an e∣quivalent Pressure with a Cylinder of external Oyl of the same Bore, the Water must conse∣quently be buoyed up to the same height in all, except the last Pipe be very small, but the dif∣ference on that account being easily distinguish∣ed, it will be no difficult matter to make an al∣lowance.

N. B. when the Oyl is poured through the Tunnel, it will be requisite to put some Cotton Wool in it, to break the force of the falling

stream, lest the violence of it should prejudice the Experiment.

PARADOX VI. If a Body placed under Water, [paradox VI] with its upper∣most Surface parallel to the Horrizon, how much Water soever there may be on this or that side above the Body, the direct Pressure sustained by the Body (for we now consider not the La∣teral or the recoiling Pressure, to which the Body may be exposed, if quite environed with Water) is no more than that of a Column of Water, having the Horizontal superficies of the Body for its Basis, and the Perpendicular depth of the Water for its height.

And so likewise, If the Water that leans upon the Body be contained in Pipes open at both ends, the Pressure of the Water is to be estimated by the weight of a Pil∣lar of Water, whose Basis is equal to the lower Orifice of a Pipe, (which we suppose to be pa∣rallel to the Horizon) and its height equal to a Perpendicular, reaching thence to the top of the Water; tho' the Pipe be much inclined towards the Horizon, or tho' it be irregularly shaped, and much broader in some Parts, than the said Orifice.

As for the first part of our Paradox, it is proposed by Stevinus in more general Terms, and thus demonstrated, (See Fig. 7. Plate the second) where, supposing A B C D to be a solid Rectangular figure of Water, whose Ba∣sis E F is parallel to the Horizon, and whose

height G E is a Perpendicular from the Surface of that Water, the bottom D E, E F, and F C cannot be charged with a greater weight than what is respectively Perpendicular, be∣cause none of them can receive an Additional weight from the Water Collaterally, but it must diminish the weight of Water Per∣pendicularly incumbent on that other bottom, else there must be a greater weight upon the Basis D E F C, than is contained in the Surface A B. C D, which is impossible.

To which instance of the learned Stevinus I shall add the following. For if Oyl be suck'd up into the Pipe represented by Fig. 8 Plate the second, and when it is at a convenient height in the longer Leg, you nimbly stop the upper Orifice, till it be depressed so low into the Wa∣ter, that the Oyl is but little above the Surface of the Water, it will rest near that station, when the upper Orifice is unstopped; and if it be depressed lower than that, the weight of the incumbent Pillar of Water will force its way into the Pipe, so far as answers the weight of a Cylinder of Water of an equal Bore with the Oyl contained in the Pipe, and on the con∣trary, if the Pipe be elevated above its first station, as much Oyl will rise out of the Pipe and emerge, as answers in weight to the part of the incumbent Pillar of Water removed by that means from gravitating upon it. And to this I shall add, that tho' Water is not con∣tained in Pipes, yet it presses as regularly upon subjacent Bodies as if it were; which will be e∣vident, if a Vessel of the shape of the Funnel de∣lineated in Fig. the 6th be imployed, for

the Liquor contained in the small Stem of that will be able to sustain the whole incumbent Wa∣ter: In confirmation of which, we made use of such a Vessel, as Plate the third, figure the first represents, and filling the parallel Leg with Oyl, and the other as well as the Ball with Water, the Oyl was elevated no higher in the longer Leg, than if the less Leg had been an uniform Tube of the same Diameter; and when the Ex∣periment was reiterated with Oyl in the Ball, and Water in the long Leg, the weight of that Oyl was not able to raise the Water in the long Leg to an equal superficies with it self; the Liquors in both these Experiments which was contained in the capacity of the Ball, being sustained by the concave sides of the Glass. And the like Experiment being tryed with Quick-silver, which was poured into the shor∣ter Leg C D, till it rought almost to the bottom of the Ball, and as high in the longer Tube A B, upon an affusion of Water into the long∣er Leg, the Mercury was buoyed up into the Ball, till it rought to H E G, where if more than what was Perpendicularly incumbent on the Tube C had pressed upon it, the Water would not have been able to keep it at such a height.

But to confirm the second part of our Para∣dox, we made use of a Glass, such as Plate the third Fig. the second represents, and having filled the Glass half full of Water, we stop∣ped it with a Cork, in which the Pipes there delineated were fixed, and likewise the Tun∣nel, the bottom of each of the Pipes, being each immersed considerably in Water, and

then pouring in Oyl through the Tunnel, we observed, that the Water was elevated to an equal height from the lower superficies of the Oyl which pressed on the Water; in which Ex∣periment, tho' the Pipes contained more Wa∣ter by being included, yet that Water pressed no more upon the imaginary Plain, than an e∣rect Pipe of equal Bore with the lower super∣ficies of the Water contained in it would have done. And if Oyl of Turpentine be poised in a Pipe in an erect Posture, and then by inclination a greater portion of it brought under Water, yet the external Water will raise the Oyl con∣tained in it; and the same was evident, when Oyl of Turpentine being contained in three Pipes of such figures as Plate the third Fig. the third represents, for in all such cases, where the Pipes are in an inclined Posture, or some Parts of them larger than ordinary, part of the weight of the Liquors contained weigh upon the sides of the Vessel, and no more presses up∣on the subjacent Liquor, than is answerable to an erect Pipe of equal Bore with the lower Orifice, and of equal height with an erect Tube, answerable to the length of one end of that Pipe from the other.

To make out what Stevinus hath asserted, viz. That if a Cylinder of Water be placed upon a subjacent Body, the Basis will sustain a weight equal to that Circular Basis, and to the Perpendicular height of it, we provided a Vessel of Laton, of the figure represented by Fig. twelve Plate the third, which being furnished with a close bottom C D, made of a flat piece of Wood, covered with a soft Bladder,

and greased on the lower side near the edges, that leaned on the rim of Wood G H, contigu∣ous every where to the inside of the Latten, that it might be easily lifted up from off the rim, and yet at other times lye so close upon it, that the Water should not be able to get out between them. To the midst of this bottom was fastned a long string, for a use to be here∣after mention'd; the Instrument being thus prepared, the Water was poured in at the top of the Pipe A B, which pressing upon the false bottom C D, against the subjacent rim G H, con∣tributed to render the Vessel more close, and to obstruct its own passage, whereupon we tyed the upper end of the string I K to a beam, and put so many weights into the opposite Scale, as were sufficient to raise the false bottom C D from the rim G H. And then deducting from that weight, the weight of the false bottom, and the Water contained in the broad Cylindri∣cal Box B E C H. G D F, we found that the Pres∣sure, which was made upon C D was much greater than what reading Stevinus would make one expect, and than all the Water contained both in the Pipe and Cylinder would have been, had it been contained in an uniform Cylin∣der.

[paradox VII] PARADOX VII. That a Body immersed in a fluid, sustains a Lateral Pressure from the fluid; and that in∣creased, as the depth of the immersed Body be∣low the Surface of the fluid increaseth.

This appears from what is represented by Plate the third, Fig. the fifth, where Oyl be∣ing sucked up into the Pipes G F K, and they sufficiently immersed in the Water contained in the Vessel A B C D, so that the Surface of the Oyl I K, may be but a little above the Wa∣ter, the Imaginary Pillar of Water H G will suspend it there, but if the Pipe be raised, the Oyl becoming too heavy to be kept up by so short a Cylinder, the incumbent Cylinder will force it out of the Orifice G, but if the Pipe be further immersed, the Water will raise the Oyl in the Tube, and fill part of the Cylindrical cavity below it.

To this Experiment I shall add, that having stopped the Mouth of the Vial ABCD, repre∣sented by Fig. six, Plate the third, with a Cork and Cement, and bored with a hot Iron, a hole to receive the Pipe G H, and the other E F, I stopped the Orifice G with a Cork and Cement likewise, and then pouring in Water through the Pipe E, till it rose to the Surface I, the Bub∣ble X was so nicely poised that it swam, but as soon as by pouring in more Water the Surface was raised to K, the Bubble X subsided to the bottom: From whence it appears, that the whole Water contained in the Pipe E, presses

upon the whole Water within the Glass, other∣wise it could not compress the Air in the Bub∣ble, and make it sink; and likewise that it not only presses upon that subjacent, but likewise upon those Parts that are latterally situated in Respect of it. And that not only the upper Parts of the Water, but even the Cork that is below the Surface of the Water I, is pres∣sed by the weight of it, and obliquely too, appears, since if the Orifice G be not closely stopped, the Water will be raised through it, and if instead of a Cork and Cement, it be only stopped with ones Thumb, one may per∣ceive an evident Pressure of the Water against it. And that the subsiding of the Bubble depended on the Pressure of the Water above it, appeared, since if part of the Water was poured off, by inclining the Vial, it would presenty e∣merge again.

And one thing in this Experiment worthy our notice, was, that if the Glass A B. C D was not wholly filled, but the space betwixt L M filled with Air, yet the Pressure of such different Fluids may be so easily communica∣ted from one to the other, that the Bubble would descend equally as if it were filled with Water.

[paradox VIII] PARADOX VIII. That Water may be made to depress a Body lighter than it self, as well as to buoy it up.

The truth of this Paradox will be easily made out by the following Experiments, for if a Glass Syphon, of the Figure represented by Fig. 7. Plate the third, be filled from H to I with Oyl of Turpentine, and immersed in the Glass A B C D, till the Orifice A of the shorter Leg be under Water, if then the Orifice E be unstopped, and the whole Tube E I F G H be depressed gradually, the incumbent, Water H K will press the Oyl out of the shorter Leg H G, into the longer E F. And,

For a further confirmation of this Paradox, as well as the foregoing, and the second, I shall subjoin; that having provided a Pipe of the Figure represented by Fig. 8. and sucked so much Oyl into it as filled the space L M N P, I immersed it in Water, and upon the opening the Orifice O, as the Pipe was gradually depressed, the Oyl was pressed out of the Pipe L M to N, and from thence to what height I pleased in the Pipe O P N.

PARADOX IX. [paradox IX] That whatever is said of Positive Levity, a par∣cel of Oyl lighter than Water may be kept in Wa∣ter, without ascending in it.

Considering that since the Surface of a Vessel of standing Water is (Physically speaking) Ho∣rizontal, the Water that presses against the lower part of the immersed Body must needs be deeper, than that which presses against the upper, and that this is the Reason why Bodies lighter than Water emerge, I concluded, that if the Water upon the upper Surface of Oyl in a Tube could be so high as to ballance the Pressure of that Water below, Oyl might be suspended betwixt two Parcels of Water. To try the Result, I sucked an Inch of Water into a Tube, and by stopping the upper Orifice, and by that means suspending the Water in the Tube, I removed it into a Vessel of Oyl, and then opening the upper Orifice till an Inch of Oyl was buoyed up into it, I removed it again in∣to a Vessel of Water, and immersed it so far in that, till the Water below the Oyl was equal in height to the Water above it, in which station the Cylinder of Oyl and Water being equal in weight with the Pressure of the exter∣nal Water, the Oyl Q. R. was suspended be∣twixt the Water S. R. and that below it P. Q. the Surface of the Water in the Pipe T. S. be∣ing so much above the Surface of the Water A D. as was requisite to make the Oyl and Wa∣ter contained in the Pipe to press equally on

the Surface G. H. with the external Water, as Plate 4. Fig. 1. represents.

PARADOX X. That the Cause of the Ascension of Water in Sy∣phony, [paradox X] and of flowing through them, may be explained without having recourse to Nature's Abhorrency of a Vacuum.

To demonstrate this, we provided a Glass Tube A B. C▪ D. of a convenient wideness, and half a yard or more in depth, as also a Sy∣phon with two Legs F K, and K G, to which is joined a Pipe E K, and to each of the Legs of that Syphon we tyed a Glass Pipe, seal∣ed at the bottom, and having Water contain∣ed in each, to the height there delineated. Things being thus prepared, Oyl of Turpen∣tine must be poured into the Tube A B. C D, (but that it may not take up too much of the Oyl, the bottom of the Vessel to X Y, may be filled with Water) till it reaches above the top of the Syphon F K G, and then by the weight of it the Water in the Pipe will be raised through the Syphon, and run into the lower Vessel H. In which Experiment the Water is raised through a Syphon by pressure, tho' at the same time there be a free communication of Air through the Pipe E K, without danger of a Vacuum. In which Experiment, if the Rea∣son be asked, why the Water does not rather run out of the Bipe H, into G, than the con∣trary? It may be answered, That tho' exter∣nally the Oyl is deeper upon the surface of the

Water in the Pipe H, and consequently pres∣ses more upon it, yet the Tube G, on the other side, instead of having that pressure of Oyl, hath a Cylinder of Water of an equal length, which being heavier than Oyl, raises the Water out of that Tube more forcibly than it is raised out of the other. And for the like Reason, when once the Water is raised in Syphons, tho' there be a longer Cylinder of Air upon that end which is immersed in the lower Vessel, yet there is a greater weight on the other, because besides the incumbent Atmosphere, there is a considerable Weight of Water: But if the Syphon be a∣bove 34 or 35 Foot high the Water will not flow through it, the pressure of the external Air being unable to raise Water to such a height. And one thing observable in these Ex∣periments is, That if when the Water is run∣ning through these Syphons, a small hole be made upon the top of a Syphon, the Air pres∣sing upon the Water within the Pipe as well as without it, it will cease to run, tho' the hole be no bigger than one made with a Needle; which hole if it be stopped with a Needle, the pres∣sure of the external Air will by that means be taken off, and the Syphon be rendred fit for use.

PARADOX XI. [paradox XI] That a Solid Body, as ponderous as any yet known, tho' near the top of the Water, it will sink by its own weight; yet if it be placed at a greater depth, than that of twenty times its own thick∣ness, it will not sink, if its descent be not as∣sisted by the weight of the incumbent Water.

To demonstrate what is contained in this Paradox, we must fill the Glass A B C D, (see Plate the 4. Fig. the third,) almost full of Water, the length of it being near three Foot; in which Water, if we suppose the Weight E F to be placed upon the surface G H, it will sink by reason of its specifick Gravity, the Water incumbent on other parts of that Plain being not equiponderant, but if we suppose it to be placed upon the Surface I K, the Pillars of Wa∣ter being above nine times as thick as it, they will counterballance it, for which Reason were there no Water upon it, it would subside no further; and were a method contrived to keep the Water from pressing upon it, the like would happen supposing it to lean upon the Surface L M.

And to shew, that were the weight so de∣pressed free from incumbent Water, it would not subside, I shall add the following Experi∣ment; let then the Brass Body E F, (see Plate 4. Fig. 4.) be the cover of a Brass valve, the valve being fastned with Cement to the Glass Pipe O P, the Body E F, must by pulling a hair fired to the button of Valve Q close the Orifice

of it, and then it being convey'd under Water a foot deep, the Cement and sides of the Glass O P, will keep the Water off the upper part of the Body E F, and consequently the imagi∣nary Surface V W will only be pressed upon by the sole weight of the Body E F, but the other Parts of that Surface by the incumbent Cylinders of Water, so that the Body E F will be bore up without the assistance of any thing else but the Water buoying up against it, but if the Tube be raised till the Body E F be above the Surface I K, and near X Y, the weight of it being greater than the weight of the incumbent Pillars of Water, the Body will be no longer supported; but if upon the first immersion, when the Body E F is let down to the Surface R S, a weight L be suspended at it, that will not be able to sever the Body from the Valve; from whence it appears, that there is no need in our Physico-mechanical Ex∣periments to fly to a Fuga Vacui to explain the Reason why two exactly polished Marbles when contiguous are so hard to be separated. To what hath been said under this Paradox, I shall add, that when the weight L is suspended at the button Q, the Body E F will be se∣parated before it rises to the Surface I K.

APPENDIX I. Objections to evince that the upper Parts of Wa∣ter press not upon the lower, answered.

The first Objection is, that if the upper Parts of the Water pressed upon the lower, the low∣er

would be condensed; but to this it is an∣swered, that Water consisting of Parts tho' minute, yet very solid, it does not therefore follow, since in a heap of the powder of Dia∣monds, the lower are no more compressed than the superficial ones,; besides it hath not been found that Water was capable of being compressed by any force we could use. And tho' it be further urged, that Plants grow in the Sea without being depressed, yet that hap∣pens, because the Pressure is not only incum∣bent but Collateral likewise, and so contributes to sustain it, and the rather because the Colla∣teral Pressure is greater than the incumbent.

Another Objection is, that a Bucket of Wa∣ter weighs no more when full in Water than the Bucket it self out of it, nor so much. But the Reason of this is very plain, for sup∣posing A B C D to be a Well, (See Plate the fourth, Figure the fifth) in which the Bucket which is contiguous to the Plain I K, is suspen∣ded by the string E F, the Water in the Buck∣et G (if it be made of Wood which is lighter in Specie than Water) and the incumbent Pil∣lar of Water not pressing upon the Surface H equally as the Water on the Surface I K, the Water below must buoy it up. And tho' the Bucket was made of something heavier than Water, yet the whole weight of it will not be perceived by the hand above, but only the Sur∣plusage of weight which surmounts the weight of an equal bulk of Water. And tho' the School-men tell us, that this Phaenomenon de∣pends on the indisposition of Water to weigh in its own place, yet I have found, that Lead

being convey'd into melted Butter contained in a wooden Box, and that being suspended in Water by a Silken-thred at the end of a ballance, we observed that this was as much indisposed to weigh as Water in Water, no more weight than what surmounted the weight of an equal bulk of Water, being made sensible by the ballance: But when it was partly raised out of the Water or wholly, a greater weight was requisite to counterballance it; for sup∣posing, that part of the Bucket N to be a∣bove the Surface of the Water L M, a great force is requisite to sustain it, the weight of Water incumbent on the Surface P Q being not able to ballance it, and consequently the bottom of the Bucket H, will scarce be pressed upwards half so strongly as before. But if the Bucket be raised to O, the Water being not at all contiguous to it, cannot contribute to the supporting of it.

All that is further contained in this Appen∣dix, being only a Repetition of what hath been already delivered on this subject, I shall pass it by as needless to be repeated again.

APPENDIX II. Why Divers, and others who descend to the bottom of the Sea, are not oppressed by the weight of the incumbent Water.

From what hath been already delivered it ap∣pearing, that Water weighs in Water, and consequently presses upon Bodies contained in

it, I shall therefore, before I propose my own opinion, briefly take notice of the follow∣ing.

And first Monsieur Des Caries tells us, that if the Body of a Man were placed in the bot∣tom of the Vessel B, so as to stop the Orifice A, he would feell the weight of the Water C B A incumbent on him, but if he were placed at B, he would not be sensible of that weight, because should his Body descend, the Water betwixt B and C would not descend with him, but supposing the Orifice A to be stopped with a solid, that would feel the weight of the Water, because it hindred the descent of the Water betwixt B and A, but since the Principles already laid down over∣throw the foundation of this Explication, I shall only add, that were the matter of fact true, the Reason would be, that when his Body was at A, the Man would sustain the weight of the incumbent Water, without any subjacent Wa∣ter at A, to buoy up against him, whereas at B, the subjacent Water buoys up as much as the other presses down or more.

But Stevinus, Hydrostat. Lib. 5. Pag. 149. says, Omni Pressu quo corpus dolore afficitur, pars aliqua corporis luxatur, sed isto Pressu nulla cor∣poris pars luxatur, isto igitur Pressu corpus dolore nullo afficitur. Sed Exemplo clarius ita intelli∣ges, esto A B C D, aqua cujus fundum D C in quo foramen E habeat Epistomium sibi insertum, cui dorso incumbat homo F, quae cum ita sint, ab aquae pondere ipsi insidente nulla pars corporis luxari poterit, cum aqua undiquaque aequaliter urgeat.

Which solution might hold, if the question was only why the Body of a Diver is not pressed down to the bottom of the Sea. But as for what he says, viz. That the equality and uni∣formness of the Pressure makes it less sensible I am of his opinion, for tho' in the Air the Pres∣sure of it is not perceivable for a like Reason, yet if ones hand be applyed to the top of a Re∣ceiver, and the Air exhausted, the Pressure of the incumbent Atmosphere will cause a sensi∣ble Pain.

And to shew that the uniformity of the Pres∣sure, and the firmness of the Bodies of Divers, may enable them to bear the Pressure of the Water, I shall add, that having included a Tad-pole in an Instrument, such as Fig. 8. Plate the fourth describes, the Plug was so far de∣pressed, that the Air in the end of the Pipe was compressed into an eighth part of the space it possessed before, so that the Pressure upon the Water was equal to the weight of a Cylinder of Water three hundred foot high, yet the Tad-pole moved up and down as nimbly as be∣fore, being not at all indisposed, tho' its Body appeared to be compressed into less room than before.

CHAP. VII. An Hydrostatical discourse &c.

ALL that is contained in this discourse, being chiefly a Repetition of what hath been before delivered in other Parts of the Author's Works, and now only repeated to obviate some Objecti∣ons of Dr. More's, and the truth's laid down by our Author in his Hydrostatical Paradoxes, and Physico-mechanical Experiments being so plain, and these Objections so trivial, it would but be needless to encrease the bulk of the Book, with what may with more Reason be avoided.

CHAP. VIII. A new Essay Instrument, and the Hydro∣statical Principle it's founded on, &c. Communicated in the Transactions of June 1675.

The first Section. Shewing the occasion of making this Instrument, and the Hydrostatical Principle it's founded upon.

HAving several years ago made of a Bub∣ble with a long Stem, to estimate the specifick Gravity of Metals, by its easie or more difficult immersion with them, I applyed it like∣wise

to estimate the weight of other Solids, by observing how Solids suspended at this Bubble would depress it variously according to their specifick Gravities; It being a general Rule in Hydrostaticks, that any solid Body in Water loses so much of its weight, as a parcel of Water of the same Dimensions would weigh in the Air, so that Gold being specifically heavi∣er than Copper, it must lose less of its weight in the Water than Copper; because proporti∣onably the Ignobler Metal possesses the space of a greater quantity of Water, whose weight, by weighing it in that fluid, is lost in the weight of the Body suspended at the Bubble. And consequently an ounce of Gold must cause that Bubble to be immersed deeper in Water, than an ounce of Brass or Copper would, the Brass by Reason of its larger Dimensions losing more of its weight than the Gold.

The second Section. Describing the Construction of this Instrument.

This Instrument may be made of any Metal or other matter, which will float in the Water, without soaking it in, but the best for the uses hereafter mentioned are those made of Glass; tho' they are not so lasting as those that consist of Copper or Silver.

This Instrument is made of three Parts, a Ball, the Stem, and that which holds the Pipe, The Ball consists of two Metalline Plates, each of the fashion of a Convex Glass; and the Cavity within must be so large, that the Air contained

in it, may be sufficient to hold as much Air as will keep the whole Stem from sinking under Water; if the Ballast which is to keep the Ves∣sel immersed in an erect posture is to be con∣tain'd within the Vessel, the Stem ought to be hollow, but otherwise to consist of a small Cy∣linder without any Cavity, and of a convenient length.

The Instrument I employ for Guineas hath its Ball as big as a Hens-egg, and the Stem a∣bout four or five Inches long, being soddered on to a hole in the Centre of the uppermost Convex part of the Ball; and to the Centre of the lowermost is fixed a piece of Wire to lay the Guiny upon, or a screwed stirrup to fix it in.

If you have a mind to try pieces of Gold of greater weight, the stirrup ought to be fixed to a small Cylinder, upon which several pieces of Metal being fixed, and having holes in the middle, that they may be put on or taken off as occasion requires, the Instrument may be ad∣justed to any piece of Gold, tho' twice or thrice as heavy as a Guiny.

To adjust this Instrument for the use of Guineas, it must be lightned by the use of a file, or made heavier by the addition of Ballast, that it may be sufficiently immersed in the Wa∣ter without sinking, and then a mark being fixed on the Stem at the Surface of the Water, a piece of Brass must be substituted in the place of the Guiny of the same weight, or a grain or two heavier in the Air, and a mark set at the Surface of the Water, when it is immersed by that weight.

In which method of adjusting, the following Particulars are to be minded.

• First, the Guinea must be placed exactly with its middle in the screw, that it may not incline the Tube, but let it stand erect.
• Secondly, Quick-silver Ballast in Metalline Instruments is apt to dissolve the sodder.
• Thirdly, the marks may be made of chewed Mastick fixed in small holes; or by fixing a Silver or a Golden Wire in a nick made round the Stem.
• Fourthly, one of the heavyest Guineas is to be made use of in adjusting this Instrument, and care must be taken that ½ of an Inch be left above the Water, because all Waters them∣selves are not of an equal weight, yet those circumstances vary not the success, since the difference in the immerging this Instrument in several Waters, is in considerable in respect of the difference betwixt a piece of Brass and Gold of an equal weight in the Air, it being an Inch and three quarters.
• Fifthly, before we can determine by this In∣strument whether the Gold be good, it must be weighed in the Air, to see whether it be of a just weight, and then this will discover whether it be genuine, for otherwise we may think the Metal not good, when it only wants weight in the Air.

The Explication of the Figures

Fig. 1.

• A B. The Stem or Pipe.
• C E. The two Parts of the Ball sodde∣red together.

• B C D E. The Ball it self.
• F. The screw.
• G. The stirrup somewhat out of its Place.
• H. The mark to which Copper of the weight of a Guinea in the Air depres∣ses it.
• I. The mark to which the Gold sinks it.

Fig. 2. The screw by it self to be taken off or put on the undermost Stem of the Instrument.

Fig. 3. The Perforated Plates to be put upon the lower Stem as ballast.

Fig. 4. The lower Stem with a Perforated Plate upon it.

Fig. 5. The stirrup which my be made use of instead of the screw.

Fig. 6.

• A. B. C. The Glass Instrument.
• D D D. The Coin supported by four Horse-hairs.

Fig. 7. The undermost Stem of a Glass Instru∣ment, to which a screw is fastned with Horse-hairs or otherwise.

Fig. 8.

• A B C D. The Instrument for esti∣mating the specifick Gravity of Li∣quors.
• E E The Quick-silver or Water em∣ployed as Ballast.

The third Section. Representing the uses of this Instrument, as re∣lating to Metals.

The first Ʋse.

Is to distinguish true Guineas from Counter∣feit.

The second Ʋse.

In examining a piece of Gold lighter than a Guinea; so much Ballast may be added as will make that amount to the weight of a Guinea, and if the Gold be heavier, so many of the perforated Plates must be taken off the Stem, that the Instrument may not be sunk by it, and when a Coin but a little heavier than a Guinea is to be tryed, it may be convenient to place a perforated Plate upon the upper screw, so that it may lye upon the Ball, and be taken off, or lightned with a file as occasion re∣quires.

That several pieces of Gold may upon some occasions be fix'd at once, the aperture of the screw ought to be wider, than what will just admit of a Guinea.

If the Instrument be well proportioned, so that a piece of Gold a little heavier than a Guinea, may not depress it under Water; it may be examined without altering the weight of the Instrument.

And acording to the method above laid down, a half Guinea may be tryed by placing a true half Guinea with it in the screw.

The third Ʋse.

This Instrument may be adjusted to try Sil∣ver Coins which are lighter than half a Crown, by weighing Silver in it, and marking the Sur∣face of the Water upon the Pipe, and then observing what difference there is betwixt that, and an equal weight of an ignobler Me∣tal in the Air. And tho' several Instruments would be more convenient for the trying of these different Metals, yet by altering the Ballast Plates, one may be made to serve the turn.

The fourth Ʋse.

And by the like method an Instrument may be adjusted, to discover whether Tin be more or less adulterated with Lead, since Tin being the lightest of Metals, the Lead will depress the Instrument lower if mixed with Tin, as Gold on the contrary is the heaviest Metal, and is lighter upon the addition of another Metal.

The fifth Ʋse.

It may enable us to guess at the Qualities of Metalline Mixtures, and the proportions of the ingredients, for by adjusting how much such a weight of Gold will depress the Stem, by af∣terwards trying how much lighter in Water

the same weight of allayed Gold in the Air will be, and at the same time observing what was the proportion of Silver in the Alloy, we may be enabled to judge how much other pieces of Gold are alloyed by comparing their weight in Water with this Standard, provided they be of the same specifick weight in the Air, with the Gold unalloyed. And the same mea∣sures may be taken to make an estimate of the alloys of Silver with Copper, or of Copper with Tin.

CHAP. IX. Observations of the growth and increase of Metals.

I am told by the Master of a Tin Mine, that after a Tin Mine had been quite drained of its Ore, by washing and vanning about 120 years after, it yielded rich Ore again, and that a good quantity of stuff being quire drained of its Ore, and laid on a heap in the Air, in thirty years it afforded Metal again. And the same Gentleman told me, that having caused the Water which washes the Earth away from the Ore, to lay down that Earth, by stopping the current of it, till its own weight made it sub∣side, that Earth being twelve years exposed to the Air, yielded a good quantity of Metal. And Relations agreeable to these I have received from another.

It hath been observed, that Lead Ore clear∣ed of its Metal, and laid in heaps for some years yields Metal a second time. And J. Gerhard in Decade questionum p. m. 22. says, Fessula∣rum mons in Hetruria Florentiae civitati imminens, lapides Plumbarios habet, qui si excidantur brevi temporis spatio novis incrementis instaurantur. And Agricola, speaking of the growth of Mines in general, testifies the same; but I am told, that this happens not in all Mines. And tho' it be believed that the Reason why the passa∣ges into some Mines grow narrower, is to be attributed to the growth of the Metal, yet I am apt to believe, that it may be caused by the powerful expansion of some frozen Water in the Earth, that encompasses those passages; and whereas it is urged as an Argument of the growth of Metals, that Lead increases its weight by being exposed to the Air on the tops of Churches, yet I am inclined to believe, that it rather proceeds from a Cerusse formed by corro∣sive Parts, uniting with the Parts of the corro∣ded Metal, and chiefly for this Reason, viz. Because I have observed, that the Wood which lyes about that Lead abounds with an Acid Spi∣rit, capable of corroding Lead, and that when they have been long exposed to this Acid, a white Lead may be scraped off better than the common Cerusse, and this is found on that side the Lead which is next the Wood, and not on that exposed to the outward Air. And I have observed, that even Alablaster and white Mar∣ble will yield an Acid Spirit, so that we que∣stion whether Lead fixed to the feet of Statues,

may not by the help of that acquire a greater bulk, and increase of weight.

We are told, not only by Pliny and Srabo, but Fallopius and Caessalpinus, that in the Island of Elva not far from the coast of Tuscany, Iron hath been observed to grow; and Agricola at∣tests the like to be observed in Germany. And Johan. Gerherd. tells us, that he was informed, that not far from Amberga, the Ore exposed to the Air for some time in heaps requires Metal∣line Parts.

I have been told, that Silver grows in the form of Vegetables, and in a Voyage to Pern I find the following relation, viz. That in the Mines of Potosi it is observed, that Earth that was dug out of the Grooves and Shafts, and thrown aside, hath such a propensity to the Production of Metals, that after some years it would yield Metal.

Tho' there is no Gold to be found on the coast of Guyny in Congo, and other Parts of Africk, where Writers mention it to be found, yet I am told, that in Hungary, the Master of that famous Gold Mine of Cremnitz hath observed, that the whole Mountain abounds with Particles of Gold, and that when they have cleared a great deal of the Soil in one Place of its Metalline Parts, they throw it into the hole again, and observe, that in a little time it will yield Gold as before; and Johan. Gerherd. gives us an In∣stance of the growth of Gold in Germany.

Postscript

Dr. Brown tells us, that he observed the pas∣sages in several Mines grown up, especially in moist places, and that the yellow Soil near Cremnitz yields some Gold.

Whether the increase of Metals depends on the influence of the Air, or some other cause, till further and more strict Observations have been made, I shall not undertake to determine; but shall only add, that a Marchasite having been shut up in Vacuo, it acquired a Vitriolate Efforescence betwixt blue and green.

CHAP. X. A Hydrostatical way of estimating Ores.

TO help me to make an estimate of the pro∣portion of Metalline or the Mineral in∣gredients of Bodies, I weighed a piece of Rock-Crystal or white Marble, first in Air and then in Water, by which I found that its weight, to an equal bulk of Water, was as 2 ¾ to 1, or as 11 to 4, and then by weighing Metalline Bo∣dies, such as Magnets and Emeri, I found that the weight of these in Water was more than that of Crystal, the proportion of the latter being as four to one; by which Tryals I was enabled to guess that these stones contain Me∣talline Parts in them: And by the same method I discovered Metalline Ingredients in some Bo∣dies

which are not generally looked upon as such, as Lapis Hematites, and American Talc.

And as it is generally a certain sign, that a Body contains mineral ingredients proportion∣ably as it is heavier than Crystal, so it is no less certain, that Bodies lighter than Crystal are not impregnated with a Metalline Ore, as Jet, Succinum, Sulphur Vive, common Sulphur, English Talc, Venetian Talc, and black Lead, whose weight to Water is but as 1 1••/100 to 1, and which by certain Tryals I have found to be a kind of Talc.

As for the advantages that may be reaped by estimating Ores, they may either respect Jewellers, Physicians, or Chymists, as when the Metalline Ingrediens are but small; or Mineralists, whose business it is to extract the Metal, when by this Hydrostatical way it appears to be suffi∣ciently impregnated. But, because there are some cruder Metalline Ingredients in some Bo∣dies, as Antimony, Bismuth, Lapis, Cala∣minaris and Pyrites, which may deceive an un∣skilful Mineralist who estimates them this way, it may be convenient to make use of other Tryals to distinguish them. And since some mineral Ores, when tryed in the lump, appear to be poorly stocked with Metalline Parts, it may be of use to beat them to powder, and to separate the Metalline Parts, by washing, or else by fire; for by that means I once found, that a Metalline Ore which was wrought for Lead, afforded a sufficient quantity of Silver to answer the charge of working it, and to this caution I must add the following, viz. That since Marcasites are generally heavier

than common Crystal, and by some looked up∣on to be plentifully stocked with Metalline Parts, because of their weight, and the glittering of their Parts, yet they may easily be undeciv∣ed, by placing them in a hot fire, for by that means the Sulphureous Parts will be consumed, and leave behind them a black Calx; but tho' Marcasites abound not with Metalline Parts, proportionable to their bulk, yet I have found by experience, that some of them have afforded not only Copper, Silver, and Gold, but some∣times a quantity of running Mercury; but whe∣ther Marcasites may be of use in graduating Gold, or not, I shall leave to others to be consi∣dered. There is this Advertisement which I must not omit, and it is that tho' some are used to employ flux powders indiffently with∣out understanding the difference of them, I have tryed, that Lead Ore being fluxed with filings of Mars, afforded a larger quantity of Metal, than with a due proportion of Nitre and Tartar fulminated together; but one part of good native Cinnabar, finely powdered, be∣ing mixed with a fix't Alkaly of Tartar, and the other with a different flux powder, we obtain∣ed twice as much Mercury from the former, as we did from the latter, tho' it was likewise a fixt Alkaly of a mineral Nature.

Some Observations about native Gold.

Tho' I once believed, that there was no such thing as a Gold Mine, in which that Metal was predominant, yet I had a Portion of Ore sent me from the East-Indies with the spar about it, which

had I broke it, I question not but that it con∣tained Parts which were malleable without the help of the fire: one piece of this had so much Spar about it, that it weighed to an equal bulk of Water, as 2 91/100 to 1. The colour of the Spar was like white Marble tinged with a dash of yellow, and it differed from Lead Ore, in as much as that is usually so soft as to be easily cut with a knife, but this was as hard as a stone, and would yield sparks when struck with a piece of Steel; and it differed further from Spar of Lead Ore, in as much as it was altogether in∣capable of being calcined, tho' kept in a Crucible red hot for some hours. Nor would it be dissolved in Acid Menstruums, as Spar of Lead Ore may. A piece of Spar in which but little Gold was contained, being weigh'd in Water, was to its proportion as 2 65/100 to 1, which is but little above the weight of common Mar∣ble.

But tho' there is such a thing as true Gold Ore, yet I would not discourage Mineralists from seeking it in Veins of other Minerals, since it hath been found not only in Copper Mines, but veins of Tin and Lead; for in a place in Scotland several grains of native Gold have been found, near the Surface of the ground over Lead Mines, some pieces of which being weighed Hydrostatically, one piece of Scotch Gold, which was native and free from adhering Spar, weighed three drachms twenty one grains, and another which had Spar sticking to it, weighed three drachms three grains, and a third of Scotch Gold weighed in Air forty

three grains, in Water thirty nine. Difference 3 × 1/••. Proport. 12 × ••/•• to one. But to distin∣guish pure Gold from impure, we are to note, that the Proportion of the finest, according to Mersennus, is as eighteen to one of Water, but according to ours, as nineteen to one. So that as it comes more or less short of that Standard we are to estimate its Purity.

And thus by weighing Gold Hydrostatically, we may be able to distinguish, that Sand-Gold which is brought from Africa, or that from Guinea, from adulterated; for having once weighed a small Parcel of good, the Weight of that will be a Standard to distinguish the bad by.

But since a great many ignorant Sea-men are concern'd in buying Gold, who understand not how to examine it Hydrostatically, I shall sub∣joyn the following method to distinguish it Chy∣mically, viz. By mixing a few Grains with Aq. fortis, Spirit of fermented Urine, or Spirit of Harts-horn; for if it be adulterated with Cop∣per or Brass, a few Grains laid upon Paper, and moistned with this, will be tinged bluish green. And even rank Urine will be able to extract a blue Tincture from Brass, if made use of in∣stead of the afore-mention'd Spirits; and the like success will happen with Sal-Armoniack dis∣solv'd in Water.

There are in England such a great varie∣ty of Stones, that it would be worth while to examine them Hydrostatically, and to compare them with Crystal; for I have found near the high Road an Eagle-Stone, which was not su∣spected to be of English growth. And I found a kind of Magnesia near a Potter's Work-house,

which he afterwards made use of to glaze his Pots. And I was brought to a Mineral Substance, which tho' it was hard to be known of what Kind it was, yet I soon discover'd it to abound with Vitriol, and that it would yield it much more plentifully than the Vitriol-Stones found near the Isle of Wight, or those made use of at the Vitriol-Works near Deptford, and elsewhere. And Ore of Bismuth hath been discover'd by a heedful Eye, when common Miners knew not what kind of Substance it was when they dug it up.

But this Hydrostatical way of estimating Ores may not only be made of use in judging of Mi∣neral Substances, but those Earths which are the Wombs of them; since, tho' they cannot be suspended by a Hair, as solid Grains of Ore, yet a Jar may be counterpoised in Water, and then being filled with such Earths, the weight of them may be discover'd, by first counterpoi∣sing them in the Air, and then having first wetted them with Water, and convey'd them into the Water in that Hydrostatical Bucket: And that this Hydrostatical way of weighing Earths may be of use appears, since it hath not on∣ly been observ'd, that a red Mud, which lay at the bottom of Water, abounded with Iron plentifully, but I have observ'd the same in an English Oker. And I have been told, that Di∣amonds, as well as Gold, have been found in a red kind of Soyl. And I have observ'd in En∣gland, curiously figur'd Crystals lodged in a Soyl of a red Colour.

And it may not only be of use to weigh di∣vers sorts of Earths in our Bucket, but also se∣veral sorts of Sands; since by a Microscope, I have discern'd several Grains to appear, as if they were made of an Aggregate of Granates; and I have experienc'd, not only Hydrostati∣cally, that that black Sand which is made use of in London, contains good store of Particles of a Martial Nature; but I have likewise been convinc'd by fluxing it, and by casting it, whilst it was melted, into the Conical Part of a Cru∣cible. And I further observ'd, that ⅞ of it would be attracted by a powerful Load-Stone.

But a Mineral of a martial Nature hath not only been observ'd in Sand, but Gold on the Banks of Guiny, and on the Banks of Tagus which runs by Lisbon and Pactolus; and some hath been found on the Banks of the Rhine, and a little River which runs down from the Moun∣tains in Savoy. But much more Gold may be got from Sand Chymically, than by picking it up, if the Sand be reduced to Glass with Li∣tharge or Minium, and then the volatil Gold be obtain'd by giving it a Body fit to retain and fix it; such as Silver, out of which I have got by Quartation, out of as much vitrify'd Sand as filled a Retort, and two or three fluxing Addi∣taments of small price, sixteen grains of pure Gold. And tho' by some it is thought strange, that there should be a necessity of fixing Gold, yet I have elsewhere made it appear, that by a small addition of another Substance, Gold may be sublimed without a naked Fire, and form se∣veral Crystals like Rubies.

And if Sands, as well as Earths and Stones, abound with Mineral Ingredients, it may be convenient to take an account where such Sub∣stances are found, and likewise to take a Sample of them, as also of the Ores of different Mines, and to try them Hydrostatically; for I have ob∣serv'd, that in English Lead Ores of several kinds, those in which thirty pound of Lead is only to be got out of an hundred of Ore, are looked upon as not worth working; those that yield half their weight of Metal are indifferent; and other Ore which yields from fifty five to sixty in the hundred is looked upon to be very good; but those that afford eighty Pound in the hun∣dred, are accounted very rich; but I have not met with any that afforded more than seventy five in a hundred weight: Which Ore seemed to consist wholly of Metal, and was made up of Parts of a Cubical Figure, and much resembling Dies placed one by another.

But besides what hath been already proposed, to be inquired after concerning Metalline Fos∣sils, not only its Proportion is to be consider'd, but the plenty or scarceness of the Mineral, the easiness or difficulty of coming at it, as also its depth and freeness from Waters, its nearness to plenty of Fuel, its nearness to Water to drive Mills, and to transport it, &c. are to be consider'd likewise before one begins to work a Mine.

An Explication of the Instruments employed in these Experiments, and those in the following Chapter.

(aa) The Beam, (bb) the Dishes, (cc) the Frame to suspend the Beam, upon which (d) a sliding Socket, (e) its Arms containing (f) a Pulley, over which (g) another Pulley passes, (h) a Line fastned to (i) a moveable Weight, by which the Beam is raised up or let down, (k) a Hair to suspend (l) the Body to be weighed in the Water, held in (m) the Glass Cistern, (n) the Bucket for Liquors, (o) the Box of grains, (p) the Forceps to manage them, (q) the Pile of Weights, (r) the Handle of the Ballance, (ssss) the Table.

CHAP. XI. Medicina Hydrostatica.

FROM what is contain'd in the fore-going Chapter, it appearing that white Marble or Crystal may be a Standard to distinguish mineral Substances from other Bodies, I shall here subjoin the way of weighing sinking Bodies in Water.

And first, the solid Body to be examin'd, is to be suspended by a Horse-hair, at one of the Scales just now described, and there to be coun∣terpoised; then the Weights being taken out, by deducing from the weight of the Body in Air the weight of it in Water, by the Remainder

divide the whole weight of the given Body in the Air, and the Quotient will shew the Propor∣tion in specifick Gravity, betwixt the examin'd Solid, and as much Water as is just equal to it in Bulk. For Example, if the Weight of a Cu∣bick Inch of Rock-Crystal be 1169 grains in the Air, and 738 in Water, the Remainder will be 431 grains; by which the 1169 grains being divided, the Quotient will be found to be 2 × 71/100 or near enough 7/10, for the proportion of the Gravity of white Marbles to Water.

In which Direction it is requisite to observe, first, That what we have said implys, that the Body weighed must be heavier than Water. Se∣condly, Horse-Hairs are more convenient than other strings, because they are nearer to a speci∣fick Gravity with Water. Thirdly, Where the Figure of a Body disabled us from suspending it by tying a hair about it, we platted a sort of net of Hairs to hold it in. Fourthly, So much of the Hair as is above the Water must be coun∣terpoised by a Weight in the other Scale. Fifth∣ly, Sometimes instead of the Scale I counter∣poised the opposite with a weight of Lead, and suspended the Horse-Hair at the String; but when I did not take off the Scale, I caused it to be perforated in the middle. Sixthly, Care must be taken that the Water below touches not the bottom of the Scale, and that the Body be freely suspended, and wholly immersed in the Water. Seventhly, Care must be taken, that no Bubbles of Air be contained in the Pores of the Body weighed, since the success will be apt to fail in some Tryals upon that account.

And these circumstances being observed, it will be easie to know, by the method proposed, the difference betwixt the specifick weight of other Bodies heavier than Water. It being agreeable to that Hydrostatical Paradox of Archimedes, That a Body, heavier than Water, weighs less in Water than in the Air, by the weight of as much Water as is equal to it in Bulk or Mag∣nitude. And,

By this Method we found, That the weight of Lapis Hematites to Water, was as four 15/100 to one, and by subliming it with Sal-Armoniack, we found by the Astringency of it, that it a∣bounded with Metalline Parts of a Martial Na∣ture; which was further confirmed, by obser∣ving that a grain of it turned an Infusion of Galls black Lapis Lazuli was to its bulk of Water in weight, as three to one. A Load-Stone, which besides Magnetical, hath Medicinal Vertues, ap∣peared to be as four 93/100 to one. Lapis Calami∣naris was as four 169/100 to one. In which Concretes, the Medicinal Virtues seem to depend on the plentiful mixture of metalline Ingredients; but some Bodies which abound less with Mineral Substances, may be as operative, by reason of some more active Particles. But,

This Hydrostatical method of weighing Bo∣dies, [Use II] may be further serviceable in distinguish∣ing Stones from Plants, or other petrified Sub∣stances, as Coral, which weighs in proportion to Water, as two 68/100 to one, and therefore ap∣pears to be a Stone, being heavier than Cry∣stal. A monstrous Pearl taken out of an Oyster, which weighed 206 grains, was to Water as two 51/100 to one. A Calculus Humanus, which

weighed six drams and a half, was in proportion to Water as one 76/100 to one; and another that weighed four drachms and a half, was to Water as one 69/100 to one. These Stones, tho' the pro∣ductions of Distempers, have been accounted better than Oriental Bezoar in their Effects. Choice Bezoar Stones, which weighed three drachms in the Air, being weighed in Water, one of them was as one 47/100 to one; another somewhat lighter, was as one 53/100 to one; a third, which was taken out of another Stone, which being weighed in the Air weighed six drachms wanting nine grains, was in proporti∣on to Water as one 55/100 to one: So that these have a much less specifick Gravity than Fossil Stones.

A third use of this Hydrostatical way of weighing Bodies, [Use III] may be to distinguish several Species of Bodies into subordinate Species, as the Load-stones of several Countries are diffe∣rent in weight; for I have observed Norwegian and the English Load-stones, to be heavier in spe∣cie, than those that came out of Italy, in which the Island of Elba abounds with Mines, whereof one intire Mass weighed a great many hundreds of Pounds.

Fourthly, [Use IV] This method may enable us to di∣stinguish counterfeit Stones, from those that are real and good, since when they are Hydrostati∣cally weighed, there will appear a manifest dif∣ference, not only in adulterated Coral, but Be∣zoar, and other valuable Stones.

Fifthly, [Use V] By this means we may be enabled to distinguish betwixt genuine Concretes used in Medicine, and those that are not genuine; as

also whether precious Stones abound more or less with Metalline Ingredients. But tho' some∣times Stones that are transparent may not be so plentifully impregnated with Medicinal and Mineral Effluvia, yet considering the Activity and great subtlety of some Pigments, the latter may be as powerful. And that every sensible part of a Body may be impregnated by a small quantity of Pigment, will appear from the fol∣lowing Experiment, viz. If five grains of Za∣phora be mixed with one ounce and half of Venice Glass finely powdered, and kept in fusion in a furnace with a violent hot fire, it will give the whole a fine blue colour, and if the proportion of the Zaphora be as one to six, the Glass will be too deeply tinged to make a handsome Gem. And to shew further, that a small quantity of Metalline matter may be sufficient to impart a virtue to Glass and even Gems, I shall add, that eight grains of the powder of a German Granate, being kept in fusion with an ounce of Crystalline Glass, it gave it a Tincture like that which Steel gives to pure Glass.

From what hath been said it appears, how the proportion of solid substances to Water may be Hydrostatically-distinguished; but since there are other substances which cannot be so weigh∣ed, being either subject to dissolve in Water, or not fit to be suspended by a Hair, by reason of their form, being either powders or liquids, to make an estimate of these, I contrived the Bucket formerly mentioned, and represented in Fig. 00, Plate the first, which being suspended in Water and counterpoised, we put a known weight of Quick-silver in it, by which means

comparing its weight in Water with its weight in Air, and dividing the greater number by the difference of its weight in Air from what it was in Water, and which was thirty four grains, we found the Quotient to be fourteen and about 1/10, so that the Mercury made use of in this Tryal was as 14 11/100 to 1, but common Mercury which is sold in the Shops we have found to weigh not above thirteen and a half to one, and indeed I have found a notable dis∣parity in the weight of most common Mercuries, especially those drawn from Gold; for the Mer∣cury being combined with that Metal becomes heavier than common Mercury. By the same measure we may know the specifick Gravity of any Liquors which are heavier than Water, and which are unapt to mix with it, such as Oyl of Cinamon, Cloves, Guajacum, &c.

And by the assistance of the same Bucket, we may be able likewise to weigh Powders, and estimate their goodness, if we put a known weight of them in the Air into the Bucket, and pour in gently as much Water as will fill up the Pores contained betwixt them, and be sufficient to expel the Particles of Air contained be∣twixt the small Parts of it; but in all these Tryals it will be requisite to suspend the Scales of the Gibbet delineated in the preceding Figure, that the Scale may hang the steddier, whilst the Body is a weighing.

But since there are several saline Bodies, as Sublimate, Mercurius dulcis, Vitriol, Rock-Al∣lom, &c. which cannot be weighed in Wa∣ter, in such cases, instead of Water, we may substitute Oyl of Turpentine, which tho' it be

of a different specifick Gravity from Water, yet by carefully weighing a parcel of any sub∣stance which is genuine in that Liquor, it may serve for a Standard to estimate the goodness of other parcels of the same substance by, and it will be no very difficult matter for one well skilled in numbers, by comparing the specifick Gravity of Oyl of Turpentine and Water to∣gether, to know what proportion the Body weighed in Oyl, would bear to an equal bulk of common Water.

Another way which may be taken to estimate the specifick Gravities of Liquors is, by mak∣ing use of a Body that will subside in all Liquors but Quicksilver, for thus by first weighing that Body in Air, and then in several Liquors, and having noted the difference betwixt the solid and each of the Liquors, it is not difficult to find the specifick weight of each, and the pro∣portions betwixt them. And since it is but one solid that is compared thus to the differing Li∣quors; whatsoever their Number is, it will not be difficult to compare the specifick Gravities of the Liquors betwixt themselves, and to dis∣cover by the weight of the first, that of any other, which ever one pleases.

But in making choice of such a solid Body, as may serve our present purpose, care must be taken, that it be such as will not be subject to be consumed by Effluvia; or too large for a tender Ballance; nor so big as to require too much Liquor to cover it; and lastly, it ought to be of such a Nature, that it may not be liable to be corroded by sharp and corrosive Liquors, or easily broke, but such as may be easily ob∣tained,

that what Experiments are tryed with it may easily be tryed by others, and communi∣cated to Posterity.

The Bodies made use of in trying these kind of Experiments, and which came nearest what we thought requisite for such Tryals was, when we examined common Water, Rain-Water, Spirit of Wine, Wine, Brandy, Vinegar, and the Liquors drawn from it, Cyder, Beer, Ale, Urine, Waters distilled from Vegetable and A∣nimal substances; Amber: But to estimate the weight of heavier Liquors, we employed a Glass-Bubble, Hermetically sealed and filled with Mercury. But this being both hard to be obtained, and harder to be preserved, I made use of the following Body in such Experiments as are to be recorded for Posterity, viz. A Globe of Rock-Crystal which was suspended by a hair which passed through a small hole in it, and which we employed to discover the diffe∣rence of those Liquors, which we could obtain greater quantities of, but for others we employ∣ed an Hexagonal Prism, with a kind of Pyra∣mid at the end, and this Body being of such a Figure we were able to employ it in small Cy∣linders, in which a small quantity of Liquor would surround it and cover it. The weight of the Ball of Crystal we employed was to its bulk of Water as 2 57/100 to 1, and the weight of the Prism as 2 66/100 to 1.

And this method of weighing Amber in diffe∣rent Liquors, may not only acquaint us with their specifick Gravities, but also from thence we may learn to know which are most Spiritu∣ous.

For tho' a piece of Amber weighed but 6 ¾ grains in Water, yet in common red French Wine it weighed 8 ½, in Nants Brandy 17 ⅛, and in rectifyed Spirit of Wine 34 ⅛.

This Hydrostatical method of estimating, may likewise contribute to discover the strength of Acid Liquors, those that are strongest causing the solid to weigh less, as they are stronger, the greater decrement of weight proceeding from the greater proportion it contains of Salts that are not Volatile. It may likewise save the wasting of several Liquors, as Spirit of Wine or Brandy, in trying their goodness. And further it may be imployed in estimating the intensive weight of Wine, Beer, Ale, Mead, Cyder, &c. and distinguish their goodness, without consuming them.

But Amber will not be heavy enough to di∣stinguish the strength of Oyl of Tartar per deli∣quium, and such heavy Bodies, since they are too heavy for it to subside in.

Besides, the afore-mentioned there may be another use made of our Hydrostatical solid, viz. To shew when Menstruums are of a con∣venient strength. For that there is a peculiar degree of Spirituousness requisite in some Sol∣vents is evident, since if Aqua Fortis be too strong, it will not be able to dissolve Silver, no more than if it be too weak, till it is diluted by an addition of Water; and it is much more fit to dissolve filings of crude Lead, when more dilute: So rectifyed Spirit of Wine is not always the most proper Menstruum for gummy Bodies, since it dissolves only the purest Resin, and leaves the Mucilaginous Parts behind, which

may be as good in Medicine as the other, and fur∣ther we see that Gum Arabick and Tragacanth are not so easily dissolved in good Spirit of Wine as in weak Liquors; and the like may be observed in dissolving Myrrh.

To what hath been said on this occasion, there is one thing to be added, that when this Ex∣pedient is made use of in Oyl of Vitriol or Tar∣tar per deliquium, it is necessary to put some∣thing into the Scale to compensate the light∣ness of the Horse-hairs, since in such Experi∣ments the specifick Gravity of the Liquors ex∣ceed the Gravity of the Hairs, and consequent∣ly they will be apt to buoy up the Body immer∣sed, and misinform us in its true specifick weight.

To the afore-mentioned ways of Hydrostati∣cally estimating Liquors, we may add the follow∣ing. And first, it may be done by filling a Vessel with a slender Stem successively, with different Liquors, and weighing them, as also it may be done by a Brass Cylinder, made heavi∣er at one end than the other, by which it may be made to float, and to swim deeper or higher above the Water, as the Liquor contain∣ed is heavier; or another way is by fitting too Bubbles together with Cement, by which their Stems being joined, and the one caused to sink lowest by a Ballast of Mercury, as the other is filled with a heavier or lighter Liquor, it will manifestly preponderate.

Another way proposed by Mersennus, is by weighing a Glass and a Stopple in Water, and then filling the Bottle quite full, and putting in the Stopple; for the weight of the Glass and

Stopple being deducted from the weight of the whole, the remaining weight will be the weight of the Liquor proposed. But instead of this we made use of a round Glass-Ball with a Glass Stopple, which being first weighed in Air and Water, and counterpoised there, we were a∣ble to discover the weight of the Liquor con∣tained, and its proportion to the bulk of the Liquor it was weighed in; and if the Bubble were too light to subside in some heavy Liquors, we would bring it to a just weight by a Ballast of Mercury. But since such Vessels as these are very hard to be got, and some other incon∣veniencies attend it, we think it less satisfacto∣ry than those other ways we made use of and proposed before.

A sixth Use that may be made of these Hy∣drostatical Tryals, [Use VI] is in reference to several Me∣dicinal Bodies, for thus the Jucies of Plants may be weighed, if when they are contained in our Hydrostatical Jar, delineated in the Figure a∣bove, they be hung at a nice Ballance in Oyl, instead of Water, since they are not subject to mix with it: And by this means we may be satis∣fied whether Juices of Plants alter their specifick Gravity, when kept a good while, and after fer∣mentation. And by this method likewise we may be able to weigh Honey, Vinegar, Ver∣juce, &c. As also we may compare and weigh the Juices of Fruits of different kinds, and the subordinate Species of each kind, as also the se∣veral Juices in their several states of Crudity or Maturity: But the use of this Hydrostatical Bucket being very tedious and difficult, to those that are not very skilful in making Ex∣periments,

the other will be more useful which are tryed with Amber.

But to what hath been already delivered on this subject I shall add, that tho' in several Try∣als made with precious substances, a nice Ballance is requisite, yet in most cases the difference be∣twixt Bodies is great enough to be discerned by a Ballance, not altogether so nice; for let the Ballance be never so nice, there is difference in the Textures and Compositions of Bodies of the same Denomination, for which, as well as in defect of a nice Ballance, allowances are easily made.

But perhaps it may be objected by some, a∣gainst the method I have been proposing, that since I generally weigh most Bodies in Wa∣ter, it will be a hard matter to make them with any exactness, since it hath been observed, that most Waters themselves differ in speci∣fick Gravity. But to this I shall briefly an∣swer, that I have not perceived so considerable a difference as will frustrate these Experiments, in which we require not a Mathematical, but a Physical certainty.

CHAP. XII. Hydrostatical Stereometry applyed to the Ma∣teria Medica.

IT being usual for Physicians in the descrip∣tions of several Parts of the Materia Medica, to signifie the size of Bodies by very indetermi∣nate Terms, I thought that they might be assisted by Hydrostaticks, to give descriptions much more exact and satisfactory; and for that end having made two hollow Brass Cubes, whose Cavities, being Cubical Inches, contained 256 grains, or a Cubical Inch of Water, it being a Law in Hydrostaticks, that whatever Body is weighed in Water, it loses so much of its weight, as an equal bulk of Water weighs, I concluded it would thence follow, that what∣ever solid was weighed in Water, if in that flu∣id it lost 256 grains of its weight, it might be said to be a Cubical Inch; and as it lost more or less, so it might be said to be of a Magnitude proportionable; for if it weighed but 128 grains less in Water, it might be said, to be of such a bulk of Water; but if it weighed 256 wanting thirty two grains, that being an eight of a whole Cubick Inch of Water, the bulk of the Body may be said to be ⅞ of a Cubick Inch. And if the Body weighs one ounce thirty two grains (amounting to 512 grains) or one ounce and a half forty eight grains (amounting to 768 grains) the bulk of the Body will be equal to two or three Cubical Inches. And if

after the Division there remains a Fraction, it will not be difficult to estimate it, and to know the exact bulk of the Body, since the Cubical Inch consists of such aliquot Parts, as are easily and regularly divided and subdivided.

And thus we may easily know the bulk of a Body that is heavier than Water, but if it be specifically lighter it will be a difficult matter. The method Mersennus proposes is this, viz.

• First, weigh the Body to be examined in the Air.
• Secondly, take a piece of Lead of a de∣terminate weight, and able to sink the other Body in Water.
• Thirdly, weigh the Plate in Wa∣ter, and the weight it loses in Water, will be the weight of Water equal in bulk to the Body weighed.
• Fourthly, tye together the Plate of Lead and the lighter Body, and note the weight of the Aggregate.
• Fifthly, weigh the Aggregate in Water, and substract the weight of it there, from its weight in the Air, and the difference will be the specifick weight of the said Body in Water.
• Sixthly, from this difference, sub∣stract the formerly found specifick Gravity of the Plate alone in Water, and the remains will give you the weight of the lighter Body in the same Liquor.

And then dividing the obtained weight of the light Body in Water by 256 grains, and it will give you the solid content of that naturally floating Body. To illustrate this me∣thod, I shall subjoin the following Experiment.

I.	The Oaken Cube in Air weighs seven drachms, thirteen grains and a half.	193 ½
II.	The weight of the Lead in Air, four drachms.	240

III.	The weight of the Lead in Water (three drachms and a half, ten grains)	220
which being substracted from its weight in Air, leaves for its specifick weight in Water.—	020
IV.	The Aggregate of the two in Air is	433 ½
V.	The weight of both together in Water is—	162
which being substracted from its weight in Air, gives the difference of both the Aggregates.—	271 ½
VI.	The difference betwixt the weight of Lead alone in Air, and in Water, or which is all one, the specifick weight of the Plate alone, viz.—	020
Being substracted from the difference of the Aggregates in Air and in Water, gives for the weight of the Cube proposed— which wants but four and a half of the weight of a Cubical Inch of Water.	251 ½

The same method that hath been taken with solids not subject to dissolve in Water, may be taken with Alloms, &c. Which is only by employing Oyl of Turpentine instead of Water; for a Cubical Inch of that weigh∣ing 221 grains and ⅛, the difference of the weight of a solid in the Air, and in that Oyl, being divided by that Number, the Quotient will give you the solid contents of the Examined Body.

But to discover the weight of Bodies, which are apt to imbibe too much of the Liquor they are weighed in, we may guard them from it by a thin coat of Bees-Wax, and having first

taken the weight of the Wax in Air, and then fast∣ned it to a Plate of Lead, substract the weight of as much Water as is equal in bulk to the Wax, and proceed with the Body contained, and the Plate of Lead as before taught; and having thus obtain∣ed the Weight of the proposed Body in Water, by dividing it by 256 grains, by the help of the Quotient we may obtain the solid contents of the proposed Body. Another way I devised for to learn the solid contents of a Body, with∣out imbibing Water into it, was, by finding the weight of a Cubick Inch of Mercury, and also the specifick weight of the Vessel, and then pouring upon the Body contained in that Vessel as much Silver as it would hold, by knowing the weight of that Quick-silver from the weight of the whole which the Vessel would contain, one might be acquainted, to how much Mercury the matter contained was equal.

Having thus proposed a Hydrostatical way of trying Bodies, I shall leave it to others to con∣trive an Instrument more apt for such uses than I have done: And shall to what I have said add, that these kind of Experiments do not always equally answer in success, being apt to be di∣versifyed, as well by the want of uniformity in the Qualities, and specifick weight of Bodies of the same Denomination, as by the difference in Water in intensely Hot and Cold Weather; as also upon the account of less exact Ballances. But another reason is the difference of weights of the same Denomination, for we are told by a diligent Mathematician, that, cum omnia grana, vel semina, quae reperiri solent in atriis venalibus Lutetiae, and stateram expendisset, vix granum

ullum, inter ejusdem Speciei grana grano alteri ex∣acte respondisset, in incertis Ludere noluit. And the same Author tells us, that 688 Roman grains are but equal to 576 French grains, and this estimate of their difference by another Ballance was found to be thirty six grains false: And the same Author receiving two accounts of the number of grains contained in a Roman ounce, the one told him there were 612, the other 576. And tho' our weights as well as those made use of by Gheraldus, have twenty four scruples in an ounce, yet he divided his scruples into twen∣ty four grains, whereas we divide ours but into twenty. And Mersennus, p. 37. lib. 16. tells us, that cum autem dixi Chelinum, undecim dici denariorum, credunt tamen alii decem duntaxat, nil assero. And.

To what hath been said, I shall only add, that tho' this method of weighing Bodies be not Mathematically exact, yet it comes as near Physical exactness as we can expect, and may be of use till some more nice way of Tryals be found out.

A Table representing not only the Weight of several Bodies in Air and Water, but their Proportions in Weight to an equal Bulk of Water.

A	Weight In Air in Gr.	In Wa∣ter in Grains.	Proportion.
AMber	306	12	1 4/100 to 1.
Agat	251	156	2 64/100 to 1.
A piece of Allom∣stone	280 ¾	152 ¼	2 18/100 to 1.
Antimony good and supposed to be Hungarian One	391	295	4 7/100 to 1.
B
Bezoar stone	187	61	1 48/100 to 1.
A piece of the same	56 ½	22	1 64/100 to 1.
A fine Oriental one	172	60	1 53/100 to 1.
Another	237	61	1 34/100 to 1.
C
Coral red	129 ¼	80 ¼	2 63/100 to 1.
Crystal	256	140	2 21/100 to 1.

	Weight In Air in Gr.	In Wa∣ter in Grains.	Proportion.
Cornelian	148	103	3 29/100 to 1.
Calculus humanus	2570	1080	1 72/100 to 1.
Coco-shell	331	85	1 34/100 to 1.
Native Crabs Eyes	77 ½	36 ½	1 89/100 to 1.
Crabs Eyes Artificial	90 ½	54	2 48/100 to 1.
Calx of Lead	138 ½	123	8 94/100 to 1.
Copper Stone	65 ½	49 ½	4 09/••••0 to 1.
Common Cinnabar	802	702	8 1/50 to 1.
Cinnabar of Anti∣mony	197	169	7 3/100 to 1.
Cinnabar Native	197	171	7 57/100 to 1.
Coral White	336	204	〈◊〉〈◊〉 54/1002 to 1.
Another piece fine	139	85	2 17/100 to 1.
Calculus humanus	302	97	1 47/100 to 1.
Copper Ore	1436	1090	4 15/100 to 1.
Copper Ore Rich	413	314	4 17/100 to 1.
Cinnabar Native, very sparkling	226	194	7 6/100 to 1.
G
Gold Ore not Rich, brought from the East Indies	1100	682	2 63/109 to 1.
Another Lump of the same	1151	717	2 65/100 to 1.
Granati Minera	217	147	3 1/10 to 1.
Granate Bohemian			4 36/100 to 1.

H	Weight In Air in Gr.	In Wa∣ter in Grains.	Proportion.
Haematites English	1574	1156	3 76/100 to 1.
I
Ivory	1732	83	1 91/100 to 1.
L
Lapis Manati	450	293	2 26/100 to 1.
A Fragment of the same	218 ½	123	2 29/100 to 1.
Another	345	197	2 33/100 to 1.
Another from Ja∣maica	2011	1127	2 27/100 to 1.
Lapis Lazuli one piece	385	256	2 98/100 to 1.
Lead Ore	686	590	7 14/100 to 1.
Another
Lapis Calaminaris	477	380	4 92/100 to 1.
Lapis Judaicus	261 ½	164	2 69/100 to 1.
M
Marcasites	814	631	4 45/100 to 1.
Another from Stal∣bridge	243	189	4 ½ to 1.

	Weight In Air in Gr.	In Wa∣ter in Grains.	Proportion.
Another more shi∣ning than ordi∣nary	287	227	4 18/100 to 1.
Mercury reviv'd from Ore
Manganese a piece	321	230	3 13/100 to 1.
Mineral Cornish, like a shining Marca∣site	145	129	9 6/100 to 1.
O
Osteocolla	195	108	2 24/100 to 1.
Ore Silver choice from Saxony	458	366	4 9••/100 to 1.
Another Piece	1120	960	7 to 1.
Ore Lead from Cum∣berland Rich	1872	1586 1/••	54/100 to 1.
R
Rhinoceros horn	8563	4260	1 99/100 to 1.
Rock-Chrystal, ano∣ther Piece	256	140	2 20/100 to 1.
S
Saphir

	Weight In Air in Gr.	In Wa∣ter in Grains.	Proportion.
Seed-Pearl
Sulphur vive	371	185	2 to 1.
Germane very fine	306	152	1 98/100 to 1.
Slate Irish	779	467	2 49/100 to 1.
T
A Piece of Talc like Lapis Amian∣thus	596	334	2 28/100 to 1.
Talc Venetian	802	508	2 73/100 to 1.
Talc Jamaican	1857	1238	3 to 1.
New English Tin Ore, Mr. Huberts.	812	613	4 8/100 to 1.
Tin Ore black Rich.	1293	984	4 18/100 to 1.
Another piece Choice.	2893	2314	5 to 1.
Tutty a piece	104	83	5 to 1.
Tin-glass	468	419	9 56/100 to 1.
V
Vitrum Antimonii per se	357 ½	282 ½	4 76/100 to 1.
Vitriol Engl. a very fine piece	1093	512	1 ••8/100 to 1.
Ʋnicorns horn a piece	407	195	1 91/100 to 1.

Notes

• Arguments against the Positive Le∣vity of e∣merging Bodies.
• The Pres∣sure of the Air's Spring on Bodies under Wa∣ter.
• Of the Ef∣fects of the differing weight of the Atmos∣phere on Bo∣dies under Water.
• Of the dif∣ferent Pres∣sure of So∣lids and Fluids.
• See Plate 2. Fig. 1.
• See Plate 2. Fig. 2.
• See Plate 2. Fig. 3.
• See Plate 2. Fig. 4.
• See Fig. 3. Plate 2.
• See Fig. 6. Plate 2.
• See Plate 3. Fig. 1.
• See Plate 3. Fig. 2.
• See Fig. 3. Plate 3.
• See Fig. 4. Plate 3.
• See Plate 3. Fig. 5.
• See Plate 3. Fig. 6.
• See Plate 3. Fig. 7.
• See Fig. 〈◊〉〈◊〉
• See Plate 4. Fig. 1.
• See Plate 4. Fig. 2.
• See Plate 4. Fig. 3.
• See Plate 4▪ Fig. 4
• Objections answered.
• See Plate 4. Fig. 5.
• See Plate 4. Fig. 6.
• See Plate 4. Fig. 7.
• See Plate 4. Fig. 8.
• A new Hy∣drostatical. Instrument and its uses proposed.
• See Plate 1. Fig. 00.
• About the growth of Tin.
• Of the growth of Lead.
• Of the growth of Iron.
• Of the growth of Silver.
• Of the growth of Gold.
• Ores Hy∣drostatical∣ly estimated.
• Observati∣ons about native Gold.
• See Plate 1. Fig. 00.
• The method of weighing Bodies.
• Cautions requisite to be observ'd.
• The first Use of this method of weighing Bodies.