A tutor to astronomie and geographie, or, An easie and speedy way to know the use of both the globes, coelestial and terrestrial in six books : the first teaching the rudiments of astronomy and geography, the 2. shewing by the globes the solution of astronomical & geographical probl., the 3. shewing by the globes the solution of problems in navigation, the 4. shewing by the globes the solution of astrological problemes, the 5. shewing by the globes the solution of gnomonical problemes, the 6. shewing by the globes the solution of of [sic] spherical triangles : more fully and amply then hath ever been set forth either by Gemma Frisius, Metius, Hues, Wright, Blaew, or any others that have taught the use of the globes : and that so plainly and methodically that the meanest capacity may at first reading apprehend it, and with a little practise grow expert in these divine sciences / by Joseph Moxon ; whereunto is added Antient poetical stories of the stars, shewing reasons why the several shapes and forms are pictured on the coelestial globe, collected from Dr. Hood ; as also a Discourse of the antiquity, progress and augmentation of astronomie.

PROB. XIII.

How to know whether it be Before or After Noon.

HAving made one Observation, you must make a Second a little while after the First; and if the Sun increase in Alti∣tude, it is Before Noon: but if it decrease in Altitude, it is After Noon.

Example.

The Sun was at 8. hor. 53. Min. elevated 40. degr. above the Horizon: A little while after (suppose for examples sake aquar∣ter of an hour,) viz. at 9. hor. 8. Min. I observe again the heigth of the Sun, and find it 42. degrees high; so that the Altitude is increased 2. degrees; Therefore I say, It is Fore-Noon: But if the Sun had decreased in Altitude, I should have said it had been After-Noon.

How to take Altitudes by the Quadrant, Astrolabe, and Cross-staff.

There are divers Instruments whereby Altitudes may be taken: but the most in use are the Quadrant, Astrolabe, and Cross-staff. A Quadrant is an Instrument comprehen∣ded between two Straight lines making a Right Angle, and an

Arch discribed upon the Right Angle, as on the Center, con∣taining 90. degrees, which is a quarter of a Circle: and therefore the Instrument is called a Quadrant. See this Figure.

[illustration]

A prepresents the Center; upon which is fastned a Plumb-line, A B the one side, A C the other side, upon which the Sights are placed: B C the Arch or Quadrant, which is divided into 90. equal parts, and numbred from B to C. D one Sight, E the other Sight: F the Plumbet fastned to the Plumb-line.

When by this Instrument you would observe the heigth of the Sun, you must turn the Center A to the Sun, and let the beams thereof dart in at the hole in the first Sight D, through the hole in the second Sight E; so shall the Plumb-line ly upon the degree in the Limb, of the Suns Elevation: As if the plumb-line ly upon the 20th degree, then shall the Alti∣tude be 20. degrees; if on 25. the Altitude shall be 25. degrees: and so for any number of Degrees the thred or Plumb-line lies on, the same number of Degrees is the Altitude of the Sun.

But if it be a Star whose Altitude you would observe; you must hold up the Quadrant, and joyn the Limb to your Cheek bone, and turn the Center towards the Star: then winking with one Ey, look through the holes of the Sights with the other Ey, till you can see the Star through those holes; so shall the Plumb-line (as before in the Sun) hang upon the degree in the Limb of the Stars Elevation.

Another sort of Quadrants is made with a moveable Index, as is represented in this Figure.

[illustration]

A is the Center, A Band A C the two sides, B C the Limb, D E two Sights fixed upon a moveable Index or Label; F G two other Sights, for observing the Horizon.

When by this Quadrant you would observe an Altitude, the side B A must be parallel to the Horizon, and the Index must be mo∣ved till the Object (be it either the Sun Moon or any Star) be seen through the holes or slitts of the Sights placed on the Index; for then the Arch D B shall be the Elevation required. You

may know when the side B A is parallel to the Horizon, by ob∣serving the parting of Heaven from the Earth through the Sights on the Side B A.

To take Altitudes by the Astrolabe.

The Astrolabe is a round Instrument, flat on either side, upon one of the flats or Plains is discribed a Circle as B C D E, divided into 360, equal parts or degrees, numbred from the line of Level B A C, with 10, 20, 30, &c. to 90. in the Per∣pendicular D C. Upon the perpendicular is fastned a Ring as F, so as the Instrument hanging by it, the line of Level may hang pa∣rallel to the Horizon. Upon the Center is a moveable Label or Ruler, as G H, whereupon is placed two Sights as I K.

[illustration]

If you desire further instructions for making this Instrument, you may peruse M^r Wright in his Division of the whole Art

of Navigation, annexed to his Correction of Errors: where he also shews the use of it at large; which in brief is as follows.

You must hold the Astrolabe by the Ring in your left hand, and turning your right side to the Sun, lift up the Label with your right hand, till the beams of the Sun entring by the hole of the uppermost Vane or Sight, doth also pierce through the hole in the nethermost Vane of Sight; and the deg. and part of deg. that the Label lies on is the height of the Sun above the Horizon.

But if it be a Star you would observe; you must use the A∣strolabe as you were directed to use the Quadrant, holding it up to your Cheek bone, and looking through the Sights, &c.

To take Altitudes by the Cross-staff.

This Instrument consists of a Staf about a yard long, and three quarters of an inch square: Upon it is fitted a Vane, (or sometimes two, or three,) so as it may slide pretty stiff upon the Staff, and stand at any of the Divisions it is set to.

[illustration]

The making is taught by M^r Wright, aforesaid: But the use is as follows.

You must put that end of the Cross-staff which is next 90. degrees to your Cheek bone, upon the outter corner of your Ey, and holding it there steddy, you must move the Vane till you see the Horizon joyned with the lower end thereof, and the Sun or Star with the higher end; then the degree and part of degree which the Vane cutteth upon the Staff, is the height of the Sun or Star.

Some of these waies for taking Altitudes have been formerly taught by others, that have treated upon the Use of Globes: and therefore because some would be apt to think this Treatise un∣compleat if I did not shew these waies also, I have thought fit to insert them: Yet the same things may be performed by the Globe alone, without troubling your self with multiplicity of In∣struments; if your Globe be made with a hollow Axis; for then if the Globe stand Horizontal, you shall by Observing the Object through the Axis have the degree of Elevation, noted by the superficies of the Horizon.