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Fig. of the Meridian, and the Horizon; the one of Brafs, the other of XXV. Wood. -Circles, indeed they are not fo properly called; for, in
the rigorous Senfe, no Line is fuppofed to have any Breadth, but both these have Breadth allowed them; that fuch Things might be written, or engraven upon them, as might render them more ufeful in all Pofitions of the Globe: And therefore, (they being of a Circular Form) notwithstanding the Impropriety of Speech, we will have it fo; and we must call them, The Meridian and Horizontal Circles. The Meridian in the Figure, is noted with the Letters Z Na, and the Horizon with HAO.
Unto this Brazen Meridian, there belong Two other Appendants, viz. An Hour-Circle, with its Index; and a Quadrant of Altitude.
Through the Body of either Globe, there runs a ftrong Wyre; the Ends whereof are fo fixed in the Brazen Meridian, that the Body of the Globe may turn about together with the Wyre. -This Wyre is called the Axis of the World, and the Ends thereof, the Poles of the World, one the Artick or North Pole, noted with P the other, the Antartick, or South Pole, noted with S.
Unto this Brafs Meridian alfo, there belongs another Appendant, called A Quadrant of Altitude, which is a thin Plate, divi- ; ded into 90 equal Parts or Degrees, and fitted with a Nut and a Screw, to move to any Degree upon the Meridian, but generally in the Vertical Point Z, the Zenith of any Place.
II. Of the feveral Pofitions, that a Globe or Sphere, mag. be pofited in its Horizon.
Here are but Three Pofitions, in which a Globe may be feated in its Horizon; viz. (1.) Direct. (2.) Parallel. (3.) Oblique. Of which, the Two firft are Particular, the third more General.
I. Of Direct Pofition.
The Globe may be fo placed in the Frame, that both the Poles thereof may reft upon (or lye directly in) the North and South Points of the Horizon, neither Pole having any Elevation: The Zenith Point being in the Aquino&ial Circle, and the Axis of the World in the Plain of the Horizon. And this is called Direal Pofition.
II. Of Parallel Pofition.
The Globe may be fo placed in the Frame, that one of the Poles fhall be in the Zenith, and the other in the Nadir Points; the Poles having so Deg. of Elevation above the Horizon: And in this Situation, the Equinoctial Circle will be in the Horizon. This Pofition is called Parallel Pofition.
III. Of Oblique Pofition.
The third Pofition of the Globe is more General; for it hath
III. How to Rectifie the Globes, fitting them for Ufe in any
Being provided of a Pair of Globes, the Meridian, Horizon, and Hour-Circle, truly turned and divided; alfo the Balls truly hung or poized upon the Axis, and the Meridian and Horizon (in all Pofitions) cutting each other at Right Angles; the Papers truly joined in their pafting upon the Bodies, &c. All which are to be performed by the Workman, (yet the Buyer ought alfo to have Inspection thereunto) you may proceed to Redifie them for Use in this manner.
1. Put the Brass Meridian into the Two Notches that are cut in the North and South Parts of the Horizon; the Graduated, or Divided, Part thereof, towards the Eaft Part of the Horizon and the plain, or undivided Side thereof, towards the Weft, and let the Meridian alfo reft in the Notch which is in the Foot, or bottom, of the Frame of the Horizon.
Fig. 2. Place the Brass Hour-Circle, or Wheel, about the Pole; fo XXV. that the Hour-Lines of 12 and 12 do lye directly over the Eaft, or Graduated, Side of the Meridian; and that the Point of the Axis of the Globe do pafs dire&tly through the Centre of the Hour-Wheel; then fhall the Two Twelves reprefent the Two Hours of 12 and 12: That towards the South Part of the Meridian 12 at Noon, and the other towards the North Part, 12 at Midnight: And the Two Sixes fhall reprefent the Two Hours of Six a Člock: That towards the Eaft, 6 in the Morning, and the other 6 at Night. Then put the Index (or Pointer) upon the end of the Axis; fo that as the Globe being turned, which way foever, the Pointer may move with it; and fo is your Hour-Circle rectified.
3. Elevate the Pole of your Globe (whether North or South) according to the Latitude of the Place of that what part of the World you are in: As fuppofe London, which hath 51 Deg. 30 Min. of North Latitude: The Meridian being in the Notches of the Horizon, and alfo in the Notch at the bottom of the Frame, as is before directed. Move the Meridian upwards or downwards in the Notches, till you find 51 Deg. 30 Min. of the Meridian, juftly to touch the upper part of the Horizon, on the North part thereof: And fo is your Globe rectified to the Latitude of 51 Deg. 30 Min.
4. The next thing to be rectified is the Quadrant of Altitude; which must be done, by having refpect to the Latitude alfo: Wherefore, the Latitude being 51 Deg. 30 Min. Count 5 1 Deg. 30 Min. North, upon the South part of the Meridian, from the Aquinodial Circle, towards the North (or elevated) Pole, and there put on the Nut, which is at the end of the Quadrant; fo that the edge of the Divifions of the Quadrant, may be directly under the Degrees of the Latitude, viz. 51 Deg. 30 Min. and there screw the Nut faft. And thus is your Globe Rectified for the Solution of all fuch Questions Cofmographical, as are to be wrought thereby in that Latitude of 51 Deg. 30 Min.
CHA P. II.
Neceffary to be known.
Here are Two kind of Motions in the Heavens, the first
is called the Common Motion of the fixed Stars and Pla
nets together; by which they go all about in 24 Hours from XXV. Eaft to Weft. The fecond Motion is called the proper Motion, by which they go about, every one in his own Time or Pcriod, from Weft to Eaft.
II. Thefe Two Motions are the Original of Two Circles, the Æ quinoctial and the Ecliptick; for the Diurnal Motion is done about the Pole of the Equinoctial either in the Equinoctial it felf, or in a Leffer Circle, parallel unto it: But the proper Motion, is about the Poles of the Ecliptick, either in the Ecliptick it felf, or in a Leffer Circle, parallel unto it..
III. The Sun's Center keepeth always upon the Ecliptick Line, but the other Planets do go from the Ecliptick on both Sides 8 Deg. Hence the broad Circle, whofe Middle is the Ecliptick, doth arife, and is called the Zodiack..
IV. The Equinoctial is in the Heavens about that Streak, which
V. The Zodiack is known by the Twelve Afterims of fixed
VI. The Two Luminaries are the Sun O, and the Moon, the
VII. The other Planets are either the Superior, as Saturn 5,
ter in 12, Mars & in 2 Years. The Inferior Planets are Venus and Mercury; Venus is 9 Months Morning Star, and other 9 Months Evening Star. Thefe Two Planets keep always near to the Sun, fo that Mercury g is for the most part covered with its Beams.
VIII. The fixed Stars move alfo from Weft to Eaft, either in the Ecliptick, or in a Parallel to the Ecliptick, but very flowly, viz. One Degree in 70 Years. Hence the Signs are diftinguifhed in Starred and Un-ftarred. The Starred Signs are the Twelve Afterifms of the Zodiack; but the Un-ftarred are every one a Twelfth part of the Ecliptick. Now the Starred Signs left their former Places, and are preceded in fome 1800 Years almost One whole Sign; fo the Starred Aries V, ftands now in the Place of the Un-ftarred Taurus; and the Starred Taurus 8, in the Place of the Un-ftarred Gemini ¤, &c.
IX. The Equinoctial and Ecliptick are immutable, for there is never but One Equinoctial, and One Ecliptick: But the Horizon and Meridian are mutable: For every Body walking upon the Superficies of the Earth, doth carry along with him his Horizon So this Circle is as manifold as there are divers Points upon the Surface of the Earth. The Horizon is determined by the Eye of the Man turning about in an even open Field, where the Heaven feemeth to join with the Earth; and its Office is to fhew the Rifing and Setting of all Heavenly Bodies.
X. The Meridian is not alter'd by, going on freight towards South or North, but only when you walk never fo little towards the Eaft or Weft, you have prefently another Meridian. It is obfervable in the Heaven, by letting fall a Plummet or Perpendicular from the Vertex, by the Sun (or any Star) being at its highest.
XI. Every one of thefe Four Circles hath its Poles, which the Cir. cle is juft between, and every way equally diftant from it, exactly dividing the Sphere into Two equal Hemispheres, and they divide each other into Two equal Semicircles: And by the Poles of each, there are defcribed Secondary Circles (the Meridian only excepted) which Secondary Circles do cut their : Principal Circle into Two Equal Parts, and at Right Angles.