LETTER XL.

USE OF THE CELESTIAL GLOBE.

THIS globe reprefents the face of the hea

vens, as the other does that of the earth. The ftars indeed are placed on a convex furface, and we fee them on a concave in the heavens. This is a facrifice to convenience, for it would be difficult to make globes big enough for people to fit in. We are not to believe, however, that the fixed stars are all placed in a concave furface, equally diftant from us, as they appear:-The imperfection of our fight causes this appearance; for when it is affifted by the telescopes we can discover thoufands more than the naked eye can perceive. It is therefore evident they are at immenfe diftances from one another, though on the globe we can only imitate their apparent fize and fituation. The Chaldeans and Egyptians were the fathers of aftronomy-in their ufual allegorical way, they registered the events in their hiftory, and the myfteries of their religion among the stars, by placing emblematic figures among them.

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The Greeks found this fo ingenious a method of making their mythology immortal, that they difplaced many of the Chaldaic conftel lations, and placed up many of their own, which is the reafon that our globes are covered with figures that have a more univerfal reference to Greek Fable than to that of any other country: Modern aftronomy has thought fit to adapt thefe, uncouth figures, For the purpofe of having a kind of out-line on the face of the heavens, by which the ftars and all other parts of the heavens might be called by diftinguifhable names. The larger ftar therefore, in each conftellation, has the first letter of the Greek alphabet placed near it; the next in fize the fecond letter, &c.So we read the two pointers in the great Bear, a Urfa Major, B Urfa Major, &c. that is alpha and beta of the great Bear. So Arcturus is called a Bootis, &c. The largest ftars are called stars of the first magnitude; the next in fize, ftars of the fecond magnitude, &c.

This globe is alfo equiped with the fame imaginary circles as the other, viz. the equator, tropick, &c.-but the ecliptic being the important line on the heavens, as the equator is on the earth, latitude is counted from it, and longitude upon it-hence this circle has

two poles as well as the equator-and is the middle of a belt or zone, called the zodiac, which reaches 8o on the north, and 8o on the fouth fide of the ecliptic, including the orbits of all the planets, and their latitudes north and fouth. This zodiac, like all other circles, is divided into 360°, or 12 figns, each containing 30°, called Aries, Taurus, Gemini,

&c.

The other diftinctions peculiar to the celeftial globe are: 1ft, The Declination of the fun, or a ftar, is its diftance from the equator north or fouth in degrees and minutes. 2d, The Latitude of the fun, moon, or ftar, is its diftance north or fouth from the nearest part of the ecliptic, 3d, The Longitude of the fun, is its distance from the first point of Aries; of a ftar, the diftance of the place where its meridian cuts the ecliptic from the first point of Aries. 4th, The Right ascension in time of the fun, or ftar, is an arch of the equinoctial between the first point of Aries, and where the meridian of the fun, or ftar, cuts the equinoctial, allowing 15° to an hour. Amplitude of the fun, or ftar, is an arch of the horizon, contained between the eaft or weft points of it, and that point on which the fun rifes or fets. Azimuths, are arches on the horizon, contained between the north and

fouth points of it, and vertical arches paffing through the fun, or ftar, and cutting the horizon at right angles. Altitude, is the height of the fun, or ftar, above the nearest part of the horizon. Tranfit, Occultation, Eclipfe, words to denote one heavenly body paffing before or behind another, in a line with the spectator.

I have already given you the characters of the twelve figns of the ecliptic, see page 273, and shall in this place present you with the characters of the fun and planets; with some others that appear in the almanac.

8 Afcending node. ▲ Trine, = 120o. Defcending node. 8 Oppofition, 180°.

These five characters were used by the

ancients to denote what they called the

afpects of the heavens, which were probably introduced by thofe who fufpected that future events depended on the position of the fun and planets with refpect to each other for an afpect was defined to be the angle formed by the rays of two planets meeting on the earth, and supposed to be capable of exciting fome natural power or influence. Thus if the angle formed by two right lines drawn from Venus and Saturn to a fpectator on the earth be 609 or 90, or 120°, or 180°, thofe planets are. faid to be fextile, quartile, trines or in oppofition. When they are in the fame fign and degree of the fign in the heavens, as feen from the earth, then they are in conjunction: the following examples, compared with Moore's Almanac and White's Ephemeris will make the matter clear:

Example 1.-On the 16th of February, fee the Almanac) the Sun and Mercury are faid to be conjunction, marked 6, and looking into the Ephemeris, I find they are both in the 27th.degree of (Aquarius): in other words, they are in conjunction.

Ex. 2.-Sextile, denoted by *, is when the planets are diftant from one another by the fixth part of a circle, or by two figns, or