395. The antients divided the starry Sphere into particular Constellations, or Systems of Stars, according as they lay near one another, so as to occupy those spaces which the figures of different sorts of animals or things would take up, if they were there delineated. And those Stars which could not be brought into any particular Constellation were called _unformed Stars_. [Sidenote: The use of this division.] 396. This division of the Stars into different Constellations or Asterisms, serves to distinguish them from one another, so that any particular Star may be readily found in the Heavens by means of a Celestial Globe; on which the Constellations are so delineated as to put the most remarkable Stars into such parts of the figures as are most easily distinguished. The number of the antient Constellations is 48, and upon our present Globes about 70. On _Senex_’s Globes are inserted _Bayer_’s Letters; the first in the Greek Alphabet being put to the biggest Star in each Constellation, the second to the next, and so on: by which means, every Star is as easily found as if a name were given to it. Thus, if the Star γ in the Constellation of the _Ram_ be mentioned, every Astronomer knows as well what Star is meant as if it were pointed out to him in the Heavens. [Sidenote: The _Zodiac_.] 397. There is also a division of the Heavens into three parts. 1. The _Zodiac_, (ζωδιακὸς) from ζώδιον _Zodion_ an Animal, because most of the Constellations in it, which are twelve in number, are the figures of Animals: as _Aries_ the Ram, _Taurus_ the Bull, _Gemini_ the Twins, _Cancer_ the Crab, _Leo_ the Lion, _Virgo_ the Virgin, _Libra_ the Balance, _Scorpio_ the Scorpion, _Sagittarius_ the Archer, _Capricornus_ the Goat, _Aquarius_ the Water-bearer, and _Pisces_ the Fishes. The Zodiac goes quite round the Heavens: it is about 16 degrees broad, so that it takes in the Orbits of all the Planets, and likewise the Orbit of the Moon. Along the middle of this Zone or Belt is the Ecliptic, or Circle which the Earth describes annually as seen from the Sun; and which the Sun appears to describe as seen from the Earth. 2. All that Region of the Heavens, which is on the north side of the Zodiac, containing 21 Constellations. And 3. that on the south side, containing 15. [Sidenote: The manner of dividing it by the antients.]