ZODIAC (OF. zodiac, zodiague, Fr. zndiaryitr, from Lat. :of/if/ens, from Gk. Natas6s, ze;dirtko, zodiac, relating to animals, from zodion, diminutive of Nov, coon, animal, from rip, zen, to live; so called because the constellations were figured as animals). The 1111111C given by the an eients to an imagilmry band extending round the celestial sphere, having us its middle line the ecliptic or apparent path of the sun. It was fixed at about IV in width so as to include the orbits of the sun and of the five planets (Mer eury, Ve1111A. Jupiter, and Saturn) which were then known; and as. of these planets, Mer envy has 1,3• far the greatest inclination of orbit to the ecliptic, and the value of that element in his case is only the width given to the zodiac was amply suffieient for the required purpose. But when the career of the planetary discovery commenced in the beginning of the nineteenth century, the first three which were discovered (Ceres, Pallas, and Juno) at once destroyed the idea which had been long seated in men's minds, that no planets existed beyond the limits of the zodiac, by exhibiting orbits inclined to the ecliptic at no less angles than I I°, 35°, and 13*; and a large number since observed have been found to wander beyond the zodiac, from which circumstance they have, along with the three above mentioned, been denominated ultra-zodi acal planets.
The stars in the zodiac were grouped into twelve constellations. to each of which 30°, or Tirth of the whole circle, was assigned, though it often did not fill up that space, but was only situated in it; and this equable division into signs was of great advantage in defining the posi tions of the sun and planets at any epoch.
The constellations, with the appropriate sym bols of the corresponding signs, are as follows: Aries (Rem) m Libra (Balance) Taurus (Bull) b' Scorpio (8corpion) 111 Gemini (Ticins) It Sagittarius (Archer) Rt Cancer 2 5 Ca prieornus ( Goat ) Leo (Lion) gl Aquarius (Water-bearer) Virgo (Virgin) ng Pisces (Fishes) )-( As one half of the ecliptic is to the north and the other to the south of the celestial equator, the line of intersection of their planes is a diam eter of each, and the two points in which this line meets the celestial sphere are known as the equinoctial (CI.V.1 points. The comparative im mobility, with respect to the ecliptic, of these points, suggested at once the employment of one or other of them as a point from which to reckon celestial meaRlIremelits of stars' positions, and accordingly that point at which the sun crosses the equinoctial from south to north was fixed upon, and called the first point (or commence ment) of Aries (q.v.). After the sun had ad
vanced eastward through this sign—i.e. 30° along the ecliptic—he entered the sign of Taurus. continuing his course onward through the others in the order in which they are given above. again crossing the equinoctial sonthward at the point where he emerged from Virgo and entered Libra. This was the case with the sun during the time of liipparehus (q.v.), hut though the equinoctial points move very slowly, yet they do so with great uniformity, and the westerly motion of 50" annually li.bieh they describe along the ecliptic has at the present time separated the sign Aries from the constellation Aries, and caused the former to correspond almost to the constellation Pisces. This gradual retrogression of the signs through the constellations of the zodiac will continue till they aceomplish, in about 25,800 years, a complete circuit; after which period the sign and constellation of Aries will again coincide, as they did in the time of llipparchus. Neither the zodiac nor its constel lations an of much use now in astronomy, ex cept as, like the other constellations, affording an easy though somewhat fantastic nomenclature for the stars, and a rude but sometimes conve nient mode of referenee to their positions.
The zodiac is probably Babylonian in origin. The figures seem to have been based on the re semblance of the lines connecting the stars in the zodiacal constellations io certain pictorial outlines which form the substratum of the As syro-Bal)ylimian cuneiform alphabets (see ('UNEI FORM 18scnirritoNs), while animal figures and outlines were chosen for animistic reasons. The greater number of the modern zodiacal eonstel lations are identical with the Babylonian, al though two or three seem to be of Occidental origin. The signs of the zodiac were carried from Ilabylonia to Greece, whenee they spread throughout the ancient civilized world, and found their way back, along with much other astro nomieal science, to India and the Far East.
Consult for the origin of the zodiac: Epping and Strassmaier, .,l&tronotainchrs nos HnhyIon (Frei burg, 1889) ; Jensen. Kovno'ogle der Babylonier (Strassimrg, 1890) ; :Yastrow. Religion of Baby lonia and .Issyria (Boston, 1898).