Zodiac

(zo'de-ak.) [From Gr. zōdiakos, a little animal.] (Ast.) An imaginary belt on the heavens, centrally divided by the ecliptic, on either side of which it extends to a distance of 9 degrees. It is divided into twelve signs, called in order Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sag it tar i us, Capric or nus, Aquarius, and Pisces (q. v. severally). Much discu ion has taken place respecting the origin of the zodiacal signs and the epoch of their invention; but the subject has never rewarded its investigators with any. result worth a tithe of the pains they have taken. -The Zodiacal Light is a faint light of a lenticular shape, seen along the zodiac near the place of the sun shortly after sunset and before sunrise. It is inclined eight or nine degrees to the ecliptic, and some astronomers consider that its mean plane is that of the sun's equator. The hypothesis usually adopted is that which regards the Z. L. as consisting of multitudes of minute bodies travelling around the sun. Though separately invisible, these bodies would be collectively visible just as the Milky Way can be seen, though not its component stars. But the hypothesis according to which the Z. L. is regarded as due to bodies travelling in nearly circular orbits around the sun can hardly be admitted in the face of what we now know respecting the actual motions of the meteoric systems. Remembering that the orbits in which these systems revolve are for the most part very eccentric, and extend into space far beyond the orbits of Saturn and Jupiter, we must explain the permanence of the Z. L. as due to a permanence in the general condition of that portion of space the light belongs to, not to a permanence in the actual constitution of the systems from which the light comes. Doubtle the meteors which at any one time supply the light, pa far away presently into space. But as their place is supplied by others, the Z. L. remains. However, it cannot but be seen that this explanation involves the recognition of the po ibility that at times noteworthy changes may take place in the appearance of the Z. L This accordingly has been found to be the case. [s. 978]