HE A YENS. 75 



spectator, and bounded by the line in wliicb the earth and 

 skies seem to meet. 



Immer'sion. — The disappearance of a celestial body by enter- 

 ing into any medium, as into the light of the sun or the 

 shadow of the earth. 



In'gress. — The moon's entrance into the earth's shadow in 

 eclipses, and the sun's entrance into a sign, especially 

 Aries. 



Latitude. — The distance of a heavenly body from the ecliptic. 



Le'o (Lat., the Lion). — The fifth sign of the zodiac, which the 

 sun enters about the 22d of July. 



Li'bra (Lat., the Balance). — The seventh sign of the zodiac, 

 which the sun enters at the autumnal equinox, in Sep- 

 tember. 



Lon'gitude. — The distance of a heavenly body from the vernal 

 equinox, reckoned on the ecliptic. 



Luna'tion. — The period of a revolution of the n)oon round 

 the earth, or the time from one new moon to the next. 



Mac'ulse. — Dark spots on the surfaces of sun and moon, and 

 on some of the planets. 



Mean. — Mean distance of a planet from the sun, a right line 

 drawn from the sun to the extremity of the conjugate axis 

 of the ellipsis in which the planet moves. 3Iean motion, 

 that by which a planet is supposed to uniformly traverse 

 its orbit, and which is always proportional to the time. 



Meteoros'copy (meteor, and Gr. skopeo, I view). — That part 

 of astronomy which treats of the more remote heavenly 

 bodies, the distances of the fixed stars, etc. 



Milky Way. — A broad, luminous path or circle in the heavens, 

 supposed to be the blended light of innumerable fixed 

 stars which are not distinguishable with ordinary tele- 

 scopes. 



Moon. — --V secondary planet or satellite of the earth, whose 

 light, borrowed from the sun, serves to dispel the darkness 

 of night. 



Na'dir. — The point of the heavens or lower hemisphere directly 

 opposite the zenith. 



Neb'ulse. — Misty appearances among the stars, usually, but not 

 always, resolved by the telescope into myriads of small 

 stars. 

 Node3. — The two points in which the orbit of a planet inter- 

 sects the ecliptic. 



