392. _The Cloven Ring Theory._--According to Mädler, the stars of the Milky-Way are entirely separated from the other stars of our system, belonging to an outlying ring, or system of rings. To account for the division of the Milky-Way, the ring is supposed to be cloven on one side: hence this theory is often referred to as the _cloven ring_ theory. According to this hypothesis, the stellar system viewed from without would present an appearance somewhat like that in Fig. 458. The outlying ring cloven on one side would represent the stars of the Milky-Way; and the luminous mass at the centre, the remaining stars of the system. 393. _Proctor's View._--According to Proctor, the Milky-Way is composed of an irregular spiral stream of minute stars lying in and among the larger stars of our system, as represented in Fig. 459. The spiral stream is shown in the inner circle as it really exists among the stars, and in the outer circle as it is seen projected upon the sky. According to this view, the stars of the Milky-Way appear faint, not because they are distant, but because they are really small. [Illustration: Fig. 459.] 394. _Newcomb's View._--According to Newcomb, the stars of our system are all situated in a comparatively thin zone lying in the plane of the Milky-Way, while there is a zone of nebulæ lying on each side of the stellar zone. He believes that so much is certain with reference to the structure of our stellar universe; but he considers that we are as yet comparatively ignorant of the internal structure of either the stellar or the nebular zones. The structure of the stellar universe, according to this view, is shown in Fig. 460. [Illustration: Fig. 460.] INDEX A. Aberration of light, 38. Aerolites, 304. Aldebaran, star in Taurus, 340, 342. Algol, a variable star, 343, 358. Almanac, perpetual, 82. Alps, lunar mountains, 126. Altair, star in Aquila, 336. Alt-azimuth instrument, 13. Altitude, 12. Andromeda (constellation), 343, 346. nebula in, 376. Angström's map of spectrum, 164. Antares, star in Scorpio, 347. Apennines, lunar mountains, 122, 124. Aphelion, 47. Apogee, 44. Aquarius, or the Water-Bearer, 350. cluster in, 354. Aquila, or the Eagle, 336. Arcturus, star in Boötes, 335, 365, 370. Argo, or the Ship, 360. nebula in, 383. variable star in, 360. Aries, or the Ram, 350. Asteroids, 223, 241. Astræa, an asteroid, 241. Auriga, or the Wagoner, 342. Azimuth, 13. B. Betelgeuse, star in Orion, 340, 370. Berenice's Hair (constellation), 334. Bode's law, 241. disproved, 273. Boötes (constellation), 334, 335. C. Calendar, the, 80. Callisto, moon of Jupiter, 250. Cancer, or the Crab, 350. tropic of, 61. Canes Venatici, or the Hunting-Dogs, 334. Canes Venatici, nebula in, 384. Canis Major, or the Great Dog, 342. Canis Minor, or the Little Dog, 340. Capella, star in Auriga, 340, 343.