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256 Carboniferous period, 179. Cassini, 76, 162. Celestial mechanics, 28, 94, 155. Ceres, 101. Challis, 123. Chemistry, indebted to the stars, 160. Clausius, 228. Clerke, Miss, 9, 164. Climate, advent of, 185. Clouds, none on Venus, 75. of Jupiter not ordered as ours, 107, 163, 167. Uranus wrapped in, 168. Neptune wrapped in, 168. Earth once wrapped in, 170, 171, 178. Collision of dark star with Sun, 25, 215. warning of, 26-29. disturbances previous to, 29, 30. rarity of event, 30. Collisions between meteorites of a flock, 11, 49. causing light, 49, 50. Columbus, 1 88. Comets, 33, 61. members of solar system, 34, 35. orbits of, 61, 100. Commensurability of orbital period, 99, 111. Congruities of solar system, 128-137. deviations from, 62, 100, 101, 130, 131, 141. specify mode of evolution, 137. Convection currents, 219. in atmosphere of Venus, 80. Copeland, Dr. 7. Copernican system, 58. Copernicus, 62. Cosmic action, 1, 22, 184. Croll, 196. Cuticle of star, effect of impact on, 11.

D Dana, 177, 186, 189. Dark stars, origin, 2. number, 2, 25. evidence of, 3-5. collision of, 10, 11. rendered visible, 26. Darwin, 62, 138, Notes 252. Day, lengthened to infinity, 70, 219. none on Venus, 83. Jovian, 163. first appreciation of, 186. coincides with month, on satellites, 225. Death of a planet, defined, 214. catastrophic cause, 215, 216. due to tidal retardation of rotation, 216-219. outcome of loss of oceans and air, 226, 233. caused by extinction of Sun itself, 234. Density, of dark star, 27. of planets, 51, Notes 243. of Mercury, 63, 64. of Venus, 90. of Jupiter, 103, 117. of Uranus, 115. Deserts, increase of, on Earth, 208-211. Devonian era, 187. Dhurmsala meteorite, 41. Diameter, of Mercury, 63, 64, 66, 67. of Venus, 90. of Earth, 90. of Mars, 91. of satellites of Mars, 92. of Jupiter, 103. of Uranus, 115-117. Dust, in atmosphere of Venus, 75.

E Earth, characteristics, not universal, 90, 91, 155. evolved from a nebula, 149. internal heat, 150. early surface temperature, 160, 169, 170. once cloud-wrapped, 170, 171, 178. solid surface formed, 171. hot seas of, 171, 172. self-sustained, 182. study of, within province of astronomy, 184. ceased to be self-centred, 187. Sun becomes dominant factor in organic life of, 190. Earth shine, 82. Eccentricity, orbital, of Mercury, 63, 65, 69, 222. of asteroids, erratic, 100, 101. 256