Diurnal motion, The, 21 Dumb-bell nebula, 43, 44, 45, 46, 50, 74, 195 Dust from Krakatoa, 185 Earth, Heat in interior of, 134, 367 ——, ——, Cause of, 153 ——, History of, 122–157, 251 ——, Rigidity of, 162 Earth-moon system, 253, 332 Earthquakes, 158–190 —— in England, 175 ——, Routes of, 171 Emission of sun heat, 373 Energy between two attracting masses, 370 —— given out in contraction of nebula, 370 —— of a system, 216, 235 Equivalent of heat, 88 Eros, 312 Evaluation of sun heat given out in contraction, 371 Everett, Professor, 149 Fire-mist, The, 268 “Flash” spectrum, 70 Foot-pound, 91 Foraminifera, 367 Friction and tides, 381 Gas in rarefaction, 118 H and K lines, 70, 276 Heat, Cause of, 153 ——, Equivalent of, 88 —— given out in contraction of nebula, 369 —— in interior of the earth, 134, 367 ——, Unit of, 80, 89 Helium, 277 Helmholtz, 86, 96, 100 Hercules, Star-cluster in, 52, 53, 56, 57, 59 Herschel, Sir William, 4, 11, 72, 73, 74 Huggins, Sir W., 60, 61, 63, 65 Huxley, Professor, and Darwinian theory, 362 Huyssen, Captain, 127 Hydrogen in spectrum of Nova Persei, 358 “Inflammation” and nebular theory, 361 Joule’s equivalent of heat, 88 Jupiter, 23, 25, 26, 29, 208, 237, 310, 327 K and H lines, 70, 276 Kant, Immanuel, 4, 5, 72, 73, 74, 327 Keeler, Professor, 45–48, 67, 73, 199, 200, 202, 245 Kelvin, Lord, 153, 162 Krakatoa, 176–189 Langley, Professor, 78 Laplace, 4, 72, 73, 74, 206 Lassell, Mr., 338, 340 Lick Observatory, 41, 43, 44, 45 Lockyer, Sir Norman, 277 Lyra, Ring nebula in, 249 Mars, 25, 26, 27, 28, 29, 311, 341, 349 ——, Satellites of, 341 _Mécanique Céleste_, 5, 8 Mercury, 23, 25, 26, 29, 208 Meteors, 37 Milky Way, 205, 206, 214, 220 Milne, Professor, 165 Moment of momentum, 222, 226, 240, 352 —— ——, Acceleration of, 377 —— ——, Change of, 375 —— ——, Conservation of, 374 Momentum, Moment of, 222, 220, 240, 352 Monoceros, Nebulous region round a cluster in, 33 Moon, Origin of, 254 ——, Surface of, 255 Nautilus, The, 367 Nebula, Contraction of, Heat given out in, 369 ——, ——, Energy given out in, 370 —— in Orion, The great, 40, 41, 42, 44, 46, 50, 74, 195, 242 —— ——, ——, Spectrum of, 63, 64, 65 ——, The great spiral, 192, 193 Nebulæ, 40, 41, 43, 45, 47, 50, 57, 58, 66, 67, 71, 73, 105, 120, 157, 191–206, 242, 247, 249, 256, 257, 258, 259, 296, 329, 345, 348–360 ——, Development of, 242 ——, Discovery of, 11 ——, Number of, 67, 200 Nebular anecdote, 362 —— Theory, The, 2, 3, 72, 74, 157, 205, 266, 292, 307, 323, 328, 331, 337–347, 362, 368 Nebulosity, Faint diffused, in Perseus, 17 Neptune, 37 ——, Satellites of, 330, 340 Newcomb, Professor, 238 Norway, Conglomerates in, 159 Nova Persei, 358 —— ——, Spectrum of, 358, 359, 360 Oak-tree and the butterfly, The, 15 Oberon, 338 Orbits of the planets, 208 Orion, 22