_L_-ring of electrons in atom, 134, 138, 289, 292, 302 Lalande 21185, 36, 265 Lane’s law, 286 Laplace, P. S., 230, 233 ff. nebular hypothesis of, 230, 231, 232 ff. Lead, radio-active, 154 Leavitt, Miss, 57 Lemaître, G., 84, 86, 174 Lenard, P., 106 Leonid shooting-stars, 250 Leslie, Sir John, 158 Leucippus, 93 Leverrier, U. J. J., 18, 19 Life in solar system, 341 in universe, 340, 342, 345 on Earth, 12, 342, 345 on Mars, 343 on Venus, 344, 347 Light, nature and composition of, 37, 50, 114 speed of, 37, 115 wave-length of, 115, 138 Light-year, 37 Lindblad, B., 67, 69 Lippershey, 1 Liquid masses in rotation, 219 ff. Liquid stars, 222, 296 ff., 300, 304, 310 Lives of stars, _see_ Stars Lockyer, Sir N., 314 Long-period variables, 56, 58, 61, 271, 319 Lowell, P., 19 Lucifer, 17 Lucretius, 93 Luminosity of stars, 48, 49, 179, 269, 278, 279, 280 _M_-ring of electrons in atom, 134, 289, 292, 293, 302 McLennan, J. C., 143 Magellanic clouds, 57, 210 and Plate XXI (p. 214) Main-sequence stars, 279, 291, 295 Major planets, 16, 17 atmospheres on, 197 Man’s life on earth: past, 12, 16 future, 345 ff. Marius, 31 Mars, 18, 19, 35 atmosphere of, 196, 343 birth of, 240, 243, 244 life on, 343 orbit of, 20, 239 rotation of, 225 satellites of, 240, 243, 250 temperature of, 21 Matter, annihilation of, 185, 191, 192, 315 conservation of, 189 Maxwell, J. C., 122, 157 Mayer, R., 176 Mercury, 4, 5, 16, 17, 19, 22, 35 absence of satellites, 243 atmosphere of, 196, 348 birth of, 240, 243 life on, 348 orbit of, 20, 45, 239 rotation of, 22, 224 Meteor, 238, 247, 248 Meteorite, 248 Michelson, A. A., 261 Milky way, 3, 23, 26, 27, 28, 30 Millikan, R. A., 143, 148 Minor planets, 16 Molecule, 94 collisions of, 97, 98, 102 equipartition of energy, 156 size of, 95 speed of, 96, 195 Moon, 4, 43 atmosphere of, 196 birth of, 243 distance of, 34, 43 eclipse of, 34 future of, 225, 226, 251 rotation of, 225 Moore, J. H., 321 Morning star, 17 Moulton, F. R., 235, 236 Moving clusters, 40, 173, 216 shape of, 216, 217 Munich 15040, 36, 264