Galactic latitude and longitude, 24, 25 Galactic nebulae, 29, Plates III (p. 29), VI (p. 37), VII (p. 44) Galactic system of stars, 23, 25, 65 ff., 211 number of, 68, 69, 215 rotation of, 66 ff., 214 weight of, 69, 215 Galileo, 1, 3, 4, 5, 8, 16, 24 Galle, J. G., 19 Gaseous masses in rotation, 206, 221 Gaseous state, nature of, 95 equipartition of energy in, 156 Gaunt, J. A., 309 Geodesy, 34 Geology, 150, 152 Gerasimovič, B. P., 321 Giant and Dwarf stars (defined), 276 Giant stars, internal constitution, 273, 290, 291, 310, 319 Globular clusters, 63, 65, 213, 216 and Plate IX (p. 63) origin of, 216 shape of, 213 Goldsbrough, G. R., 250 Graham, T., 158 Gravitation, law of, 41, 45, 78, 161 cause of, 76 Gravitational instability, 197, 210, 237, 245, 246 Great Bear (cluster), 173, 216, 217 (constellation), 32, 39 Great nebulae, _see_ Extra-galactic nebulae H.D. 1337, _see_ Pearce’s star Halley, E., 151 Halley’s comet, 247, 251 Halm, J., 163 Hayford, J. F., 34 Heat, nature of, 100 effect of, on electrical structures, 141, 144 transport of, in a star, 307 Heat-death, 329, 330 Helium atom, 110, 119, 185, 305 Helmholtz, H., 177, 285 Henderson, T., 33 Herschel, Sir John, 23, 24, 211 Herschel, Sir William, 18, 23, 24, 25, 26, 28, 65, 70, 211 Hertzsprung, E., 59, 223, 275 Hesperus, 17 Hess, V. F., 143 Highly penetrating radiation, 143, 144, 191, 298, 299 Hinks, A. R., 65 Holmes, A., 152 Hubble, E., 71, 73, 77, 83, 84, 202, 204, 206, 208, 210 Humason, M. L., 82 Huyghens, C., 23 Hydrogen atom, 110, 119, 130, 135, 146 annihilation of, 146, 147, 192 electron orbits in, 128, 130, 192 Hyperbola, 46 Instability, dynamical, 202 gravitational, 197, 210, 237, 245, 246 Interferometer, 261, 272 Interstellar matter, 29, 30, 63 Interstellar space, temperature of, 102 Inverse square law, (electric), 129 (gravitational), 44, 45, 47 (luminosity), 24, 33 Invisible radiation, 115, 258, 259 Irregular nebulae, 206 Irregular variables, 55, 58 Island universes, 28, 31, 68 Isotopes, 118 Jeffreys, H., 155, 225, 226, 239 Jupiter, 4, 16, 17, 19, 207 birth of, 240 ff., 243, 244 rotation of, 168, 225 satellites of, 4, 23, 196, 240, 241, 243, 250 size of, 17 temperature of, 21 weight of, 45 _K_-ring of electrons in atom, 134, 138, 289, 291, 292, 302, 304, 318 Kant, I., 176, 230, 231 Kapteyn, J. C., 27, 65, 212, 214 Kelvin, Lord, 177, 285 Kepler, J., 5, 33, 46 Klein, O., 146, 148 Kolhörster, W., 143 Kramers, H. A., 309, 310 Kruger 60, 48, 278, 279, 280, 317 system of, 267, 279, 280