Galaxy. _See_ Milky Way. Galilean telescope, 109 Galileo, 55, 109, 172, 197, 206, 232-235, 242 Galle, 24, 211, 244 Ganymede, 233-234 Gas light, spectrum of, 122 Gegenschein, 181-182 "Gem" of meteor ring, 271 Gemini, or the Twins (constellation), 22, 296-297 Geminorum, [z] (Zeta), 304 Geometrical groupings of stars, 292 "Giant" planet, 230, 238-239 Gibbous, 183, 185 Gill, Sir David, 211, 258, 291, 317-318 Gold, 145 Goodricke, 307 Gore, J.E., 63, 285, 303, 307-308, 310, 323-324, 331, 337, 347 Granulated structure of photosphere, 134 Gravitation (or gravity), 39, 41-45, 128, 306 Greek ideas, 18, 158, 161-162, 171, 186, 197 Green (rays of light), 121 Greenwich Observatory, 143-144, 232, 255, 303 Gregorian telescope, 113-114 Grimaldi (lunar crater), 199 "Grindstone" theory, 319-322 "Groombridge, 1830," 281-282, 326, 330 Groups of stars, 306-307 Grubb, Sir Howard, 118 _Gulliver's Travels_, 224 Hale, G.E., 119, 140 Half moon, 183, 185 Hall, Asaph, 223 Hall, Chester Moor, 115 Halley, Edmund, 91, 255, 264-265, 306 Halley's Comet, 255, 264-265 Haraden Hill, 91 Harvard, 118, 302 Harvest moon, 190-192 Hawaii, 221 Heat rays, 127 Heidelberg, 226, 232 Height of lunar mountains, how determined, 201 Height of objects in sky, estimation of, 196 Helium, 138, 145, 182 Helmholtz, 128, 335 Hercules (constellation), 295 Herod the Great, 101-102 Herodotus, 84 Herschel, A.S., 269 Herschel, Sir John, 92, 322 Herschel, Sir William, 22, 36, 114-115, 204, 213, 235, 283, 292, 308, 319-320, 326-328 Herschelian telescope, 114, 119 Hesper, 109 Hesperus, 150 Hevelius, 111 Hezekiah, 85 Hi, 83 Hindoos, 18 Hipparchus, 106, 177, 290, 311 Ho, 83 Holes in Milky Way, 321-323 Holmes, Oliver Wendell, 213 Homer, 223 Horace, Odes of, 106 Horizon, 159 Horizontal eclipse, 169 Horrox, 44, 151-152 Hour Glass Sea, 212 Huggins, Sir William, 94, 125, 317 Humboldt, 270 "Hunter's moon," 192 Huyghens, 111-112, 240, 242-243 Hyades, 296-297, 307 Hydrocarbon gas, 254 Hydrogen, 94, 131, 138, 140, 144, 156, 182, 254 Ibrahim ben Ahmed, 270 Ice-layer theory: Mars, 219; moon, 205, 219 Illusion theory of Martian canals, 219 Imbrium, Mare, 197 Inclination of orbits, 36-37 Indigo (rays of light), 121 Inferior conjunction, 147, 149 Inferior planets, 20, 22, Chap. XIV., 229 Instruments, pre-telescopic, 106-107, 172 International photographic survey of sky, 290-291 Intra-Mercurial planet, 25-26 _Introduction to Astronomy_, 31 Inverted view in astronomical telescope, 116-117 Io, 233-234 Iridum, Sinus, 197 Iron, 145, 254 _Is Mars Habitable?_ 221 Jansen, 108 Janssen, 94, 236, 258 Japetus, 240 Jessenius, 89 Job, Book of, 299 Johnson, S.J., 103, 340 Josephus, 101, 262 Juno, 225