Jupiter, 26, 68 mass of, 235 satellites of, 149, 178 rotation of, 219 orbital velocity of, 251, 265 size of, 235 distance from sun, 242, 251 density of, 242 and comets, 305 Kant, 317 Kelvin, Lord, 43, 71, 77, 80, 95, 216, 227 on aether, 56-7 on vortex atom, 63 on compressible aether, 291, 315 on light, 151 Kepler's laws, 32 first, 33, 256-9 second, 36, 260-2 third, 37, 263-5 on vortex motion, 221-2 Kinetic energy, 89 electro, 217 Kirchhoff, 43 Laplace, 317 nebular hypothesis, 317 Larmor, Dr., 22, 44, 56, 63, 93, 163 on electrons, 284 on aetherial physics, 22, 327-9 Lavoisier, 42 Law of gravitation, 24 of inverse squares, 27 Laws of electricity, 184 of light, 145 of heat, 113 of motion, 9, 15, 233 Lead, 88, 333 Lebedew, 32, 76, 153 Le Verrier, 25 discovery of Neptune, 25 Leyden jar, 157 Liebnitz, 223 Light, 75 a mode of motion, 122 corpuscular theory of, 123 undulatory theory of, 123, 136 electro-magnetic theory of, 156 path of a ray of, 144 intensity of, 145 reflection of, 136 refraction of, 135 aberration of, 149 composition of, 139 velocity of, 148 zodiacal, 277 transverse vibration of, 130 Lines of force, electric, 173 magnetic, 201-3 Liquefaction of gases, 47 Liquid air, 47 Liquids, 48 Little Bear, 307 Dog, 307 Lockyer, 109 Lodge, Dr., 219 on aether density, 69 on aether, 284, 289, 328, 332 on electric inertia, 330 on electricity, 64, 69, 284, 285 on force, 17 on gravitation, 283 Lorentz on light, 154 Lyra, 307 MacLaurin, 2, 10, 17 Magnesium, 79 Magnet, 21 Magnets, bar, 199 moving, 211 Magnetic axis, 202 field, 199 lines of force, 200 shells, 205 equator, 202 induction, 199 variation, 208 molecules of, 193 polarity, 194 Magnetism of earth, 207-12 of planets, 211 cause of solar, 211 Ampère's theory of, 193 Mars, 68, 79 a magnet, 196 rotation of, 219 size of, 236 orbital velocity of, 251 satellites of, 178 orbit of, 33 Mass, 27, 53, 187 of earth, 235, 242 of planets, 235, 242 of sun, 190 Matter, elements of, 40 properties of, 42, 50 and motion, 41, 322 conservation of, 42 divisibility of, 44 four states of, 48 aetherial basis of, 48, 333 physical constitution of, 334 Maxwell, J. C., 43, 73, 85, 151, 211 on physical lines of force, 168, 203-5, 288 on aether, 59, 206 on magnetism, 205 on electro-kinetic energy, 180, 217 on aether, 58 Mayer, 84, 86, 114, 118 McCullagh, 75 Mechanical energy, 87 Medium, Descartes on a, 221 Kepler on a, 222 Mercury, 68, 79 a magnet, 196 rotation of, 219 eccentricity of orbit, 33 mass of, 242 orbital velocity of, 251 Meteorites, 95, 118 Meteors, 31, 85, 118 Michelson and Morley, 7, 67 Milky way, 79, 309, 314 Molecules, 44 Momentum, 20 Moon, 61