Kant, cosmological speculations, 20-28, 60-62, 252, 254; tidal effects, 27, 84-5; Saturn's rings, 49; status of comets, 73 Kelvin, Lord, Lesage's theory of gravitation, 174; vortex-atoms, 187; dissipation of energy, 229; origin of life, 268, 280 Kepler, physical astronomy, 10 Kirkwood, objection to nebular hypothesis, 50, 51; effects of solar tidal friction, 67 Lambert, sidereal construction, 17-18 Langley, mass of meteoric infalls, 119 Laplace, hypothesis of planetary origin, 25, 29-31, 33, 36-42, 52-3, 58-9, 60-62, 235; Saturn's ring-system, 49; _Mécanique Céleste_, 57; status of comets, 73, 136 Larmor, scheme of molecular physics, 188; definition of ether, 189, 193 Lenard, cathode-rays, 157 Lesage, rationale of gravity, 172-3, 175 Lewis, masses of double stars, 226 Ligondès, scheme of planetary growth, 77-8, 81, 252; comets as survivals, 253, 256 Lockyer, Sir Norman, meteoritic hypothesis, 125-7; enhanced lines, 223 Lorentz, electrical hypothesis of gravity, 177-8, 185 Magellanic clouds, spiral conformation, 213 Marchand, plane of the zodiacal light, 263 Mars, rotation of, 47-8 Maxwell, origin of matter, 161; corpuscular theory of gravitation, 173 Mayer, J. R., effects of tidal friction, 87 Mercury, action upon of solar tides, 88, 96; eccentric orbit, 242 Meteoritic formation of planets, 28-9, 119-122, 125, 128, 131-3; of comets, 122-4; of nebulæ, 126-7, 134 Meteors, abundance, 119, 133; mineralogy, 121-2, 134; hyperbolic orbits, 133; attendance on the sun, 236 Meteor-swarms, progressive dispersal, 72, 124; constitution, 122-4, 128-131; primitive existence, 134 Milky Way, theories regarding, 16-17, 215; undeveloped condition, 201, 207; relation to sun's movement, 247 Mohl, protoplasm, 270 Moment of momentum, 23, 40, 44, 45, 65, 209 Moon, origin, 87-92, 97, 139, 145; retreat from the earth, 244 Moulton, nebular cosmogony, 44, 51, 82 Myers, systems of β Lyræ and U Pegasi, 109-110 Nebulæ, gaseous composition, 37, 153, 201, 205; illusory resolution, 53; spiral structure, 79-80, 106, 146, 190, 204-208, 211-214; classification, 199; development, 200-202, 205, 207-211; relation to stars, 202-3, 205; helium ingredient, 230, 255 Nebular hypothesis, propounded by Kant, 22-8; by Laplace, 29-31, 38, 52-3, 61; difficulties, 39-52, 54-6; amendments, 60-82 Nebulium, a constituent of nebulæ, 54, 153, 201 Neptune, retrograde system of, 43, 52, 237 Newcomb, transverse observation of the zodiacal light, 260 Newton, transmission of gravity, 184, 185 Nova Persei, nebulous appurtenance, 206 Perrine, new Jovian satellites, 240 Pezénas, notice of the counterglow, 259 Phobos, anomalous revolution, 47-8, 237 Phœbe, retrograde motion, 96, 237-8 Pickering, E. C., binary nature of V Puppis, 112; structural relations of the Looped Nebula, 213