Lever of first kind, 224 Lever, no gain of power in it, 227 Lever of second kind, 231 Lever of third kind, 232 Leyden jar, 384, 385 Life-boats, 139 Light, nature of, 334 Light, sources of, 335 Light, diffusion of, 337 Light, velocity of, 338 Light, reflection of, 340 Light, refraction of, 345 Light moves in straight lines, 336 Light shown to be compound, 360 Light, colors in, 360 Light, recomposition of, 362 Light, chemistry of, 369 Lightning-rods, 393 Liquids, movability of their particles, 9, 57 Liquids, incompressibility of, 36 Liquids, attraction in, 56 Liquids, globular shape of drops of, 58 Liquids, cause of level surface of, 111 Liquids, pressure of, in proportion to depth, 121 Liquids, lateral pressure of, 123 Liquids, pressure of, equal in all directions, 125 Liquids, upward pressure as depth, 127 Liquids, in what like gases, 153 Liquids, friction of, in tubes, 197 Liquids, friction of, in streams, 198 Liquids, expansion of, by heat, 275 Loadstones, 397 Machines not sources of power, 222 Machinery, friction in, 245 Magic lantern, 351 Magdeburg hemispheres, 156 Magnetism, origin of term, 397 Magnetism, attraction of, 398 Magnetism, repulsion of, 401 Magnet, poles of, 399 Magnets, artificial, 403 Magnets, horseshoe, 404 Magnetic needle, 405 Malleability, 28 Man a tool-making animal, 247 Mariner's compass, 405 Matter distinguished from spirit, 1 Matter, effects of, on senses, 6 Matter, forms of, 7 Matter, nature of, 14 Matter, constitution of, 14 Matter, variety in properties of, 17 Matter, divisibility of, 18, 51 Matter, minute division of, 19 Matter, pores and spaces in, 22 Matter, relation of heat to spaces of, 23 Matter, inertia of, 48 Matter, impenetrability of, 45 Matter equally inclined to rest and motion, 50 Mechanical powers, real advantages of, 246 Mercury, freezing of, 318 Microscopes, 350 Microscopical animals, 19 Mirages, 347 Mirrors, 342 Mirrors, curved, 344 Moth's wing, 19 Motion, causes of, 181 Motion, universality of, 180 Motion, absolute and relative, 191 Motion, obstacles to, 192 Motion, reflection of, 206 Motion, compound, 212 Motion, curved, 213 Motion in orbits, 221 Motion disposed to be straight, 211 Motion, that of falling bodies projectile, 220 Motion and rest, 189 Momentum, 201 Mountains, size limited, 92 Nature, order in, 65 Near-sightedness, 355 Needle, magnetic, 399 Needle, declination of, 406 Needle, dip of, 407 Noise, how it differs from musical sound, 263 Non-conductors of heat, 298 Non-conductors of electricity, 375 Notes, musical, how produced, 264 Odors, minuteness of their particles, 19 Order in nature, 65 Papin's digester, 292 Pendulum, 208-210 Perpetual motion attempted, 118 Persia, accident to, 274