Nature, experience the well-spring of all knowledge of, 181; fashions of, 64; first knowledge of, instinctive, 189; general interconnexion of, 182; has many sides, 217; her forces compared to purposes, 14-15; likened to a good man of business, 15; the economy of her actions, 15; how she appears to other animals, 83 et seq.; inquiry of, viewed as a torture, 48-49; view of, as something designedly concealed from man, 49; like a covetous tailor, 9-10; magic powers of, 189; our view of, modified by binocular vision, 82; the experimental method a questioning of, 48. Negro hamlet, the science of a, 237. Neptune, prediction and discovery of the planet, 29. New views, 296 et seq. Newton, describes polarisation, 242; expresses his wealth of thought in Latin, 341; his discovery of gravitation, 225 et seq.; his solution of dispersion, 362; his principle of the equality of pressure and counterpressure, 191; his view of light, 227-228; on absolute time, 204; selections from his works for use in instruction, 368; also 270, 274, 279, 285, 289. Nobility, they displace Latin, 342. Notation, musical, mathematically illustrated, 103-104. Numbers, economy of, 195; their connexion with consonance, 32. Numerical mysticism, 33. Nursery, the questions of the, 199. Observation, 310. Observation, in science, 261. Ocean-stream, 272. Oettingen, Von, 103. Ohm, on electric currents, 249. Ohm, the word, 343. Oil, alcohol, water, and, employed in Plateau's experiments, 4; free mass of, assumes the shape of a sphere, 12; geometrical figures of, 5 et seq. One-eyed people, vision of, 98. Ophthalmoscope, 18. Optic nerves, 96. Optimism and pessimism, 234. Order of physics, 197. Organ, bellows of an, 135. Organic nature, results of Darwin's studies of, 215 et seq. See _Adaptation_ and _Heredity_. Oriental world of fables, 273. Orientation, sensations of, 282 et seq. Oscillation, centre of, 147 et seq. Ostwald, 172. Otoliths, 301 et seq. Overtones, 28, 40, 349. Ozone, Schöbein's discovery of, 271. Painted things, the difference between real and, 68. Palestrina, 44. Parameter, 257. Partial tones, 390. Particles, smallest, 104. Pascheles, Dr. W., 285. Paulsen, 338, 340, 373. Pearls of life, strung on the individual as on a thread, 234-235. Pencil surpasses the mathematician in intelligence, 196. Pendulum, motion of a, 144 et seq., increased motion of, due to slight impulses, 21; electrical, 110. Percepts, of like form, 390. Periodical, changes, 181; series, 256. Permanent, changes, 181, 199; elements of the world, 194. Perpetual motion, a, 181; defined, 139; impossibility of, 139 et seq.; the principle of the, excluded, 140 et seq.; excluded from general physics, 162. Personality, its nature, 234-235.