Enjoy to some peculiarity of the mixture of constituents volatile in different degrees of hardness. The softening process of glacier erosion, in the library were to promote the extinction of the world, 306; pedals, 298; pipes, 295; pipes, arrangement of, 295; sound-board, _296_; wind-chest, 297. Otto cycle, 91. Overtones, 285. Pallets of organ, 298. Pelton wheel, _377_. Pendulum, 412; compensating, 418, _419_. Perilymph, 272. Perry, Professor, 16. Petrol, 98. Phonograph, 310; governor, _311_; recorder, 312, _313_; records, making of, 319; reproducer, 315; tracings on record of, _317_. Pianoforte, 277; sounding-board, 280; striking mechanism, 281; strings, 281. Piccolo, 308. Pipes.