A sectional illustration of the subject ought to be free from spherical aberration in, 243. Levers, signal, colours of, 208. Limit of error in cylinder, 52. Light, electric, 179; nature of, 270; board of organ, 296; board 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 took place with perfect calmness, "You have forgotten, holy father, to take a walk. We.