272; round, in ear, 272; round, in ear, 272. Wireless telegraphy, 137; advance of, 145; receiver, 140, 141; syntonic, 143; transmitter, 138, _139_. Yale lock, 436. Combustion, 26, 393; perfect, 28. Compensating gear, 107, _108_. Gear-box of motor cars, 109. Siphon, _351_. Slide-valve, 49, 50, 51; setting of, 53. Sliders, 297. Sound, nature of, 270; board of organ, 298. Pelton wheel, _377_. Pendulum, 412; compensating, 418, _419_. Perilymph, 272. Perry.