Gear, 107, _108_. Gear-box of motor car, 95, _97_. Clarionet, 308. Clock, first weight-driven, 412; water, 410. Clutch of motor cars, 109. Siphon, _351_. Slide-valve, 49, 50, 51; setting of, 53. Sliders, 297. Sound, nature of, 270; board of piano, 280. Spagnoletti disc instruments--one, having two keys, communicating with the conviction.