Water-gauge--The steam-gauge--The water supply to, 39; water-tube, 21. Brakes, hydraulic, 188; motor car, 105. Coal, as fuel, 15; gas, 394; gas plant, _396_; gas, purification of, 397. Cochlea, 273. Coherer, 140. Coil, Ruhmkorff, 121. Coke, 395. Combinations in Chubb lock, 436; Yale lock, 436. Combustion, 26, 393.