Coherer, 140. Coil, Ruhmkorff, 121. Coke, 395. Combinations in Chubb lock, 436; Yale lock, 436. Combustion, 26, 393; perfect, 28. Compensating gear, 107, _108_. Compound engines, 59; arrangement of, 295; sound-board, _296_; wind-chest, 297. Otto cycle, 91. Overtones, 285.