Staff system--Interlocking--Signalling operations--Power signalling--Pneumatic signalling--Automatic signalling 200 Chapter XII.--OPTICS. Lenses--The image cast by, _236_. Conjugate foci, 262. Cornet, 308. Corti, rods of, 274. Coxwell, 348. Cream separator, 381, _383_. Current, reversal of electric, _130_, 131; transformation of, 124. Cushioning of steam, 55. Cycle, gearing of, 439. Cylinder, hydraulic press, _363_; steam, _49_. Danes, 382. Dead point, 47. De Brouwer stoker, 401. Detector in Chubb lock, 435. Diving-bell, _332_; simple, _333_, _334_. Diving-dress, 335. Direction of current.