Natural facts, as I gaze and breathe through a train 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, 56. Faraday, Michael, 159. Field, magnetic, 159; magnets, 171; ring, 174. Filters, 374; Maignen, _373_; Berkefeld, 374. Filtration beds, 372. Flute.