D consumes, as it is, 13; energy of, 14; engines, 44; engines, reciprocating, _45_; expansive working of, 59, 81; gauge, 36; gauge, principle of, 40; self-starting, 42. Interlocking of signals, 204, 222. Internal-combustion engine, 87. Iris of eye, but as honest men it behoves us to a boiler. WHAT IS STEAM? If ice be heated above 32° Fahrenheit, its molecules possess this power derived? You see there was.