INDEX.

Hele, Peter, 412. Helmet, diver's, 336 . Helmholtz, 274, 308. Hero of Alexandria, 74. Herschel, 261. Hertz, Dr., 138. Hertzian waves, 138. Hot-water supply, 386. Hour-hand train in timepieces, 429 . Household water supply, 364. Hughes type-printer, 134. Hydraulic press, 361, 362 . Hydro, 385. Ignition of charge in motor-car cylinder, 100, 101 . Image and object, relative positions of, 239; distortion of, 245. Incandescent gas mantle, 407; electric lamp, 179. Incus, 272. Index mechanism of water-meter, 37. Indicator of electric bell, 119. Induction coil, 121; uses of, 125. Injector, 39; Giffard's, 41 ; principle of, 40;