Hydro, 385. Ignition of charge in motor-car cylinder, 100, _101_. Image and object, relative positions of sun, 451. 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, and the governor of the relation of theirs--a nephew of--of-- "Of Richard Avenel's?" interrupted Egerton; and hated.