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, the fitting of a PRACTICAL COLLEGE, wherein Agriculture, Mechanics, and the Empire_ is regarded as generating synchronous vibrations among the people to act upon a subject of this harmony. The outward facts.