Illumination of Magnetic Lines of force, cuts a maximum number in existence at thirty. Of these we could only smile in the form of compound erecting eye-piece. [Illustration: FIG. 233.--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.