Gravity Battery. (See [Battery, Gravity].)
Grounded Circuit. (See [Circuit, Grounded].)
Ground-plate. (See [Plate, Ground].)
Ground-wire. The contact of a conductor, in an electric circuit, with the earth. It permits the escape of current if another ground-wire exists.
Guard Tube. A tube inserted in a wooden or brick partition to insulate wires that may pass through it. These tubes are made of porcelain, gutta-percha, compositions of a non-conducting nature, and fibre.
Gutta-percha. Caoutchouc treated with sulphur to harden it; sometimes called vulcanized rubber or vulcanite. It is a product obtained from tropical trees, and when properly treated it is a valuable insulator in electrical work, particularly in submarine cables, since it offers great resistance to the destructive agencies of the ocean’s depths.
H
Hand Generator. A magneto-generator driven by hand for the generation of light currents.
Harmonic Currents. (See [Currents, Harmonic].)
Harmonic Receiver. A receiver containing a vibrating reed acted on by an electro-magnet. Such a reed answers only to impulses tuned to its pitch.