Telegraphy and how to learn it; with brief chapters on elementary science, embracing various kinds of electricity, electrical measurements, thermo-frictional electricty, batteries, magnets and magnetism (1901)
Frederic, Wilson. [from old catalog] · Chicago, The Henneberry co · leaf 32
wo wires, in-sulated with gutta-percha orsealing wax, terminating inplatinum strips, which are in-troduced a little way into thetube. The tube is filled withwater slightly acidulated withsulphuric acid, and its orificeis immersed in the same kind of liquid,which partly fills the bottle. When… … 30 TELEGRAPHY. measuring current-strength is the magneticneedle, which, besides its ordinary use asa galvanoscope, performs the still more im-portant office of a galvanometer. The sim-ple magnetic needle, used as already de-scribed, answers tolerably well when thecurrents are strong, but it is not…
Telegraph
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