Page:Popular Science Monthly Volume 3.djvu/415

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THE

POPULAR SCIENCE

MONTHLY.



AUGUST, 1873.



ELECTRIC TELEGRAPHS.[1]
By Prof. A. P. DESCHANEL.

THE discovery that electricity could be transmitted instantaneously to great distances at once suggested the idea of employing it for signalling. Bishop Watson performed several experiments of this kind in the neighborhood of London, the most remarkable being the transmission of the discharge of a Leyden jar through 10,600 feet of wire suspended between wooden poles at Shooter's Hill. This was in 1747. A plan for an alphabetical telegraph to be worked by electricity is minutely described in the Scot's Magazine for 1753, but appears to have been never experimentally realized. Lesage, in 1774, erected at Geneva a telegraph-line, consisting of twenty-four wires connected with the same number of pith-ball electroscopes, each representing a letter. Reusser, in Germany, proposed, in the same year, to replace the electroscopes by spangled panes exhibiting the letters themselves. The difficulty of managing frictional electricity was, however, sufficient to prevent these and other schemes founded on its employment from yielding any useful results. Volta's discoveries, by supplying electricity of a kind more easily retained on the conducting wires, afforded much greater facilities for transmitting signals to a distance. Several suggestions were made for receiving-apparatus to exhibit the effects of the currents transmitted from a voltaic battery. Sommering, of Munich, in 1811, proposed a telegraph, in which the signals were given by the decomposition of water in thirty-five vessels, each connected with a separate telegraph-wire. Ampere, in 1820, proposed to utilize Œrsted's discovery by employing twenty-four needles, to be deflected by currents sent through the same number of wires; and Baron Schilling exhibited, in Russia, in 1832, a telegraphic model, in

  1. Abridged from Deschanel's "Natural Philosophy," Part III.: "Electricity and Magnetism."