Page:Heroes of the telegraph (IA cu31924031222494).djvu/25

 destined to give way to those actuated by the voltaic current, as the chemical mode of signalling was superseded by the electro-magnet. In 1820 the separate courses of electric and magnetic science were united by the connecting discovery of Oersted, who found that a wire conveying a current had the power of moving a compass-needle to one side or the other according to the direction of the current.

La Place, the illustrious mathematician, at once saw that this fact could be utilised as a telegraph, and Ampère, acting on his suggestion, published a feasible plan. Before the year was out, Schweigger, of Halle, multiplied the influence of the current on the needle by coiling the wire about it. Ten years later, Ritchie improved on Ampère's method, and exhibited a model at the Royal Institution, London. About the same time, Baron Pawel Schilling, a Russian nobleman, still further modified it, and the Emperor Nicholas decreed the erection of a line from Cronstadt to St. Petersburg, with a cable in the Gulf of Finland but Schilling died in 1837, and the project was never realised.

In 1833-5 Professors Gauss and Weber constructed a telegraph between the physical cabinet and the Observatory of the University of Göttingen. At first they used the voltaic pile, but abandoned it in favour of Faraday's recent discovery that electricity could be generated in a wire by the motion of a magnet. The magnetic key with which the message was sent Produced by its action an electric current which, after traversing the line, passed through a coil and deflected a suspended magnet to the right or left, according to the direction of the current. A mirror attached to the suspension magnified the movement of the needle, and indicated the signals after the manner of the Thomson mirror galvanometer. This telegraph, which was large