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Such needle instruments are, up to the present day, employed in Great Britain. At the principal telegraph station, in London, there are now not less than thirty double, and four single needle instruments in use.
About a week before the above-mentioned first and perfectly successful trial of telegraphing by Cooke and Wheat-stone in England, Steinheil, at Munich, had completed the junction of his house in the Lerchenstrasse with the building of the Academy of Sciences, and with the Royal Observatory at Bogenhausen, by means of 36,000 feet of wire for conducting the current from a magneto-electric machine both ways, the wires being suspended in the air. He occasionally signalised between these places, having contrived to make a deflecting needle either strike a bell or mark black dots on a stripe of paper. It was here that Steinheil first applied his so highly valued discovery that the earth may serve for conducting the return current, so that one half of the suspended wires became useless.
Already, in 1833, the Cabinet of natural philosophy,, of the University at Göttingen, had been, by means of wires in the air, united by Professor Wilhelm Weber, with the Astronomical Observatory, distant 3,000 feet, to
