Two years later it was greatly simplified by Schweigger, of
Halle; and there is reason to believe that but for the discovery of
electro-magnetism by Oersted, in 1824 the chemical telegraph would have
come into practical use.
In 1806, Ralph Wedgwood submitted a telegraph based on frictional
electricity to the Admiralty, but was told that the semaphore was
sufficient for the country. In a pamphlet he suggested the
establishment of a telegraph system with public offices in different
centres. Francis Ronalds, in 1816, brought a similar telegraph of his
invention to the notice of the Admiralty, and was politely informed that
'telegraphs of any kind are now wholly unnecessary.'
In 1826-7, Harrison Gray Dyar, of New York, devised a telegraph in which
the spark was made to stain the signals on moist litmus paper by
decomposing nitric acid; but he had to abandon his experiments in Long
Island and fly the country, because of a writ which charged him with a
conspiracy for carrying on secret communication. In 1830 Hubert Recy
published an account of a system of Teletatodydaxie, by which the
electric spark was to ignite alcohol and indicate the signals of a code.
But spark or frictional electric telegraphs were destined to give way to
those actuated by the voltaic current, as the chemical mode of
signalling was superseded by the electro-magnet.
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