He
introduced a unit of resistance, namely, a foot of copper wire weighing
one hundred grains, and showed how it might be applied to measure the
length of wire by its resistance. He was awarded a medal for his paper
by the Society. The same year he invented an apparatus which enabled
the reading of a thermometer or a barometer to be registered at a
distance by means of an electric contact made by the mercury. A sound
telegraph, in which the signals were given by the strokes of a bell, was
also patented by Cooke and Wheatstone in May of that year.
The introduction of the telegraph had so far advanced that, on September
2, 1845, the Electric Telegraph Company was registered, and Wheatstone,
by his deed of partnership with Cooke, received a sum of L33,000 for the
use of their joint inventions.
>From 1836-7 Wheatstone had thought a good deal about submarine
telegraphs, and in 1840 he gave evidence before the Railway Committee of
the House of Commons on the feasibility of the proposed line from Dover
to Calais. He had even designed the machinery for making and laying the
cable. In the autumn of 1844, with the assistance of Mr. J. D.
Llewellyn, he submerged a length of insulated wire in Swansea Bay, and
signalled through it from a boat to the Mumbles Lighthouse.
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