Page:Heroes of the telegraph (IA cu31924031222494).djvu/85



On gaining a fellowship at his college, he spent some time in the laboratory of the celebrated Regnault, at Paris; but in 1846 he was appointed to the chair of natural philosophy in the University of Glasgow. It was due to the brilliant promise he displayed, as much as to the influence of his father, that at the age of twenty-two he found himself wearing the gown of a learned professor in one of the oldest Universities in the country, and lecturing to the class of which he was a freshman but a few years before.

Thomson became a man of public note in connection with the laying of the first Atlantic cable. After Cooke and Wheatstone had introduced their working telegraph in 1839; the idea of a submarine line across the Atlantic Ocean began to dawn on the minds of men as a possible triumph of the future. Morse proclaimed his faith in it as early as the year 1840, and in 1842 he submerged a wire, insulated with tarred hemp and india-rubber, in the water of New York harbour, and telegraphed through it. The following autumn Wheatstone performed a similar experiment in the Bay of Swansea. A good insulator to cover the wire and prevent the electricity from leaking into the water was requisite for the success of a long submarine line. India-rubber had been tried by Jacobi, the Russian electrician, as far back as 1811. He laid a wire insulated with rubber across the Neva at St. Petersburg, and succeeded in firing a mine by an electric spark sent through it; but india-rubber, although it is now used to a considerable extent, was not easy to manipulate in those days. Luckily another gum which could be melted by heat, and readily applied to the wire, made its appearance. Gutta-percha, the adhesive juice of the Isonandra gutta tree, was introduced to Europe in 1842 by Dr. Montgomerie, a Scotch surveyor in the service