The Story of the Atlantic Telegraph

This was higher by forty degrees than the temperature of the Atlantic. The insulation is improved by cold; so that, if it remained perfect in this warm water, it could not fail in the icy depths of the ocean. After passing through such elaborate tests, all will be glad to see the final product of so much care and skill. As the long line begins to reel off from the great wheels and drums, we may examine it in its completed and more perfect form. It is only necessary to compare it with the cable laid in 1858, to show its immense superiority. A glance at the two as they appear on the preceding page will show that the cable had grown since first it was planted in the ocean, as if it were a living product of the sea. This growth had been in every part, from core to circumference. First, the central copper wire, which was the spinal cord, the nerve along which the centre current was to run, was nearly three times as large as before. Prof. Thomson had long seen that this was a condition of success. While joining heartily in the attempts of 1857-58, he felt that an error was committed in the smallness of the cable; that the copper conductors and the gutta-percha covering should both be much larger. The old conductor was a strand consisting of seven fine wires, six laid round one, and weighed only one hundred and seven pounds to the mile. The new was composed of the same number of wires, but weighed three hundred pounds to the mile. As it was made of the finest copper that could be obtained in the world, it was a perfect conductor. Next, to secure insulation, it was first imbedded for solidity in Chatterton's compound, a preparation impervious to water, and then covered with four layers of gutta-percha, which were laid on alternately with four thin layers of Chatterton's compound. The old cable had but three coatings of gutta-percha, with nothing between. Its entire insulation weighed but two hundred and sixty-one pounds to the mile, while that of the new weighed four hundred pounds.