From 1858 to 1864, the Company were engaged in the difficult task of raising fresh funds, and in endeavouring to secure grants from the British and American Governments. Their men of science, meanwhile, were devising improvements in the form of cable, and contriving fresh apparatus to facilitate its submersion. Eventually the Telegraph Construction and Maintenance Company, an union of the Gutta Percha Company with the celebrated firm of Glass and Elliott, constructed an entirely new cable, which was not only costlier, but thicker and stronger than the preceding one. The conductor, three hundred pounds per mile, and one-seventh of an inch thick, consisted of seven No. 18 copper wires, each one-twentieth of an inch in thickness. The core or heart of the cable, says a writer in "Chambers's Encyclopædia," was formed of four layers of gutta percha alternating with four of Chatterton's compound (a solution of gutta percha in Stockholm tar); the wire and conductor being seven hundred pounds per mile, and nine-twentieths of an inch thick. Outside this was a coating of hemp or jute yarn, saturated with a preservative composition; while the sheath consisted of ten iron wires, each previously covered with five tarred Manilla yarns. The whole cable was an inch and one eighth thick, weighed thirty-five and three-quarter hundredweights per mile, and was strong enough to endure a breaking strain of seven tons and three-quarters. During the various processes of manufacture, the electrical quality of the cable was tested to an unusual extent. The portions of finished core were tested by immersion in water at various temperatures; next submitted to a pressure of six hundred pounds to the square inch, to imitate the ocean pressure at so great depth; then the conducting power of the copper wire was tested by a galvanometer; and various experiments were also made on the insulating property of the gutta percha. The various pieces having been thus severely put to the proof, they were spliced end to end, and the joints or splicings tested. In a word, nothing was left undone that could insure the success or guarantee the stability of the new cable.
When completed, the cable measured two thousand three hundred miles, and weighed upwards of four thousand tons. It was felt that such a burden could only be intrusted to Brunel's "big ship," the _Great Eastern_. For this purpose three huge iron tanks were built, in the fore, middle, and aft holds of the vessel, each from fifty to sixty feet in diameter, and each twenty and a half feet in depth; and in these the cable was deposited in three vast coils.