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The British Government promised Mr. Field a subsidy of £1,400 a year, and the loan of ships to lay the cable. On 10 June 1858 the fleet sailed for mid-Atlantic (Bright's plan was now adopted), but again failure ensued, and the ships returned to Plymouth ; though one section of the directors was ready to abandon the whole scheme, it was finally decided to make one further attempt. A member of a political party requested the defendant to suspend a political banner, which he furnished, across one of the principal streets in the borough of Dubois, between the Commercial Hotel and the Deposit National Bank. Sir William (then Professor) Thomson first solved the difficulty by his invention of the 'mirror galvanometer,' and rendered at the same time the first Atlantic cable company a commercial success. There was another consideration, however, which at this time was rather a puzzle. In overland lines the current traverses the wire suddenly, like a bullet, and at its full strength, so that if the current be sufficiently strong these instruments will be worked at once, and no time will be lost. He descended in their midst like the very genius of electricity, and helped them out of all their difficulties.

Next summer a steamboat was fitted out for the purpose, and the cable was submerged. The first clear message was sent through the cable on 13 Aug., and it continued working till 20 Oct., during which period 732 messages passed through the cable, and then it finally broke down ; probably the insulation had given way owing to the excessively strong currents used at first in working it. Till now the enterprise had been purely American, and the funds provided by American capitalists, with the exception of a few shares held by Mr. J. W. Brett. He induced the American Government to despatch Lieutenant Berryman, in the Arctic, and the British Admiralty to send Lieutenant: Dayman, in the Cyclops, to make a special survey along the proposed route of the cable. The speed of a signal through the conductor of a submarine cable is thus diminished by a drag of its own making. That is to say, in any particular cable the speed of a signal is diminished to one-fourth if the length is doubled, to one-ninth if it is trebled, to one-sixteenth if it is quadrupled, and so on. The siphon and reservoir are together supported by an ebonite bracket, separate from the rest of the instrument, and insulated from it; that is to say, electricity cannot escape from them to the instrument.

The Morse and other instruments, however suitable for land lines and short cables, were all but useless on the Atlantic line, owing to the retardation of the signals; but the mirror instrument sprang out of Thomson's study of this phenomenon, and was designed to match it. The best operators cannot send over thirty-five words per minute by hand, but a hundred and twenty words or more per minute can be transmitted by an automatic sender, and the recorder has been found on land lines and short cables to write off the message at this incredible speed. It appeared to these far-sighted politicians that England, the hereditary foe, was 'literally crawling under the sea to get some advantage over the United States.' The Bill was only passed by a majority of a single vote. He solicited an equal help from Congress, but a large number of the senators, actuated by a national jealousy of England, and looking to the fact that both ends of the line were to lie in British territory, opposed the grant. He at once adopted the scheme of Gisborne as a preliminary step to the vaster undertaking, and promoted the New York, Newfoundland, and London Telegraph Company, to establish a line of telegraph between America and Europe.

The accuracy of Thomson's law was disputed in 1856 by Dr. Edward O. Wildman Whitehouse, the electrician of the Atlantic Telegraph Company, who had misinterpreted the results of his own experiments. Faraday had said to Mr. Field that a signal would take 'about a second,' and the American was satisfied; but Professor Thomson enunciated the law of retardation, and cleared up the whole matter. Mr. Field himself supplied a quarter of the needed capital; and we may add that Lady Byron, and Mr. Thackeray, the novelist, were among the shareholders. But all these instruments have one great drawback for delicate work, and, however suitable they may be for land lines, they are next to useless for long cables. The cable consisted of a strand of seven copper wires, one weighing 107 pounds a nautical mile or knot, covered with three coats of gutta-percha, weighing 261 pounds a knot, and wound with tarred hemp, over which a sheath of eighteen strands, each of seven iron wires, was laid in a close spiral.

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