from the monocle which Thomson, being short-sighted, wore round his neck on a ribbon.
The first attempt to lay the Atlantic cable was made in 1857 and failed, and in subsequent endeavours Thomson played a more active part. His discovery that the conductivity of copper was greatly affected — to an extent of 30 or 40 per cent. — by its purity led him to organise a system of testing conductivity at the factory where the additional lengths were being made, and he was in charge of the test-room on board the Agamemnon, which in 1858 was employed in cable-laying in the Atlantic. Whitehouse was unable to join the expedition, and Thomson, at the request of the directors, also undertook the post of electrician without any recompense, though the tax on his time and energies was great.
After various mishaps, success crowned the promoters' efforts. Throughout the voyage Thomson's mirror galvanometer was used for the continuity tests and for signalling to shore, with a battery of seventy-five Daniell's cells. The continuity was reported perfect, and the insulation improved on submersion. On 5 Aug. the cable was handed over to Whitehouse and reported to be in perfect condition. Clear messages were interchanged, but the insulation was soon found to be giving way, and on 20 Oct., after 732 messages had been conveyed, the cable spoke no more. The cause of the collapse was the mistaken use in defiance of Thomson's tested conclusions, by Whitehouse, of induction coils working at high voltage. Thomson's self-abnegation and forbearance throughout this unfortunate afiair are almost beyond belief. He would not suffer any personal slight to interfere with his devotion to a scientific enterprise.
During the next eight years Thomson sought to redeem the defeat. Throughout the preparations for the cables of 1865 and 1866, the preliminary trials, the interrupted voyage of 1865 when 1000 miles were lost, the successful voyage of 1866, when the new cable was laid and the lost one recovered and completed, Thomson was the ruling spirit, and his advice was sought and followed. On his return from the triumphant expedition he was knighted. He had in the meantime made further improvements in conjunction with Cromwell Fleetwood Varley [q. v.]. In 1867 he patented the siphon recorder, and, in conjunction with Fleeming Jenkin [q. v.], the curb-transmitter. He was consulted on practically every submarine cable project from that time forth. In 1874 Thomson was elected president of the Society of Telegraph Engineers, of which, in 1871, he had been a foundation member and vice-president. In 1876 he visited America, bringing back with him a pair of Graham Bell's earliest experimental telephones. He was president of the mathematical and physical section of the British Association of that year at Glasgow. In the winter of 1860-1 Thomson had met with a severe accident. He fell on the ice when curling at Largs, and broke his thigh. The accident left him with a slight limp for the rest of his life.
Meanwhile much beside the submarine cable occupied Thomson's fertile mind, and his researches were incessant. In 1859-60 he was studying atmospheric electricity. For this end he invented the water-dropping collector, and vastly improved the electrometer, which he subsequently developed into the elaborate forms of the quadrant instrument and other types. He also measured electro-statically the electromotive force of a Daniell's cell, and investigated the potentials required to give sparks of different lengths in the air. At the same time he urged the application of improved systems of electric measurement and the adoption of rational units. In 1861 he cordially supported the proposal of Bright and Clark to give the names of ohm, volt, and farad to the practical units based on the centimetre-gramme-second absolute system, and on his initiative was formed the Committee of Electrical Standards of the British Association, which afterwards went far in perfecting the standards and the methods of electrical measurement. He was largely responsible for the international adoption of the system of units by his advocacy of them at the Paris Congress in 1881. He was an uncompromising advocate of the metric system, and lost no opportunity of denouncing the 'absurd, ridiculous, time-wasting, brain-destroying British system of weights and measures.'
A long research on the electrodynamic qualities of metals, thermoelectric, thermo-elastic, and thermomagnetic, formed the subject of his Bakerian lecture of 1856, which occupies 118 pages of the reprinted 'Mathematical and Physical Papers.' He worked long also at the mathematical theory of magnetism in continuation of Faraday's labours in diamagnetism. Thomson set himself to investigate Faraday's conclusions mathematically. As early as 1849 and 1850, with all the elegance of a mathematical disciple of Poisson
