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 Hooper left Plymouth in June, and after touching at Madeira, where Sir William was up 'sounding with his special toy' (the pianoforte wire) 'at half-past three in the morning,' they reached Pernambuco by the beginning of August, and laid a cable to Para.

During the next two years the Brazilian system was connected to the West Indies and the River Plate; but Jenkin was not present on the expeditions. While engaged in this work, the ill-fated La Plata, bound with cable from Messrs. Siemens Brothers to Monte Video, perished in a cyclone off Cape Ushant, with the loss of nearly all her crew. The Mackay-Bennett Atlantic cables were also laid under their charge.

As a professor Jenkin's appearance was against him; but he was a clear, fluent speaker, and a successful teacher. Of medium height, and very plain, his manner was youthful, and alert, but unimposing. Nevertheless, his class was always in good order, for his eye instantly lighted on any unruly member, and his reproof was keen.

His experimental work was not strikingly original. At Birkenhead he made some accurate measurements of the electrical properties of materials used in submarine cables. Sir William Thomson says he was the first to apply the absolute methods of measurement introduced by Gauss and Weber. He also investigated there the laws of electric signals in submarine cables. As Secretary to the British Association Committee on Electrical Standards he played a leading part in providing electricians with practical standards of measurement. His Cantor lectures on submarine cables, and his treatise on Electricity and Magnetism, published in 1873, were notable works at the time, and contained the latest development of their subjects.

He was associated with Sir William Thomson in an