In 1866 Jenkin was appointed to the professorship of Engineering in University College, London. Two years later his prospects suddenly improved; the partnership began to pay, and he was selected to fill the Chair of Engineering, which had been newly established, in Edinburgh University. What he thought of the change may be gathered from a letter to his wife: 'With you in the garden (at Claygate), with Austin in the coach-house, with pretty songs in the little low white room, with the moonlight in the dear room upstairs--ah! it was perfect; but the long walk, wondering, pondering, fearing, scheming, and the dusty jolting railway, and the horrid fusty office, with its endless disappointments, they are well gone. It is well enough to fight, and scheme, and bustle about in the eager crowd here (in London) for awhile now and then; but not for a lifetime. What I have now is just perfect. Study for winter, action for summer, lovely country for recreation, a pleasant town for talk.'
The liberality of the Scotch universities allowed him to continue his private enterprises, and the summer holiday was long enough to make a trip round the globe.
The following June he was on board the Great Eastern while she laid the French Atlantic cable from Brest to St. Pierre. Among his shipmates were Sir William Thomson, Sir James Anderson, C. F. Varley, Mr. Latimer Clark, and Willoughby Smith. Jenkin's sketches of Clark and Varley are particularly happy. At St. Pierre, where they arrived in a fog, which lifted to show their consort, the William Cory, straight ahead, and the Gulnare signalling a welcome, Jenkin made the curious observation that the whole island was electrified by the battery at the telegraph station.
Jenkin's position at Edinburgh led to a partnership in cable work with Sir William Thomson, for whom he always had a love and admiration.
Jenkin's clear, practical, and business-like abilities were doubtless an advantage to Sir William, relieving him of routine, and sparing his great abilities for higher work. In 1870 the siphon recorder, for tracing a cablegram in ink, instead of merely flashing it by the moving ray of the mirror galvanometer, was introduced on long cables, and became a source of profit to Jenkin and Varley as well as to Sir William, its inventor.
In 1873 Thomson and Jenkin were engineers for the Western and Brazilian cable. It was manufactured by Messrs. Hooper & Co., of Millwall, and the wire was coated with india-rubber, then a new insulator. The 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 ANDMAGNETISM, 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 ingenious 'curb-key' for sending signals automatically through a long cable; but although tried, it was not adopted. His most important invention was Telpherage, a means of transporting goods and passengers to a distance by electric panniers supported on a wire or conductor, which supplied them with electricity.
It was first patented in 1882, and Jenkin spent his last years on this work, expecting great results from it; but ere the first public line was opened for traffic at Glynde, in Sussex, he was dead.
In mechanical engineering his graphical methods of calculating strains in bridges, and determining the efficiency of mechanism, are of much value. The latter, which is based on Reulaux's prior work, procured him the honour of the Keith Gold Medal from the Royal Society of Edinburgh. Another successful work of his was the founding of the Sanitary Protection Association, for the supervision of houses with regard to health.
In his leisure hours Jenkin wrote papers on a wide variety of subjects.
