Jenkin, Henry Charles Fleeming

(b. near Dungeness, Kent, England, 25 March 1833; d. Edinburgh, Scotland, 12 June 1885)

engineering.

Fleeming (pronounced “Fleming”) Jenkin was the only child of Charles Jenkin, a naval officer, and the former Henrietta Camilla Jackson, a political liberal and popular novelist. He received his early schooling in Edinburgh. His family, in reduced financial circumstances, lived in Frankfurt, Paris, and Genoa during the period 1846-1851; he received the M.A. degree from the University of Genoa in the latter year.

After ten years of employment in various British engineering firms, mainly in the design and manufacture of the earliest long submarine cables (such as that under the Red Sea) and the associated cablelaying equipment, Jenkin in 1861 formed a consulting engineering partnership in London. In the same year his close friend William Thomson initiated the Committee on Electrical Standards of the British Association for the Advancement of Science, of which Jenkin was appointed reporter. Jenkin’s lasting reputation in electrical science rests largely on his contributions to the work of this committee, through policy direction, participation in experiments, and the writing or editing of six reports between 1862 and 1869. Of major importance was the establishment of the ohm as an absolute unit of resistance, including the preparation of materials for construction of reliable resistance units, and the development of precision methods (0.1 percent) for resistance measurement. In 1867 he made the first absolute measurement of capacitance. Collaborators in the committee’s activities included Thomson, James Clerk Maxwell, Carey Foster, Latimer Clark, and Charles Wheatstone.

Taking part in numerous cable-laying expeditions after 1861, Jenkin often shared the consultant duties with Thomson. Of his thirty-five British patents, many on cable-laying inventions were held jointly with Thomson. The patents and consulting work eventually made him financially independent.

Jenkin was a man of extremely broad interests. In a long essay written in 1867 he advanced detailed arguments—based on animal breeding experiments, genetic probabilities, and contemporary estimates of the geological time scale —for rejecting the two principal evolution mechanisms (indefinite variation and natural selection) proposed by Darwin in the first four editions of The Origin of Species. Jenkin asserted that a large body of available evidence dictated two conclusions opposing Darwin’s views. First, the possible variations of an existing species must be considered as quite limited and “contained within a sphere of variation” centered on a norm. Second, the probability of favorable variations in a single individual becoming incorporated in a population must be slight, since such considered as quite limited and “contained within a sphere of variation” centered on a norm. Second, the probability of favorable variations are infrequent and their effect is diluted by the breeding of the rest of the population. The remainder of his essay questioned Darwin’s implicit assumption of the indefinite age of the earth. In the fifth (1869) edition, and in correspondence with others, Darwin acknowledged that he had modified some of his opinions substantially after reading Jenkin.

After 1876 Jenkin waged a vigorous campaign against unsanitary plumbing practices in Edinburgh and elsewhere, and he actively promoted the automated electric transport of industrial raw materials by monorail and cable car (telpherage.)

The Royal Society (London) elected Jenkin a fellow in 1865; the Royal Society of Edinburgh followed suit in 1869, and he was its vice-president in 1879. He was also a member of the Institution of Civil Engineers and held an honorary LL.D. from the University of Glasgow (1883).

BIBLIOGRAPHY

BIBLIOGRAPHY

Papers Literary, Scientific, etc. by the Late Fleeming Jenkin, F. R. S., Sidney Colvin and J. A. Ewing, eds., 2 vols. (London, 1887), contains, principally, the Stevenson memoir (see below) and Jenkin’s nontechnical writings. Of interest are a short note by Kelvin on Jen-kin’s contributions to electricity, a longer note by A. Ferguson on Jenkin’s contributions to sanitary reform, a concise list of Jenkin’s patents, and brief abstracts of all of his scientific and engineering papers.Electricity and Magnetism (London, 1873) is an elementary textbook that went through many English and foreign-language eds. Jenkin edited Reports of the Committee on Electrical Standards (London, 1873), which contains the six reports of the committee, a summary report by Jenkin, and Jenkin’s five lectures on submarine telegraphy to the Royal Society of Arts in 1866. His arguments for rejecting Darwin’s two main evolution mechanisms are in “The Origin of Species,” in NorthBritish Review,46, no. 92 (June 1867), 277-318.

Robert Louis Stevenson, Memoir of Fleeming Jenkin, was written, out of friendship for Jenkin and his wife, as a preface for the collected papers edited by Colvin and Ewing. Its first separate appearance was an American ed. (New York, 1887). Stevenson had studied under Jenkin at Edinburgh and became a lifelong friend. This book-length biography is an unusual account of an unusual man. Its principal technical information is in Jenkin’s letters written during cable-laying expeditions. It is included in most eds. of Stevenson’s collected works.

A modern view of Jenkin’s influence on Darwin’s thought is Peter Vorzimmer, “Charles Darwin and Blending Inheritance,” in Isis, 54 (Sept. 1963), 371-390. See also LOren Eisley, Darwin’s Century: Evolution and the Men Who Discovered It (New York, 1958). ch. 8, which contains a summary of Jenkin’s opposition to Darwin’s theory of evolution and states that Mendel’s work eventually proved Darwin correct.

Robert A. Chipman