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Percy, John


(b. Nottingham, England, 23 March 1817; d. London, England, 19 June 1889)


Percy was the third son of Henry percy, a solicitor. Persuaded, against his inclination, to prepare for a medical career, he studied in Paris (where he met Gay-Lussac, Thenard, and Jussieu) and Edinburgh, where he graduated M.D. in 1838. His thesis, on the presence of alcohol in the brain, won a gold medal. Although he obtained a hospital post in Birmingham in 1839, he never established a practice; instead, his early interest in chemistry was reawakened by the local metal industries. In the same year he married Grace Piercy, who died in 1880.

In 1846 Percy studied the nature of slags; he later turned to the extraction of silver from its ores by a process dependent upon the solubility of silver chloride in sodium thiosulfate (a phenomenon discovered by Herschel in 1819). He was appointed lecturer at the Metropolitan School of Science (later the Royal School of Mines), which was then under the direction of Sir Henry de la Beche. He subsequently became professor and thus exerted a profound influence on the progress of British metallurgy; many of his pupils achieved great distinction. His teaching was both methofical and innovative; and Percy transformed metallurgy from a repertoire of practices into a scientific discipline. The inventions of his pupils (for example, the Thomas-Gilchrist process for making iron from phosphorus-rich ores) were, however, more important than Percy’s own.

Using the results of a large number of chemical analyses, Percy made a survey of the national resources of iron ore. This survey was incorporated into his large, unfinished work on metallurgy; perhaps the first writer since the Renaissance to attempt to achieve the comprehensiveness of Agricola and Ercker. Percy held many official lectureships, including one at the Royal Military Academy in Woolwich, and was called upon for technical advice on many military defense questions. He disapproved of the removal by the government of the Royal School of Mines to South Kensington, and he resigned in 1879.

Percy made two personal collections during his life; one of watercolors and engravings, which was dispersed by sale after his death, and one of metallurgical specimens of historical interest, which has fortunately survived intact and is now in the Science Museum at South Kensington. He was a lifelong student of political and social questions, often forcefully expressing himself in public, both in speech and writing, although he was not always sensitive to the appropriateness of the occasion.


Percy’s major work was A Treatise on Metallurgy, 4 vols. (1864–1880). See also J. F. Blake, Catalogue of the Collection of Metallurgical Specimens Formed by the Late John Percy, Esq., … (London, 1892).

Obituary notices are found in Athenaeum, 1 (1889), 795; Journal of the Iron and Steel Institute, 1 (1889), 210; and Proceedings of the Geological Society, 46 (1890), 45.

Frank Greenaway

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