Dictionary of National Biography, 1912 supplement/Kerr, John
KERR, JOHN (1824–1907), physicist, born on 17 Dec. 1824 at Ardrossan, Ayrshire, was second son of Thomas Kerr, a fish-dealer. He was educated at a village school in Skye, and proceeded to the University of Glasgow, attending classes from 1841 to 1849. From 1846 he studied under William Thomson, afterwards Lord Kelvin [q. v. Suppl. II], and on graduation in 1849 he obtained Lord Eglinton's prize as the most distinguished student in mathematics and natural philosophy. Although a divinity student, he was one of the earliest to engage in research work in the 'coalhole' in which Thomson had set up the first physical laboratory in Great Britain. After some time spent in teaching, Kerr was ordained a minister of the Free church, but did not take clerical duty. In 1857 he was appointed lecturer in mathematics to the Glasgow Free Church Training College for Teachers. This post he held for forty-four years, until his retirement in 1901. Here he set up a small laboratory, spending all his spare time in research. His name is associated with two great discoveries affecting the nature of light — the bi-refringence caused in glass and other insulators when placed in an intense electric field, and the change produced in polarised light by reflection from the polished pole of an electromagnet. The series of papers describing the first of these phenomena appeared in the 'Philosophical Magazine' from 1875 onwards; the second discovery was communicated to the British Association at its Glasgow meeting in 1876, and caused intense excitement among the physicists there. The mathematical theory of this 'Kerr effect' was first worked out by George Francis FitzGerald [q. v. Suppl. II], and more recently by Sir Joseph Larmor. Kerr's only independently published works are 'The Metric System' (1863) and 'An Elementary Treatise on Rational Mechanics' (1867). The latter of these procured him the honorary degree of LL.D. from his university. He was elected F.R.S. in 1890, and received the royal medal in 1898. He continued to publish the results of his researches in the 'Philosophical Transactions' till near his death. He was awarded in 1902 a civil list pension of l00l. a year. He died at Glasgow on 18 Aug. 1907. He married Marion, daughter of Col. Balfour of Orkney, and had three sons and four daughters.
[Proc. Roy. Soc, 82a, 1909, p. 1; The Times, 19 Aug. 1907; Nature, 3 Oct. 1907; Who's Who, 1907.]