# Dictionary of National Biography, 1885-1900/Ivory, James (1765-1842)

​IVORY, Sir JAMES, (1765–1842), mathematician, born in Dundee in 1765, was the eldest son of James Ivory, a watchmaker there. At the age of fourteen he matriculated at St. Andrews University, and after six years' study with a view to becoming a minister of the Scottish Church, went to Edinburgh to complete his theological course, accompanied by John (afterwards Sir John) Leslie (1766–1832) [q. v.], a fellow-student at Aberdeen, who like himself had already evinced a strong mathematical bias. Ivory returned to Dundee in 1786, and for three years taught in the principal school, introducing the study of algebra, and raising the standard of general instruction. He afterwards joined in starting a flax-spinning mill at Douglastown, on the Carbet, near Forfar, and acted as managing partner. Ivory devoted all his leisure to mathematical work, especially to analysis as it was then taught on the continent, and Henry Brougham, at the time a young advocate, cultivated his acquaintance, and visited him at Brigton, near the flax-factory, when on his way to the Aberdeen circuit. Four mathematical papers of his, the first dated 7 Nov. 1796, were read to the Royal Society of ​Edinburgh at this time, on rectifying the ellipse, solution of a cubic, and of Kepler's problem, &c. (Edinb. Roy. Soc. Trans. iv. 177–90, v. 20–2, 99–118, 203–46).
The flax-spinning partnership was dissolved in 1804, and soon afterwards Ivory was appointed professor of mathematics in the Royal Military College, then at Marlow, Buckinghamshire, and subsequently removed to Sandhurst. His work at the Royal Military College was thorough and successful, though the higher parts of the science were considered by some to absorb too much of his attention. He prepared an edition of Euclid's ‘Elements’ for military students, which simplified the geometrical treatment of proportion and solids. Resigning his professorship in 1819, he was allowed the full retiring pension, although his period of office was shorter than the rule required.
Ivory's skill in applying the infinitesimal calculus to physical investigations gave him a place beside Laplace, Lagrange, and Legendre. In 1809 Ivory read his first paper to the Royal Society, enouncing a theorem which has since borne his name, and which completely resolves the problem of attractions for all classes of ellipsoids. Ivory's theorem was received on the continent ‘with respect and admiration.’ He received three gold medals from the Royal Society, of which he was elected fellow in 1815: viz. the Copley, in 1814, after showing a new method of determining a comet's orbit; the royal medal, in 1826, for a paper on refractions, which was acknowledged by Laplace to evince masterly skill in analysis; and the royal medal a second time in 1839, for his ‘Theory of Astronomical Refractions,’ which formed the Bakerian lecture of 1838. Fifteen papers by Ivory are printed in the ‘Philosophical Transactions.’ All are characterised by clearness and elegance in the methods employed (Phil. Trans. 1812, 1814, 1822, 1824, 1831, 1832, 1833, 1838, 1842; Tilloch, Phil. Mag. 1821, &c.; Quarterly Journal of Science, 1822, &c.)
In 1831, on the recommendation of Lord Brougham, then lord chancellor, Ivory received the honour of knighthood, in company with Herschel and Brewster, and his civil list pension was at the same time raised to 300l. a year. Ivory was elected member of the Royal Academy of Sciences of France, the Royal Academy of Berlin, and the Royal Society of Göttingen.
In 1829 he made an offer of his scientific library to the corporation of Dundee, his native town, and as there was then no public building suitable for the purpose, James, lord Ivory [q. v.], his nephew and heir, kept the books in his own collection, until his death in 1866, when they became part of the Dundee public library in the Albert Institute. Ivory died unmarried at Hampstead, London, on 21 Sept. 1842.
[Norrie's Dundee Celebrities, p. 70; Weld's Hist. Roy. Soc. pp. 570, 573; private information.]
R. E. A.