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burgh 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.

IVORY, JAMES, Lord Ivory, (1792–1866), Scottish judge, son of Thomas Ivory, watchmaker and engraver, was born in Dundee in 1792. Sir James Ivory [q. v.] the mathematician was his uncle. After attending the Dundee academy he studied for the legal profession at Edinburgh University, was admitted a member of the Faculty of Advocates in 1816, and in that year was enrolled as a burgess of his native town. When, in 1819, the select committee of the House of Commons was engaged in making inquiries into the state of the Scottish burghs, Ivory was examined with reference to the municipal condition of Dundee, and strongly advocated the abolition of self-election, which was then prevalent in the town councils of Scotland, and continued in force till 1833. Ivory was chosen advocate-depute by Francis Jeffrey, lord advocate, in 1830; two years afterwards he was appointed sheriff of Caithness, and in 1833 was transferred to a similar office in Buteshire. He was solicitor-general of Scotland under Lord Melbourne's ministry in 1839, was made a lord-ordinary of session in the following year, and sat as judge in the court of exchequer. In 1849 he was appointed a lord of justiciary (taking the title of Lord Ivory), and served both in the court of session and the high court of justiciary until his retirement in October 1862. For several years before that date he was the senior judge of both courts. Ivory died at Edinburgh on 18 Oct. 1866. He married, in 1817, a daughter of Alexander Lawrie, deputy gazette writer for Scotland. His eldest son, William Ivory, has long been sheriff of Inverness-shire.

As a lawyer Ivory was distinguished by the subtlety of his reasoning, his minuteness of detail, and profound erudition. He was not a fluent orator, but in the early part of his career, when legal argument was conducted in writing, he obtained a high reputation.

[Millar's Roll of Eminent Burgesses of Dundee, p. 249; Norrie's Dundee Celebrities, p. 273; Dundee Advertiser, 19 Oct. 1866.]

A. H. M.

IVORY, THOMAS (1709–1779), architect, practised his profession in Norwich. He was admitted a freeman of the town as a carpenter 21 Sept. 1745. He lived in the parish