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 by one of his master's customers. In 1838, on Faraday's recommendation, Tennant was appointed teacher of geological mineralogy at King's College, the title being afterwards changed to professor. In 1853 the professorship of geology was added, but he resigned that post in 1869, retaining the other till his death. He was also from 1850 to 1867 lecturer on geology and mineralogy at Woolwich. He had an excellent practical knowledge of minerals, and, when diamonds were first found in South Africa, maintained the genuineness of the discovery, which at first was doubted. He was an earnest advocate of technical education, giving liberally from his own purse to help on the cause, and persuading the Turners' Company, of which he was master in 1874, to offer prizes for excellence in their craft. The results of this proceeding proved highly satisfactory. When the koh-i-nor was recut Tennant superintended the work, becoming mineralogist to Queen Victoria in 1840, and he had the oversight of Miss (afterwards Baroness) Burdett-Coutts's collection of minerals. He was elected a fellow of the Geological Society in 1838, and president of the Geological Association (1862–3). He died, unmarried, on 23 Feb. 1881. A portrait, painted by Rogers, was in the collection of Lady Burdett-Coutts. A copy was placed in the Strand vestry in commemoration of services to the church schools and parish.

Tennant wrote the following books or pamphlets: He also, in conjunction with David Thomas Ansted and Walter Mitchell, contributed ‘Geology, Mineralogy, and Crystallography’ to Orr's ‘Circle of Sciences’ in 1855.
 * 1) ‘List of British Fossils,’ 1847.
 * 2) ‘Gems and Precious Stones,’ 1852.
 * 3) ‘Catalogue of British Fossils in the Author's Collection,’ 1858.
 * 4) ‘Description of the Imperial State Crown,’ 1858.
 * 5) ‘Descriptive Catalogue of Gems, &c., bequeathed to the South Kensington Museum by the Rev. Chauncy Hare Townshend’ (1870), with two or three scientific papers, one on the koh-i-nor.



TENNANT, SMITHSON (1761–1815), chemist, born on 30 Nov. 1761 at Selby, Yorkshire, was son of Calvert Tennant, vicar of Selby, by his wife Mary Daunt. After receiving his early education in the grammar schools at Tadcaster and Beverley, he studied medicine in 1781 at Edinburgh, where he attended the lectures of [q. v.] In 1782 he became pensioner and then fellow commoner at Christ's College, Cambridge, where he studied chemistry and botany, and satisfied himself of the truth of the antiphlogistic theory of combustion, which was not at that time generally accepted in England. In 1784 he travelled in Denmark and Sweden, and visited the Swedish chemist Scheele. He was elected a fellow of the Royal Society in 1785, and in 1786 he removed from Christ's College to Emmanuel. He graduated M.B. in 1788. During the following years he travelled in Europe, and on his return took up his residence in London in the Temple, and in 1796 graduated M.D. at Cambridge. At this period he became interested in agricultural matters, and, after some preliminary trials in Lincolnshire, purchased land in Somerset, near Cheddar, which he farmed with some success, although resident for the greater part of the year in London. He lived a very retired life, occupied in literary and scientific studies. In 1804 he was awarded the Copley medal of the Royal Society, in recognition of his investigations. In 1812 he delivered a course of informal lectures on mineralogy in his chambers to a number of friends. In 1813 he was appointed professor of chemistry at Cambridge, and in 1814 delivered his first and only course of lectures, which met with a good reception. On 22 Feb. 1815 he accidentally met his death in France, near Boulogne, through the collapse of a bridge over which he was riding.

Although Tennant's published work is small in volume, it includes several discoveries of capital importance. In his first paper (Phil. Trans. 1791, ii. 182) he demonstrated that when marble is heated with phosphorus, the carbon of the fixed air which it contains is liberated. This experiment affords the analytical proof of the composition of fixed air (carbonic acid gas) which had been synthetically proved by Lavoisier. In his next paper, ‘On the Nature of the Diamond’ (ib. 1797, p. 123), Tennant proved that this precious stone consists of carbon, and yields the same weight of carbonic acid gas as had been previously obtained by Lavoisier from an equal weight of charcoal. In 1799 he showed (ib. 1799, ii. 305) that the lime from many parts of England contains magnesia, and that this substance and its carbonate are extremely injurious to vegetation. In 1804 he published his discovery of two new metals, osmium and iridium, which occur in crude platinum and are left behind when the metal is dissolved in aqua regia (ib. 1804, p. 411).

Tennant was a man of wide culture and of severe taste in literature and arts. He