THOMSON, THOMAS (1773–1852), Scottish chemist, was born at Crieff, Perthshire, on the 12th of April 1773. He was educated at the universities of St Andrews and Edinburgh, and after taking the degree of M.D. at the latter place in 1799 established himself there as a teacher of chemistry. From 1796 to 1800 he was sub-editor of the Encyclopaedia Britannica, in succession to his elder brother, James Thomson (1768–1855), who filled that position in 1795–1796, and who in 1805 was ordained to the parish of Eccles, Berwickshire; and the chemical and mineralogical articles which he contributed to the supplement to the third edition formed the basis of his System of Chemistry, the first edition of which was published in 1802 and the seventh in 1831. At first this work was merely a compilation, but in the later editions many of his original results were incorporated; the third edition (1807) is noteworthy as containing the first detailed account of the atomic theory, communicated to him by John Dalton himself. In 1811 he left Edinburgh, and after a visit to Sweden went to London, where in 1813 he began to edit the Annals of Philosophy, a monthly scientific journal which in 1827 was merged in the Philosophical Magazine. In 1817 he became lecturer in chemistry at Glasgow University, and in the following year was appointed to the regius professorship. This chair he retained until his death, which happened on the 2nd of July 1852 at Kilmun, Argyleshire; but from 1841 he was assisted by his nephew and son-in-law Robert Dundas Thomson (1810–1864), who subsequently became medical officer of health for St Marylebone, London, and after 1846 he ceased active work altogether. He was a most energetic professor, and, according to his colleague, but no relation, Lord Kelvin (Sir William Thomson), founded the first chemical laboratory for students at a time when practical work was scarcely recognized as a necessary part of chemical education. He did much to spread a knowledge of Dalton’s atomic theory, and carried out many experiments in its support, but his strong predilections in favour of Prout’s hypothesis tended to vitiate his results, many of which were sharply criticized by J. J. Berzelius and other chemists. In addition to various textbooks he, published a History of Chemistry (1830–1831) which has provided material for many Chemical biographers, but which, although it reads very plausibly, cannot be regarded as an authority of unimpeachable accuracy. His eldest son, Thomas Thomson (1817–1878) graduated as M.D. at Glasgow in 1839, accompanied Sir J. D. Hooker on his travels in Sikkim in 1850, and collaborated with him in publishing his Flora indica in 1855 and in 1854 was appointed superintendent of the botanic gardens at Calcutta, also acting as professor of botany at the Calcutta medical college.