# Dictionary of National Biography, 1885-1900/Thomson, Thomas (1773-1852)

​THOMSON, THOMAS (1773–1852), chemist, born on 12 April 1773 at Crieff, was son of John Thomson by his wife, Elizabeth Ewan. He received his early education at the parish school of Crieff and at the borough school of Stirling, and in 1787 obtained a bursary at St. Andrews, where he remained for three years. In 1790 he became tutor in the family of Mr. Kerr of Blackshields. In 1795 he commenced to study medicine at Edinburgh, attending the chemistry lectures of Joseph Black [q. v.], and graduated doctor of medicine in 1799. During this period he contributed the article ‘Sea’ to the third edition of the ‘Encyclopædia Britannica,’ and edited the supplement to that edition, writing the articles on ‘Chemistry,’ ‘Mineralogy,’ and ‘Vegetable, Animal and Dyeing Substances.’ These formed the basis of his ‘System of Chemistry,’ 1802; 7th edit. 1831. The first edition is largely drawn from pre-existing works, but later issues contain many of his own discoveries besides those of contemporaries. The work helped to improve the system of classification adopted in chemical science. In 1800 he instituted in Edinburgh a course of lectures on chemistry and, having opened a laboratory for the practical instruction of pupils, continued to teach this subject in Edinburgh until 1811. This is stated to have been the first chemical laboratory opened in the United Kingdom for purposes of instruction. At the same time he made investigations on behalf of the Scottish excise board upon the subjects of brewing and distillation, and invented the instrument known as Allan's ‘Saccharometer.’ On 28 March 1811 he was elected a fellow of the Royal Society of London, and in 1812 he published a history of the society containing an account of the most important papers in each branch of science which had appeared in the ‘Philosophical Transactions.’ In the autumn of the same year he visited Sweden, and in the following year published an account of his travels, paying special attention to the mineralogy and geology of the country. On his return from Sweden he resided in London and edited the ‘Annals of Philosophy,’ a monthly journal of science. He was succeeded in 1821 by Richard Phillips [q. v.], and in 1827 the journal was purchased by Richard Taylor [q. v.] and merged in the ‘Philosophical Magazine.’ In 1817 he was appointed lecturer in chemistry at the university of Glasgow, and in 1818 was made regius professor at the instance of the Duke of Montrose. His career as professor was one of great scientific activity. He continued to perform the whole duties of his chair until 1841, and then associated with himself his nephew, Robert Dundas Thomson [q. v.] His bodily powers were now failing, and after 1846 his nephew discharged the entire duties of the professorship. Thomson was president of the Philosophical Society of Glasgow from 1834, and in November 1850 made his last communication to this society in the form of a biographical account ​of his friend Wollaston, who had just died. His own strength gradually declined, until on 2 July 1852 he died, while residing near the Holy Loch.
Thomson married, in 1816, Agnes Colquhon, the daughter of a distiller near Stirling, and left a son, Thomas Thomson (1817–1878) [q. v.], well known as a botanist and explorer, and a daughter, who married Robert Dundas Thomson.
As a chemist Thomson is best known for the warm and effective support which he accorded to Dalton's atomic theory. He visited Dalton in Manchester on 26 Aug. 1804, and received from him an account of the new theory which he introduced into the third edition of his ‘System’ (pp. 425 et seq.) published in 1807. This was the first detailed public announcement of the theory, for Dalton did not publish his ‘New System of Chemical Philosophy’ until 1808. After the publication of the second part of the first volume of Dalton's work in 1810, Thomson issued a long series of papers (Annals of Phil. 1813–14) in which the atomic theory was applied to elucidate the composition of a very large number of compounds. These contributed largely to making the theory known, especially on the continent of Europe.
In 1819 Thomson commenced a series of experimental researches with the view of testing, or rather of confirming, the theory of William Prout [q. v.], that the atomic weights of all the elements are exact multiples of that of hydrogen. The results of the many thousands of experiments which he conducted with this object were extremely favourable to the theory and were published in 1825 under the title ‘An Attempt to establish the First Principles of Chemistry by Experiment,’ in two volumes, primarily intended for the use of his students. The analyses recorded had not been carried out with sufficient care to justify the claim of high accuracy made for them by the author, and the work was very severely criticised, especially by the Swedish chemist Berzelius, himself an analyst of extraordinary skill, who went so far as to accuse the author of having done ‘much of the experimental part at the writing table’ (Berzelius, Jahresbericht, 1827, vi. 77). The statements which induced this suspicion are explained by Walter Crum as follows: ‘The results which appear so perfect in the First Principles are not to be understood as the actual results of any one experiment, or even as the mean of several experiments, but as results which might fairly be deduced from them, and which, being in round as well as more perfect numbers, were more suitable for a school book’ (Proc. Phil. Soc. Glasgow, vol. iii. 1855). It has been claimed for Thomson that he introduced the use of symbols into chemistry (Edinb. New Phil. Journal, 1852–3, liv. 86). This claim is, however, unfounded, for symbols were in constant use among the earlier chemists; while Dalton introduced the modern atomic symbol, although he used signs instead of letters.
Besides the works already mentioned Thomson was the author of: 1. ‘Elements of Chemistry,’ 1810. 2. ‘History of Chemistry,’ 2 vols. 1830–1. 3. ‘An Outline of the Sciences of Heat and Electricity,’ 1830. 4. ‘Chemistry of Inorganic Bodies,’ 1831. 5. ‘Outlines of Mineralogy,’ 1836. 6. ‘Chemistry of Organic Bodies,’ 1838. 7. ‘Chemistry of Animal Bodies,’ 1843. 8. ‘Brewing and Distillation,’ 1849. No fewer than 201 scientific papers, including numerous articles in the ‘Annals of Philosophy’ and the ‘Records of Science,’ are placed to Thomson's credit in the Royal Society's catalogue; these deal chiefly with the atomic theory, analyses and preparation of salts, and with subjects connected with mineralogy, geology, and agriculture, in all of which he took an active interest. He was also the author of a pamphlet, ‘Remarks on the “Edinburgh Review” of Dr. Thomson's System of Chemistry, by the Author of that Work,’ Edinburgh, 1804. Thomson's portrait figures in the engraving, by Walker & Son, of the distinguished men of science of Great Britain living in the years 1807–8.
A. H.-n.