THOMAS DRUMMOND, (1797-1840), was born at Edinburgh in October 1797, and was educated at the High School there. He was appointed to a cadetship at the Royal Military Academy, Woolwich, in February 1813 ; and by Christmas of that year he had entered the Second Academy. He early distinguished himself by his aptitude for mathematics, and an original demonstration in conic sections, discovered by him whilst still in the junior Academy, was published in Leybourn's Mathematical Repository. In 1815 he entered the Royal Engineers. In 1819, when meditat-ing the renunciation of military service for the bar, he made the acquaintance of Colonel Colby, from whom in the following year he received an appointment on the trigonometrical survey of Great Britain. During his winters in London he applied himself indefatigably to the higher branches of mathematics, and attended the chemical lectures of Brande and Faraday at the Royal Institution. The mention at one of these of the brilliant luminosity of lime when incandescent suggested to him the employment of that material instead of the Argand lamp for making surveying stations visible when far distant. In the autumn of 1824 he assisted Captain Colby in the selection of. stations for the great triangulation, and the best situation as a base for the survey ordered to be made in Ireland. His lime-light apparatus (the Drummond light) and heliostat, both completed in 1825, he first put to a practical test in 1826 at the stations of the Irish survey. In the next season he brought into use an improved form of his heliostat, in which the telescope was dispensed with. Through the recommendation of Mr Bellenden Ker, Drummond was in 1831 appointed by Lord Brougham to be superintendent of the Boundary Commission. On the passing of the Reform Act he resumed his duties on the survey,—which, however, he soon finally quitted in order to become private secretary to Lord Althorp, the chancellor of the exchequer. In 1834, on the dissolution of the Government, he received a pension of £300 a year, which he drew until September 30, 1835. In July of that year he was made under-secretary of state for Ireland; and when, in 1836, the bill for municipal reform in that country was introduced into Parliament, he undertook the direction of the officers appointed to determine the boundaries of the boroughs. He was in October 1836 made head of the Irish Bailway Commission, the report of which was completed in 1838. The health of Captain Drummond,—impaired originally by exposure during the Irish survey, and further injured by his unwearied exertions on the Boundary Commission-—had, through his last labours in connection with the railways of Ireland, received a strain from which it never recovered. His strength gradually gave way, and he died on the 15th April 1840.

See Life by J. I\ M'Lennan, 1867, and Lareom in Papers on the Duties of the Royal Engineers, vol. iv., 1840.