# Dictionary of National Biography, 1885-1900/Desaguliers, Thomas

​DESAGULIERS, THOMAS (1725?–1780), lieutenant-general and colonel commandant of the royal artillery, was the grandson of Jean des Aguliers, protestant pastor of Aitré, near La Rochelle, and after the revocation of the edict of Nantes minister of the French chapel in Swallow Street, and youngest son of Dr. John Theophilus Desaguliers [q. v.] He entered the regiment of royal artillery as a cadet on 1 Jan. 1740, and was promoted second lieutenant on 1 Sept. 1741, first lieutenant on 1 Feb. 1742, captain-lieutenant on 3 April 1743, and captain on 1 Jan. 1745. He first saw service in Flanders in 1744, when he joined the royal artillery train under Colonel Belford, and remained on the continent until the close of the war of the Austrian succession in 1748, being present at the battle of Fontenoy, as well as many minor engagements. On his return to England, Captain Desaguliers was made chief firemaster at Woolwich on 1 April 1748, a post which he held for thirty-two years, until his death in 1780. The chief firemaster was the superintendent of Woolwich arsenal, and Desaguliers was the first scientific maker of cannon and the first regular investigator into the powers of gunnery in the English army. He was promoted lieutenant-colonel on 5 Feb. 1757, and in 1761 was summoned from his experiments and manufactures to take command of the siege train and the force of artillerymen intended to accompany the expedition to the island of Belleisle, off the west coast of France. This was the first opportunity for testing on a large scale the improvements made in siege artillery since the days of Marlborough, and Desaguliers was able to put his ideas into practice. General Studholme Hodgson was in command, with ​Generals Crauford, William Howe, John Burgoyne, and Guy Carleton under him, and when Desaguliers arrived at Belleisle on 12 April with the temporary rank of brigadier-general, one unsuccessful attempt had already been made to disembark. Desaguliers at once volunteered to reconnoitre, and, by putting some of his heavy guns into ship's boats, managed to cover the landing of the army. The island soon submitted, and General Hodgson directed Desaguliers to form the siege of the citadel. The manuscript journal which he kept during the siege of all his operations is still preserved in the Royal Artillery Institution's Library at Woolwich, and forms the basis of the interesting account given of the siege by Colonel Duncan in his ‘History of the Royal Regiment of Artillery’ (vol. i. chap. xxi. pp. 227–41). Desaguliers got thirty guns and thirty mortars into battery, fired seventeen thousand shot and twelve thousand shells into the citadel, had great difficulties to contend with owing to the flooding of the trenches, and was wounded five days before the capitulation of the fortress on 7 June. On his return to England he was promoted colonel on 19 Feb. 1762, and made colonel commandant of the royal regiment of artillery on 19 Feb. 1762, and devoted himself for the rest of his life to his work at Woolwich. His work there was most valuable; he invented a method of firing small shot from mortars, and made the earliest experiments with rockets, and Desaguliers' instrument is still in use at the royal gun factories for examining and verifying the bores of cannon. In recognition of his scientific work he was elected a fellow of the Royal Society in 1763, being the first officer of royal artillery who won that distinction. He was promoted major-general on 25 May 1772, and lieutenant-general on 29 Sept. 1777, and died at Woolwich on 1 March 1780. Colonel Duncan, in speaking of the early artillery officers, says justly: ‘The early history of the regiment is marked by the presence in its ranks of men eminent in their own way and perfectly distinct in character, yet whose talents all worked in the same direction, the welfare of their corps. Who could be more unlike than Borgard and his successor, Colonel Belford? and yet a greater difference is found between the scientific Desaguliers and the statesmanlike Pattison. These four men are the milestones along the road of the regiment's story from 1716 to 1783’ (Duncan, i. 152).
H. M. S.