# Dictionary of National Biography, 1885-1900/Desaguliers, John Theophilus

​DESAGULIERS, JOHN THEOPHILUS (1683–1744), natural philosopher, son of Jean Desaguliers, pastor of a protestant congregation at Aitré, was born on 13 March 1683 at La Rochelle. On the revocation of the edict of Nantes in 1685 his father fled to England, bringing with him John Theophilus. The latter, it has been said, was concealed in a barrel, and thus carried on board the Refugee vessel. As a boy he read classics with his father, who, after a brief residence in Guernsey, became minister of the French chapel in Swallow Street, London, and kept a school at Islington, with his son as assistant. After his father's death Desaguliers matriculated from Christ Church, Oxford. Here he took the degree of B.A., and entered into deacon's orders in 1710, in which year he was also appointed successor to Dr. Keil as lecturer on experimental philosophy in Hart Hall. He followed the method adopted by his predecessor, and lectured on hydrostatics, optics, and mechanics. On 3 May 1712 he proceeded M.A., and in the following year took up his residence in Channel Row, Westminster, and there continued his lectures. In July 1714 he was elected a fellow of the Royal Society, and invited to become their demonstrator and curator. He was held in great esteem by Sir Isaac Newton, then president of the society, and became chaplain in the same year (1714) to the Duke of Chandos, who presented him with the living of Stanmore Parva, or Whitchurch, Middlesex. In 1717 he lectured before George I, who rewarded him with a benefice in Norfolk, worth 70l. a year, which was afterwards exchanged for a living in Essex on the presentation of George II. About this time he was appointed chaplain to Frederick, prince of Wales. On 16 March 1718 he completed his degrees at Oxford as bachelor and doctor of laws. In February 1741–2 he received the Copley gold medal from the Royal Society in acknowledgment of his successful experiments. When old Westminster Bridge was built (1738–9) his opinion on the structure was often sought, but his house with Channel Row had to be pulled down. Desaguliers removed to a lodging in Bedford Coffee-house, over the great piazza in Covent Garden, where he continued his lectures with great success until his death on 29 Feb. 1744. He was buried in the Savoy on 6 March following. In personal appearance he was unattractive, short and thickset, of irregular features, and extremely near-sighted. He was a member of the Gentlemen's Society at Spalding (Nichols, Lit. Anecdotes, vi. 81). He is said to have been the first to deliver learned lectures to the general public. His lectures were attended by the most learned men of the day, and were made interesting by skilful experiments. In a journey through Holland his lectures likewise attracted the attention of men like ​Huyghens and Boerhaave. He was the inventor of a machine called the planetarium, which served to determine the exact distances of the heavenly bodies according to the systems of Newton and Copernicus. He also erected a ventilator, by order, in a room over the House of Commons. Desaguliers contributed a vast number of papers on light, colours, the barometer, &c., to the ‘Philosophical Transactions,’ a list of which is to be found in Maty's index to the ‘Philosophical Transactions.’ James Cawthorn, in his poem ‘The Vanity of Human Enjoyments,’ credits Desaguliers with poverty at death. A portrait is in Nichols's ‘Anecdotes,’ ix. 640–1. He left three sons, of whom John Theophilus (1718–1752) was vicar of Cratfield and Lexfield, Suffolk. Thomas, the youngest, is separately noticed.
He published also: 1. ‘Treatise of Fortifications,’ trans. from French, Oxford, 1711, 8vo. 2. ‘Fires Improved; being a new Method of Building Chimneys, so as to prevent their Smoaking,’ London, 1716, 8vo; the author broke with the publisher Curll because of his shameless puffs. 3. ‘Physics: Mechanical Lectures,’ London, 1717, 8vo. 4. A translation of ‘The Motion of Water and other Fluids,’ London, 1718, 8vo. 5. A translation of Gravesande's ‘Mathematical Elements of Natural Philosophy,’ London, 1721, 4to. Other editions 1726, 1736, and 1747. 6. ‘The Constitutions of the Free-Masons; containing the History of that Fraternity,’ London, 1732, 4to. Desaguliers and J. Anderson were the joint compilers of this publication, which forms a part of Kenny's Masonic Archæological Library. 7. ‘A Course of Mechanical and Experimental Philosophy,’ written in French and English [London, 1724], 8vo; a second edition in 1725. 8. ‘An Experimental Course of Astronomy’ [a syllabus only], 1725, 8vo. 9. ‘The Newtonian System, an allegorical poem,’ London, 1728, 4to. 10. A translation of the second edition of Gregory's ‘Elements of Catoptrics and Dioptrics,’ with an account, in the appendix, of reflecting telescopes, London, 1734–5, 8vo. 11. ‘A Course of Experimental Philosophy,’ London, 1734, 2 vols. 4to, of which a second edition was published in 1745, and a third in 1763. ‘A System of Experimental Philosophy proved by Mechanics,’ London, 1719, 4to, published in Desaguliers's name by Paul Dawson, was disavowed by him. 12. ‘Examen des trois dissertations publiées sur la figure de la terre,’ Oldenburg, 1738, 12mo; second edition in 1741, 8vo. 13. ‘Dissertation on Electricity,’ London, 1742, 8vo, a disquisition for which he was awarded the prize of the academy of Bordeaux for the best essay on electricity. A French version of the work was published the same year at Bordeaux. 14. ‘An Account of the Mechanism of an Automaton playing on the German Flute,’ translated from the French, London, 1742, 4to. In theology he seems to have left only a thanksgiving sermon preached at Hampton Court in 1716 before George I.
R. H.