John Theophilus Desaguliers FRS (12 March 1683 – 29 February 1744) was a British natural philosopher, clergyman, engineer and freemason who was elected to the Royal Society in 1714 as experimental assistant to Isaac Newton. He had studied at Oxford and later popularized Newtonian theories and their practical applications in public lectures. Desaguliers's most important patron was James Brydges, 1st Duke of Chandos. As a Freemason, Desaguliers was instrumental in the success of the first Grand Lodge in London in the early 1720s and served as its third Grand Master.
Biography
Early life and education
Desaguliers was born in La Rochelle, several months after his father Jean Desaguliers, a Protestant minister, had been exiled as a Huguenot by the French government. Jean Desaguliers was ordained as an Anglican by Bishop Henry Compton of London, and sent to Guernsey. Meanwhile, the baby was baptised Jean Théophile Desaguliers in the Protestant Temple in La Rochelle, and he and his mother then escaped to join Jean in Guernsey.
In 1692, the family moved to London where Jean Desaguliers later set up a French school in Islington. He died in 1699. His son, who now used the anglicised name John Theophilus, attended Bishop Vesey's Grammar School in Sutton Coldfield until 1705 when he entered Christ Church, Oxford and followed the usual classical curriculum and graduated BA in 1709. He also attended lectures by John Keill, who used innovative demonstrations to illustrate difficult concepts of Newtonian natural philosophy. When Keill left Oxford in 1709 Desaguliers continued giving the lectures at Hart Hall, the forerunner of Hertford College, Oxford. He obtained a master's degree there in 1712. In 1719, Oxford granted him the honorary degree of Doctor in Civil Laws, after which he was often referred to as Dr Desaguliers. His doctorate was incorporated by Cambridge University in 1726.
Desaguliers was ordained as a deacon in 1710, at Fulham Palace, and as a priest in 1717, at Ely Palace in London.
Lecturer and promoter of Newtonian experimental philosophy
In 1712, Desaguliers moved back to London and advertised courses of public lectures in Experimental Philosophy. He was not the first to do this, but became the most successful, offering to speak in English, French or Latin. By the time of his death, he had given over 140 courses of some 20 lectures each on mechanics, hydrostatics, pneumatics, optics and astronomy. He kept his lectures up to date, published notes for his auditors, and designed his own apparatus, including a renowned planetarium to demonstrate the solar system, and a machine to explain tidal motion. In 1717, Desaguliers lodged at Hampton Court and lectured in French to King George I and his family.
Demonstrator at the Royal Society
In 1714, Isaac Newton, President of the Royal Society, invited Desaguliers to replace Francis Hauksbee (1660–1713) as demonstrator at the Society's weekly meetings; he was soon thereafter made a Fellow of the Royal Society. Desaguliers promoted Newton's ideas and maintained the scientific nature of the meetings when Hans Sloane took over the Presidency after Newton died in 1727. Desaguliers contributed over 60 articles to the Philosophical Transactions of the Royal Society. He received the Society's prestigious Copley Medal in 1734, 1736 and 1741. The last award was for his summary of knowledge to date on the phenomenon of electricity. He had worked on this with Stephen Gray, who at one time lodged at the Desaguliers' home. Desaguliers's "Dissertation concerning Electricity" (1742), in which he coined the terms conductor and insulator, was awarded a gold medal by the Bordeaux Academy of Sciences.
Patronage of the Duke of Chandos
James Brydges, 1st Duke of Chandos appointed Desaguliers as his chaplain in 1716, but probably as much for his scientific expertise as his ecclesiastic duties. He was also gifted the living of St Lawrence Church, Little Stanmore, which was close to the Duke's mansion called Cannons, then under construction at nearby Edgware. The church was rebuilt in the baroque style in 1715. As the chapel at Cannons was not completed until 1720, the church was the location of first performances of the so-called Chandos Anthems by George Frideric Handel who was, in 1717/18, like Desaguliers, a member of the Duke's household.