John Theophilus Desaguliers (pronounced day-za-güly-ay) (13 March 1683 – 29 February 1744) was a natural philosopher born in France. He was a member of the Royal Society of London beginning 29 July 1714. He was presented with the Royal Society's highest honour, the Copley Medal, in 1734, 1736 and 1741, the 1741 award being for his "discovery of the properties of Electricity". He studied at Oxford, became experimental assistant to Sir Isaac Newton, and later popularized Newtonian theories and their practical applications. He invented the planetarium.

Biography

Born in La Rochelle, Desaguliers was an immigrant to England from France. He was born into a Huguenot (Protestant) family and fled to England at the age of 11 (1694) to escape the consequences of the Revocation of the Edict of Nantes. He was educated at Christ Church, Oxford, and succeeded Dr. Keill in reading lectures on experimental philosophy at Hart Hall. He was the first who introduced the reading of lectures in London, where he had for his auditors not only the learned and the great, but also George I and George II and the royal family. In 1714, he was chosen a member of the Royal Society, to whose Transactions he communicated some valuable papers. In 1718, he completed his degrees at Oxford as bachelor and doctor of laws. Desaguliers' reputation as a scientist was sealed not only by his three awards from the Royal Society, but also by publication of a two volume work entitled A Course of Experimental Philosophy. Publication of the first volume coincided with the year he first received the Copley Medal (1734), while the second volume's publication came 10 years later in 1744, the year of his death. The first volume concerns theoretical and practical mechanics with an explanation of the basics of Newtonian physics. The second volume contains material oriented toward practical application of scientific findings.

An inventor as well as a scientist, Desaguliers improved upon the steam engine design of Thomas Savery through the addition of a safety valve. He also designed methods for heating liquid boilers with steam rather than fire, presumably increasing their safety significantly.

Additionally, Desaguliers was a Freemason, elected as the third Grand Master in 1719, Deputy Grand Master in 1723 and 1725 of the newly formed Premier Grand Lodge of England.

Desaguliers was also a priest in the Church of England, and was for many years the Rector of St Lawrence, Little Stanmore (sometimes called Stanmore Parva), at Edgware in Middlesex, and domestic chaplain to James Brydges, 1st Duke of Chandos. The church at Stanmore was at the edge of the duke's estate, Canons Park. Here Desaguliers would no-doubt have been party to the first performances of the so-called Chandos Anthems, by George Frideric Handel, who was then, like Desaguliers, a member of the Duke's household. Desaguliers played an important role in directing the Duke's patronage of scientific and engineering projects.

There are at least three surviving portraits of Desaguliers dating to 1725 (42 years of age), all held by the National Portrait Gallery in London and available for on-line viewing.

Personal life

On 14 October 1712 he married Joanna Pudsey, daughter of William and Anne Pudsey of Kidlington, near Oxford. They had four sons and three daughters, for most of whom they acquired aristocratic godparents, but only two children survived beyond infancy: John Theophilus (1718?1751) graduated from Oxford, became a clergyman, and died childless, while Thomas Desaguliers (1721?1780) led a distinguished scientific military career.

Decline

Desaguliers had long suffered from gout every winter, and died after several months of severe illness at his home in the Bedford Coffee House, Covent Garden, London, on 29 February 1744; he was buried on 6 March in the Savoy Chapel, Savoy Street, London.

Notes

1. Copley archive winners 1799-1731. The Royal Society. Retrieved 2005-02-12. The work honored is not detailed on this site.
2. Fellows of the Royal Society - D. The Royal Society. Retrieved 2005-02-12. This PDF document also contains birth and death dates.
3. Gory, Paul. A Course of experimental philosophy. Retrieved 2005-02-12. Translated French=>English using Babel Fish, 2005-02-12.
4. John Theophilus Desaguliers, French-born scientist and inventor, 1725. Science & Society Picture Library. Retrieved 2005-02-12.
5. John Theophilus Desaguliers (1683-1744), Natural philosopher. Sitter in 3 portraits. The National Portrait Gallery. Retrieved 2005-02-12.