John Theophilus Desaguliers

Dates: 1683–1744.

Summary: John Theophilus Desaguliers popularized Isaac Newton’s work and experimented with steam engines and electricity.

John Theophilus Desaguliers was born at La Rochelle, France, on March 12, 1683. His parents were Huguenots (French Calvinists) who fled France after the revocation of the Edict of Nantes in 1685 by Louis XIV. His father, Jean Desaguliers (1644–99), was a minister and teacher; his mother, Marguerite Thomas la Chapelle (ca. 1640–1722), immigrated to Guernsey with the family. In 1690, the family moved to London where the Reverend Desaguliers became an Anglican minister of the Swallow Street French Chapel. He soon opened the French School in Islington, Middlesex, which young John attended until Reverend Desaguliers’s death. John taught at the French School before entering Christ Church, Oxford, in 1705.

John graduated from Oxford in 1709 with a B.A. He lectured on natural philosophy at Hart Hall (Hertford College) in the style of his predecessor, James Keill. He received an M.A. from Hart Hall in 1712. In 1711, he published a translation of Traité de la fortification (1694)( A Treatise on Fortification), by French mathematician Jacques Ozanam (1640–1718). He then moved to Channel Row, Westminster, in order to find a more profitable audience for his commercially offered science lectures. Desaguliers offered public lectures for a fee in the style in James Keill. He also became an Anglican minister. He accepted several appointments to pulpits, but apparently did little ministering. Soon thereafter, he became a Freemason in No. 4 Lodge, which met at the Rummer and Grapes Inn. By 1719, he had become its third grand master. It is believed that he persuaded the Prince of Wales to become a Freemason.

Desaguliers had practical abilities that induced Isaac Newton in 1714 to suggest to the Royal Society that he be put to work replicating some of Newton’s experiments on heat. After a short while, Desaguliers had become the de facto curator of experiments. On July 29, 1714, he was inducted into the Royal Society. He was to be a life-long experimenter. He would win the Copley Medal three times for experimental ingenuity. Desaguliers was also prolific as an author of scientific papers. He produced over 50 between 1716 and 1742 that were published in Philosophical Transactions. His earlier papers were on optics and mechanics, while the later ones were on electricity. In 1717, he published Psycho-Mechanical Lectures, which was an 80-page summary of his 22-lecture science course. A pirated version circulated until he published a full version in 1734. Desaguliers sided with Newton during the vis viva controversy with Gottfried Wilhelm Leibniz, Johann Bernoulli, and others. He ultimately pointed out that the debate was a verbal conflict because the quantities they used were different.

In examining mechanics, Desaguliers analyzed machines on the basis of statics, and later basic dynamics. He was able to make practical improvements to a variety of devices. One device was the pyrometer for measuring the expansion of metal when it is heated, developed by Pieter van Musschenbroek (1692–1761). Another device was Stephen Gray’s (1666–1732) barometric level. Other devices were Stephen Hales’s (1667–1761) sea-gauge for ship soundings, Joshua Haskins’s force pump, and Thomas Savery’s (1650–1715) steam engine, which was an atmospheric steam engine. With the help of Henry Beighton, Desaguliers was able to issue a work on the state of the art for mechanical practices. Included were discussions of steam engines.

From his studies and experiments, Desaguliers completely rejected any idea of a perpetual motion machine. A number of experiments in optics designed to replicate Newton’s earlier optical work were conducted by Desaguliers. These usually verified the accuracy of Newton’s findings, as well as his theoretical conclusions, although in some cases improvements were made. Many of Desaguliers’ electrical experiments were conducted with Stephen Gray, who had found that electricity flows. They conducted experiments that showed that objects hundreds of feet away could acquire electrical charges if connected with wires or other conducting materials.

After the death of Gray, Desaguliers began to publicly demonstrate electrical experiments. Gray, who had won the Copley Medal in 1731, had received the credit for advances in electrical science. Desaguliers now continued their collaborative work as he described experiments and in many cases demonstrated them to the Royal Society. A great many of the demonstrations served to popularize the emerging science of electricity. Among his experiments were those that dealt with conduction, attraction, and repulsion, charging and discharging whether in dry or wet conditions. For example, before the Prince of Wales he demonstrated that a string when wet could have electricity pass along it, but not when it was dry. In order to distinguish between materials that could acquire a static charge from rubbing and those that could not, he distinguished between what he called “electrics per se” and “non-electric bodies.” The former could acquire an electrical charge directly, while the latter “non-electric bodies” could not. However, he was unaware that some materials could be electrical when properly insolated. He also did not understand discharging and leakage through grounding.

In 1734, Desaguliers published A Course of Experimental Philosophy. He had by then given his popular commercial lectures in astronomy, mechanics, hydrostatics, optics, machinery, and electricity over 100 times. He made the case that, without experimentation and demonstrations of those experiments, science would be merely a catalog of terms, most likely in unintelligible jargon. Desaguliers died in London March 10, 1744.

Bibliography

Carpenter, Audrey, T. John Theophilus Desaguliers: A Natural Philosopher, Engineer and Freemason in Newtonian England. New York: Continuum Intl. Publishing, 2011.

Gwynn, Robin D. The Huguenots of London. Brighton, UK: Alpha Press, 1998.

Hurst, Wilfred R. An Outline of the Career of John Theophilus Desaguliers. London: privately published, 1928.

Mackey, Albert G. “John Theophilus Desaguliers.” In Encyclopedia of Freemasonry. http://www.search.com/reference/John‗Theophilus‗Desaguliers.

Stewart, Larry. The Rise of Public Science: Rhetoric, Technology, and Natural Philosophy in Newtonian Britain, 1660–1750. Cambridge: Cambridge University Press, 1992.