Jean-André De Luc

As Jean-André De Luc (1727-1817) is a little-known figure today even among historians of science, a brief account of his life and work is in order. In his own day De Luc had a formidable reputation as a geologist, meteorologist and physicist. He received his early education from his father, François De Luc -- a clockmaker, radical politician and author of pious religious tracts, who was once described by Jean-Jacques Rousseau as "an excellent friend, the most honest and boring of men." (Tunbridge 1971, 15) The younger De Luc maintained equally active interests in science, commerce, politics and religion. To his credit were some very popular natural-theological explanations of geological findings, strenuous arguments against Lavoisier's new chemistry, and a controversial theory of rain postulating the transmutation of air into water (On the controversy surrounding De Luc’s theory of rain, which was also the cornerstone of his objections to Lavoisier's new chemistry, see Middleton 1964a and Middleton 1965). One of the early "scientific mountaineers," De Luc made pioneering excursions into the Alps (with his younger brother Guillaume-Antoine), which stimulated and integrated his scientific interests in natural history, geology, and meteorology.

His decisive improvement of the method of measuring the heights of mountains by barometric pressure was a feat that some considered sufficient to qualify him as one of the most important physicists in all of Europe (Journal des Sçavans, 1773, 478). More generally he was famous for his inventions and improvements of meteorological instruments, and for the keen observations he made with them. Despite his willingness to theorize, his empiricist leanings were clearly encapsulated in statements such as the following: "the progress made towards perfecting [measuring instruments] are the most effectual steps which have been made towards the knowledge of Nature; for it is they that have given us a disgust to the jargon of systems . . . spreading fast into metaphysics." (De Luc 1779, 69)

In 1772 De Luc's business in Geneva collapsed, at which point he retired from commercial life and devoted himself entirely to scientific work. Soon thereafter he settled in England, where he was welcomed as a Fellow of the Royal Society (initially invited to the Society by Cavendish), and also given the prestigious position of "Reader" to Queen Charlotte. De Luc became an important member of George III's court and based himself in Windsor to his dying day, though he did much travelling and kept up his scientific connections particularly with the Lunar Society of Birmingham and a number of German scholars, especially in Göttingen.

De Luc's first major scientific work, the two-volume Inquiries on the Modifications of the Atmosphere, published in 1772, had been eagerly awaited for the promised discussion of the barometric measurement of heights. When it was finally published after a delay of 10 years, it also contained a detailed discourse on the construction and employment of thermometers, with an explanation that De Luc had originally become interested in thermometers because of the necessity to correct barometer readings for variations in temperature (De Luc 1772, 1:219-221, §408). Other aspects of De Luc's work in thermometry are discussed in Chang (2004), chapters 2 and 3.

Read more about De Luc's work on the boiling point of water.

The most convenient brief source on De Luc's life and work is the entry in the Dictionary of National Biography, 5:778-779. For more detail see De Montet 1877-78, 2:79-82, and Tunbridge 1971. The entry in the Dictionary of Scientific Biography, 4:27-29, is also informative, though distracted by the contributor's own amazement at De Luc's seemingly unjustified renown. Similarly, W. E. K. Middleton's works contain a great deal of information about De Luc, but suffer from a strong bias against him.

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