Jean-André Deluc or de Luc (8 February 1727 – 7 November 1817) was a Swiss geologist and meteorologist.
He was born at Geneva, descended from a family which had emigrated from Lucca and settled at Geneva in the 15th century. His father, François Deluc, was the author of some publications in refutation of Mandeville and other rationalistic writers, which are best known through Rousseau's humorous account of his ennui in reading them; and he gave his son an excellent education, chiefly in mathematics and natural science. On completing it Jean-André engaged in commerce, which principally occupied the first forty-six years of his life, without any other interruption than that which was occasioned by some journeys of business into the neighboring countries, and a few scientific excursions among the Alps.
During these, however, he collected by degrees, in conjunction with his brother Guillaume Antoine Deluc, a splendid museum of mineralogy and of natural history in general, which was afterwards increased by his nephew J. André Deluc (1763–1847), who was also a writer on geology. He at the same time took a prominent part in politics. In 1768 he was sent to Paris on an embassy to the duc de Choiseul, whose friendship he succeeded in gaining. In 1770 he was nominated one of the Council of Two Hundred.
Three years later unexpected reverses in business made it advisable for him to quit his native town, which he only revisited once for a few days. The change was welcome insofar as it set him entirely free for scientific pursuits, and it was with little regret that he removed to England in 1773. He was made a fellow of the Royal Society in the same year, and received the appointment of reader to Queen Charlotte, which he continued to hold for forty-four years, and which afforded him both leisure and a competent income.
In the latter part of his life he obtained leave to make several tours in Switzerland, France, Holland and Germany. In Germany he passed the six years from 1798 to 1804; and after his return he undertook a geological tour through England. When he was at Göttingen, in the beginning of his German tour, he received the compliment of being appointed honorary professor of philosophy and geology in that university; but he never entered upon the active duties of a professorship. He was also a correspondent of the French Academy of Sciences, and a member of several other scientific associations. He died at Windsor, Berkshire, Englandin 1817.
His favorite studies were geology and meteorology. The situation of his native country had naturally led him to contemplate the peculiarities of the earths structure, and the properties of the atmosphere, as particularly displayed in mountainous countries, and as subservient to the measurement of heights. According to Georges Cuvier, he ranked among the first geologists of his age. His principal geological work, Lettres physiques et morales sur les montagnes et sur l'histoire de la terre et de l'homme, first published in 1778, and in a more complete form in 1779, was dedicated to Queen Charlotte. It dealt with the appearance of mountains and the antiquity of the-human race, explained the six days of the Mosaic creation as so many epochs preceding the actual state of the globe, and attributed the deluge to the filling up of cavities supposed to have been left void in the interior of the earth. He published later an important series of volumes on geological travels in the north of Europe (1810), in England (1811), and in France, Switzerland and Germany (1813). These were translated into English.
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