Jean-André Deluc (8 February 1727 – 7 November 1817) was a
SwissSwitzerland , officially the Swiss Confederation , is a federal republic consisting of 26 states named cantons, with Bern as the seat of the federal authorities...
geologistGeology is the science and study of the solid and liquid matter that constitutes the Earth. The field of geology encompasses the study of the composition, structure, physical properties, dynamics, and history of Earth materials, and the processes by which they are formed, moved, and changed...
and meteorologist.
He was born at
GenevaGeneva, is the second-most-populous city in Switzerland and is the most populous city of Romandie...
, descended from a family which had emigrated from
LuccaLucca is a city in Tuscany, central Italy, situated on the river Serchio in a fertile plain near the Ligurian Sea. It is the capital city of the Province of 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
AlpsThe Alps are one of the great mountain range systems of Europe, stretching from Austria and Slovenia in the east; through Italy, Switzerland, Liechtenstein and Germany; to France in the west....
.
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
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
in 1773. He was made a fellow of the
Royal SocietyThe Royal Society of London for the Improvement of Natural Knowledge, known simply as the Royal Society, or even the Royal, is a learned society for science that was founded in 1660 and is considered by most to be the oldest such society still in existence...
in the same year, and received the appointment of reader to
Queen CharlotteCharlotte of Mecklenburg-Strelitz was the queen-consort of the United Kingdom as wife of King George III.Queen Charlotte was a patroness of the arts, known to Johann Christian Bach and Wolfgang Amadeus Mozart, among others. She was also an amateur botanist who helped establish Kew Gardens...
, 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
GöttingenGöttingen is a college town in Lower Saxony, Germany. It is the capital of the district of Göttingen. The Leine river runs through the town. In 2006 the population was 129,686.-General information:...
, 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 SciencesThe French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
, and a member of several other scientific associations. He died at
WindsorWindsor is a suburban town in the Royal Borough of Windsor and Maidenhead in Berkshire, England. It is best known as the site of Windsor Castle....
in 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 CuvierGeorges Léopold Chrétien Frédéric Dagobert Cuvier was a French naturalist and zoologist. Of humble working class origins, he belonged to a new class of self-made scholars who worked their way to the top of academe...
, 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.
Deluc's original experiments relating to meteorology were valuable to the natural philosopher; and he discovered many facts of considerable importance relating to heat and moisture. He noticed the disappearance of heat in the thawing of ice about the same time that
Joseph BlackJoseph Black was a Scottish physician, physicist, and chemist, known for his discoveries of latent heat, specific heat, and carbon dioxide. He was a founder of thermochemistry who developed many pre-thermodynamics concepts, such as heat capacity, and was the mentor for James Watt...
founded on it his ingenious hypothesis of
latent heatThe expression latent heat refers to the amount of energy released or absorbed by a chemical substance during a change of state that occurs without changing its temperature, meaning a phase transition such as the melting of ice or the boiling of water...
. He ascertained that water was denser about 40 F. (4 C.) than at the temperature of freezing, expanding equally on each side of the maximum; and he was the originator of the theory, afterward readvanced by
John DaltonJohn Dalton FRS was an English chemist, meteorologist and physicist. He is best known for his pioneering work in the development of modern atomic theory, and his research into colour blindness .-Early life:John Dalton was born into a Quaker family at Eaglesfield, near Cockermouth in Cumberland,...
, that the quantity of aqueous vapour contained in any space is independent of the presence or density of the air, or of any other elastic fluid.
His
Recherches sur les modifications de l'atmosphere (2 vols. 4to, Geneva, 1772; 2nd ed., 4 vols. 8vo, Paris, 1784) contains many accurate and ingenious experiments upon moisture, evaporation and the indications of
hygrometerHygrometers are instruments used for measuring relative humidity. A simple form of a hygrometer is specifically known as a psychrometer and consists of two thermometers, one of which includes a dry bulb and the other of which includes a bulb that is kept wet to measure wet-bulb temperature...
s and
thermometerA thermometer is a device that measures temperature or temperature gradient using a variety of different principles. A thermometer has two important elements: the temperature sensor A thermometer (from the Greek θερμός (thermo) meaning "warm" and meter, "to measure") is a device that measures...
s, applied to the
barometerA barometer is an instrument used to measure atmospheric pressure. It can measure the pressure exerted by the atmosphere by using water, air, or mercury. Pressure tendency can forecast short term changes in the weather...
employed in determining heights. In. the
Phil. Trans., 1773, appeared his account of a new hygrometer, which resembled a mercurial thermometer, with an ivory bulb, which expanded by moisture, and caused the mercury to descend. The first correct rules ever published for measuring heights by the barometer were those he gave in the
Phil. Trans., 1771, p. 158. His
Lettres sur l'histoire physique de la terre (8vo, Paris, 1798), addressed to Professor
Johann Friedrich BlumenbachJohann Friedrich Blumenbach was a German physician, physiologist and anthropologist, one of the first to explore the study of mankind as an aspect of natural history, whose teachings in comparative anatomy were applied to classification of human races, of which he determined...
, contains an essay on the existence of a General Principle of Morality. It also gives an interesting account of some conversations of the author with
VoltaireFrançois-Marie Arouet , better known by the pen name Voltaire, was a French Enlightenment writer, essayist, and philosopher known for his wit and his defense of civil liberties, including both freedom of religion and free trade.Voltaire was a prolific writer and produced works in almost every...
and Rousseau. Deluc was an ardent admirer of Bacon, on whose writings he published two works;
Bacon tel quil est (8vo, Berlin, 1800), showing the bad faith of the French translator, who had omitted many passages favorable to revealed religion, and
Prcis de la philosophic de Bacon (2 vols 8vo, Paris, 1802), giving an interesting view of the progress of natural science.
Lettres sur le Christianisme (Berlin and Hanover, iSo,, 1803) was a controversial correspondence with Dr
TellerTeller may refer to:* a bank teller, a bank employee responsible for receiving and disbursing money; sometimes referred to as a cashier* a Teller who counts the votes in an election, vite, or poll.* an automated teller machine...
of Berlin in regard to the Mosaic cosmogony. His
Trail elementaire de geologie (8vo, Paris, 1809, also in English, by de la Fite, the same year) was principally intended as a refutation of
James HuttonJames Hutton MD was a Scottish geologist, physician, naturalist, chemist and experimental farmer. He is considered the father of modern geology...
and
John PlayfairJohn Playfair FRSE, FRS was a Scottish scientist and mathematician, and a professor of natural philosophy at the University of Edinburgh. He is perhaps best known for his book Illustrations of the Huttonian Theory of the Earth , which summarized the work of James Hutton...
. They had shown that geology was driven by the operation of internal heat and erosion. Their system required much more time than Deluc's
MosaicMosaic is the art of creating images with an assemblage of small pieces of colored glass, stone, or other materials. It may be a technique of decorative art, an aspect of interior decoration, or of cultural and spiritual significance as in a cathedral...
variety of
NeptunismNeptunism is a discredited and obsolete scientific theory of geology proposed by Abraham Werner in the late 18th century that proposed rocks formed from the crystallisation of minerals in the early Earth's oceans....
allowed.
He sent to the Royal Society, in 1809, a long paper on separating the chemical from the electrical effect of the dry pile a form of
Voltaic pileA voltaic pile is a set of individual Galvanic cells placed in series. The voltaic pile, invented by Alessandro Volta in 1800, was the first electric battery...
, with a description of the electric column and aerial electroscope, in which he advanced opinions so little in unison with the latest discoveries of the day, that the council deemed it inexpedient to admit them into the
Transactions. The paper was afterwards published in
Nicholson's Journal (xxvi.), and the dry column described in it was constructed by various experimental philosophers. His improvements to the dry pile has been regarded as his most important work although he was not in fact its inventor.
Many other of his papers on subjects kindred to those already mentioned are to be found in the
Transactions and in the
Philosophical Magazine. See Philosophical Magazine (November 1817).