Editing Jean-André Deluc (section)

=== Observations and theory ===
Deluc's main interests were geology and meteorology; [[Georges Cuvier]] mentions him as an authority on the former subject.<ref name=Cuvier/> His major geological work, ''Lettres physiques et morales sur les montagnes et sur l'histoire de la terre et de l'homme'' (6 vol., 1778–1780), was dedicated to Queen Charlotte. He published volumes on geological travels: in northern Europe (1810), in England (1811), and in France, Switzerland and Germany (1813).{{sfn|Chisholm|1911|p=976}}

Deluc noticed the disappearance of heat in the thawing of ice about the same time that [[Joseph Black]] made it the foundation of his hypothesis of [[latent heat]]. He ascertained that water was densest at about 5&nbsp;°C (and not at the freezing temperature).<ref name=Recherches/> He was the originator of the theory, later reactivated by [[John Dalton]], that the quantity of [[water vapour]] contained in any space is independent of the presence or density of the air, or of any other elastic fluid.{{sfn|Chisholm|1911|p=976}}

His book ''Lettres sur l'histoire physique de la terre'' (Paris, 1798), addressed to [[Johann Friedrich Blumenbach]], develops a theory of the Earth divided into six periods modelled on the six days of Creation. It contains an essay on the existence of a [[Moral realism|General Principle of Morality]] and gives an interesting account of conversations with [[Voltaire]] and [[Rousseau]]. Deluc was an ardent admirer of [[Francis Bacon]], on whose writings he published two works: ''Bacon tel qu'il est'' (Berlin, 1800), showing the bad faith of the French translator, who had omitted many passages favorable to revealed religion, and ''Précis de la philosophie de Bacon'' (2 vols 8vo, Paris, 1802), giving an interesting view of the progress of natural science. ''Lettres sur le christianisme'' (Berlin and Hanover, 1803) was a controversial correspondence with [[Wilhelm Abraham Teller]] of Berlin in regard to the [[Moses|Mosaic]] [[cosmogony]]. His ''Traité élémentaire de géologie'' (Paris, 1809, translated into English by Henry de la Fite the same year) was principally intended as a refutation of [[James Hutton]] and [[John Playfair]]. They had shown that geology was driven by the operation of internal heat and erosion, but their system required much more time than Deluc's [[Moses|Mosaic]] variety of [[neptunism]] allowed.{{sfn|Chisholm|1911|p=976}}

Many other papers were in the ''Journal de Physique'', in the ''Philosophical Transactions'' and in the ''[[Philosophical Magazine]]''.{{sfn|Chisholm|1911|p=976}}