Jean Rey (c. 1583 – c. 1645) or (''in English'') John Rey was a French physician and chemist. Born in

Le Bugue Le Bugue (; oc, Al Buga or ''Lo Buga'') is a commune in the Dordogne department in southwestern France. Geography Le Bugue is located on the banks of the river Vézère a few kilometres before the confluence of the Vézère with the Dordogne a ...

, in the

Périgord Périgord ( , ; ; oc, Peiregòrd / ) is a natural region and former province of France, which corresponds roughly to the current Dordogne department, now forming the northern part of the administrative region of Nouvelle-Aquitaine. It is div ...

(

Dordogne Dordogne ( , or ; ; oc, Dordonha ) is a large rural department in Southwestern France, with its prefecture in Périgueux. Located in the Nouvelle-Aquitaine region roughly half-way between the Loire Valley and the Pyrenees, it is named ...

département In the administrative divisions of France, the department (french: département, ) is one of the three levels of government under the national level (" territorial collectivities"), between the administrative regions and the communes. Ninety ...

''), he studied medicine at the

University of Montpellier The University of Montpellier (french: Université de Montpellier) is a public research university located in Montpellier, in south-east of France. Established in 1220, the University of Montpellier is one of the oldest universities in the wor ...

. He practised medicine in his native town and corresponded with Descartes and

Mersenne Marin Mersenne, OM (also known as Marinus Mersennus or ''le Père'' Mersenne; ; 8 September 1588 – 1 September 1648) was a French polymath whose works touched a wide variety of fields. He is perhaps best known today among mathematicians for ...

. He discovered that the weight of

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...

and tin increases when they are calcinated, and attributed this phenomenon to the weight of air, which he believed to become denser when heated (''Essays'', 1630). He explained the greater weight of calcinated lead and tin by supposing that calcination involves the incorporation of air in the metal. This hypothesis would later be confirmed by Lavoisier, over a century later in 1789. His discovery of the weight of air also made possible the invention of the

barometer A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis ...

by Torricelli in 1643. He also developed a device called a "Thermoscope", a precursor of the

thermometer A thermometer is a device that measures temperature or a temperature gradient (the degree of hotness or coldness of an object). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer ...

. Jean Rey died in

, where he had lived all his life. The exact date of his death is disputed.

References

1580s births 1640s deaths 17th-century French chemists 17th-century French physicians People from Dordogne {{France-scientist-stub