A custom thermometer scale and a detailed scientific panorama of the Alps stand as the technical legacies of Jacques-Barthélemy Micheli du Crest. Born in 1690 to an aristocratic Genevan family, he transitioned from a military career into a life defined by political dissent, prolonged exile, and rigorous scientific observation while held as a state prisoner.
Military Service and Political Conflict
Du Crest graduated from the Collège de Genève in 1705 before entering French service in 1709. He participated in the War of the Spanish Succession, achieving the rank of captain by 1712 and qualifying as a military engineer at 23. Upon returning to civilian life in 1721, he joined the Council of Two Hundred in Geneva. His tenure was marked by vocal opposition to the local oligarchy, particularly regarding a controversial city wall project. His published pamphlets, notably Maxims of a Republican, led to the revocation of his citizenship, the seizure of his lands, and a death sentence in absentia in 1735, accompanied by the public beheading of his effigy.
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During his exile, Du Crest focused on the standardization of temperature measurement. He devised a scale based on two fixed points: the boiling point of water and the constant temperature of the earth found in a cellar 84 feet below the Paris Observatory. Rejecting mercury due to purification difficulties, he engineered alcohol-based thermometers. He utilized alcohol that passed the gunpowder test, arguing that the substance provided more reliable and regular expansion than mercury. His temperature scale remained a standard fixture in scientific and public life throughout Switzerland and parts of Europe until the 19th century.
Cartographic Innovation at Aarburg Castle
Following his arrest in 1746 for his involvement in the Samuel Henzi conspiracy, Du Crest spent the remainder of his life confined in Aarburg Castle. Lacking modern surveying equipment, he developed rudimentary yet effective methods to map the Alps. He calculated mountain heights using an eight-meter long gutter filled with water for leveling, paired with a sighting rod. By integrating these measurements with the 1712 Scheuchzer map, he produced the first scientific panorama of the Alpine range. He continued his meteorological studies and publication output until his death in 1766 in Zofingen.
Fast facts
- Born: 28 September 1690, Geneva
- Died: 29 March 1766, Zofingen
- Citizenship: Republic of Geneva
- Key Occupations: Military engineer, physicist, cartographer
- Education: Collège de Genève, 1705
- Incarceration: Aarburg Castle
- Religion: Reformed
Questions readers ask
Why did Du Crest prefer alcohol over mercury in his thermometers?
He believed alcohol was easier to purify and expanded more regularly than mercury, allowing for higher calibration accuracy.
How did he measure mountain heights without a theodolite?
He used an eight-meter water-filled gutter for leveling and a sighting rod, cross-referencing his measurements with the 1712 Scheuchzer map.
Achievements
- Recorded as physicist, cartographer and military engineer
