Jacques-Barthélemy Micheli du Crest (

Geneva Geneva ( , ; ) ; ; . is the List of cities in Switzerland, second-most populous city in Switzerland and the most populous in French-speaking Romandy. Situated in the southwest of the country, where the Rhône exits Lake Geneva, it is the ca ...

, 28 September 1690 –

Zofingen Zofingen () is a city in the canton of Aargau in Switzerland. It is the capital of the district of Zofingen. Zofingen is a walled city and home to an ancient monastic settlement. History In ancient times Zofingen was a settlement of the Celtic ...

, 29 March 1766) was a military engineer, physicist and cartographer from the

Republic of Geneva The Canton of Geneva, officially the Republic and Canton of Geneva, is one of the Cantons of Switzerland, 26 cantons of the Switzerland, Swiss Confederation. It is composed of forty-five Municipality, municipalities, and the seat of the governme ...

, now in

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. Born into the aristocracy, he eventually fled to France as an enemy of Geneva and spent his later years in Aarburg Castle as a political prisoner. During his time there, he mapped the

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accurately using rudimentary tools. One of his other major accomplishments whilst in exile was to create a thermometer and a temperature scale, which was commonly used in Switzerland and around Europe until it became obsolete in the 19th century.

Early life and career

Du Crest was born in Geneva to Jacques Micheli du Crest, a captain in the mercenary troops of France, and Elisabeth Calandrini. He graduated from the

Collège de Genève In France, secondary education is in two stages: * ''Collèges'' () cater for the first four years of secondary education from the ages of 11 to 14. * ''Lycées'' () provide a three-year course of further secondary education for students between ...

in 1705. Du Crest entered French service in 1709 and fought in the

War of the Spanish Succession The War of the Spanish Succession was a European great power conflict fought between 1701 and 1714. The immediate cause was the death of the childless Charles II of Spain in November 1700, which led to a struggle for control of the Spanish E ...

, reaching the rank of captain in 1712. He became a military engineer by the age of 23. In 1721, after leaving the army, Du Crest took up his place as a member of Geneva's Council of Two Hundred, as was his family's right, specialising in security. During his time in the parliament, Du Crest argued against the Genevan

oligarchy Oligarchy (; ) is a form of government in which power rests with a small number of people. Members of this group, called oligarchs, generally hold usually hard, but sometimes soft power through nobility, fame, wealth, or education; or t ...

and was an outspoken critic of the planned wall around Geneva. Eventually, due to his views and publishing pamphlets such as "Maxims of a Republican", he was declared an enemy of Geneva, his rights as a citizen were revoked, and his lands were confiscated. Du Crest fled to

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in 1731. In 1735, he was sentenced to death ''in absentia'' and his

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was symbolically beheaded in Geneva.

Life in exile and as a political prisoner

Whilst in France, Du Crest spent much of his time dedicated to scientific study. He made advances in the study of temperature and came up with a recognised temperature scale which was used in Switzerland for many years. Du Crest was still outspoken regarding political issues, and lost the support of the people protecting him in France. He was forced to flee again across Europe in 1744, stopping in major cities such as Zurich and Bern, until he became ill and was hospitalised in Bern's Inselspital, where he was arrested in 1746. He was moved to Aarburg Castle, after getting involved with

Samuel Henzi Samuel Henzi (19 April 1701 in Bümpliz of Bern – executed 17 July 1749 in Bern) was a Swiss writer, politician and revolutionary. He is chiefly known for his role in the "Henzi conspiracy" of June 1749, which aimed to overthrow the patrician ...

's conspiracy, where he was held as a political prisoner for the remainder of his life.

Scientific achievements

Du Crest devoted a significant portion of his life in exile to scientific study, making pioneering developments in cartography and the measurement of temperature.

Temperature scale

Du Crest believed that the temperature of the Earth was fundamentally fixed, based on the supposition that cellars and mines maintained an equal temperature. He used this "temperature of the terrestrial globe" as one fixed point, measured in a cellar below

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, and the temperature of boiling water as a second fixed point. His scale between these points was then divided into one hundred equal degrees.

Thermometer

Du Crest rejected mercury thermometers, stating that the substance was too difficult to purify, preferring instead alcohol which had passed the gunpowder test. He created a thermometer based the expansion of alcohol, calibrated using mercury. He further published works that explained his belief that alcohol expanded more regularly than mercury, and his experiments matched his scale more accurately than mercury did.

Mapping the Alps

During his time at Aarburg Castle he published many meteorological papers and created a cartographical drawing of the Alps as viewed from the castle. Without any modern equipment, such as a

theodolite A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and ...

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

he instead used an eight-meter long gutter pipe, filled with water to measure levels and a small rod held in front of it, he could measure the heights of the peaks. He then used the Scheuchzer map of 1712 to calculate the distances away, and drew the first scientific panorama of the Alps.

References

{{DEFAULTSORT:Micheli du Crest, Jacques-Barthelemy 1690 births 1766 deaths 18th-century physicists from the Republic of Geneva 18th-century politicians from the Republic of Geneva 18th-century military personnel of the Republic of Geneva 18th-century cartographers Military engineers French military personnel of the War of the Spanish Succession People sentenced to death in absentia Prisoners who died in Swiss detention