1740 in science

The year 1740 in science and technology involved some significant events.

Mathematics

Jean Paul de Gua de Malves publishes his work of analytic geometry, {{sic|Usages de l'analyse de Descartes pour découvrir, sans le secours du calcul differentiel, les propriétés, ou affections principales des lignes géométriques de tous les ordres}}.

Benjamin Huntsman develops the technique of crucible steel production at Handsworth, South Yorkshire, England.{{cite book|first=Samuel|last=Smiles|authorlink=Samuel Smiles|title=Industrial Biography|year=1879|page=99}}

Jacques-Barthélemy Micheli du Crest creates a spirit thermometer, making use of two fixed points, 0 for "Temperature of earth" based on a cave at Paris Observatory and 100 for the heat of boiling water.{{cite book|last=Hutton|first=Charles|title=A Philosophical and Mathematical Dictionary: Volume 2|year=1815|publisher=S. Hamilton|location=Weybridge, Surrey|page=509|url=https://books.google.com/books?id=lsdJAAAAMAAJ}}
Émilie du Châtelet publishes Institutions de Physique, including a demonstration that the energy of a moving object is proportional to the square of its velocity (E_k = {{frac|1|2}}mv²).
Louis Bertrand Castel publishes L'Optique des couleurs in Paris, including the observation that the colours of white light split by a prism depend on distance from the prism.

Henry Hindley of Yorkshire invents a device to cut the teeth of clock wheels.{{cite book|last=Williams|first=Hywel|title=Cassell's Chronology of World History|url=https://archive.org/details/cassellschronolo0000will|url-access=registration|location=London|publisher=Weidenfeld & Nicolson|year=2005|isbn=0-304-35730-8|page=[https://archive.org/details/cassellschronolo0000will/page/308 308]}}

Copley Medal: Alexander Stuart{{cite web |title=Copley Medal {{!}} British scientific award |url=https://www.britannica.com/science/Copley-Medal |website=Encyclopedia Britannica |accessdate=21 July 2020 |language=en}}

February 17 – Horace Bénédict de Saussure, Genevan pioneer of Alpine studies (died 1799)
March 28 (bapt.) – James Small, Scottish inventor (died 1793)
June 27 – John Latham, English physician and naturalist, "grandfather of Australian ornithology" (died 1837)
July 1 – Franz-Joseph Müller von Reichenstein, Austrian mineralogist and discoverer of tellurium (died 1825)
August 26 – Joseph Michel Montgolfier, French pioneer balloonist (died 1810)
September 29 – Thomas Percival, English reforming physician and medical ethicist (died 1804)
December 24 – Anders Johan Lexell, Finnish-Swedish astronomer and mathematician (died 1784)
unknown – William Smellie, Scottish naturalist and encyclopedist (died 1795)