Joseph-Nicolas de L'Isle (Delise)

Joseph-Nicolas de I'Isle (Delisle), known as Delisle the younger or the younger, born in Paris on April 4, 1688, and died in the same city on September 11, 1768, is an astronomer, cartographer, and professor of French.

He is one of the eleven sons of Claude Delisle (1644–1720). Like many of his brothers, and notably Guillaume Delisle (1675–1726), he undertook classical studies, but he quickly turned to astronomy under the direction of Jacques Cassini (1677–1756). In1714, he entered the Academy of Sciences as a student of Giacomo Filippo Maraldi. Become assistant, then associate astronomer at the Academy in 1716 and 1719, professor at the College of France in 1718 and member of the Academy of Rouen, he has for students Jean-Paul Grandjean de Fouchy, Joseph Jérôme Lefrançois de Lalande and Charles Messier.

Although a good scientist and a member of a wealthy family, he did not have much money. His life changed radically when he was called by the Emperor of Russia Peter the Great to Saint Petersburg in 1725 to found and direct a school of astronomy at the Russian Academy of Sciences, where he called, in 1726, his brother Louis. He founded the Saint Petersburg observatory. He became relatively rich and famous there, so much so that when he returned to Paris in 1747, he received the title of astronomer and could create his own observatory at the Hôtel de Cluny; this observatory was later made famous by Charles Messier.

Delisle showed in particular that rainbows are caused by the separation of light from the sun by the water drops. He also worked on the calculation of the distance from Earth to the Sun and observed the transit of Mercury and the transit of Venus. It is best known for a temperature scale, invented in1732, the Delisle scale.

He made meteorological observations in Saint Petersburg from 1727 to 1747 which were used by Father Cotte in his treatise on meteorology. He continued in Paris until 1760 and used several types of Mercury and wine spirit thermometers in order to be able to make intercomparisons between the instruments. These data are kept at the Paris Observatory.

He died octogenarian, poor and forgotten.

He was a member of the Russian Academy of Sciences 5 (since 1747) and a foreign member of the Royal Swedish Academy of Sciences (since 1749).

Eponymic The Delisle lunar crater was named in his honor in 1935. On the Moon too, Mons Delisle. The asteroid (12742) Delisle, discovered by Eric Walter Elst, also pays tribute to him.

Bibliography Jean-Paul Grandjean de Fouchy , Praise of M. de L'Isle , in Histoire de l'Académie royale des sciences - Year 1768 , Imprimerie royale, Paris, 1770, p. 167-183

Joseph-Nicolas Delisle, on the Mathematics Genealogy Project website

Jean-Pierre Poussou, French influence in Russia in the xviii the century, Presses Paris Sorbonne 2004, p. 504–517

A member of the Royal Academy of Sciences