Dominique, comte de Cassini

Jean-Dominique, comte de Cassini (30 June 1748 – 18 October 1845) was a French astronomer, son of César-François Cassini de Thury.

Cassini was born at the Paris Observatory. In 1784 he succeeded his father as director of the observatory; but his plans for its restoration and re-equipment were wrecked in 1793 by the animosity of the National Assembly. His position having become intolerable, he resigned on 6 September and was thrown into prison in 1794, but released after seven months. He then withdrew to Thury, where he died in 1845.

He published in 1770 an account of a voyage to America in 1768, undertaken as the commissary of the French Academy of Sciences with a view to testing Pierre Le Roy’s watches at sea. In 1783 he sent a memoir to the Royal Society in which he proposed a trigonometric survey connecting the observatories of Paris and Greenwich for the purpose of better determining the latitude and longitude of the latter. His proposal was accepted, resulting in the Anglo-French Survey (1784–1790). The results of the survey were published in 1791. He visited England for the purposes of the work with Pierre Méchain and Adrien-Marie Legendre, and the three met William Herschel at Slough. He completed his father’s map of France, which was published by the Academy of Sciences in 1793. It served as the basis for the Atlas National (1791), showing France in departments. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1788.

Cassini’s Mémoires pour servir à l’histoire de l’observatoire de Paris (1810) embodied portions of an extensive work, the prospectus of which he had submitted to the Academy of Sciences in 1774. The volume included his Eloges of several academicians, and the autobiography of his great-grandfather, Giovanni Cassini.

His youngest son Henri was a botanist of some note.