Beschreibung:

Cassini (Jean-Dominique, Comte de, 1748-1845). Extrait des Observations Astronomiques et Physiques faités par ordre de Sa Majeste, a l'Observatoire Royale, en année 1785. Sous le Ministere de M. le Baron de Breteuil. M. le Comte de Cassini, Directeur. M.rs de Villeneuve & Ruelle, Elèves, 1st edition, Paris, De l'Imprimerie Royale, 1786, front blank, title, viii + 24pp., with contemporary manuscript errata slip in brown ink pasted to inside rear wrapper, at end, untrimmed, original marbled wrappers, worn with some soiling and fraying, slim 4to Jean-Dominique Cassini IV (1748-1845) was the fourth generation of the Cassini family to engage in important astronomical work as director of the Paris Observatory, his great-grandfather being Giovanni Domenico Cassini (or Jean Dominique after he was granted French citizenship, 1625-1712), who discovered four of Jupiter's moons, and correctly identified the rings of Saturn as divided into two parts (the 'Cassini Division'). Cassini IV, as the younger Cassini is known, set up a perpetual course of observations at the Royal Observatory in Paris, with the assistance of three students (Jacques Perny de Villeneuve, Nicolas-Antoine-Nouet and Alexandre Ruelle) who worked under his direction from 1785, taking turns continuously day and night; their observations were drawn up, calculated and published each year in the form of a report inserted in the Memoires de l'Academie Royale des Sciences. 100 separately-issued copies of each extract were distributed to fellow astronomers across Europe (this copy presumably one of these). See Charles Wolf, Histoire de l'Observatoire de Paris de sa fondation à 1793, Paris, 1902, pp. 265-269).