CASSINI

cassini, the name of an italian family of astronomers, four generations of whom succeeded each other in official charge of the observatory at paris. giovanni domenico cassini (1625-1712), the first of these, was born at perinaldo near nice on the 8th of june 1625. educated by the jesuits at genoa, he was nominated in 1650 professor of astronomy in the university of bologna; he observed and wrote a treatise on the comet of 1652; was employed by the senate of bologna as hydraulic engineer; and appointed by pope alexander vii. inspector of fortifications in 1657, and subsequently director of waterways in the papal states. his determinations of the rotation-periods of jupiter, mars and venus in 1665-1667 enhanced his fame; and louis xiv. applied for his services in 1669 at the stately observatory then in course of erection at paris. the pope (clement ix.) reluctantly assented, on the understanding that the appointment was to be temporary; but it proved to be irrevocable. cassini was naturalized as a french subject in 1673, having begun work at the observatory in september 1671. between 1671 and 1684 he discovered four saturnian satellites, and in 1675 the division in saturn's ring (see saturn); made the earliest sustained observations of the zodiacal light, and published, in _les elements de l'astronomie verifies_ (1684), an account of jean richer's (1630-1696) geodetical operations in cayenne. certain oval curves which he proposed to substitute for kepler's ellipses as the paths of the planets were named after him "cassinians." he died at the paris observatory on the 11th of september 1712. a partial autobiography left by giovanni domenico cassini was published by his great-grandson, count cassini, in his _memoires pour servir a l'histoire des sciences_ (1810). see also c. wolf, _histoire de l'observatoire de paris_ (1902); max. marie, _histoire des sciences_, t. iv. p. 234; r. wolf, _geschichte der astronomie_, p. 450, &c. jacques cassini (1677-1756), son of domenico cassini, was born at the paris observatory on the 8th of february 1677. admitted at the age of seventeen to membership of the french academy of sciences, he was elected in 1696 a fellow of the royal society of london, and became _maitre des comptes_ in 1706. having succeeded to his father's position at the observatory in 1712, he measured in 1713 the arc of the meridian from dunkirk to perpignan, and published the results in a volume entitled _de la grandeur et de la figure de la terre_ (1720) (see geodesy). he wrote besides _elemens d'astronomie_ (1740), and died on the 18th of april 1756 at thury, near clermont. the first tables of the satellites of saturn were supplied by him in 1716. see c. wolf, _histoire de l'observatoire de paris_; max. marie, _histoire des sciences_, vii. 214; r. wolf, _geschichte der astronomie_, p. 451; j.c. houzeau, _bibl. astronomique_; j. delambre, _histoire de l'astronomie au xviii'e siecle_, pp. 250-275 (unfairly depreciatory); j.f. montucla, _hist. des mathematiques_, iv. 145, 248.