Petit, Peter

, a considerable mathematician and philosopher of France, was born at Montlugon, in the diocese of Bourges, in 1598, according to some, but in 1600 according to others. He first cultivated the mathematics and philosophy in the place of his nativity; but in 1633 he repaired to Paris, to which place his reputation had procured him an invitation. Here he became highly celebrated for his ingenious writings, and for his connections with Pascal, Des Cartes, Mersenne, and the other great men of that time. He was employed on several occasions by cardinal Richelieu; particularly to visit the sea-ports, with the title of the king’s engineer; and was also sent into Italy upon the king’s business. He was at Tours in 1640, where he married; and was afterwards made intendant of the fortifications. Baillet, in his Life of Des Cartes, says, that Petit had a great genius for mathematics; that he excelled particularly in astronomy; and had a singular passion for experimental philosophy. About 1637 he returned to Paris from Italy, when the dioptrics of Des Cartes were much spoken of. He read them, and communicated his objections to Mersenne, with whom he was intimately acquainted, and yet soon after embraced the principles of Des Cartes, becoming not only his friend, but his partisan and defender. He was intimately connected with Pascal, with whom he made at Rouen the same experiments concerning the vacuum, which Torricelli had before made in Italy; and was assured of their truth by frequent repetitions. This was in 1646 and 1647; and though there appears to be a long interval from this date to the time of his death, we meet with no other memoirs of his life. He died August 20, 1667, at Lagny, near Paris, whither he had retired for some time before his decease. | Petit was the author of several works upon physical and astronomical subjects; the principal of which are, 1. “Chronological Discourse,” &c. 1636, 4to, in defence of Scaliger. 2. “Treatise on the Proportional Compasses.” 3. “On the Weight and Magnitude of Metals.” 4. “Construction and Use of the Artillery Calibers.” 5. “On a Vacuum.” 6. “On Eclipses.” 7. “On Remedies against the Inundations of the Seine at Paris.” 8. “On the Junction of the Ocean with the Mediterranean Sea, by means of the rivers Aude and Garonne.” 9. “On Comets.” 10. “On the proper Day for celebrating Easter.” 11. “On the nature of Heat and Cold,” &c. ¹