PETIT, PIERRE, a French mathematician, was born at Montluçon in 1594, and removed from his native place to Paris in 1633. His aptitude for the exact sciences soon opened up for him a career of distinction. The French government employed him to inspect the seaports of France and Italy, and appointed him provincial commissary of ar-
tillery and intendant-general of fortifications. Several scientific works in the meanwhile proceeded from his pen, and increased his reputation as a man of learning. He was also honoured to take part in the celebrated discussions touching the "Dioptrics" of Descartes, and to assist Pascal in making experiments on the phenomena of the common pump. The death of Petit took place at Lagny, on the Marne, in 1677. The following is a list of the most important works of Petit: L'Usage du Compas de Proportion, 8vo, Paris, 1634; Observations touchant le Vide, 4to, Paris, 1647; Dissertation sur la Nature des Comètes, 4to, Paris, 1665; and Dissertation sur la Nature du Chaud et du Froid, 12mo, Paris, 1671.