FERMAT, PIERRE DE (1601-1665), a famous mathematician, was born at Beaumont-de-Lomagno near Montauban. While still young he, along with Paseal, made some discoveries in regard to the properties of numbers, on which he afterwards built his method of calculating probabilities. He discovered a simpler method of quadrating parabolas than that of Archimedes, and a method of finding the greatest and smallest ordinates of crooked lines analogous to that of the then unknown differential calculus. His method of maxima and minima brought him into conflict with Descartes, but the dispute was due chiefly to a want of explicitness in the statement of Fermat. Fermat was for some time councillor for the parliament of Toulouse, and in the discharge of the duties of that office he was distinguished both for legal knowledge and for strict integrity of conduct. Though the sciences were the principal objects of his private studies, he was also an accomplished general scholar and an excellent linguist. He died at Toulouse in 1665. Ho left a son, Samuel de Fermat, who was a man of some learning, and published translations of several Greek authors.

The Opera Ilicahematica of Fermat were published at Toulouse, in 2 vols. folio, 1670 and 1679 ; they have now become very scarce. The first contains the "Arithmetic of Diophantus," with notes and additions. The second includes a " Method for the Qnadrature of Parabolas," and a treatise " on.Maxima and Minima, on Tangents, and on Centres of Gravity," containing the same solutions of a variety of problems as were afterwards incorporated into the more extensive method of fiuxions by Newton and Leibnitz. In the same volume are treatises on " Geometric Loci, or Spherical Tangeneies," and on the " Rectification of Curves," besides a restoration of "Apollonius's Plane Loci," together with the author's correspondence addressed to Descartes, Pascal, Roberval, Huygens, and others.