CLAIRAUT, ALExis CLAUDE, a celebrated French mathematician and natural philosopher, was born at Paris on the 13th of May 1713. His father, Jean Baptiste Clairaut, who was a teacher of mathematics at Paris, and member of the Rnyal Academy of Sciences at Berlin, had no fewer than 21 children. Our author was the se cond child, and the third was carried off by a premature death at the age of 16, after he had published an able work on the quadrature of the circle, and the hyperbola.
Young Clairaut was taught the alphabet upon the fi gures of Euclid's Elements, and such was the rapidit% of his progress, that, at the age of 4 years, he was able both to write and read. lie was instructed in the prin ciples of arithmetic by the most simple and ingeniotr methods ; and a love of the military profession, which he early displayed, was employed by his father as a power ful stimulus to the study of mathematics, and uthet branches of knowledge, which were represented as neces sary accomplishments in a young soldier.
At the age of time years, his attention was directed to M. Guisnee's Treatise on the Application of Algebra to Geometry. With the help which he received from his father, he speedily read this work, and, after studying it a second and a third time by himself, he resolved the greater number of the problems in a more simple and ingenious manner than the author himself. Clairaut now began to experience the delight which springs from the successful exercise of genius, and he continued his stu dies with an intensity of application, which, if not season ably checked, would have endangered his health. At the age of ten, he read the Marquis de L'Hopital's Conic Sections, but he experienced considerable difficulty in making himself master of the subject. M. de Lisle, who was visiting his father, happened to see young Clairaut with this volume in his hands, and remarked, with a kind of sarcastic severity, that he could understand this book only by its title and its cover. The young geometer was affronted with the remark, though he felt it to a certain degree true, and he gave himself no rest till he was com pletely master of the subject. He next studied the analysis of infinites of the sante author, and initiated him self into the differential and integral calculus.
The reputation of Clairaut, which was hitherto confined to his own friends, now began to extend with rapidity.
The celebrated M. Nericaut Destouches having just ar rived from England with his lady, who was about to be confined, took lodgings immediately below the house of Clairaut, and sent up a request to the family to make as little noise as possible, both on account of his wife's in disposition, and as he was himself employed in writing his fine tragedy of the Philosophc Marie. This request was so scrupulously attended to, that M. Destouches went in person to thank M. Clairaut for his kindness. He was surprised to find, that he had been living below a family of 11 children; and he was so much pleased with the young mathematician, that he introduced him to the Abbe Bignon, and to other celebrated members of the Academy.
About this time M. Clairaut removed to another house in which there was a small room, which was allotted to the use of our author and his younger brother, of whom we have already spoken. This room was so situated, that they could go in and come out without being per ceived, and the two brothers did not fail to abuse this ad vantage. They procured a flint, by means of which they might light their candle, and when the familv imagined them to be buried in sleep, they were eagerly engaged in the study of geometry. Alexis was now secretly occupied with a memoir on four curves of the third order, which he had newly discovered, and by means of which he could find any number of mean proportionals between two given lines, and he wished to surprise his father with this memoir when completed. Before it was finished, however, the geometrical plot was detected, and the young culprits received a severe reprimand. Delighted with the discovery of the new curves, M. Clairaut pre sented his son to the Academy of Sciences, for the purr pose of reading his memoir to that learned body ; but his size bore so slender a proportion to the abilities which were displayed, that it was only after a rigid examination of the young man, that the academicians believed hint to be the author of the discovery. Father Heyman, whose .1nalyse Demontree had first roused the genius of D'Alem bert, and who was present at this meeting of the Academy, burst into tears of joy at the exhibition of such wonderful and premature talents. The memoir of our author was published in the Miscellanea Berolinensia for 1724, with an honourable certificate from the Academy.