PARENT (Unsoigne), a mathematician, was born at Paris in 1666. He showed an early propensity to mathematics. He accustomed himself to write remarks upon the margins of the books which he read; and he had filled a variety of books with a kind of commentary at the early age of thirteen. At fourteen he was put under a master, who taught rhetoric at Chartres. It was here that he happened to see a dodecoëdron, upon every face of which was delineated a sun-dial, except the lowest, whereon it stood. Struck as it were instantaneously with the curiosity of these dials, he attempted drawing one himself: but having a book which only showed the practical part without the theory, it was not till after his rhetoric master came to explain the doctrine of the sphere to him that he began to understand how the projection of the circles of the sphere formed sun-dials. He then undertook to write a Treatise upon Gnomonics. The piece was indeed rude and unpolished; but it was entirely his own, and not borrowed. About the same time he wrote a book of Geometry, in the same taste, at Beauvais. His friends then sent for him to Paris to study the law; and, in obedience to them, he studied a course in that faculty: which was no sooner finished than, urged by his passion for mathematics, he shut himself up in the college of Dormans, that no avocation might take him from his beloved study: and, with an allowance of less than 200 livres a-year, he lived content in this retreat, from which he never stirred but to the Royal College, in order to hear the lectures of M. de la Hire or M. de Sauveur. When he found himself capable of teaching others, he took pupils: and fortification being a branch of mathematics which the war had brought into particular notice, he turned his attention to it; but after some time began to entertain scruples about teaching what he had never seen, and knew only by the force of imagination. He imparted this scruple to M. Sauveur, who recommended him to the Marquis d'Aligre, who luckily at that time wanted to have a mathematician with him. Parent made two campaigns with the marquis, by which he instructed himself sufficiently in viewing fortified places; of which he drew a number of plans, though he had never learned the art of drawing. From this period he spent his time in a continual application to the study of natural philosophy, and mathematics in all its branches, both speculative and practical; to which he joined anatomy, botany, and chemistry. His genius managed every thing, and yet he was incessant and indefatigable in his application. M. de Billettes, who was admitted in the academy of sciences at Paris in 1699, with the title of their mechanician, nominated for his disciple Parent, who excelled chiefly in this branch. It was soon discovered in this society, that he engaged in all the various subjects which were brought before them; and indeed that he had a hand in every thing. But this extent of knowledge, joined to a natural impetuosity of temper, raised in him a spirit of contradiction, which he indulged on all occasions; sometimes to a degree of precipitancy highly culpable, and often with but little regard to decency. Indeed the same behaviour was shown to
him, and the papers which he brought to the academy were often treated with much severity. He was charged with obscurity in his productions; and he was indeed so notorious for this fault, that he perceived it himself, and could not avoid correcting it. The king had, by a regulation in 1716, suppressed the class of scholars of the academy, which seemed to put too great an inequality betwixt the members. Parent was made a joint or assistant member for geometry: but he enjoyed this promotion but a short time; for he was taken off by the small-pox the same year, at the age of 50. He was author of a great many pieces, chiefly on mechanics and geometry.