Hire, Philip De La

, an eminent French mathematician and astronomer, was born at Paris, March 18, 1640. His father Laurence, who was painter in ordinary to dm king, professor in the academy of painting and sculpture, and much celebrated, intended him also for the same occupation; and with that view taught him the principles of design, and some branches of mathematics, but died when Philip was no more than seventeen. Falling afterwards into a bad habit of body, he projected a journey into Italy; which he conceived might contribute not less to the recovery of his health, than to bring him to perfection in his art. He accordingly set out in 1660, and soon found himself well enough to contemplate the remains of antiquity, with which Italy abounds, and also to study geometry, to which he had indeed more propensity than to painting, and which soon afterwards engrossed him entirely. The retired manner in which he spent his time in Italy, very much suited his disposition; and he would willingly have continued longer in that country, but for the importunity of his mother, who prevailed upon him to return, after an absence of about four years.

Being again settled in Paris, he continued his mathematical studies with the utmost intenseness: and published some works, which gained him so much reputation, that he was made a member of the academy of sciences in | 1678. The minister Colbert having formed a design of a better chart or map of the kingdom than any whica tiad hitherto been taken, de la Hire was nominated, with Picard, to make the necessary observations. He went to Bretagne in 1679, to Cayenne in 1680, to Calais and Dunkirk in 168, and into Provence in 1682. In these peregrinations he did not confine nis attention to their main object, but philosophized upon every thing that occurred, and particularly upon the variations of the magnetic needle, upon refractions, and upon the height of mountains, as determined by the barometer. In 1683 he was employed in continuing the meridian line, which Picard had begun in 1669. De la Hire continued it to the north of Paris, while Cassini pushed it on to the south: but Colbert dying the same year, the work was left unfinished. He was next employed, with other geometricians of the academy, ’in. taking the necessary levels for those grand aqueducts which Louis XIV. was about to make.

Geometry, however, did not take up all his time and labour; he employed himself upon other branches of mathematics and philosophy. Even painting itself, which he may seem to have discarded so long ago, had a place in those hours which he set apart for amusement. The great number of works which he published, togetner with his continual employments as professor of the royal college, and of the academy of architecture, to which places his merit had raised him, give us a very great idea of the labours he underwent. His days were always spent in study, his nights very often in astronomical observations; and he seldom sought any other relief from his labours, but a change of one for another. He was twice married, and had eight children. He had the exterior politeness, circumspection, and prudence of Italy, for which country he had a singular regard; and on this account appeared in the eyes of the French, too reserved. He is also said to have been a very honest disinterested man, and a good Christian. He died April 21, 1718, aged 78.

The principal of his works are: “Nouvelle Methode en Geometric pour les sections des superficies coniques & cylindriques,” 1673, 4to. 2. “De la Cycloide,” 1677, 12mo. 3. “Nouveaux Elemens des sections coniques: les lieux Geometriques; la construction ou effection des equations,” 1679, 12mo. 4. “La Gnomonique,” &c. 1682, J2mo. 5. “Sectiones Conicse in noveui hbfos distributee,” 1655, | folio. This was considered as an original work, and gained the author a great reputation all over Europe. 6. & “Tabulas Astronomicae,” 1687 and 1702, 4to. 7. “Veterum Mathematicorum Opera, Graece & Latine, pleraque nunc primum edita,” 16i>3, folio. This edition had been begun by M. Thevenot; who dying, the care of finishing it was committed to de la Hire. It shews that the author’s strong application to mathematical and astronomical studies, had not hindered him from acquiring a very competent knowledge of the Greek tongue. Besides these and other smaller works, there are a vast number of his pieces scattered up and down in journals, and particularly in the “Memoirs of the Academy of Sciences.” M. de Fontenelle wrote an eulogium upon him. ¹