HIRE (Philip de la)
, an eminent French mathematician and astronomer, was born at Paris in 1640. His father, who was painter to the king, intending him for the same occupation, taught him drawing and such branches of mathematics as relate to it: but died when the son was only 17 years of age. Three years after this, he travelled into Italy for improvement in that art, where he spent 4 years. He applied himself also to mathematics, which gradually engrossed all his attention. On his return to Paris, he continued his mathematical studies with great eagerness, and he afterwards published some works, which gained him so much reputation, that he was named a member of the Academy of Sciences in 1678.
The minister Colbert having formed a design for a better chart or map of France than any former ones, De la Hire was appointed, with Picard, to make the necessary observations for that purpose. This occupied him some years in several of the provinces; and, beside the main object of his peregrinations, he was not unmindful of other branches of knowledge, 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, de la Hire was employed in continuing the meridian line, which Picard had begun in 1669. He continued it from Paris northward, while Cassini carried it on to the south: but Colbert dying the same year, the work was dropped before it was finished. De la Hire was next employed, with other members of the academy, in taking the necessary levels for the grand aqueducts, which Louis the 14th was about to make.
The great number of works published by our author, together with his continual employments, as professor of the Royal College and of the Academy of Architecture, give us some idea of the great labours he underwent. His days were always spent in study; his nights very often in astronomical observations; seldom seeking any other relief from his labours, than a change of one for another. In his manner, he had the exterior politeness, circumspection, and prudence of Italy; on which account he appeared too reserved in the eyes of his countrymen; though he was always esteemed as a very honest disinterested man. He died in 1718, at 78 years of age.
Of the numerous works which he published, the principal are, 1. Traité de Mechanique; 1665.— 2. Nouvelle Methode en Geometrie pour les Sections des Supersicies Coniques & Cylindriques; 1673, 4to. —3. De Cycloide; 1677, 12mo.—4. Nouveaux Elemens des Sectiones Coniques: les Lieux Geometriques: la Construction, ou Effection des Equations; 1678, 12mo.—5. La Gnomonique, &c; 1682. 12mo.—6. Traité du Nivellement de M. Picard, avec des additions; 1684. —7. Sectiones Conicæ in novem libros distributæ; 1685, folio. This was considered as an original work, and gained the author great reputation all over Europe —8. Traité du Mouvement des Eaux, &c; 1686.— 9. Tabulæ Astronomicæ; 1687 and 1702, 4to.—10. Ecole des Arpenteurs; 1689.—11. Veterum Mathematicorum Opera, Græcè & Latinè, pleraque nunc primùm edita; 1693, folio. This edition had been begun by Thevenot; who dying, the care of finishing it was committed to de la Hire. It shews that our author's strong application to mathematical and astronomical studies had not hindered him from acquiring a very competent knowledge of the Greek tongue. Beside 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, viz, from 1666 till the year 1718.
