HIRE, PHILIPPE DE LA

HIRE, PHILIPPE DE LA, a distinguished French geometer of the seventeenth and eighteenth centuries, was born in Paris in 1640. His father, Laurent de la Hire, was a painter and engraver of considerable note, and the son's education was at first shaped so as to fit him for the same career. In his twentieth year La Hire made a pilgrimage into Italy, and while at Venice fell in with the Conic Sections of Apollonius, which determined his taste for mathematical study. His own treatise on this subject, published in 1685, under the title of Sectiones Conicæ in Novem Libros Distributæ, is the most important of all his works. In 1678 he was admitted into the Academy of Sciences, and was afterwards appointed by Colbert to assist Picard in conducting the surveys for a general map of France. A few years later it devolved upon him to continue, along with Cassini, the measurements of the meridian begun by Picard in 1669, and the work was progressing happily till stopped by the untimely death of Colbert. He was subsequently employed on a great number of public works, of which the most important were connected with the supply of water to Versailles and Paris. "France might have had in La Hire," says Fontenelle, "an entire Academy of Sciences." He was a quiet man, of great practical prudence, very reserved in manner, and of the most spotless integrity of personal character. His piety was as much admired by his friends as his probity. He was twice married, and two of his sons were admitted into the Academy of Sciences, the one on the score of his geometrical, the other of his botanical knowledge. La Hire died suddenly in 1718. His principal works are—

Nouvelle Méthode de Géométrie pour les Sections des Surfaces Coniques et Cylindriques, Paris, 1673, in 4to; De Cycloïde Opusculum, ibid. 1676, in 4to; Nouveaux Éléments des Sections Coniques, les Lignes Géométriques, la construction ou affection des Équations, ibid. 1679, in 12mo; La Géométrie, ou l'art de tracer des cadranes, ibid. 1682, in 12mo; Sectiones Conicæ, in ix. libros distributæ, ibid. 1685, in folio; Tabula Astronomica, Ludovici Magni iussu et

munita exarata, ibid. 1702, in 4to; L'Ecole des Arpenteurs, avec un Abrégé du Nivellement, ibid. 1689, in 8vo; Traité de Mécanique, où l'on explique tout ce qui est nécessaire dans la pratique des Arts, ibid. 1675, in 12mo; besides a great number of Mémoires, in different journals, and in the Collection of the Academy. La Hire was also editor of the Traité du Nivellement by Plearde; of the Traité du Mouvement des Eaux by Mariotte, and joint editor with Bolvin and Thévenot of the Veteres Mathematici Græc. et Latin., 1693.