HIRE, PHILIP DE LA, a French mathematician and astronomer of eminence, was born at Paris in the year 1640.
Hire 1640. His father, who was painter to his majesty, de-
Hitchfield signing to bring him up to the same occupation, taught
him drawing and such parts of the mathematics as are
intimately connected with it. At the age of 20 he took
a journey into Italy, to enlarge his knowledge of his
favourite art, in which country he resided for about four
years. The study of the mathematics afterwards occu-
pied all his attention, which he continued to prosecute
on his return to his native city; and the publication of
some works having procured him so high a reputation,
he was chosen a member of the Academy of Sciences in
the year 1678.
When the celebrated minister Colbert conceived the
design of constructing a better map of France than any
at that time to be met with, De la Hire was nominated
in conjunction with Picard, to make the necessary obser-
vations, which engaged his attention for some years in
different provinces. But besides the chief object of his
journey, he philosophized upon every thing that occu-
rred to him, in a particular manner on the variations of
the magnetic needle, on refractions, and the height of
mountains as ascertained by the barometer.
In the year 1687 he was employed in continuing the
meridian line which had been begun by Picard in 1669.
He continued it from Paris towards the north, and Cas-
sini carried it on towards the south; but on the death
of Colbert, which happened the same year, the work
was laid aside in an unfinished state. He was afterwards
employed, in conjunction with other eminent philoso-
phers, in taking the necessary levels for the grand aqued-
ucts which Louis XIV. was about to make.
The works which have been published by De la Hire
are very numerous; and as he was professor of the Royal
College and Academy of Architecture, he must have
been constantly employed. He had the politeness, circumspection,
and prudence of Italy, which made him
appear too reserved in the estimation of his versatile coun-
trymen, yet he was regarded by all as an honest, disin-
terested man. He died in the year 1718, at the great
age of 78.
He published Traité de Méchanique; Nouvelle Méthode en Géométrie pour les Sections des Superficies Coniques et Cylindriques; De Cycloïde; Nouveaux Éléments des Sections Coniques; les Lieux Géométriques; la Construction ou Effection des Équations; La Géomonomie, and several others of less importance. That which gained him the greatest reputation all over Europe, was his Sections Coniques in novem libros distributas, considered by the best judges as an original work.