CHAZELLES (John Matthew)

, a French mathematician and engineer, was born at Lyons in 1657, and educated there in the college of Jesuits, from whence he removed to Paris in 1675. He first became acquainted with Du Hamel, secretary to the Academy of Sciences, and through him with Cassini, who employed him with himself at the Observatory, where Chazelles greatly improved himself, and also assisted Cassini in the measurement of the southern part of the meridian of France. Having, in 1684, instructed the duke of Montemar in the mathematical sciences, this nobleman procured him the appointment of hydrography-professor to the galleys of Marseilles. In discharging the duties of this department, he made numerous geometrical and astronomical observations, from which he drew a new map of the coast of Provence.— He also performed many other services in that department, and as an engineer, along with the armies and naval expeditions. To make observations in Geography and Astronomy, he undertook also a voyage to the Levant, and among other things he measured the pyramids of Egypt, and found the four sides of the largest of them exactly to face the four cardinal points of the compass. He made a report of his voyage, on his return, to the Academy of Sciences, upon which he was uamed a member of their body in 1695, and had many papers inserted in the volumes of their Memoirs, from 1693 to 1708. Chazelles died at Marseilles the 16th of January 1710.

CHEMIN des Ronds, in Fortification, the way of the rounds, or a space between the rampart and the low parapet under it, for the rounds to go about it.