Chazelles, John Matthew De

, a French mathetician and engineer, was born at Lyons July 24, 1657, and educated there in the college of Jesuits, from whence he removed to Paris in 1675. He first made an acquaintance with du Hamel, secretary to the academy of sciences; who, observing his genius to lie strongly towards astronomy, presented him to Cassini. Cassini took him with him to the observatory, and employed him under him, where he made a very rapid progress in the science. In 1683, the academy carried on the great work of the meridian to the north and south, begun in 1670, and Cassini having the southern quarter assigned him, took in the assistance of Chazelles. In 1684, the duke of Montemart engaged Chazelles to teach him mathematics, and the year after procured him the preferment of hydrography-professor for the gallies of Marseilles, where he set up a school for young pilots designed to serve on board the gailies. In 1686, the gallies made four little campaigns, or rather four courses, for exercise, during which Chazelles always went on board, kept his school on the sea, and shewed the practice of what he taught. He likewise made a great many geometrical and astronomical observations, which enabled him to draw a new map of the coast of Provence. In 1687 and 1688 he made two other sea campaigns, and drew a great many plans of ports, roads, towns, and forts, which were so much prized as to be lodged with the ministers of state. At the beginning of the war which ended with the peace of Ryswick, Chazelles and some marine officers fancied the gailies might be so contrived as to live upon the ocean, and might serve to tow the men of war when the wind failed, or proved contrary; and also help to secure the coast of France upon the ocean. He was sent to the western coasts in July 1689 to prove this scheme; and in 1690 fifteen gailies, new-built, set sail from Rochefort, cruised as far as Torbay in England, and proved serviceable at the descent upon Tinmouth. Here he performed the functions of an engineer, and shewed the courage of a soldier. The general officers he served under declared that when they sent him to take a | view of any post of the enemy, they could rely entirely upon his intelligence. The gallies, after their expedition, came to the mouth of the Seine into the basons of Havre de Grace and Honfleur; but could not winter because it was necessary to empty these basons several times, to prevent the stagnation and stench of the water. He proposed to carry them to Rohan; and though all the pilots were against him, objecting insuperable difficulties, he succeeded in the undertaking* While he was at Rohan he digested into order the observations which he had made on the coasts, and drew distinct maps, with a portulan to them, viz. a large description of every haven, of the depth, the tides, the dangers and advantages discovered, &c. which were inserted in the “Neptune Francois,” published in 1692, in which year he was engineer at the descent at Oneille. In 1693 M. de Pontchartrain, then secretary of state for the marine, and afterwards chancellor of France, resolved to get the “Neptune François” carried on to a second volume, which was also to include the Mediterranean. Chazelles desired that he might have a year’s voyage in this sea, for making astronomical observations; and, the request being granted, he passed by Greece, Egypt, and the other parts of Turkey, with his quadrant and telescope in his hand. When he was in Egypt he measured the pyramids, and found that the four sides of the largest lay precisely against the four quarters of the world. Now as it is highly probable that this exact position to east, west, north, and south, was designed 3000 years ago by those that raised this vast structure, it follows, that, during so long an interval, there lias been no alteration in the situation of the heavens; or, that the poles of the earth and the meridians have all along continued the same. He likewise made a report of his voyage in the Levant, and gave the academy all the satisfaction they wanted concerning the position of Alexandria: upon which he was made a member of the academy in 1695. Chazelles died Jan. 16, 1710, of a malignant fever. He was a very extraordinary and useful man; and, besides his great genius and attainments, was also remarkable for his moral and religious endowments. 1


Eloge by Fontenelle. —Moreri. —Hutton’s Dict.