Dechales, Claudius Francis Millet

, an excellent mathematician, mechanic, and astronomer, was born at Chamberry, the capital of Savoy, in 1611; and descended from a noble family, which had produced several persons creditably distinguished in the church, the law, and the army. He was a great master in all the parts of the mathematics, and printed several books on that subject, which were very well received. His principal performances are, an edition of Euclid’s Elements, where he has struck out the unserviceable propositions, and annexed the use to those he has preserved; a discourse of fortification; and another of navigation. These performances, with some others, were first collected into three volumes in folio, under the title of “Mundus Mathematicus,” comprising a very ample course of mathematics. The first volume includes the first six books of Euclid, with the eleventh and twelfth; an arithmetical tract; Theodosius’s spherics; trigonometry; practical geometry; mechanics; statics; universal geography; a discourse upon the loadstone; civil architecture, and the carpenter’s art. The second volume furnishes directions for stone-cutting; military architecture; hydrostatics; a discourse of fountains and rivers hydraulic machines, or contrivances for waterworks; navigation; optics; perspective; catoptrics, and dioptrics. The third volume has ki it a discourse of music pyrotechnia, or the operations of fire and furnace a discourse of the use of the astrolabe gnomonics, or the art | of dialling; astronomy; a tract upon the calendar; astrology; algebra; the method of indivisible and conic sections. The best edition of this work is that of Lyons, printed in 1690; which is more correct than the first, is considerably enlarged, and makes four vols. in folio. Dechales, though not abounding in discoveries of his own, is yet allowed to have made a very good use of those of other men, and to have drawn the several parts of the science of mathematics together with great clearness and judgment. It is said also, that his probity was not inferior to his learning, and that both these qualities made him generally admired and beloved at Paris; where for four years together he read public mathematical lectures in the college of Clermont He then removed to Marseilles, where he taught the art of navigation; and aiterwards became professor of mathematics in the university of Turin, where he died March 28, 1678, aged 67. ¹