DECHALES (Claud-Francis-Milliet)

, an excellent mathematician, mechanist, and astronomer, was born at Chambery, the capital of Savoy, in 1611. He chiefly excelled in a just knowledge of the mathematical and mechanical sciences: not that he was bent upon new discoveries, or happy in making them; as his talent rather lay in explaining those sciences with ease and accuracy; which perhaps rendered him equally useful and deserving of esteem. Indeed it was generally allowed that he made the best use of the productions of other men, and that he drew the several parts of the mathematical sciences together with great judgment | and perspicuity. It is also said of him, 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.—— From hence he removed to Marseilles, where he taught the art of navigation and the practical mathematical sciences.—He afterward became professor of mathematics in the university of Turin, where he died March 28, 1678, at 67 years of age.

Among other works which do honour to his memory, are,

1. An edition of Euclid's Elements; in which he has omitted the less important propositions, and explained the uses of those he has retained.

2. A Discourse on Fortification; and another on Navigation.

3. These performanoes, with some others, were collected in 3 volumes folio, under the title of Mundus Mathematicus, being indeed a complete course of mathematics. And the same was afterward much enlarged, and published at Lyons, 1690, in 4 large volumes, folio.