DECHALES, CLAUDE FRANcOIS MILLIET, was born at Chambery, the capital of Savoy, in 1611. Ile wrote largely on several branches of mathematical, mechanical, and astronomical science; but the only work by which he Is generally known is his edition of Euclid, which was long a favourite text-book in France and in other parts of the continent. It was also translated iuto English, but did not obtain great popularity among our countrymen, whose taste in geometry continued, till recently, to partake strongly of the pure severity of the ancient Greek writers.
DechSles was however an accurate and elegant writer on the subjects which he treated; and there are interspersed through his works many marks of considerable invention as well as of a happy power of adaptation of the knowledge of his predecessors and contemporaries. Still he was not one of those men who had the power greatly to extend the boundaries of science; it was his province rather to place it in such a light as to facilitate its acquisition by others.
He was appointed professor of mathematics in the college of Cler mont, the chair of which ho appears to have filled for about four years; and thence he removed to Marseille, where be taught navi gation, military engineering, and the applications of mathematics to science. From Marseille be went to Turin, where he was
appointed professor of mathematics in the university, and died in that city in 1678, being sixty-seven years of age.
As a teacher, Decheles was remarkable for his urbanity, and for the adaptation of his instruction to the previous acquirements of his pupils ; and as a man, his probity and amiable spirit gained for him the admiration and love of all with whom be was associated.
The works of Dechales were published at Lyon in 1690, in four folio volumes, under tho title of Mundus Mathematicos. A former edition of these was also published in three volumes; but this edition ie far less complete than that of 1690.
DL'ClUS CAIUS 3IESSIUS QUINTUS TRAJANUS, the Roman emperor, succeeded Philip, and chiefly distinguished himself for his violent persecution of the Christians. He and his son fell in an expe dition against the Goths, about A.D. 25L