(Lewis Betrand), a learned Jesuit, was born at Montpellier in 1688, and entered among the Jesuits in 1703. He studied polite literature in his youth; and at length applied himself entirely to the study of mathematics and natural philosophy. He distinguished himself by writing on gravity; the mathematics; and on the music of colours, a very whimsical idea, which he took great pains to reduce to practice. His piece on gravity, entitled Traité de la Physique universelle, was printed at Paris, in 1724. He afterwards published his Mathematique universelle, which occasioned his being unanimously chosen a fellow of the Royal Society of London, without the least solicitation. He was also a member of the academies of Bordeaux and Rouen; but his Clavicle

oculaire made the most noise; and he spent much time and expense in making an harpsichord for the eye, but without success. He also wrote for and against Sir Isaac Newton, and published several other works; the principal of which are, Le Plan du Mathématique abrégé, and a treatise entitled Optique des Couleurs. He led a very exemplary life, and died in 1757.