Pieter Van Musschenbroek, a Dutch mathematician, born in Leyden, March 14, 1692, died there, Sept. 19, 1761. He was educated at Leyden, and in 1717 formed an intimacy with 'sGravesande, who subsequently cooperated with him in introducing the Newtonian system of philosophy into Holland. In 1718 he took his degree of doctor of medicine, and soon afterward visited England for the purpose of seeing Newton and making himself acquainted with his system. In 1719 he was appointed professor of philosophy and mathematics and professor extraordinary of medicine in the university of Duisburg, which he resigned in 1723 for the chair of philosophy and mathematics at Utrecht. Here he remained till 1739, and about 1740 he accepted the chair of mathematics at Leyden, which he filled during the remainder of his life. His works contain many original researches in experimental physics, and are among the earliest expositions of the Newtonian philosophy; the cohesion of bodies, the phosphorescent properties which many bodies acquire from exposure to light, magnetism, capillary attraction, and the size of the earth being among the subjects most successfully treated.