MUSSCHENBROEK, Pieter van(1692-1761), natural philosopher, was born at Leyden in March 1692, and studied at the university of his native city. The teacher from whom he derived the most profit was the eminent mathematician Gravesande. A scientific partnership was formed in 1717 between the master and the pupil for the prosecution of natural philosophy according to the principles of Newton, and in opposition to those of Descartes; Gravesande concentrating his attention on the theoretical part of the study, while Musschenbroek conducted the experiments. The consequence was that the downfall of Cartesianism and the establishment of Newtonianism were very much accelerated in Holland. Graduating in 1715 with a dissertation, De aeris praesentia in humoribus animalium, Musschenbroek was appointed professor at Duisburg in 1719. In 1723 he was promoted to the chair of natural philosophy and mathematics at Utrecht. In 1731 he dechned an invitation to Copenhagen, and was promoted in consequence to the chair of astronomy at Utrecht in 1732. The attempt of George II. of England in 1737 to attract him to the newly-established university of Göttingen was also unsuccessful. At length, however, the claims of his native city overcame his resolution to remain at Utrecht, and he took possession of the mathematical chair at Leyden in 1739, where, declining all offers from abroad, he continued till his death in September 1761....