Peter Van, an eminent mathematician and natural philosopher, was born at Leyden on the 14th of March 1692. Having studied languages under Perizonius and Gronovius, he applied himself to philosophy, chemistry, and medicine under Senguird, Bidloo, Le Clerc, Burmann, Albinius, Boerhaave, and Rau, and proved a disciple worthy of such masters. He was received as doctor in 1718, after having published and defended his inaugural dissertation *De Aëris Presentia in Humoribus Animalium*; a masterly production, containing a record of new experiments carefully performed, and several curious facts discussed with much sagacity. Having visited London, he there became acquainted with Newton and Desaguliers, and was elected a member of the Royal Society; and, on his return to his own country, he was appointed professor of mathematics and natural philosophy at Utrecht, where he remained twelve years (from 1723 to 1735), and acquired the greatest celebrity. In 1739 he succeeded Wittichius in the same situation at Leyden, where he remained till the time of his death, which took place on the 19th of September 1761, at the age of sixty-nine. He published various works in Latin, all evincing great penetration and accuracy. The principal of these are, 1. Epitome Elementorum Physico-mathematicorum, Leyden, 1729, in 4to; 2. Dissertationes Physice Experimentalis et Geometricae, ibid, 1729, in 4to; 3. A Latin translation of the *Saggi di Naturali Esperienze fatte nell' Accademia del Cemento*, Leyden, 1731, in 4to; 4. Elementa Physicæ, 1734, in 8vo, translated in English by Colson, 1744, in two vols. 8vo. His *Introductio ad Philosophiam Naturalem*, which he began to print in 1760, was completed by Lulofs, and published at Leyden in 1762, soon after the death of the author. A translation of this work into French by Rigaud de Lafond was published at Paris in 1769, in three vols. 4to. Musschenbroek had always paid great attention to meteorology, several papers on which, containing numerous observations by him, were printed in the Memoirs of the French Academy of Sciences, and in the Transactions of the Royal Society of London, besides a dissertation on barometers which appeared in the Memoirs of the Academy of St Petersburg.