a native of the Netherlands, who founded a sect the professors of which were called Picards. See PICARDS.

Picard (John), an able mathematician, and one of the most learned astronomers of the 17th century, was born at Flèche, and became priest and prior of Rillie in Anjou. Going to Paris, he was in 1656 received into the Academy of Sciences in quality of astronomer. In 1671, he was sent, by order of the king, to the castle of Uraniburg, built by Tycho Brahe in Denmark, to make astronomical observations there; and from thence he brought the original manuscripts wrote by Tycho-Brahe, which are the more valuable as they differ in many places from the printed copies, and contain a book more than has yet appeared. He made important discoveries in astronomy; and was the first who travelled through several parts of France, to measure a degree of the meridian. His works are, 1. A treatise on levelling. 2. Fragments of dioptics. 3. Experimenta circa aquas effluentes. 4. De mensuris. 5. De mensura liquidorum & aridorum. 6. A voyage to Uraniburg, or astronomical observations made in Denmark. 7. Astronomical observations made in several parts of France, &c. These, and some other of his works, which are much esteemed, are in the fifth and seventh volumes of the Memoirs of the Academy of Sciences.