Astronomer and mathematician, born near London; determined the rotation of the sun from the spots on its surface, and the position of 350 stars; discovered in 1680 the great comet called after his name, which appeared again in 1825; was entrusted with the publication of his "Principia" by Sir Isaac Newton; made researches on the orbits of comets, and was appointed in 1719 astronomer-royal (1656-1742).