GEMMA (Remus.), a learned Dutch physician and mathematician in the six teenth century, was born at Dockum, in Friesland, in the year 1508. He was edu cated to the medical science, of which he became a professor in the university of Louvain. But he was particularly eminent for his proficiency in mathematics and astronomy, which he taught with distin guished reputation, and the character of being one of the best astronomers of his time. The fame of his great scientific knowledge, and of the excellent instru ments which he made uk of in the illus tration of it, occasioned his being fre quently invited to the court of the Empe ror Charles V.; but he always modestly declined the overtures made to him, pre ferring the tranquillity of his literary re treat to the honours which he might ex pect from princely favour. He died at Louvain, in 1555, when only forty-seven years of age. He has sometimes had the surname of Friscius given him, from the country in which he was born. The most
celebrated of his works were " Methodus Artihmeticx ;" "De usu Annuli Astrono mici ;" "De Locornm describendorum Ratione, deque Distantils eorum invenien dis;" "Libellus de Principiis Astronomix et Cosmographia," &c. " Demonstratio nes Geometricx de usu Radii Astronomi ci," &c. ; and "De Astrolabio Catholico Liber." The author had a son, named Come But, who was born at Louvain, in 1535, and died in 1579. He was a poet, philo sopher, and physician, and taught the ma thematical sciences at Louvain with consi derable reputation. He was the author Of " De Arte Cyclognomicx," &c. ; " De Nattirpe divinis Characterismis, seu Cos mocritico ;" and " De Prodigiosa Specie Naturaque Cometm," occasioned by the extraordinary new star in the constellation Cassiopeia, in 1572, which disappeared after being visible for eighteen months; and other pieces.