Gregory, James, 1638–75, Scottish mathematician. He invented a reflecting telescope (1661), which he described in his Optica promota (1663). In 1668 he became professor of mathematics at the Univ. of St. Andrews and, in 1674, professor of mathematics at the Univ. of Edinburgh. He originated a photometric mode of measuring the distance of stars and wrote Geometriae pars universalis (1668) and Exercitationes geometricae (1668).
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