Claudius, a celebrated mathematician and astrologer, was born at Pelusium in Egypt. He flourished at Alexandria in the second century, under the reigns of Hadrian and Marcus Aurelius, about the 138th year of the Christian era. There are still extant his Geography, and several learned works on astronomy, the principal of which are, 1. The Almagest; 2. De Judiciis Astrologiae; 3. Planisphaerium. His system of the world was for many years adopted by philosophers and astronomers; but the learned have long rejected it for the system of Copernicus.