SOSIGENES  ,

Greek astronomer and mathematician, probably of Alexandria, flourished in the 1st century B.C . According to Pliny (Nat . Hist. xviii . 25), he was employed by Julius Caesar in the reform of the Roman calendar (46 B.c.), and wrote three treatises, which he conscientiously corrected . From another passage of Pliny (ii . 8) it is inferred that Sosigenes maintained the doctrine of the motion of Mercury round the sun, which is referred to by his contemporary Cicero, and was also held by the Egyptians . The astronomer is to be distinguished from the Peripatetic philosopher of the same name, who lived at the end of the 2nd century A.D . He was the tutor of Alexander of Aphrodisias, the most famous of the commentators on Aristotle . He wrote a work on Revolving Spheres, from which some important extracts have been preserved iri Simplicius's commentary on Aristotle's De caelo (the subject is fully discussed by T . H . Martin, " Sur deux Sosigene," in Annales de la lac. des letires de Bordeaux, i., 1879) .