# Sosigenes

, an Egyptian mathematician, whose principal studies were chronology and the mathematics in general, and who flourished in the time of Julius Cxsar, is represented as well versed in the mathematics and astronomy
of the ancients; particularly of those celebrated mathematicians, Thales, Archimedes, Hipparchus, Calippus, and
many others, who had undertaken to determine the quantity of the solar year; which they had ascertained much
nearer the truth than one can well imagine they could,
with instruments so very imperfect; as may appear by reference to Ptolomy’s Almagest. It seems Sosigenes made
great improvements, and gave proofs of his being able to
demonstrate the certainty of his discoveries; by which
means he became popular, and obtained repute with those
who had a genius to understand and relish such inquiries.
Hence he was sent for by Julius Caesar, who being convinced of his capacity, employed him in reforming the
calendar; and it was he who formed the Julian year, which
begins 45 years before the birth of Christ. His other works
are lost since that period. ^{2}

^{2}

Hutton’s Dict. Plinii Nat. Hist. Brucker.