HIPPARCHUS, the founder of mathematical astronomy, was born at Nicaea in Bithynia. The years of his birth and death are both unknown, but the period of his activity, according to the evidence of his observations, which have been preserved by Ptolemy, must have been between 160 and 125 b.c. Of his writings only one has come down to US, Των ’Αράτου και Έυδό£ου φαινομένων cζηγησeωv βιβλία γ', published by Vittorius at Florence, 1567, and by Petaviαs in his Uranologia, Paris, 1630. For a notice of his discoveries see Astronomy, vol. ii. p. 749.