166 THE GREEK ASTRONOMY. 



Sect. 4. — Period from Hipparchus to Ptolemy. 



We have now to speak of the cultivators of astronomy from the 

 time of Hipparchus to that of Ptolemy, the next great name which 

 occurs in the history of this science ; though even he holds place 

 only among those who verified, developed, and extended the theory 

 of Hipparchus. The astronomers who lived in the intermediate time, 

 indeed, did little, even in this way ; though it might have been sup- 

 posed that their studies were carried on under considerable advan- 

 tages, inasmuch as they all enjoyed the liberal patronage of the kings 

 of Egypt. 17 The " divine school of Alexandria," as it is called by 

 Synesius, in the fourth century, appears to have produced few persons 

 capable of carrying forwards, or even of verifying, the labors of its 

 great astronomical teacher. The mathematicians of the school wrote 

 much, and apparently they observed sometimes ; but their observations 

 are of little value ; and their books are expositions of the theory and 

 its geometrical consequences, without any attempt to compare it with 

 observation. For instance, it does not appear that any one verified 

 the remarkable discovery of the precession, till the time of Ptolemy, 

 250 years after ; nor does the statement of this motion of the heavens 

 appear in the treatises of the intermediate writers ; nor does Ptolemy 

 quote a single observation of any person made in this long interval of 

 time ; while his references to those of Hipparchus are perpetual ; and 

 to those of Aristyllus and Timocharis, and of others, as Conon, who 

 preceded Hipparchus, are not unfrequent. 



This Alexandrian period, so inactive and barren in the history of 

 science, was prosperous, civilized, and literary ; and many of the works 

 which belong to it are come down to us, though those of Hipparchus 

 are lost. We have the " Uranologion" of Geminus, 18 a systematic 

 treatise on Astronomy, expounding correctly the Hipparchian Theories 

 and their consequences, and containing a good account of the use of 

 the various Cycles, which ended in the adoption of the Calippic 

 Period. We have likewise '"The Circular Theory of the Celestial 

 Bodies" of Cleomedes, 19 of which the principal part is a development 

 of the doctrine of the sphere, including the consequences of the glob- 

 ular form of the earth. We have also another work on " Spherics" 

 by Theodosius of Bithynia, 20 which contains some of the most import- 

 ant propositions of the subject, and has been used as a book of in- 



" Delamb. A. A. ii. 240. « b. c. 70. 19 b. c. 60. ao b.c. 50. 



