PRELUDE TO THE EPOCH OF HIPPARCHUS. 171 



of the most uniform motion, required no after-cor- 

 rection. But this manifest simplicity, this easy and 

 obvious explanation, did not apply to the move- 

 ment of all the heavenly bodies. The planets, the 

 "wandering stars," could not be so easily under- 

 stood ; the motion of each, as Cicero says, " under- 

 going very remarkable changes in its course, going 

 before and behind, quicker and slower, appear- 

 ing in the evening, but gradually lost there, and 

 emerging again in the morning 1 ." A continued 

 attention to these stars would, however detect 

 a kind of intricate regularity in their motions, 

 which might naturally be described as " a dance." 

 The Chaldeans are stated by Diodorus 2 , to have 

 observed assiduously the risings and settings of 

 the planets, from the top of the temple of Belus. 

 By doing this, they would find the times in which 

 the forwards and backwards movements of Saturn, 

 Jupiter, and Mars recur; and also the time in 

 which they come round to the same part of the 

 heavens 3 . Venus and Mercury never recede far 

 from the sun, and the intervals which elapse while 

 either of them leaves its greatest distance from 



1 Cic. de Nat. D. lib. ii. p. 450. " Ea qua; Saturni stella 

 dicitur, ^cuWque a Grascis nominatur, quas a terra abest pluri- 

 mum, xxx fere annis cursum suum conficit ; in quo cursu multa 

 mirabiliter efficiens, turn antecedendo, turn retardando, turn ves- 

 pertinis temporibus delitescendo, turn matutinis se rursum ape- 

 riendo, nihil immutat sempiternis sseculorum aetatibus, quin 

 eadem iisdem temporibus efficiat." And so of the other planets. 



2 Del. A. A.; i. p. 4. 3 Plin. H. N. ii. p. 204. 



