172 THE GREEK ASTRONOMY. 



the sun and returns again to the greatest distance 

 on the same side, would easily be observed. 



Probably the manner in which the motions of 

 the planets were originally reduced to rule was 

 something like the following : In about 30 of our 

 years, Saturn goes 29 times through his Anomaly, 

 that is, the succession of varied motions by which 

 he sometimes goes forwards and sometimes back- 

 wards among the stars. During this time, he goes 

 once round the heavens, and returns nearly to the 

 same place. This is the cycle of his apparent 

 motions. 



Perhaps the eastern nations contented them- 

 selves with thus referring these motions to cycles 

 of time, so as to determine their recurrence. Some- 

 thing of this kind was done at an early period, 

 as we have seen. 



But the Greeks soon attempted to frame to 

 themselves a sensible image of the mechanism by 

 which these complex motions were produced : nor 

 did they find this difficult. Venus, for instance, 

 who, upon the whole, moves from west to east 

 among the stars, is seen, at certain intervals, to 

 return or move retrograde a short way back from 

 east to west, then to become for a short time 

 stationary, then to turn again and resume her 

 direct motion westward, and so on. Now this can 

 be explained by supposing that she is placed in the 

 rim of a wheel, which is turned edgeways to us, 

 and of which the center turns round in the heavens 



