198 THE GREEK ASTRONOMY. 



or easily traced, any one may satisfy himself by 

 endeavouring, from a general conception of the 

 moon's real motions, to discover the rules which 

 regulate the occurrences of eclipses; or even to 

 explain to a learner, of what nature the apparent 

 motions of the moon among the stars will be. 



The unquestionable evidence of the merit and 

 value of the theory of epicycles is to be found in 

 this circumstance; that it served to embody all 

 the most exact knowledge then extant, to direct 

 astronomers to the proper methods of making it 

 more exact and complete, to point out new objects 

 of attention and research ; and that, after doing this 

 at first, it was also able to take in, and preserve, all 

 the new results of the active and persevering la- 

 bours of a long series of Greek, Latin, Arabian, and 

 modern European astronomers, till a new theory 

 arose which could discharge this office. It may, 

 perhaps, surprise some readers to be told, that the 

 author of this next great step in astronomical 

 theory, Copernicus, adopted the theory of epicycles ; 

 that is, he employed that which we have spoken of 

 as its really valuable characteristic. "We 14 must 

 confess," he says, "that the celestial motions are 

 circular, or compounded of several circles, since 

 their inequalities observe a fixed law and recur in 

 value at certain intervals, which could not be, ex- 

 cept they were circular ; for a circle alone can make 

 that which has been, recur again." 



14 Copernicus. De Rev. 1. i. c. 4. 



