154 THE GREEK ASTRONOMY. 



It is true, that the real motions of the heavenly bodies are simpler 

 than the apparent motions ; and that we, who are in the habit of 

 representing to our minds their real arrangement, become impatient of 

 the seeming confusion and disorder of the ancient hypotheses. But 

 this real arrangement never could have been detected by philosophers, 

 if the apparent motions had not been strictly examined and successfully 

 analyzed. How far the connection between the facts and the true 

 theory is from being obvious or easily traced, any one may satisfy 

 himself by endeavoring, 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 astron- 

 omers 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 labors of a long series of Greek, 

 Latin, Arabian, and modern European asti'onomers, 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 astronomi- 

 cal theory, Copernicus, adopted the theory of epicycles ; that is, he 

 employed that which we have spoken of as its really valuable charac- 

 teristic. " 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, except that they were circular ; for a circle alone can 

 make that which has been, recur again." 



In this sense, therefore, the Hipparchian theory was a real and in- 

 destructible truth, which was not rejected, and replaced by different 

 truths, but was adopted and incorporated into every succeeding astro- 

 nomical theory ; and which can never cease to be one of the most im- 

 portant and fundamental parts of our astronomical knowledge. 



A moment's reflection will show that, in the events just spoken of, 

 the introduction and establishment of the Theory of Epicycles, those 

 characteristics were strictly exemplified, which we have asserted to be 

 the conditions of every real advance in progressive science ; namely, 



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



