SEQUEL TO THE EPOCH OF HIPPARCHUS. 233 



service to astronomy, however extensive the pro- 

 gress of the science might be. It was, in fact, 

 as we have already said, the modern process of 

 representing the motion by means of a series of 

 circular functions. 



4. But though the doctrine of eccentrics and 

 epicycles was thus admissible as an Hypothesis, 

 and convenient as a means of expressing the laws 

 of the heavenly motions, the successive occasions 

 on which it was called into use, gave no countenance 

 to it as a Theory ; that is, as a true view of the 

 nature of these motions, and their causes. By 

 the steps of the progress of this Hypothesis, it 

 became more and more complex, instead of be- 

 coming more simple, which, as we shall see, was 

 the course of the true Theory. The notions con- 

 cerning the position and connexion of the heavenly 

 bodies, which were suggested by one set of phe- 

 nomena, were not confirmed by the indications of 

 another set of phenomena; for instance, those 

 relations of the epicycles which were adopted to 

 account for the Motions of the heavenly bodies, were 

 not found to fall in with the consequences of their 

 apparent Diameters and Parallaxes. In reality, as 

 we have said, if the relative distances of the sun 

 and moon at different times could have been accu- 

 rately determined, the Theory of Epicycles must 

 have been forthwith overturned. The insecurity of 

 such measurements alone maintained the theory to 

 later times (i). 



