SEQUEL TO THE EPOCH OF H1PPARCHUS. 237 



suspicion that the motions of the heavenly bodies 

 might be subject to many inequalities ; that when 

 one set of anomalies had been discovered and re- 

 duced to rule, another set might come into view ; 

 that the discovery of a rule was a step to the 

 discovery of deviations from the rule, which would 

 require to be expressed in other rules ; that in the 

 application of theory to observation, we find, not 

 only the stated phenomena, for which the theory 

 does account, but also residual phenomena, which 

 remain unaccounted for, and stand out beyond 

 the calculation; that thus nature is not simple 

 and regular, by conforming to the simplicity and 

 regularity of our hypotheses, but leads us forwards 

 to apparent complexity, and to an accumulation 

 of rules and relations. A fact like the Evection, 

 explained by an Hypothesis like Ptolemy's, tended 

 altogether to discourage any disposition to guess 

 at the laws of nature from mere ideal views, or 

 from a few phenomena. 



2. The discovery of Evection had an import- 

 ance which did not come into view till long 

 afterwards, in being the first of a numerous series 

 of inequalities of the moon, which result from 

 the Disturbing Force of the sun. These inequal- 

 ities were successively discovered; and led finally 

 to the establishment of the law of universal gravi- 

 tation. The moon's first inequality arises from a 

 different cause; from the same cause as the 

 inequality of the sun's motion ; from the motion 



