SEQUEL TO THE EPOCH OF HIPPARCHUS. 157 



CHAPTER IV. 



Sequel to the Inductive Epoch of Hipparchus. 



Sect. 1. — Researches which verified the Theory. 



THE discovery of the leading Laws of the Solar and Lunar Motions, 

 and the detection of the Precession, may be considered as the 

 great positive steps in the Hipparchian astronomy ; — the parent dis- 

 coveries, from which many minor improvements proceeded. The task 

 of pursuing the collateral and consequent researches which now of- 

 fered themselves, — of bringing the other parts of astronomy up to the 

 level of its most improved portions, — was prosecuted by a succession 

 of zealous observers and calculators, first, in the school of Alexandria, 

 and afterwards in other parts of the world. We must notice the 

 various labors of this series of astronomers ; but we shall do so very 

 briefly ; for the ulterior development of doctrines once established is 

 not so important an object of contemplation for our present purpose, 

 as the first ''onception and proof of those fundamental truths on which 

 systematic doctrines are founded. Yet Periods of Verification, as well 

 as Epochs of Induction, deserve to be attended to ; and they can 

 nowhere be studied with so much advantage as in the history of as- 

 tronomy. 



In truth, however, Hipparchus did not leave to his successors the 

 task of pursuing into detail those views of the heavens to which his 

 discoveries led him. He examined with scrupulous care almost every 

 part of the subject. "We must briefly mention some of the principal 

 points which were thus settled by him. 



The verification of the laws of the changes which he assigned to 

 the skies, implied that the condition of the heavens was constant, ex- 

 cept so far as it was affected by those changes. Thus, the doctrine 

 that the changes of position of the stars were rightly represented by 

 the precession of the equinoxes, supposed that the stars were fixed 

 with regard to each other ; and the doctrine that the unequal number 

 of days, in certain subdivisions of months and years, was adequately 

 explained by the theory of epicycles, assumed that years and days 

 were always of constant lengths. But Hipparchus was not content 

 with assuming these bases of his theory, he endeavored to prove them. 



