156 THE GREEK ASTRONOMY. 



heavens takes place about the poles of the ecliptic, and uot about those 

 of the equator. The care with which he collected this motion from 

 the stars themselves, may be judged of from this, that having made 

 his first observations for this purpose on Spica and Eegulus, zodiaca. 

 stars, his first suspicion was that the stars of the zodiac alone changed 

 their longitude, which suspicion he disproved by the examination of 

 other stars. By his processes, the idea of the nature of the motion, 

 and the evidence of -its existence, the two conditions of a discovery, 

 were fully brought into view. The scale of the facts which Hipparchus 

 was thus able to reduce to law, may be in some measure judged of, by 

 recollecting that the precession, from his time to ours, has only carried 

 the stars through one sign of the zodiac ; and that, to complete one 

 revolution of the sky by the motion thus discovered, would require a 

 period of 25,000 years. Thus this discovery connected the various 

 aspects of the heavens at the most remote periods of human history ; 

 and, accordingly, the novel and ingenious views which Newton pub- 

 lished in his chronology, are founded on this single astronomical fact, 

 the Precession of the Equinoxes. 



The two discoveries which have been described, the mode of con- 

 structing Solar and Lunar Tables, and the Precession, were advances 

 of the greatest importance in astronomy, not only in themselves, but 

 in the new objects and undertakings which they suggested to astron- 

 omers. The one discovery detected a constant law and order in the 

 midst of perpetual change and apparent disorder ; the other disclosed 

 mutation and movement perpetually operating where every thing had 

 been supposed fixed and stationary. Such discoveries were well adapt- 

 ed to call up many questionings in the minds of speculative men ; 

 for, after this, nothing could be supposed constant till it had been as- 

 certained to be so by clo'se examination ; and no apparent complexity 

 or confusion could justify the philosopher in turning away in despair 

 from the task of simplification. To answer the inquiries thus suggest- 

 ed, new methods of observing the facts were requisite, more exact and 

 uniform than those hitherto employed. Moreover, the discoveries 

 which were made, and others which could not fail to follow in their 

 train, led to many consequences, required to be reasoned upon, sys- 

 tematized, completed, enlarged. In short, the Epoch of Induction led, 

 as we have stated that such epochs must always lead, to a Period of 

 Development, of Verification, Application, and Extension. 



