OF NATURAL PHILOSOPHY. 



CHAP. III. 



OF COSMICAL PHENOMENA. 



Astronomy and Celestial Mechanics. 



(293.) ASTRONOMY, as has been observed in the 

 former part of this discourse, as a science of observ- 

 ation, had made considerable progress among the 

 ancients : indeed, it was the only branch of physical 

 science which could be regarded as having been cul- 

 tivated by them with any degree of assiduity or real 

 success. The Chaldean and Egyptian records had 

 furnished materials from which the motions of the 

 sun and moon could be calculated with sufficient ex- 

 actness for the prediction of eclipses ; and some re- 

 markable cycles, or periods of years in which the 

 lunar eclipses return in very nearly the same order, 

 had been ascertained by observation. Considering 

 the extreme imperfection of their means of measuring 

 time and space, this was, perhaps, as much as could 

 have been expected at that early period, and it was 

 followed up for a while in a philosophical spirit of 

 just speculation, which, if continued, could hardly 

 have failed to lead to sound and important conclu- 

 sions. 



(294.) Unfortunately, however, the philosophy of 

 Aristotle laid it down as a principle, that the celestial 

 motions were regulated by laws proper to themselves, 

 and bearing no affinity to those which prevail on 



