270 AGGREGATE FORCES 



It is generally conceded by philosophers, 

 that all the operations of nature are referable to 

 attraction and repulsion, which I have proved in 

 the preceding chapters, are resolvable into the 

 agency of caloric alone. But if the stupendous 

 forces of chemistry, geology, and meteorology, 

 are determined by the agency of solar radiation, 

 why should it not be adequate to produce the 

 annual and diurnal revolutions of planets ? That 

 rays of subtile matter, capable of producing heat 

 and light, are continually proceeding from the 

 centre of our system, is self-evident from expe- 

 rience and observation. It would, therefore, be 

 contrary to all analogy, and the indications of 

 common sense, to refer the planetary motions to 

 some unknown hypothetical influence exerted 

 through a vacuum, while there is a known cause 

 sufficient to explain the phenomena. It is im- 

 possible to conceive how the sun could exert any 

 agency whatever upon the earth, independent 

 of his potent beams. Besides, what can be more 

 simple and natural than the inference, that the 

 same power which aggregates and holds together 

 the particles of planets, guides their movements 

 round the heavens? 



It was laid down by Newton himself, as a 

 fundamental axiom, that no more causes of na- 

 tural things ought to be admitted, than such as 

 are both true and sufficient to explain the pheno- 

 mena. (Principia, Book iii.) 



