352 LAPLACE. 



they could explain every thing mechanically according 

 to the simple evolutions of atoms, excepted gravity from 

 their speculations. 



Descartes attempted what Leucippus, Democritus, Epi- 

 curus, and their followers thought to be impossible. 



He made the fall of terrestrial bodies depend upon the 

 action of a vortex of very subtle matter circulating 

 around the earth. The real improvements which the 

 illustrious Huyghens applied to the ingenious conception 

 of our countryman were far, however, from imparting to 

 it clearness and precision, those characteristic attributes 

 of truth. 



Those persons form a very imperfect estimate of the 

 meaning of one of the greatest questions which has occu- 

 pied the attention of modern inquirers, who regard New- 

 ton as havins; issued victorious from a struggle in which 



O c5O 



his two immortal predecessors had failed. Newton did 

 not discover the cause of gravity any more than Galileo 

 did. Two bodies placed in juxtaposition approach each 

 other. Newton does not inquire into the nature of the 

 force which produces this effect. The force exists, he 

 designates it by the term attraction; but, at the same 

 time, he warns the reader that the term as thus used by 

 him does not imply any definite idea of the physical 

 process by which gravity is brought into existence and 

 operates. 



The force of attraction being once admitted as a fact, 

 Newton studies it in all terrestrial phenomena, in the 

 revolutions of the moon, the planets, satellites, and com- 

 ets ; and, as we have already stated, he deduced from 

 this incomparable study the simple, universal,' mathemati- 

 cal characteristics of the forces which preside over the 

 movements of all the bodies of which our solar system 

 is composed. 



