LAPLACE. 1,57 



completely beyond the reach of our senses and the ordinary resources 

 of buman intelligence, that the philosophers of antiquity, who supposed 

 that they could explain everything ineclianically acco^rding to the simple 

 evolutions of atoms, excepted gravity from their speculations. 



Descartes attempted what Leucippus, Democritus, Eijicurus, 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 circu- 

 lating 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 charac- 

 teristic attributes of truth. 



Those persons form a very imperfect estimate of the meaning of one 

 of the greatest questions which have occupied the attention of modern 

 inquirers, who regard I^ewton as having issued victorious from a strug- 

 gle in which his two immortal predecessors had failed. I^ewton did not 

 discover the cause of gravity any more thau Galileo did. Two bodies 

 placed in juxtaposition approach each other. Newton does not inquire 

 into the nature of the force which produces this eflect. The force ex- 

 ists. 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 detinite idea of the physical process by which gravity is brought 

 into existence and operates. 



The force of attraction being once admitted as a fact, l^ewton studies 

 it in all terrestrial phenomena, ia the revolutions of the moon, the plan- 

 ets, satellites, and comets ; and, as we have already stated, he deduced 

 from this incomparable study the simple, universal, mathematical char- 

 acteristics of the forces which i^reside over the movements of all the 

 bodies of which our solar system is composed. 



The applause of the scientific world did not prevent the immortal au- 

 thor of the Principia from hearing some persons refer the principle of 

 gravitation to the class of occult qualities. This circumstance induced 

 Newton and his most devoted followers to abandon the reserve which 

 they had hitherto considered it their duty to maintain. Those persons 

 were then charged with ignorance who regarded attraction as an essen- 

 tial property of matter, as the mysterious indication of a sort of charm ; 

 who supposed that two bodies may act upon each other without the in- 

 tervention of a third body. This force was then either the result of the 

 tendency of an ethereal fluid to move from the free regions of space, 

 where its density is a maximum, toward the planetary bodies, around 

 which there exists a greater degree of rarefaction, or the consequence 

 of the impulsive force of some fluid medium. 



Newton never expressed a definitive opinion respecting the origin of 

 the impulse which occasioned the attractive force of matter — at least iu 

 our solar system. But we have strong reasons for supposing, in the 

 present day, that, in using the word imjmlse the great geometer was 

 thinking of the systematic ideas of Variguon and Fatio de Duillier, sub- 



