GRADUAL PROPAGATION OF ATTRACTION. 353 



The applause of the scientific world did not prevent 

 the immortal author 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 essential property of matter, as 

 the mysterious indication of a sort of charm ; who sup- 

 posed that two bodies may act upon each other without 

 the intervention 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, towards the planetary bodies around which 

 there exists a greater degree of rarefaction, or the conse- 

 quence of the impulsive force of some fluid medium. 



Newton never expressed a definitive opinion respect- 

 ing the origin of the impulse which occasioned the attrac- 

 tive force of matter, at least in our solar system. But 

 we have strong reasons for supposing, in the present 

 day, that in using the word impulse, the great geometer 

 was thinking of the systematic ideas of Varignon and 

 Fatio de Duillier, subsequently reinvented and perfected 

 by Lesage : these ideas, in effect, had been communi- 

 cated to him before they were published to the world. 



According to Lesage, there are, in the regions of 

 space, bodies moving in every possible direction, and 

 with excessive rapidity. The author applied to these 

 the name of ultra-mundane corpuscles. Their totality 

 constituted the gravitative fluid, if indeed, the designa- 

 tion of a fluid be applicable to an assemblage of particles 

 having no mutual connexion. 



A single body placed in the midst of such an ocean of 



