NEW MECHANICS AND ASTRONOMY. 243 



high velocities. An isolated body in space will not 

 be affected apparently by the collisions with these 

 corpuscles, since the collisions are distributed equally 

 in all directions. But if two bodies, A and B, are in 

 proximity, the body B will act as a screen, and inter- 

 cept a portion of the corpuscles, which, but for it, 

 would have struck A. Then the collisions received 

 by A from the side away from B will have no counter- 

 part, or will be only imperfectly compensated, and will 

 drive A towards B. 



Such is Lesage's theory, and we will discuss it first 

 from the point of view of ordinary mechanics. To begin 

 with, how must the collisions required by this theory 

 occur? Must it be in accordance with the laws of 

 perfectly elastic bodies, or of bodies devoid of elasticity, 

 or in accordance with some intermediate law ? Lesage's 

 corpuscles cannot behave like perfectly elastic bodies, 

 for in that case the effect would be nil, because the 

 corpuscles intercepted by the body B would be replaced 

 by others which would have rebounded from B, and 

 calculation proves that the compensation would be 

 perfect. 



The collision must therefore cause a loss of energy 

 to the corpuscles, and this energy should reappear in 

 the form of heat. But what would be the amount of 

 heat so produced ? We notice that the attraction 

 passes through the body, and we must accordingly 

 picture the Earth, for instance, not as a complete 

 screen, but as composed of a very large number of 

 extremely small spherical molecules, acting individually 

 as little screens, but allowing Lesage's corpuscles to 

 travel freely between them. Thus, not only is the 

 Earth not a complete screen, but it is not even a 



