92 MECHANICS. 



is the reverse of what occurs in disunited bodies, 

 and the nearer they are pressed together the more 

 they seem to repel. 



La Places Theory of Elastic Fluids. 



La Place's theory of elastic fluids is founded on 

 the principle that each molecule is subject to the 

 action of three forces : 



1. The attraction of the surrounding molecules. 



2. The attraction of the caloric of the same mole- 

 cules. 



3. The repulsion of its caloric by the caloric of 

 the other molecules. 



The two first forces tend to make the particles 

 approach each other, and the third tends to separate 

 them. The three states, solid, fluid, and gazeous, 

 depend on the respective predominance of these 

 forces. 



