THEORY OF COHESION. 179 



diately converted into the solid state, and incor- 

 porated with the ice by virtue of the same force 

 ^ which causes universal attraction. 



It is by the attraction of caloric for ponderable 

 matter that it combines with different bodies 

 and produces their liquidity ; it is also by virtue 

 of the same attraction, that liquids are enabled 

 to dissolve and combine with other bodies. Phi- 

 losophers have generally assumed, that cohesion 

 is the antagonist of chemical affinity, and that 

 they are produced by different causes : but the 

 most obvious phenomena of nature demonstrate 

 that they are produced by one and the same 

 cause, and that all molecular combinations result 

 from the attraction of caloric for ponderable mat- 

 ter. The only difference between cohesion and 

 chemical attraction is, that the one is exerted 

 between homogeneous atoms, and the other 

 between heterogeneous atoms, which vary in 

 size, and in the degrees of their affinity for 

 caloric. It is owing to the attraction of caloric 

 for ponderable matter, that when a piece of tin 

 is laid on a portion of melted lead, the tin is dis- 

 solved, and its particles intimately blended with 

 those of the lead. In all such cases, it is un- 

 deniable that the atoms of the liquid are forced 

 to combine with those of the solid, by the agency 

 of caloric alone ; for the obvious reason, that no 

 other agent has been employed to produce the 

 effect. 



