246 CHEMICAL FORCES HOW EXERTED. 



It was before shewn, that when tin, lead, cop- 

 per, silver, and other metals, are converted into 

 the liquid state by heat, their power of combining 

 with each other is greatly augmented ; and that 

 whenever a melted metal unites with a solid 

 metal, there is a transition of caloric from the 

 one to the other. 



In like manner, when mercury, gold, silver, 

 &c. are converted into vapour, under plates of 

 copper, iron, and other solid bodies, there is a 

 transition of caloric from the former to the latter, 

 by which the particles of metallic vapour are 

 transported to, and intimately combined with the 

 solids, for the same reason that melted tin unites 

 chemically with copper and iron vessels when 

 poured into them, as in the process of tinning ; 

 or for the same reason that aqueous vapour is 

 attracted by cold bodies, and combined with 

 them in the form of dew or frost ; that is, by 

 virtue of an attraction of their caloric for bodies 

 that contain less of it. 



But if the attractive power of all bodies be 

 modified by every change in their relations to 

 caloric, it is unphilosophical to refer the effect to 

 electricity, unless it be a modification of caloric ; 



The force of chemical attraction is equally evident from the 

 manner in which it overcomes the cohesion of solid bodies. The 

 attraction of nitric acid for the atoms of silver, copper, and iron, 

 must exceed that of their cohesion ; for it tears them asunder, 

 but iu an almost imperceptible manner, and atom by atom. 



