180 THEORY OF COHESION. 



It is in this way that all metallic alloys are 

 formed. If six drachms of solid zinc be brought 

 in contact with an ounce of melted copper, there 

 is a transition of caloric from the one to the 

 other, by which the particles of zinc are trans- 

 ported from their original place, and intimately 

 combined with those of the copper, by the same 

 power which unites the atoms of individual 

 metals. The simple matter of fact is, that all 

 the elements of nature may be united by fusing 

 them together, and again separated by larger 

 proportions of the same agent. If a mass of 

 granite, or basalt, were plunged into a cauldron 

 of burning lava, they would be intimately in- 

 corporated throughout by the transition of caloric 

 from the lava to the solid rock. It is scarcely 

 necessary to add, that the various materials of 

 which all volcanic rocks are formed, are thus 

 united and held together, by the same power 

 which maintains the solidity and cohesion of the 

 earth. 



The internal constitution of metals is so far 

 modified by their different degrees of purity, 

 that no two series of experiments hitherto per- 

 formed for the purpose of ascertaining their 

 respective degrees of cohesion and conducting 

 power have presented the same results. Ac- 

 cording to Emmerson, the cohesion of gold wire, 

 one-tenth of an inch in diameter, supports 500 

 pounds weight, and iron wire of the same size, 

 4-50 pounds ; whereas other experimenters have 



