THEORY OF COHESION. 181 



found the tenacity of iron to exceed that of gold 

 and all other metals. 



That the cohesion of metals is determined by 

 the relative degrees of their affinity for caloric, 

 would appear from a variety of considerations. 

 It was ascertained by Buffon, that when equal 

 quantities of tin, lead, silver, copper, gold, and 

 iron were heated to an equally high temperature, 

 the tin and lead cooled in the shortest time; 

 silver next, then gold, copper, and lastly iron ; 

 corresponding very nearly with the relative de- 

 grees of their cohesion, as determined by Mr. 

 George Rennie. (Phil. Transactions for 1818.) 

 But, as observed before, the cohesive force of 

 different metals has been so variously stated by 

 different individuals, that little reliance can be 

 placed in any of them. It will be seen hereafter, 

 that the radiating power of different bodies, 

 cceteris paribus, is inversely as their attraction for 

 caloric ; from which it will follow, that if iron 

 require a longer time to cool a given number of 

 degrees than copper, gold, silver, tin, and lead, 

 it must have a stronger attraction for caloric. 

 It is for the same reason, that when these metals 

 are reduced to a very low temperature, iron and 

 copper abstract caloric from the living body 

 more rapidly than mercury, lead, tin, arsenic, 

 potassium, sodium, and all other bodies, the co- 

 hesion and conducting power of which are small, 

 and the radiating power of which is proportion- 

 ally great. 



