56 ORIGIN OF THE 



oxides of the various metals which were exposed 

 to its action. We are aware that this oxidized 

 surface would be specifically lighter, and would 

 occupy more space, than the metals did before 

 being oxidized ; and we know that the weight 

 of the mass would be increased exactly in pro- 

 portion to the weight of the oxygen with which 

 it would combine. We know, too, that heat 

 expands metallic bodies ; and, consequently, a 

 diminution of the heat of fluidity would contract 

 them. The earth, then, as it parted with its 

 caloric, or source of heat, would occupy much 

 less space, when it should become solid, than it 

 would before having parted with its caloric of 

 fluidity ; and this law, it is believed, would 

 act uniformly, from the time the matter of the 

 earth existed in the state of gas, to the time 

 when it would become (if it ever should) a per- 

 fect solid. From what we have said above, 

 however, it will be seen, that the surface of the 

 earth, by its union with oxygen and other gases, 



