408 TRANSACTIONS OF THE 



counted for, the high temperature of the South American 

 minesj as recorded by Humboldt, situated at the height 

 of 7000 feet above the level of the sea ? And will this 

 accord with the well known fact of the very low tem- 

 perature of the water of the ocean, and of lakes at very 

 great depths ? 



It is obvious, that however high the temperature at 

 which the earth might have been formed, it must have 

 been, within a certain time, cooljed down to the mean 

 heat of the atmosphere in which it was placed. If then 

 it be true that at certain moderate depths under the sur- 

 face, the earth continues to be of a temperature very 

 considerably above the mean of the atmosphere at its 

 surface, the conclusion inevitably is, that there must 

 even now exist some means of constantly renewing the 

 supply of caloric in the interior of the earth. If we ac- 

 knowledge the existence of a permament source of heat 

 in the interior of the earth, it might be conceived that 

 the caloric process was restricted to a nucleus of a 

 greater or less radius ; that the source from whence it 

 emanates may be far beneath an investing stratum of a 

 determinate depth under the surface, and that in conse- 

 quence of the more conducting nature of earth and rocks, 

 the heat is slowly evolved at the remote distance of the 

 surface of the earth ; and then might be accounted for 

 the high temperature in mines, by considering that the 

 metallic lodes being the best conductors, and evidently 

 placed in fissures of later origin than the rocks which 

 contain them, they may prove to be most direct chan- 

 nels to that interior source ; and to descend more into 

 minutiae, as copper lodes are of later origin than tin, 

 may this not be the cause of the opinion, which is well 

 received, of copper mines being warmer than tin. 



(7b be continued.) 



