408 VOLTAIC ACTION, AND 



the Fold ice mine, at the temperature of from 90 

 to 100 ; while the mine is only one hundred and 

 seventy-six fathoms deep. It is therefore evi- 

 dent that the temperature is not proportional to 

 depth. 



On the other hand, when we reflect that water 

 is continually acting upon metals, causing their 

 oxidation, and that chemical action is the grand 

 process by which latent heat is disengaged, we 

 need be at no loss to account for its accumulation 

 at great depths beneath the surface, where metals 

 are abundant. 



It is impossible to know with certainty how 

 far the waters of the ocean penetrate beneath 

 the surface probably not beyond the depth of 

 a few miles ; nor is there any good reason to 

 suppose that there is much chemical action at 

 greater depths, owing to the superincumbent 

 pressure ; while it is known that on the surface 

 of the earth there is very little chemical action 

 without moisture. This much however is cer- 

 tain, that so far as we can trace back the history 

 of our planet, it has been composed as at pre- 

 sent, of mountains and valleys, seas and plains, 

 and stocked with plants and animals that have 

 successively arisen and passed away, leaving 

 their fossil remains as a record of their former 

 existence. We have the most indubitable proofs, 

 that our mountains of granite, gneiss, basalt, &c. 

 were formed during long geological epochs, by 

 successive volcanic movements, and contempo- 



