33 



forces of frost and snow, they discover few or no signs 

 of disintegration. I have examined them with particu- 

 lar attention, and neither in their crevices, fissures, nor 

 cavities, could I find satisfactory proofs of disintegra- 

 tion : mot even in the chasms down between the rocks, 

 some of which appeared ten feet deep, were any grains 

 of sand to be seen ; on the contrary, their points and 

 angles appear almost as sharp and entire as if recently 

 broken up from the quarry. 



5thly. Having taken a cursory view of some of the pre- 

 vailing; rocks that compose the crust of our earth, 1 shall 

 examine, lastly, the several species that are considered 

 as most abundant, and such as occupy the widest and 

 most extensive range in the structure of this globe, viz. 

 Granite, gneiss, sieuite, and limestone, including their 

 several modifications. 



These likewise are believed to be in a progressive 

 state of decay, and being most prevalent, must, of 

 course, contribute most abundantly to the soil of the 

 surrounding country. Nay, their decomposition is con- 

 sidered as essential to the superincumbent soil, beneath 

 ivhich they lie. This part of tbe subject is highly im- 

 portant, and deserves a more critical examination than 

 is consistent with my present views ; I shall therefore 

 pursue the course at first pointed out. 



In the first place, let us inquire what are the sub- 

 stances that compose these rocks? Granite, with its se- 

 veral modifications, is composed mostly of quartz, 

 felspar, hornblende, and mica ; the three first of which, 

 when perfectly formed, may be considered as nearly 



