no ILLUSTRATIONS OF THE 



the rock, which is the bafis of it, has been car- 

 ried ; and confequently, of the great difference 

 between the elevation and fhape of the earth's 

 furface in the prefent, and in former ages. 

 107. The veins of tin fiirnifh an argument of 



fame kind 



1 



The ores of this metal are very 

 deftrudible, and little fubjcd to decompofi- 

 tion, fo that they remain very long in the ground 

 without change. Where there are tin veins, as 

 in Cornwall, the tin-done or tin-ore is found in 

 great abundance in fuch vallies and llrearas 

 as have the fame diredion with the veins • 

 and hence the Jlreaming^ as it is called, or 

 wafliing of the earth, to obtain the tin Hone 

 from it. Now, if it be confidered, that none of 

 this ore can have come into the foil Dut f 



rem 



parts of a vein adually deftroyed, it muil ap- 

 pear evident that a great wafte of thefe veins has 

 taken place, and confequently of the fchiilus or 

 granite in which they are contained. 



108, Thefe leffons, which the geologift is 



taught in flat and open countries, become more 

 ftriking, by the ftudy of thofe Alpine trads, 

 where the furflice of the earth attains its great- 

 eft elevation. If we fuppofe him placed for 

 the firil time in the midft of fuch a fcene, as 

 foon as he has recovered from the impreflion 

 made by the novelty and magnificence of tliQ 

 fpedacle before him, he begins to difcover the 



footfteps 



