Outlines of Geology. 251 



Having therefore pointed out the composition of these rocks, 

 as far as necessary to their definition, it remains to notice their 

 aspects as mountain masses, to examine the circumstances 'tiiat 

 attend their junctions and alternations, and lastly, to examine how 

 far the received theories of their formation are consistent with 

 the appearances which they present, and upon which the Wer- 

 nerians and Huttonians must he regarded as mainly differing. 



The largest granite tract of England is that of Devonshire and 

 Cornwall, where its sides are covered by slate, but where it rises 

 in several places to the surface, and also forms the rocky promon- 

 tory at the Land's-end. There is here nothing either pictu- 

 resque or sublime belonging to the granite formation. Dartmoor 

 appears the head-quarters of dreariness and desolation, forming a 

 large mountain tract of nearly 80,000 acres in extent, strewed 

 with granite boulders, and fragments of rocks, and appearing to set 

 cultivation at defiance. 



This granitic district is nowhere of any considerable elevation ; 

 its highest point is the hill called Brown Willey, near Bodmin, 

 which is about 1360 feet above the ocean's level. 



The peculiarities of theWest-of-Eugland granite are best seen 

 at the Land's -end, where a large patch of it protrudes in a wedge- 

 shaped promontory upon the coast ; it appears formed of frag- 

 ments and masses placed upon each other in the rudest disorder, 

 and sometimes in fantastic piles and insulated blocks, which, 

 though arising from the peculiar manner in which the rock is de- 

 composed and dislodged by the weather, have been mistaken for 

 monuments of ancient heroes, and for druidical remains. 



These Tors, as they are called, have been described by Dr. 

 Mac Culloch in the Geological Transactions, and some of them are 

 depicted in the engravings annexed to his paper. One, called the 

 Cheese -wring, at Liskeard, consists of five blocks, of which the 

 upper are larger than the lower, the whole pile being about 15 

 feet high. The stones composing this, and other similar piles, 

 suffer by the action of the weather most rapidly upon their edges 

 and angles, which gradually become rounded, until the blocks 



