Outlines of Geology. 241 



mass of any other substance, I should call such rock grauwacke. 

 The mountainous part of Somersetshire included in its north- 

 west district ; the great slate formation of Cornwall ; the ridge that 

 follows the Malvern Hills ; these have sometimes been adduced as 

 grauwacke ; but they do not come within the definition I have 

 proposed. We must resort to Cumberland for illustrative speci- 

 mens of this rock, and to the scenery of the lakes for a notion of 

 its mountainous aspect. There is something exquisitely beautiful 

 in the mountains that environ the southern extremity of Derwent- 

 water; their forms, tints, and general association and outline, are 

 perfectly peculiar — they have not the craggy summits and frag- 

 mented precipices that belong to a true slaty texture, nor do they 

 form those bold masses and blocks which announce mountain 

 limestone to the eye of the distant observer — they shew an union 

 of softness and grandeur which marks them as a distinct forma- 

 tion ; and if there be a difficulty, which there often is, in deciding 

 respecting hand-specimens, grauwacke may, in general, soon be 

 recognised, where the forms of its hills can be traced. 



Associated with these rocks, and next in order of succession, 

 are several varieties of slate, which, however, may, without any 

 inconvenience or inconsistency, be referred to the great clay-slate 

 formation, of which in England we have abundant and grand 

 instances, especially in the northern and western parts, and which 

 constitutes the greater portion of the mountainous district of 

 North Wales. It is an abundant rock in Cumberland and West- 

 moreland, but is there so interwoven with the varieties of grau- 

 wacke, and has been so completely confounded with that rock in 

 geological descriptions, that it is extremely difficult to draw the 

 line of distinction between them, or to say where the one ends 

 and the other begins. The cluster of hills, however, of which 

 Skiddaw forms the highest elevation, may probably be referred 

 to genuine clay-slate, and in Devonshire and Cornwall, the gra- 

 nitic range which traverses the promontory like a back-bone, 

 beginning on Dartmoor, and ending at the Land's -end, has slate 

 overlaying it on both sides. All the magnificent scenery of 

 Falmouth, Fowey, Looe, Tintagell, and of other places too nu- 



