of the Cumbrian Mountains. 63 



Craven fault. The transverse section from the hills above Brough to the 

 hills above Kirkby Stephen, shows the singular relations of these dislocated 

 masses*. 



It thus appears, that during the elevation of the central carboniferous chain 

 of the North, there were great changes of level among the component strata, 



and that the points of greatest stress not being upon the same straight line, 



the fractures were sometimes inclined to each other — that the great Craven 

 fault and the great Cross FtW fault, intersecting each other at a considerable 

 angle near the centre of the chain, shattered and cut off from it a great trian- 

 gular mass of the component strata — and that this triangular mass, being thus 

 cut off by the disruptive forces of elevation, underwent a change in its rela- 

 tive level, and was at the same moment affected by a great downcast move- 

 ment; of which we have a most convincing proof in the present extraordinary 

 position of the mineral masses at the foot of Stainmoor, and on the line of 

 section. 



I am far from supposing that in the preceding details I have pointed out all 

 the great movements whereby our northern mountain chains have been af- 

 fected. All I have attempted to do has been to explain the nature of certain 

 great dislocations of which we have direct evidence, and of which we can 

 determine the geological epoch ; and thence to show the general effects they 

 have produced on certain mountain groups in the North of England. 



If I wished to speculate on the causes of these great movements among the 

 integuments of the mountains, I should point to the porphyries of the Cheviots 

 and the syenite of Charnwood Forest, rising at the two extremities of the 

 carboniferous chain. I should also point to the granitoid rocks near Dufton 

 Pike ; and perhaps also to the Whin Sill, and the other masses of augitic 

 trap, associated so largely with the calcareous system of Cross Fellf. 



If it were objected, that the porphyry of the Cheviots sometimes resembles 

 the old felspathic rocks of Cumberland, and sometimes passes into syenite and 

 granite ; and further that we have proofs of its existence before the conglo- 

 merates of the old red sandstone : we might on the other hand reply, that 

 such facts throw no difficulties in the way of supposing, that the Cheviot por- 

 phyry (like some of the other crystalline formations of Scotland), was elevated 

 en masse at some period subsequent to its first formation ; especially as we 

 can show, to the north of the Tweed, derangements exactly answering to such 

 an elevation. We might further reply, that the red porphyries of the Scotch 

 Border, however like each other in mineral structure, are not all of the same 



• See PI. V. fig, 7. t See Geol. Trans,, First Series, vol. iv. p. 109, &c. 



