﻿Vol. 66.] SKIDDAW GBANITE AND ITS METAMORPHISM. 123 



part of the area is occupied by a very broad band of hard grey grit, 

 which stretches from the southern side of Carrock Pell to the 

 western face of Skiddaw. To the north of this again comes another 

 belt of flags, and then a repetition of the soft black slates of the 

 southern side. This series seems to be cut off by a fault on the north 

 bringing in the coarse grits of Great Cockup, previously referred to 

 as possibly of pre-Cambrian age. 



Prom this brief sketch of the distribution of the different rock- 

 types, it appears that the same sequence is repeated in inverse order 

 on either side of a central line running from the southern side of 

 Carrock Fell towards Skiddaw, approximately along the upper 

 course of the Caldew. Such a structure must be either an anticline 

 or a syncline ; and, if we take into account the relation of the 

 different rock-bands to the form of the ground, the former alterna- 

 tive seems to agree better with the observed facts : thus the outcrop 

 of the central grit-band is much narrower on the high ground of 

 Skiddaw than in the comparatively low ground at the eastern 

 extremity, and it is in part concealed by the arching over of the outer- 

 members of the series, which on this supposition are higher in 

 stratigraphical order. There is no doubt that in detail the structure 

 is much more complicated than a simple anticline ; and, taking 

 into account the frequent alternations of different types of sediment 

 and the known repetition of certain fossiliferous bands, the con- 

 ception of a deeply denuded anticlinorium, pitching towards the 

 south-west, seems best to meet the necessities of the case. 



The position of the granite intrusion is in entire harmony with 

 this view, since it would thus appear to have been intruded along 

 the main axis of the anticlinorium, and in all probability its in- 

 jection closely followed or even accompanied the folding. Direct 

 evidence of the age of the granite is wanting, but it almost certainly 

 belongs to the same phase of igneous activity as the granites of 

 Shap and Eskdale, that is, to late Silurian or early Devonian times. 

 The rocks of this district were certainly uplifted, folded, and denuded 

 before the deposition of the Polygenetic Conglomerate, which is 

 almost certainly of Devonian age, though commonly assigned to the 

 base of the Carboniferous. 



A point of some interest, which arises in the course of the in- 

 vestigation, refers to the peculiar relations existing between the 

 metamorphic aureole and the topography of the district. Since the 

 general effect of the metamorphism is to increase the apparent 

 hardness of the rocks affected, it would naturally be expected that 

 the altered area would stand up as elevated ground. But in actual 

 fact this is far from being the case : the aureole, broadly speaking, 

 forms a great basin, which is bounded by the highest mountains in 

 the neighbourhood, such as Bowscale Fell, Saddleback, Skiddaw, 

 Great Calva, Carrock Fell, etc., while the exposures of granite 

 occupy a limited area in the floor of the Caldew valley. More 

 remarkable still, it so happens that the outer limits of the aureole, 



