256 MB. E. H. EASTALL OX THE [May I906, 



fications are always marginal, and numerous traverses have failed 

 to disclose any such in the inner parts of the large masses. 



On the whole, dykes are scarce. There are a few interesting 

 examples in Burtness Combe, Buttermere, and a very complex 

 system of dykes on Yewbarrow ; but as the latter may, and 

 probably do, belong to the Eskdale Granite, I have not attempted 

 to describe them. 



The generalized strike of the Lower Palaeozoic rocks of this 

 part of the Lake District is nearly due north-east and south-west, 

 with a south-easterly dip ; on the western side the strike swings 

 round more towards north and south, and the outcrop of the 

 granophyre-mass closely follows this somewhat curved line. On the 

 whole, the intrusion seems to be intimately connected with the plane 

 of junction between the Skiddaw Slates and the succeeding Volcanic 

 Series. It may be regarded as consisting of a series of laccolites, 

 which are possibly, in part, of the ' cedar-tree ' type. This applies 

 especially to the southern part of the area, where it appears that 

 the intrusion has penetrated into the Volcanic Series. The top 

 of Illgill Head, east of Wastwater, consists of the base of the 

 Scawfell Ashes ; hence, the slope covered by the Wastwater Screes 

 must be occupied by the ' streaky ' * series : therefore, unless there 

 is an enormous fault down Wastwater, the top of the southern 

 granophyre must be well up in the Volcanic Series. The base of 

 the granophyre, near the head o£ Crummock Water, obviously rests 

 upon the Skiddaw Slates : hence, it appears that the granophyre not 

 only arches up the Volcanic Series, but penetrates into it as well. 



The peculiar form of the northern part of the exposure seems 

 most easily explicable on the supposition of two laccolites : a 

 small one on the north, connected with a very large one on the 

 south of it by a narrow neck, which is exposed on Little Dodd. 

 These two laccolites appear to be, on the whole, at the same 

 horizon, namely, the plane of junction of the Skiddaw Slates and 

 the Volcanic Series : this plane seems to have undergone a certain 

 amount of warping, as the result of subsequent movements. 



The northern or Buttermere laccolite is of a somewhat lenticular 

 shape : it is certainly truncated at its western end, but it appears 

 to be bounded on this side by a line of disturbance, and it 

 is possibly faulted. Near this north-western corner are a few 

 lenticular patches of Skiddaw Slate resting upon the granophyre, and 

 these suggest that the original outline of this mass was irregular, 

 somewhat of the ' cedar-tree ? type. The eastern end of the lacco- 

 lite is undoubtedly connected with the small igneous complex 

 of Burtness Combe ; and there is an isolated mass of granophyre in 

 Burtness Wood, which probably forms an easterly continuation of 

 the same mass. 



A series of specimens taken from this laccolite show interesting 

 variations. Those from near the margin [4748-50, 4752] 2 are 



1 E. E. Walker, Quart. Journ. Geol. Soc. vol. lx (1904) p. 89. 



2 Numbers in square brackets, throughout this paper, refer to slides in the 

 collection of the Sedgwick Museum, Cambridge. 



