Vol. 65.] INTRUSIVE ROCKS IK THE NEIGHBOURHOOD OP ESKDALE. 55 



4. On some Intrusive Rocks in the Neighbourhood of Eskdale 

 (Cumberland). By Arthur Richard Dwerryhouse, D.Sc, 

 F.G.S. (Read November 18th, 1903.) 



[Plate III — Microscope-sections.] 



Page 



I. Introduction 55 



II. The Eskdale Granite 55 



III. The small Intrusions near Peers Gill 71 



IV. The Dykes 73 



V. General Relations of the Intrusive Rocks 75 



I. Introduction. 



Chief amongst the group of intrusive rocks which it is my 

 purpose to describe is the granite of Eskdale and Wasdale Head, 

 which possesses petrological characters of peculiar theoretical 

 interest ; but I shall also deal with certain minor intrusions near 

 the foot of Peers Gill in Upper Wasdale, and with several groups 

 of dykes which have been usually thought to be associated with 

 the Eskdale Granite, but appear to me to have had a separate 

 origin at a period remote from that of the intrusion of the granite. 



II. The Eskdale Granite. 



The granite comes to the surface in two exposures. The larger 

 and more southerly of these occupies an extensive tract of country 

 in Eskdale and Mitredale, and extends southwards as far as Bootle 

 Pell, while it reaches to within a mile of the sea in the neighbour- 

 hood of Ravenglass. 



The smaller outcrop lies in the floor of Upper Wasdale and 

 extends from Down-in-the-Dale, beneath the hotel at Wasdale 

 Head, and up the valley to about half a mile above Burnthwaite 

 Parm. The larger outcrop has a total length of some 12 miles 

 and a breadth of 4 at its widest part, while the smaller mass 

 measures about 1 mile in length by half a mile in breadth, and is 

 roughly elliptical in form. 



The rock is mentioned by Clifton Ward in a paper entitled ' The 

 Granitie, Granitoid, & Associated Metamorphic Rocks of the Lake 

 District,' * and also in the Geological Survey memoir on the district. 2 

 In the former paper Ward describes the granite as being the ulti- 

 mate product of the metamorphism of the rocks of the Borrowdale 

 Volcanic Series. This view is, of course, unsupported by modern 

 work, and indeed the composition of the rock itself is inconsistent 

 with such a mode of origin. 



1 Quart. Journ. Geol. Soc. vol. xxxi (1875) pp. 568-602 & vol. xxxii (1876) 

 pp. 1-34. 



2 ' The Geology of the Northern Part of the English Lake District ' Mem. 

 Geol. Surv. 1876. 



