Vol. 65.] INTRUSIVE EOCKS IN THE NEIGHBOURHOOD OF ESKDALE. 77 



waterfalls, and thence to Flass Knotts and Peers Gill, and one or 

 two minor offshoots of these. These dykes are certainly connected 

 with the intrusions of ' bastard granite ' at Peers Gill, and form a 

 continuation of the two main dykes in Little Narrow Cove. 



The other set consists of the great dyke of granite-porphyry 

 already mentioned (p. 73) as connected with the Eskdale Granite, 

 and a smaller offshoot of the same. 



Reference to fig. 6 (p. 76) will show that the dykes connected 

 with the Peers-Gill intrusions are cut, and in one instance displaced, 

 by the dyke of granite-porphyry, indicating that this is the younger 

 intrusion. 



Thus, there appear to be five well-marked groups of intrusions in 

 this district : — 



(a) The andesitic dykes in the neighbourhood of Allen Crags and Angle 



Tarn. 



(b) The dykes of the spherulitic and felsitic group on Yewbarrow and 



High Fell, 

 (e) The dioritic (' bastard granite ') bosses of Peers Gill, Lingmell Crag 



and Bursting Knotts, with their associated dykes. 

 (d) The Eskdale Granite, with the granite-porphyry dyke running from 



Great Bank to Wasdale Head and thence to Kirkfell Crags. 



(c) The dolerite-dykes, having a general north-west to south-east trend. 



The dykes of series (a) bear a very strong petrological resem- 

 blance to the Borrowdale volcanic rocks into which they were in- 

 truded. Furthermore, they are weathered to much the same extent, 

 and have developed the same secondary minerals, among which 

 epidote is conspicuous. They appear to me to be of Borrowdale 

 age, and roughly contemporaneous with the lavas and ashes among 

 which they are intruded. 



The spherulitic series (b) is more acid in type ; but here again 

 the amount of alteration is very great, and the rocks are similar to 

 many of the rhyolitic lavas found in the upper part of the Borrow- 

 dale Series. These also are considered to be of Borrowdale age, 

 although probably somewhat later than the andesitic series («). 



The rocks of the dioritic group (c), though less altered than 

 those of groups (a) & (6), are still far from fresh; and, further- 

 more, the changes which have taken place in them are similar to 

 those that have affected the Borrowdale lavas, a notable feature 

 being the great development of secondary epidote. These may well 

 be the holocrystalline and hypabyssal equivalents of the Borrowdale 

 lavas, and I am of opinion that they also are of Ordovician age. 



My chief reason for thinking that these rocks have had a separate 

 origin from the Eskdale Granite is the marked contrast in com- 

 position which they show to that rock. As I have already pointed 

 out, the principal felspars in the granite are orthoclase and perthite 

 (orthoclase-oligoclase) ; but, in the smaller intrusions of Peers Gill, 

 orthoclase is uncommon and perthite wholly absent, while oligo- 

 clase-andesine and andesine, unknown in the granite, are present in 



