Vol. 62.] THE BTJTTERMERE ASTD ENNERDALE GRANOPHYRE. 255 



The larger mass on the south is almost cut in two by the alluvium 

 of the Ennerdale Valley ; and it might be supposed that this valley 

 was determined by a strip of softer rock between two intrusions : 

 but I have examined all the lowest accessible points in the floor of 

 the valley, and everywhere found granophyre in situ. I have no 

 doubt, therefore, that the intrusion is perfectly continuous ; and the 

 detailed mapping at the western extremity certainly suggests that 

 the true form of the intrusion is shown by simply joining up the 

 boundary-lines on each side of the lake. It is probable that 

 Ennerdale is a line of weakness on a large scale, which is due 

 to subsequent earth-movement. There is a great fault running in 

 a north- north-westerly direction, from the head of Smithy Beck 

 towards Eloutern Tarn, which shifts the outcrop more than a mile 

 to the north-west, and this helps to make the outline appear more 

 complicated. 



The western boundary is fairly simple to the south of Ennerdale 

 Water. It runs in a sinuous manner, with a general southerly 

 direction, for some distance south of the Bleng Valley, and then it 

 suddenly turns to the north-east. Throughout this whole distance 

 of some 6 miles the line is very difficult to follow accurately, 

 although easy enough to map approximately. The outcrop is 

 occasionally shifted for a short distance bj' small faults, but no 

 important dislocations seem to occur. 



Returning again to Ennerdale, a very fine junction-section can 

 be seen in the bed of the River Liza, close to the new bridge below 

 the Pillar mountain. Here the volcanic rocks have been much 

 hardened and injected by veins of granophyre, and this hard band 

 has given rise to a small gorge, which affords a fine exposure. 

 The junction here appears to be very irregular. 



Erom High Beck westwards, the line of junction with the 

 Borrowdale Series presents some interesting features. The faults 

 indicated on the 1-inch map seem to be non-existent ; but, from 

 a consideration of the outcrop of the line of junction in relation to 

 the contour-lines, it is evident that the plane of separation between 

 the Volcanic Series and the granophyre is here dipping north- 

 westward, instead of south-eastward as usual. This dip is at a 

 gentle angle, perhaps 5° ; and the upper surface of the granophyre 

 is nearly always brecciated along the plane of junction. Hence, it 

 seems probable that there has been a certain amount of movement 

 along this plane. 



On the hillside west of Buckbarrow appears a small lenticular 

 patch of similar rock, and south of this again comes a larger mass, 

 occupying most of the low ground to the west of the foot of 

 Wastwater. This mass is very badly exposed, especially round its 

 margin, and was only mapped with great difficulty. v 



As will appear from the petrographical descriptions which follow, 

 this great series of intrusions is far from uniform. The great bulk 

 of the rock is highly acid ; but in many parts there are more basic 

 modifications, which require separate description. These basic modi- 



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