126 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 1, 



Kirkstone Pass, where it is a purely crystalline rock without clea- 

 vage, but flanked at each end of the Pass by slaty semicrystalline 

 rocks gradually passing into slate. 



The slaty porphyry of Grasmere is overlaid by a hard green slate, 

 which has been quarried largely at the head of Rydal Water, where 

 it dips S. 25° E. 30°, with a cleavage which dips N. 45° W. 80° : 

 the rock is too hard to work for roofing, yet it is the continuation of 

 the beds which supply the excellent roofing-slates of Langdale. 



South of Rydal, the usual dip of all the beds is to the southward 

 (generally about S.S.E.), although there are many local changes of 

 the dip and repetitions of the beds : it is therefore clear that on 

 quitting the porphj^ry of Grasmere we have passed the axis of eleva- 

 tion of the district. Apparently all the porphyritic rocks between 

 Helvellyn and Grasmere must be regarded as one great band of 

 igneous eruption ; the intervening metamorphic slates being perhaps 

 overlying masses raised up on the surface of the porphyry. The 

 total width of the bands of porphyry thus united is about four miles, 

 and their direction ver}^ nearly east : the slates rest on them and dip 

 away from them on each side, and they thus form the axis of the 

 elevation of the southern area of the Lake district. 



The green slate of Rydal Water is succeeded by a metamorphic 

 semicrystalline slate, which, as far as its obscure bedding can be 

 seen, dips S. 25° E. 25°, reaching from Rydal Water nearly to Am- 

 bleside, with a faint cleavage dipping N. 70° and N. 80°. But in 

 Loughrigg Fell, a little to the west of the line of section 3, we find a 

 mass of igneous rock without bedding or cleavage bearing east ; and 

 some distance to the eastward, a similar igneous rock breaks out on 

 the same line in Kentmere and Long Sleddale : thus the metamor- 

 phic slates appear to cover a band of igneous rock below. In this 

 instance the cleavage strikes east in accordance with the direction of 

 the band of porphyry, instead of following the usual direction of 

 E.N.E., which is the ordinary strike of the cleavage and bedding of 

 the slates throughout the Lake ^Moun tains. 



At Ambleside the green slate dips south, and the cleavage is per- 

 pendicular with a strike to the east ; but this position is connected 

 with some faults at the head of Windermere which require w^orking 

 out. In Wans Fell the green slate dips S. 25° E. 50° to 40°, the 

 cleavage dipping N. 25° W. 85°. 



In Troutbeck the green slate is overlaid by the fossiliferous series 

 of the Coniston beds, which have been often described ; at the junc- 

 tion of the two formations the cleavage is perpendicular, striking with 

 the beds E. 25° N., but it soon returns to a dip to N. 25° W., the 

 angle of inclination gradually diminishing from 85° to 70°. 



The flagstones above the Coniston beds have been referred by 

 Professor Sedgwick to the Denbighshire flagstone, or in other words 

 to the Wenlock formation : I formerly combated this opinion, but 

 now concur in its accuracy, having seen the face of the flags of Ap- 

 plethwaite Common covered with the remains of Creseis and Grap- 

 tolites similar to those of Denbighshire. In these beds the cleavage 

 is still marked, but its planes are more distant than in the true slates. 



