THE SIIAI' GKANITE AND ASbOClATEl) ROCKS. 305 



formed into thoroughly crystalline quartz. Such bands alternate in 

 the slides with others composed of a minutely crystalline aggregate 

 of felspar and quartz, probably representing shells of rhyolite, 

 •which had not been much altered before the metamorphism. Again, 

 parallel with these alternating zones there are sometimes strings of 

 mica-flakes, mostly brown, but some colourless, which seem to 

 answer to the well-known shells of the substance which Mr. Gren- 

 Tille Cole has compared with " pinite." 



We now come to the rocks which we have classed as rhyolitic 

 ashes and breccias. Owing to the much faulted state of these rocks 

 and the want of continuous sections in some critical places, the 

 precise succession in the Rhyolitic Group is a matter of inference 

 rather than of demonstration. The order of the rocks actually ex- 

 posed seems to be as follows, in descending order :- — 



Rhyolite, faulted against the Lower Coniston Limestone in 

 Rlea Reck. 



Rreccias and ashes, seen in the Summit railway-cutting and to 

 the south, and on the moor west of the Hotel ; these in 

 Blea Reck rest on 



Rhyolites, east of Rlea Reck Rridge. 



Pine ashes seen beside the old road to the north of Rlea Reck 

 Rridge ; these have an abnormal strike (east and west) 

 and their horizon is therefore rather doubtful. 



Rhyolites, with subordinate fine ashes, covering the tract north 

 of Rlea Reck between the old and new high roads. 



Fine ashes, with subordinate breccias, seen on the eastern 

 margin of the granite and on the high road and neigh- 

 bouring moorland ; also on the west side of the granite, 

 occupj^ing the ground from Wasdale Pike to near Was- 

 dale Head Parm. 



On the whole the f ragmen tal rocks of the upper part of the group, 

 which are entirely missing on the west side of the intrusion, contain 

 a larger proportion of macroscopic fragments, mostly of pink rhyolite, 

 than those of the lower part, so that, in the field, we have termed 

 many of them breccias ; but the presence of these relatively large 

 fragments in the fine matrix is the only character to distinguish 

 the breccias from the associated rocks mapped as ashes. The 

 rhyolite fragments are often angular or subangular, as in many 

 similar rocks throughout the Lake District, and are clearly the 

 results of explosive volcanic action. A comparison of the numerous 

 rocks of. this type in the Rorrowdale series seems to show that the 

 fragments cannot in general be ascribed to rhyolitic lava-flows 

 broken through by the eruptions, but must represent a shattered 

 crust of rhyolite formed within the volcanic vents. 



The fragments in our breccias are by no means so exclusively 

 composed of acid lava as might be supposed from the prominence of 

 the pink rhyolite upon the dark matrix. Andesite is also well 

 represented, in fragments of generally subangular or rounded form, 

 besides occasional pieces- of quartz-porphyry [1076, &c.], abundant 



