CEYSTA LLLSTE SCHISTS OP THE MALVEE1* HILLS. 



535 



Schistosity , ivhether produced before or after Consolidation. — The 

 evidence I have submitted points towards the latter alternative. In 

 some of the diorites of the North Hill we have seen that the in- 

 trusive veins passed along planes of jointing and contained fragments 

 of the enclosing rock, as in Galway. Then, too, the schists formed 

 from the granite and the felsite are the effect of crushing. I prefer, 

 however, to postpone the more adequate discussion of this question. 



Pig. 3. — Plan of Vein-structure in Schistose Rocks. 



A. Coarse granitoid rock with biotite. 



B. Bands composed of granite-veins, with seams of dark mica and of coarse 



rock (A) foliated. 



C. A rein macroscopically like a fine-grained diorite. Under the microscope it 



is seen to consist of hornblende, two micas, epidote, and quartz, and has a 

 rude foliation in a specimen taken at the margin. 



D. Black schist, chiefly mica, penetrated by small granite-veins.' 



5. SlJMMAEY. 



1. Many of the gneissic and schistose rocks of the Malvern Hills 

 were formed out of igneous masses and veins. Amongst the materials 

 which underwent the metamorphism were several varieties of diorite, 

 a granite, and a felsite. 



2. The parallel structure has been caused by regional pressure. 

 This conclusion is proved by the intense contortion of granite-veins, 

 and by the mechanical effects recognized in the rocks under the 

 microscope. 



3. The products of the metamorphism are divided into (1) Simple 

 and (2) Injection-schists, the former elaborated out of one kind of 

 rock, the latter out of at least two kinds, one being intrusive in the 



