Genesis of the Crystalline Schists of the Malvern Hills. 219 



folia often retained their parallelism, and this was accounted for 

 partly by the slowness of the intrusion, partly by regional pressure. 

 Even when mere flakes of the schist were enclosed in granite there 

 was no passage between the two. The granite, both in masses' and 

 veins, was often foliated, but the blocks of included diorite were 

 not ; and this seemed to suggest that the foliation of the granite 

 was acquired before complete congelation of the larger masses. 

 There was also a foliation concentric to included blocks of diorite. 



At the town of Galway the " metamorphic sedimentary " rocks 

 were a coarse-grained hornblendic gneiss of Hebridean aspect, and 

 in some parts of it was a structure similar to that of the " meta- 

 morphosed conglomerate ; " but the included blocks of diorite had 

 acquired a definite orientation, apparently due to pressure. An 

 igneous origin for some of the coarser gneisses was thus suggested. 

 It was concluded that there was no proof of the conversion of schists 

 into igneous rocks, the evidence collected tending to show, on the 

 other hand, that igneous rocks were sometimes converted into schists. 



3. " A Preliminary Inquiry into the Genesis of the Crystalline 

 Schists of the Malvern Hills." By C. Callaway, Esq., D.Sc, E.G.S. 



The Author's researches amongst the crystalline rocks of Con- 

 naught had suggested certain lines of investigation which had sub- 

 sequently been followed out in the Malvern district. He had satis- 

 fied himself that many of the Malvern schists had been formed out 

 of igneous rocks; but at present he limited himself to certain 

 varieties. 



The materials from which these schists were produced were dio- 

 rite (several varieties), granite, and felsite. 



The metamorphism had been brought about by lateral pressure. 

 Evidence of this was seen in the intense contortion of granite- veins 

 and in the effects of crushing as observed under the microscope. 



The products of the metamorphism were divided iuto two 

 groups : — 



A. Simple schists, or those formed from one kind of rock. The 

 varieties described were the following : — Hornblende-gneiss, or dio- 

 rite which had been crushed and modified. Mica-gneiss, formed 

 from granite. In the first stage of the crushing, the quartz and 

 felspar lay in lenticular fragments, separated from each other by 

 cracks, the fragments and cracks being roughly parallel. As the 

 metamorphism proceeded, the cracks became less evident, and the 

 respective minerals were flattened out into comparatively uniform 

 folia. Mica gradually came in, at first in the form of a partial 

 coating to felspar crystals, and, at a further stage, in regular 

 folia. Mica-schist, formed from felsite. The felsite gradually 

 acquired a parallel structure. Pari 'passu with this mechanical 

 alteration, a mineral change was observed. Mica at first appears 

 in very small quantity, either filling cracks or accentuating the 

 parallelism. In a more advanced stage, the mica lies in imperfect 

 folia, and sometimes forms a partial coating to grains of quartz. 

 At last there is little left but quartz and mica, the latter in folia, 

 and enveloping individual quartz granules. 



