IIAf. XII! KM. 'KINS 189 



deposition, there may quite well have been considerable 



Jutt as cleavage does not always efface the original 

 bedding of stratified rocks, so foliation 

 leaves an earlier structure still traceable. 

 gneisses, for example, have undergone a second process 



not quite effaced by the newer. 

 No more profitable task can be undertaken by a 

 geologist anxious to study the difficult problems of 

 regional metamorphi&m, than the careful investigation of 

 a district where the stratified rocks have been crumpled, 

 cleaved, and dislocated, but where their original sedi- 

 mentary characters still remain distinct. He can there 

 make himself familiar with details of structure which, in the 

 processes of mineralisation embraced in metamorphi&in, 

 gradually become cflaced. Thus the structure of the 

 cleaved kMas or slate of Cornwall is precisely similar to 

 that of the schists of south-western Argyllshire. Only in 

 the latter region, mineralisation has already set in, and the 

 sediments have become partly crystalline. By successive 

 stages, the crystalline re arrangement becomes more 

 developed, as the strata are followed further into the 

 Highlands, until the original sediments can no longer be 

 recognised in mica-schists and gneisses. 



In connection with the schistose rocks I may refer to 

 Miiu-r.il Veins which so often traverse these 

 though also found abundantly 



