THE GLACIAL PERIOD 77 



broken down by the fingers, especially when it is somewhat 

 weathered. Schists are commonly named from the mineral that 

 is so predominant as to give them their chief character, as mica 

 schist, chlorite schist, etc. 



Granites seem also to have been transformed directly by 

 metamorphic agencies into gneiss and the schists, so that the 

 end result of metamorphism on such igneous rocks and on sedi- 

 mentary rocks derived from them may be identical. 



