MOUNT GRFA'LOCK. 



145 



larlv some of the schists on Bald mountain, near where specimen Ui'ul (Fig. 

 41) was obtained, show nothing but cleavage planes, and even under the 



Fig. 43.— Thin section of part of specimen, Fig. 42, enlarged 2h diameters, showing a minute, plicated stratification 

 foliation crossing a fine cleavage foliation. Fractures in preparing slide took place along thecleavage which here domi- 

 nates. 



microscope barely reveal the other foliation. The structural character and 

 relations of these foliations appear in Figs. 44 and 45, which show how the 

 crinkling, and sometimes the exceedingly minute faulting of the small 



Fig. 44.— Thin section of a specimen of schist froi ar the top of Mount Greylock, enlarged 2} diameters, allowing 



tin development nl' slip cleavage lYom the crinkling of the laminae of quartz and folia of mica anil chlorite, flic fracture 

 on the right follows mainly the direction of the cleavage. From a photograph. 



lamina' of quartz and folia of muscovite and chlorite of the stratification 

 foliation produce cleavage planes. The schists of the Taconic range show 

 these foliations on a still more minute scale. 

 MOH XXIII 10 



