MOUNT GREYLOGK. 



147 



dips 60° east. Within a space of 2 inches the schistose part of the speci- 

 men shows as many as twenty cleavage planes crossing- the stratification 

 foliation, besides quite a number of incipient cleavage planes. Within the 

 same space the quartz is traversed by nine to ten fissures which, although 

 not always continuous with the cleavage planes of the schist, yet preserve 

 their general direction. All the minute undulations in the schist are gen- 

 eralized in the quartz. This is also shown in a specimen from the west side 

 of Deer hill. Here there are two undulating quartz lamina? generally par- 

 allel to each other. While the thicker one makes an >S-shaped curve, the 



Fig. 46. — Specimen of schist from locality 550, about J mile south of Greylook summit, in natural position Bhowing in 

 upper part a quartz lamina about 1 inch thick, conforming to the general course of the minute plications, which dipa west 

 :.t a low angle while the cleavage flips 60° cast. From a photograph. 



thinner one is plicated in the same distance as many as nine or ten times. 

 As geologists have observed, such coarse quartz lamina 1 in schist often 

 run parallel to the cleavage foliation. In order to arrive at their true strati- 

 graphic significance, not only should their general dip over a large surface 

 he noted, but allowance should be made for their passing into the cleavage 

 foliation for any considerable distance, especially when the dip of that 

 foliation forms a considerable angle with that of the stratification foliation. 

 Fig. 47 illustrates the relation of quartz laminae to the cleavage foliation. 

 The cleavage here dips about 50°; the lamina? in a few places, and for short 



