158 GREEN MOUNTAINS IN MASSACHUSETTS. 



The lamination in schist or limestone may be either stratification 

 foliation or cleavage foliation, or possibly a combination of both. False 

 bedding occurs in limestone also. Therefore the conformability of two 

 adjacent rocks is only shown by the conformability of the stratification 

 foliation of both. 



Stratification foliation is indicated by : («) the course of minute plica- 

 tions visible to the naked eye, (J>) the course of the microscopic plications, 

 (c) the general course of the quartz laminae whenever they can be clearly 

 distinguished from those which lie in the cleavage planes. 



Cleavage foliation may consist of: (a) planes produced by or coincident 

 with the faulted limbs of the minute plications, Q>) planes of fracture re- 

 sembling joints on a very minute scale, with or without faulting of the pli- 

 cations, (r) a cleavage approaching ''slaty cleavage," in which the axes of 

 all the particles have assumed either the direction of the cleavage or one 

 forming a very acute angle to it, and where stratification foliation is no 

 longer visible. These forms may all occur in close proximity. 



A secondary cleavage, resembling a minute jointing, occurs in scattered 

 localities, and, although not vet very satisfactorily observed on Greylock, 

 original cleavage foliation may become plicated by secondary pressure. 



The degree and direction of the pitch of a fold are often indicated by 

 those of the axes of the minor plications on its sides. 



The strike of the stratification foliation and cleavage foliation often 

 differ in the same rock, and are then regarded as indicating a pitching fold. 



Such a correspondence exists between the stratification and cleavage 

 foliations of the great folds and those of the minute plications that a very 

 small specimen, properly oriented, gives, in many cases, the key to the 

 structure over a large portion of the side of a fold. 



STRUCTURAL TRANSVERSE SECTIONS. 



( hi these principles twelve complete and three partial transverse sec- 

 tions have been constructed across the Greylock mass; there are also three 

 across Stone hill, to which reference will be made in Appendix A. All of 



