12 



JOSEPH H. PERRY 



when there was extensive sericitization, development of tourma- 

 lines, and folding with fracture accompanying the intrusion of 

 granite. 



Another point of interest in the study of Monadnock is to 

 determine, if possible, why this rockmass has survived the pro- 

 found erosion to which this region has been subjected. Dr. 



Fig. 5. — Fold in schist of Monadnock, near the top, on west side. Also shows 

 banding in the schist. 



Gulliver,' speaking of this mountain, attributes its survival to the 

 greater resistance of the rock. In making such a comparison, it 

 is well to bear in mind that there is an element of uncertainty in 

 that the rocks that have been removed from above an area are not 

 always the same, at least in this region, as those that now appear 

 at the surface, on account of the extensive intrusions of eruptives. 

 Dr. Haye's^ points out, in his study of the Chattanooga district, 



^Bulletin of the Geological Society of America, Vol. X, p. 19. 



^ Nineteeftth Annual J^eport of the U. S. Geological Survey, Fart II, p. 39. 



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