280 MIDDLEMISS: GEOLOGY OF HAZARA AND BLACK MOUNTAIN 



We have already seen, when considering the various zones, that 

 beginning from the south we can find a gradual increase in the visible 

 folding of the rocks as we pass from the most southern to the most 

 northern zone. But it is only in the last, that is, the crystalline and 

 metamorphic zone, that a change in the effects of the lateral thrusts 

 of the earth's crust begins to be appreciable : the large visible folds at 

 last give way, the beds flatten out more and more, and we must look 

 now for these effects to the deformation of the intimate structural 

 particles of the rock. 



There is nothing anomalous in this : earth stresses at work in the 

 younger zones of incoherent or but slightly consolidated rocks of *? 

 varying texture and solidity, and with a great free surface above, 

 naturally resulted in undulating folds of the same, varying 

 in size and sharpness of the folding according to the epochs 

 through which they have acted. At stated periods as we have seen, 

 after a certain packing of the rocks had taken place, a great block 

 of such rocks has yielded as a whole and gone sliding over the zone 

 to the south, or under the zone to the northy producing a thrust- 

 plane, and marking off two disturbance zones from each other. 



But if we substitute the solid and uniform (internally) crystalline 

 granite of the central axis in place of the ordinary strata of the 

 southern zones, and if we believe (as we have a right to do from con- 

 siderations as to the deep-seated nature of granite) that very great 

 thicknesses of the slate or schistose rocks once overspread that crys- 

 talline core, we can understand that lateral stresses, if sufficiently 

 powerful and long-continued, acting on such a material would be 

 unable to violently fold and plicate them on a large scale, but would 

 spend themselves in minute deformation of the rocks, in shearing, 

 and in other ways characteristic of dynamic metamorphism. 



It has sometimes been remarked that in the bottoms of deep glens 

 and river-beds, the rocks show far more severe 



Some peculiarities in 



the disturbance of the plications and other evidence of disturbance, 

 than do the rocks or the heights rising thou- 

 sands of feet above them. General McMahon once offered the sug- 

 gestion that this might be due to much of the disturbance (packing 

 ( 280 ) 



