32 TKANSACTIONS oF THE [Sess. lxxx 



We have already seen good reason to believe that the 

 parallel divides have been gradually pushed up from the 

 west, and if we suppose that the whole area has been 

 bodily pushed up over older rocks, by a movement from 

 the west, we might account for the westward tilt. The 

 highest ranges would thus be found in the east, not only 

 because they would be pushed furthest up the inclined 

 plane, but also because they would have been longest 

 subjected to the pressure. Such a movement might also 

 account for the river goi'ges, for on cessation of the pressure 

 the weight of the anticlines would tend to drag the mass 

 down the slope again, and the synclines might break. The 

 objection to this is that, if tlie synclines broke, faulting 

 would almost certainly take place, and probably be con- 

 spicuous. I can only say that I have never seen any trace 

 of a fault in any of the river beds, the continuity of the 

 rocks on both sides usually being obvious. On the other 

 hand, some such external force seems to have played a 

 part in the moulding of the country, for the rivers flow 

 <iuite independently of the strike or dip of the strata, at 

 one point parallel to and a few hundred yards beyond at 

 right angles to the strike, so that apart from such con- 

 siderations as liDW much spade-work a river is able to 

 perform under certain conditions, it seems that the valleys 

 have not been simply eroded. Taken in connection with 

 the amount of granite we have seen building up some of 

 the ranges, however, there is another possible explanation 

 of this valley formation. When wc consider the pushing 

 lip of a tremendous range like the Himalayas, it is evident 

 that a great tension must be set up in the adjacent crust, 

 and lines of weakness would be liable to appear at right 

 angles to the axis of the range, running in this case from 

 north to south. Any subsequent pressure acting from one 

 side — say, from the west — would then be apt to make itself 

 felt particularly along these lines of weakness, and in the 

 case of igneous rocks, with the region in a state of greater 

 or less volcanic activity, it would be along such lines that 

 the originally deep-seated granite would be squeezed out. 

 As it burst through and was further ruckled up by the 

 pressure, the natural result would be for it to throw aside 

 the strata, which would tlius come to stand vertically, strik- 



