118 OLDHAM: THE STRUCTURE OF THE HIMALAYAS, ETC. 



to the disturbance which the strata have undergone in the Siwalik 

 hills, but is a general tilt, which may reasonably be attributed to 

 a general displacement of the crust, and to a continuation of the 

 general uplift which is indicated in the outer hills, which, in this 

 case, must extend beyond the limits of the hills into a region where 

 its further progress can only be traced by inference from the 

 ^eodctic data. It may also be pointed out that this interpreta- 

 tion is in accordance with, and may in some respects be regarded 

 as a confirmation of, the conclusions, independently reached, that 

 the great boundary faults of the sub- Himalayan region are the 

 result of tectonic processes in the outer part of the crust, and do 

 not extend downwards to its lower limit. 



The conclusions which have been elaborated, as to the excess 

 of support in the central part of the Himalayas, and the uplift which 

 has thereby been superimposed on the mountain building processes 

 in the outer hills, are of great importance in attaining an under- 

 standing of what these processes are, and to what causes they may 

 be attributed. In one respect the question of the origin of the 

 mountains may be regarded as having been put in a new light, 

 for, hitherto, it has been usual to regard the visible range as the 

 primary problem and the provision of support, or compensation, 

 as a secondary one ; but, in the light of the results of geodetic work 

 in the Himalayas, the order must apparently be reversed, the 

 primary phenomenon being the production of an excess of buoyant:) 7 

 under the range, in virtue of which the range is uplifted, and the 

 range itself becomes but a secondary, though the most conspicuous, 

 effect of the processes at work. 



[ 26G 1 



