ti-ik suppoht of the Himalayas. 117 



monically distributed over a wave-length of nearly 400 miles, 1 a 

 degree of strength which is much greater than is needed to allow 

 of the local departures from equilibrium which are met with in the 

 Himalayas. 



It will be of interest to find where the position of the right hand 

 zero point of fig. 8 lies with regard to the outer edge of the Hima- 

 layas. In this connexion we li«ive a suggestion in the fact that the 

 llayford anomaly near the outer edge of the hills, after allowing 

 for the effect of the Gangetic trough, seems to have a small positive 

 value, of the order of -01 dyne, on both the Dehra Dun and the 

 Sikkim sections. Too much weight must not be attached to this 

 coincidence, as the actual compensation will not be identical with 

 that adopted in the tables computed by Messrs. llayford and Bowie, 

 but it is suggestive of the conclusion that the zero point, where 

 the uplift of the outer Himalayas comes to an end, lies beyond 

 the edge of the hills, and under the northern part of the alluvial 

 plain. 



This conclusion receives some support on the geological side. 

 Everywhere along the foot of the hills there is a gravel slope, com- 

 posed as a rule of much coarser material, and having a steeper 

 surface gradient, than the alluvial plain beyond. This gravel slope 

 known in part of Upper India as the b/tubar, is the result of deposit 

 of coarser material by the streams as they leave the hills, and the 

 steeper surface gradient has generally been attributed to the steeper 

 slope of deposit of this coarser material, as compared with the 

 finer silt of the plain proper. On some sections, however, the 

 increase of surface gradient towards the hills results in a slope 

 too steep to be accounted for in this way, and almost everywhere 

 we find the streams cutting their way through the old gravel 

 deposits at a lower level, and on a lower gradient, than the general 

 slope of the surface. To some extent this may be due to climatic 

 change, but this explanation does not seem adequate, and there 

 remains a distinct suggestion, even where there is not a practical 

 certainty, that there has been a general tilting of the surface and 

 an uplift on the side towards the mountains. It is important to 

 note that this surface tilt is too even and regular to be referred to 

 any compression, folding, or similar process; it is not analogous 



1 Vol. XXIII, p. 30. Not, he it observed, in addition to the weight of the crust 

 itself. This is supposed to bo everywhere isostatically supported ; it is only the v un- 

 supported excess or defect which is borne by the strength of the crust. 



[ 205 J 



