INTRODUCTORY. 9 



(G) At the other extremity of the Gangetic plain we find the 

 alluvium extending southwards, across the gap between the Penin- 

 sula proper and the plateau of the Assam range. The rocks ot 

 these two areas are similar in character and the Assam range must 

 be regarded as, stratigraphically, part of the same geological area 

 as the Peninsula. There is some geological suggestion that the 

 stretch of alluvium, through which the Ganges and Brahmaputra 

 reach the Bay of Bengal, forms no part of the depression, or trough, 

 of the Gangetic plain of Upper India, and that the alluvium is a 

 comparatively shallow covering over a rock barrier connecting 

 the Rajmahal and Garo Hills. 1 



These are the geological problems in which elucidation may 

 be helped by geodetic observations, they do not comprise the whole 

 of those in which assistance from this line of research may be 

 looked for, but the necessary observations are wanting for dealing 

 with the others, and especially with the very important one of 

 what has taken place in the regions at either end of the Himalayan 

 ranges, where they pass into the mountain systems of Indo-China 

 on the one hand and of Afghan Turkestan on the other. 



1 Manual, 2nd cd.. p. 443. 



I. uw, ;i 



