PHYSICAL FEATURES. 
3 
one another, almost due west-east, but coalescing at the point where 
the Tsangpo takes a sudden bend to the south and cuts its way 
through the hills to the plains of Assam. To the north of the 
Tsangpo a third equally well-defined range is shown as the Gangri 
mountains. 
In the second edition of the Manual of the Geology of India,' 
Mr. R. D. Oldham has expressed some doubt as to the correctness 
of this delineation of the Tibetan and Himalayan mountain systems, 
suggesting that the conditions were possibly by no means so simple 
as represented. Recent work has thrown new light on this question, 
and we are now in possession of detailed topographical maps of 
the whole course of the Tsangpo from its source down to the 
91st meridian, while, for the area to the east of this, as far as the 
bend, the maps prepared by A — k* afford much valuable information. 
From these it can be seen that, to the north of Kumaon and Nepal, 
as far east as the 88th meridian, both agree in showing an apparently 
distinct and well-defined mountain range adhering closely to the 
Tsangpo and separated from the chain of high snowy peaks by broad 
and open plains interrupted here and there by transverse spurs. 
In the publications of the Geological Survey this range is known as 
the northern range of the Central Himalaya, and it has already been 
pointed out by Mr. Griesbach and numerous other observers that 
its crest constitutes the line of water-parting between the small north- 
ward-flowing tributaries of the upper Tsangpo and the large rivers 
which find their way through the southern range of snowy peaks 
to the Gangetic plain. ^ 
In the neighbourhood of the 88th meridian and from thence east- 
wards, the orographical conditions have now been found to be by 
no means so simple as was formerly supposed, for the northern range 
ceases to exist as a definite unit and merges into a mass of variously 
" p. 460. 
' See J. B. N. Hennessey : Report on the Explorations in Great Tibet and 
Mongolia, made by A — k in 1879—82 (1884). 
' Mem. Geol. Sttrv. Ind., XXIII (1891), 23, 
{ ) 
B 2 
