PHYSICAL FEATURRS. 
II 
Hram Tso occupies the northern part of the great Tiina plain, 
lying to the north of the Tang La. It is fed 
Hram Tso. , n • • r ^.i. t 
by streams flowing in from the surrounding 
ranges and, unlike most Tibetan lakes, has also, except in the depth of 
winter when all streams are frozen, a permanent outflow; this 
escapes through a narrow gorge eroded out of the Jurassic slates at 
the extreme northern end of the lake at Tsalu, whence a small river 
runs to Kala Tso, into which it falls near the village of Kalashar. 
The latter lake lies in an open valley running approximately 
W.-S.W. to E.-N.E. and some 20 miles long by 
Kala Tso. r , , , • , 
4 miles wide ; the area of the lake is now only 
about 17 square miles, but there is ample evidence to prove that it was 
formerly very much larger. Terraces showing the former shores 
of the lake can be clearly seen at about 30 feet above its present 
level, whilst the old bed, now dry, extends far across the plain 
towards Mangtsa. At about seven miles to the east of the present 
lake an old river-course, with several terraces, indicates the former 
outlet ; this, however, is now dry and outflow takes place by under- 
ground percolation. 
Like Kala Tso, Yamdrok Tso has now no outlet. The lake 
occupies a basin between 600 and 700 square 
Yamdrok Tso. . . , / ^ 
miles in extent, in the centre of which is a 
mass of hills. In the eastern portion of this basin lies the greater 
part of the lake, a wide expanse some 30 miles long by 8 miles 
wide : thence a narrow arm, at one time probably a river valley, runs 
northward, occupying a deep valley (PI. 7) and curving round so as 
to almost completely encircle the central mass of hills. Opposite 
Nangkartse lies the Dumo Tso, which, although once part of Yamdrok 
Tso, is now separated from it by strips of low-lying marsh-land. 
Numerous old terraces can be seen on the hill-sides above the 
shores of the lake ; they are as a rule rather indistinct, but two still 
remain well-marked, one being at about 100 feet and the other at 30 
feet above the present level. It is evident, therefore, that the lake has 
contracted in volume, and that at one time it must have completely 
( 132 ) 
