The Land of Deep Corrosions 269 
structure, the floor ascending in three or four big steps 
to the valley head, so that the streams alternately wander 
sluggishly in divided bands of water through a flat region 
of sand and shingle, and presently come tumbling in a 
cascade over heaps of boulders to the next level. Small 
lakes, sometimes occupying obvious rock-basins of con- 
siderable depth, occur in almost every valley, and in the 
bigger hanging valleys there may be as many as four 
or five, one at each level. In the smaller valleys there 
is commonly one only at the foot of the screes surrounding 
the valley head, where confused heaps of angular rock- 
fragments are piled indiscriminately at the base of the 
crags, and mounds of scree material, which might be lateral 
moraines, occur here and there bounding the valleys. Of 
striae or perched blocks however I could find no definite 
trace. : 
One further piece of indirect evidence may be adduced 
in favour of previous glaciation. I have spoken of a big 
snow mountain on the Mekong-Yang-tze watershed to the 
south-east of A-tun-tsi, known to the Chinese as Pei-ma- 
shan, and from the Tung-chiu-ling road I obtained good 
views of its glaciers. Their bottle-shaped snouts and the 
fact that the terminal moraine was, in one case at least, 
some distance from the foot of the glacier, indicated that 
they were in a state of retreat, and moreover that they 
were retreating rapidly; no very big snow-fields were 
visible, and a great deal of bare rock was exposed. Evi- 
dently the glaciers of Pei-ma-shan are mere shrunken 
remnants of their former selves. 
There are on this divide numerous peaks rising to 18,000 
feet and more, but all save the two referred to are clear of 
snow for perhaps three months in the year. Were the 
rainfall doubled this emphatically would not be the case. 
If then glaciers, which have since disappeared, did once fill 
these valleys, their disappearance is almost certainly to be 
traced to a reduction of the rainfall. 
Now if we imagine the high Mekong-Salween watershed 
swept away, the next ridge to the east, namely the Mekong- 
Yang-tze watershed, would receive the heavy rains which 
under. existing conditions deluge the former. As previously 
stated, snow lay deep on the Mekong-Salween divide at 
