The Land of Deep Corrosions 263 
but deep snow lay as low as 12,000 feet when we crossed on 
November 5, while at the same time there was no trace of 
snow on the Mekong-Yang-tze divide below 15,000 feet. 
These facts lead me to think that the snow-line is con- 
siderably lower than 19,000 feet on the Salween-Mekong 
watershed and the ridges to the west of it. 
Further evidence for the sudden cessation of the mon- 
soon rainfall on the Mekong-Yang-tze ridge is afforded by 
a glance at the vegetation on the one hand and at the 
structure of the peaks on the other. To the former I have 
already alluded, comparing the dense forests of deciduous- 
leaved trees and the meadows of tall grasses and magnifi- 
cent flowers, with the sombre forests of conifers, the barren 
screes, and the alpine pastures clothed with dwarf flowers. 
Two great square buttresses of roughly-hewn rock rise 
above the snow-line on the Mekong-Yang-tze divide; the 
snow clings to their wall-like faces in patches and bands 
following the lines of stratification, and the glaciers descend 
from them like cataracts of ice. They have been carved 
out of these ridges by dry denuding agents, by sunshine 
and frost, which have splintered them this way and that. 
The watersheds to the west, on the other hand, are crowned 
by gently-rounded peaks and graceful pyramids tapering 
up into needle-like summits, which rise into the regions of 
eternal snow and frequently remind us of the majestic 
Matterhorn. 
In the Salween valley the heavy summer rainfall con- 
tinues as far north as T‘sam-p‘u-t‘ong, in spite of the snow- 
clad range overlooking that village. I found rich forest in 
the shady ravines, and the epiphytic orchids and ferns, 
numerous lianas, and incipient plank-buttresses supporting 
the tall straight-limbed trees gave a distinct hint of the 
tropics; and this exuberance of vegetation is continued 
southwards throughout the Salween valley. 
In the corresponding region of the Mekong, however, 
conditions are quite different. I followed this valley south- 
wards almost continuously for 200 miles as the river flows 
and was astonished at its barren aspect. Forest, or more 
generally scrub, predominates in the rainy belt between 
Tsu-kou and Hsiao-wei-hsi, but south of this the valley 
becomes arid once more, and only grass partially conceals 
