The Land of Deep Corrosions 261 
of pot-holes and smoothed cavities in the rock between low 
and high water-marks, and above the road exactly similar 
pot-holes were visible thirty or forty feet higher up, well 
above the highest flood-mark. Again, at Samba-dhuka in 
Tibet, the confined waters of the Mekong race between 
fluted limestone cliffs through which the river has evidently 
cut its way, and a short distance back from the top of the 
cliff, which is several tens of feet above the highest level 
now reached by the water, a second fluted wall of limestone 
caps a small river-terrace, and may be traced for some 
hundreds of yards. So exactly similar is it to that which 
now confines the Mekong, that I could not doubt they owed 
their origin to the same cause. 
For let us remember the summer rise in these confined 
gorges—due to the terrific rainfall on the Tibetan plateau 
being synchronous with the melting of the snows—is very 
great. On the upper Salween in December, when the water 
had not yet touched its lowest level, I noticed a water-mark 
on the face of a gorge nearly thirty feet higher up, and this 
some distance south of that country to which the above 
descriptive name is more particularly given. A rise of 
thirty feet in a river averaging sixty yards in breadth and 
flowing with a strong current implies a force which is almost 
beyond belief till one has seen it at work. We have already 
seen how in roughly the same latitude the Yang-tze, Mekong, 
and Salween flow at successively lower altitudes, and still 
further south this difference appears to be accentuated in 
the case of the two latter rivers, for Major Davies states 
that on the main T‘eng-yueh-Tali road (lat. 25°) the height 
of the Mekong above the Salween is as much as 1700 feet. 
The rapid changes of climate—or I should say perhaps 
its local character, since it is only the traveller who passes 
swiftly from a region of continuous and appalling rains to 
one of extreme desiccation—I have attempted to describe 
in my travels; but as the subject is one of great importance 
not only to the present aspect of the country but also to 
the changes which may be wrought here in the future of 
geological time, it will be necessary to discuss the subject 
in more general terms. 
The prevailing wind is undoubtedly the south-west 
monsoon which, blowing across the plains of Assam and 
