152 F. Kingdon Ward — "Land of Deep Corrosions." 



with a wide opening and gradually contracts as it descends, till finally 

 it slits open the enclosing wall of the main river with a narrow gorge, 

 the last thousand feet or so being over a series of high falls, or, more 

 usually, down a long stairway.] 



More interesting is a comparison of the Salween-Mekong divide with 

 the Mekong- Yangtze divide (Plate V), the climatic difPerence being 

 emphasized by the very different appearance of the peaks in the two 

 cases, those on the Mekong-Salween divide being pyramids, showing 

 clearly the curve of water-erosion, while the Mekong-Yangtze 

 divide is crowned by towers and square-faced buttresses, splintered 

 out by the action of such ' dry ' denuding agents as rapid and extreme 

 alterations of temperature, frost, wind, and so on. 



The conservative action of the snow blanket on the Mekong- 

 Salween divide must also be taken into consideration, for not only is 

 the snow-line at least 3,000 feet higher on the Mekong-Yangtze 

 divide, but the snow above 14,000 feet on the latter ridge disappears 

 in the spring long before it does from the same altitude on the former, 

 and similarly the Mekong- Yangtze divide is still bare in the autumn 

 long after the Mekong-Salween divide is covered up. Yet these two 

 divides are only 20 miles apart as the crow flies. 



Hence, while the Mekong-Salween divide is protected against 

 weathering, there is also available a much greater quantity of water 

 for purposes of transport, so that we do not find here those vast 

 screes which are such a characteristic feature of the Mekong- 

 Yangtze ridge. (Plate V.) 



Such differences of climate, of course, cause a marked difference 

 in the vegetation of the two ridges which in turn has its effect 

 on the rocks, partly conservative, partly destructive; but apart from 

 the mere appearance so produced, this is not of great importance 

 to us just now. It will suffice to say that while the rainy Mekong- 

 Salween divide is richly carpeted with plants as high as the 

 snow-line, the scree-clad Mekong-Yangtze divide presents an expanse 

 of semi-desert for the last two thousand feet or so below the 

 snow-line. 



As regards the rocks exposed in this region, they may be broadly 

 classed under three heads: (1) limestone, (2) a coarse-grained grey 

 granite, and (3) various metamorphic rocks, though, so far as my 

 experience goes, never with a schistose structure ; but whereas 

 similar rocks, limestone, granite, and metamorphic, are common to 

 all three valleys, there is considerable divergence between the two 

 great divides (each of which I crossed by three passes), the Mekong- 

 Salween being capped by igneous rocks and the Mekong- Yangtze by 

 limestone, which readily lends itself to splintering. The region is 

 doubtless rich in minerals, and I have on one occasion climbed 

 a mountain which seemed to consist almost entirely of some 

 metalliferous ore. 



We will now pass on to consider an important point in connexion 

 with the Mekong- Yangtze divide, namely, the evidence for previous 

 glaciation. 



I have mentioned two snow mountains on this divide, one of which 

 I saw very clearly, though I did not visit it ; but the glaciers are 



