1915-16.J BOTANICAL SOCIETV OF EDINBURGH 21 



sketch) the moraine was clothed with scrub and forest 

 growing amongst boulders, the material increasing in size 

 from below upwards. Across the valley on the side facing 

 north, the ice lay tlat against the sloping valley side a little 

 above the general c^lacier level, and above that again came 

 a smooth bank of bare rock and gravel, with no plants, 

 evidently left uncovered by the sinking glacier. Fir forests 

 extend right down to the upper limit of this bare bank. 



The last half-mile of the glacier surface was fairly smooth 

 and not much crevassed, such crevasses as there were 

 being mostly longitudinal or radial ; but looking up the 

 gorge I perceived that the ice stood well away from the 

 clitfs on the north (south-facing) side, so that any material 

 falling from above was, like the streams, instantly engulfed, 

 leaving no trace of a lateral moraine. The Tibetans told 

 me that forty or tifty years ago the ice extended further 

 down the valley, and indeed the boulder-gravel banks and 

 a certain planed appearance of the rocks suggested that it 

 had once nearly reached the Mekong, a distance of little 

 over two miles from the present snout. Finally, at the 

 point where the ice came pouring over the precipice in a 

 fantastic procession of seracs, I found just below the narrow 

 cliff path which winds up the ice of the spur high above 

 the glacier, the well-preserved remains of yet another lateral 

 moraine at least 200 feet above the ice and stranded in a 

 bay of the cliffs. 



Now is this retreat of the ice apparent or real ? — has the 

 glacier merely carved out this gorge sinking lower and 

 lower, and stranding these moraines as it did so, like certain 

 deceptive "'raised " beaches, or has the ice actually decreased 

 in volume owing to diminished snowfall ? Bearing in 

 mind that we have established the actual retreat of the ice 

 on the Mekong- Yangtze divide, there is good a priori 

 evidence for its retreat in this case also. But we have 

 definite proof of its actual retreat in the extension of a 

 lateral moraine not only for three hundred feet above the 

 glacier (see sketch), but also for half a mile beyond the 

 present glacier foot. As to how these extraordinary gorges 

 were produced in the first instance, whether eroded by 

 water or ice, is not material, though I confess it is a pretty 

 problem to which I can at present give no answer. The 



