Sept. 1849. RIVER AND MORAINES AT MOMAY. 121 



The Laclioong is here twelve or fifteen yards wide, and 

 runs over a pebbly bed, cutting a shallow channel through 

 the deposits, down to the subjacent rock, which is in some 

 cases scooped out six or eight feet deep by its waters. I 

 do not doubt that the flatness of the floor of the Momay 

 valley is caused by the combined action of the streams that 

 drained the three glaciers which met here; for the tendency 

 of retiring glaciers is to level the floors of valleys, by giving 

 an ever-shifting direction to the rivers which drain them, 

 and which spread detritus in their course. Supposing 

 these glaciers to have had no terminal moraines, they might 

 still have forced immense beds of gravel into positions that 

 would dam up lakes between the ice and the flanks of the 

 valleys, and thus produce much terracing on the latter.* 



On our arrival, we found that a party of buxom, good- 

 natured looking girls who were tending yaks, were 

 occupying the hut, which, however, they cheerfully gave 

 up to my people, spreading a black tent close by for them- 



these most delicate scratches retained in all their sharpness on rocks clothed 

 with seaweed and shells, and exposed at every tide, in the bays of Western 

 Scotland ! 



* We are still very ignorant of many details of ice action, and especially of the 

 origin of many enormous deposits which are not true moraines. These, so con- 

 spicuous in the lofty Himalayan valleys, are not less so in those of the Swiss Alps : 

 witness that broad valley in which Griudelwald village is situated, and which is 

 covered to an immense depth with an angular detritus, moulded into hills and 

 valleys ; also the whole broad open Upper Rhone valley, above the village of 

 Munster, and below that of Obergestelen. The action of broad glaciers on gentle 

 slopes is to raise their own beds by the accumulation of gravel which their lower 

 surface carries and pushes forward. I have seen small glaciers thus raised 300 

 feet ; leaving little doubt in my mind that the upper Himalayan valleys were thus 

 choked with deposit 1000 feet thick, of which indeed the proofs remain along the 

 flanks of the Yangma valley. The denuding and accumulating effects of ice thus 

 give a contour to mountain valleys, and sculpture their flanks and floors far more 

 rapidly than sea action, or the elements. After a very extensive experience of ice 

 in the Antarctic ocean, and in mountainous countries, I cannot but conclude that 

 very few of our geologists appreciate the power of ice as a mechanical agent, 

 which can hardly be over-estimated, whether as glacier, iceberg, or pack ice, 

 heaping shingle along coasts. 



