Skit. 1849. DONKIA GLACIER. 137 



that looking down it : gigantic blocks are poised on some. 

 The lowest of the ancient moraines completely crosses the 

 river, which finds its way between the boulders. 



Under the red cliff of Forked Donkia the valley 

 becomes very broad, bare, and gravelly, with a confusion 

 of moraines, and turns more northwards. At the angle, 

 the present terminal moraine rises like a mountain (I 

 assumed it to be about 800 feet high),* and crosses the 

 valley from N.N.E. to S.S.W. From the summit, which 

 rises above the level of the glacier, and from which I 

 assume its present retirement, a most striking scene 

 opened. The ice filling an immense basin, several miles 

 broad and long, formed a low dome,f with Forked Donkia 

 on the west, and a serried range of rusty-red scarped 

 mountains, 20,000 feet high on the north and east, separat- 

 ing large tributary glaciers. Other still loftier tops of 

 Donkia appeared behind these, upwards of 22,000 feet 

 high, but I could not recognise the true summit (23,170 

 feet). The surface was very rugged, and so deeply honey- 

 combed that the foot often sank from six to eight inches in 



* This is the largest and longest terminal moraine backed hy an existing glacier 

 that I examined with care : I doubt its being so high as the moraine of the Allalein 

 glacier below the Matmaark sea in the Sachs valley (Valais, Switzerland) ; but it 

 is impossible to compare such objects from memory : the Donkia one was much 

 the most uniform in height. 



f This convexity of the ice is particularly alluded to by Forbes (" Travels in 

 the Alps," p. 386), as the " renflement " of Rendu and " surface bombee " of 

 Agassiz, and is attributed to the effects of hydrostatic pressure tending to press 

 the lower layers of ice upwards to the surface. My own impression at the time 

 was, that the convexity of the surface of the Donkia glacier was due to a subjacent 

 mountain spur running south from Donkia itself. I know, however, far too little 

 of the topography of this glacier to advance such a conjecture with any con- 

 fidence. In this case, as in all similar ones, broad expanses being covered to an 

 enormous depth with ice, the surface of the latter must in some degree be modified 

 by the ridges and valleys it conceals. The typical " surface bombee," which is 

 conspicuous in the Himalaya glaciers, I was wont (in my ignorance of the 

 mechanical laws of glaciers) to attribute to the more rapid melting of the edges of 

 the glacier by the radiated beat of its lateral moraines and of the flanks of the 

 valley that it occupies. 



