MOULINS GRAVEL CONES GLACIER TABLES. 241 



glacier that we commonly find internal cascades, or " moulins." 

 These arise from the superficial water of a glacier being col- 

 lected into a considerable mass by a long course over its un- 

 broken surface, and then precipitated with violence into the first 

 fissure it meets with. The descending cascade keeps open its 

 channel, which finally loses the form of a fissure, presenting 

 that of an open shaft, often of immense depth. 



Nearly connected in their origin with the internal cascades 

 are the gravel cones, occasionally seen on the surface of glaciers, 

 which appear to be formed in this way : a considerable amount 

 of earthy matter derived by the superficial water-runs from the 

 moraine, accumulates in heaps in the inequalities of the ice, or 

 at the bottom of the " moulins." As the glacier surface wastes 

 by the action of the sun and rain, these heaps are brought to 

 the surface, or rather the general surface is depressed to their 

 level. If the earthy mass be considerable, the ice beneath is 

 protected from the radiation of the sun and from the violent 

 washing of the rain ; it at length protrudes above the general 

 level of the glacier, and finally forms a cone which appears to 

 be entirely composed of gravel, but is in fact ice at the heart, 

 with merely a protecting cover of earthy matter. These singu- 

 lar cones are very well seen on the Glacier of the Aar, but on 

 most others they are comparatively rare. 



The similar protective action of large stones detached from 

 the moraines and lying on the surface of the ice often produces 

 the striking phenomenon of glacier tables. Stones of any consi- 

 derable size almost invariably stand upon a slightly elevated 

 pillar of ice ; but when they are broad and flat they occasionally 

 attain a height of six and even of twelve feet above the general 

 level. A striking instance has been described and drawn in my 

 Travels in the Alps of Savoy. 



To this peculiar tendency of glaciers apparently to elevate 

 heavy and opaque bodies above their surface in reality to have 

 their surface depressed beneath them is no doubt mainly owing 

 the striking, and at first sight perplexing, fact, that stones or 

 dirt are scarcely ever seen imbedded in the massive ice of 



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