When rocks are covered up by a sheet of glacier they do enjoy an almost invariable temperature. The extremes of summer and winter are unknown to rocks which are so covered up,—a range of a very few degrees is the most that is possible underneath the ice.[163] There is, then, little or no disintegration from unequal expansion and contraction. Frost, then, does not penetrate into the heart of the rock, and cleave off vast masses. The rocks, then, sustain grinding instead of cleaving. Atoms, then, come away instead of masses. Fissures and overhanging surfaces are bridged, for the ice cannot get at them; and after many centuries of grinding have been sustained, we still find numberless angular surfaces (in the lee-sides) which were fashioned before the ice began to work.
The points of difference which are so evident between the operations of heat, cold, and water, and those of glaciers upon rocks, are as follow. The former take advantage of cracks, fissures, joints, and soft places; the latter do not. The former can work underneath overhanging masses; the latter cannot. The effects produced by the former continually increase, because they continually expose fresh surfaces by forming new cracks, fissures, and holes. The effects which the latter produce constantly diminish, because the area of the surfaces operated upon becomes less and less, as they become smoother and flatter.
What can one conclude, then, but that sun, frost, and water, [pg 214]have had infinitely more to do than glaciers with the fashioning of mountain-forms and valley-slopes? Who can refuse to believe that powers which are at work everywhere, which have been at work always, which are so incomparably active, capable, and enduring, must have produced greater effects than a solitary power which is always local in its influence, which has worked, comparatively, but for a short time, which is always slow and feeble in its operations, and which constantly diminishes in intensity?
Yet there are some who refuse to believe that sun, frost, and water have played an important part in modelling the Alps, and hold it as an article of their faith that the Alpine region “owes its present conformation mainly to the action of its ancient glaciers”![164]
My reverie was interrupted by Croz observing that it was time to be off. Less than two hours sufficed to take us to the glacier plateau below (where we had left our baggage); three quarters of an hour more placed us upon the depression between the Grand Cornier and the Dent Blanche (Col du Grand Cornier[165]), and at 6 P.M. we arrived at Abricolla. Croz and Biener hankered after milk, and descended to a village lower down the valley; but Almer and I stayed where we were, and passed a chilly night on some planks in a half-burnt chalet.[166]
CHAPTER XIII.
THE ASCENT OF THE DENT BLANCHE.
“God help thee, Trav’ller, on thy journey far;