Page:Whymper - Scrambles amongst the Alps.djvu/386

330 the existing glaciers of the Alps. Their angularity is a certain proof that they were borne upon the glaciers, and were not transported under them. For, if they had been forced along underneath the ice, they would most certainly have become, at the least, subangular, or rounded or scratched. It is well known that this is what takes place at the present time in regard to débris underneath glaciers, and that the pebbles and boulders which are moved along in such a way acquire a character of their own which is unmistakable. The moraines, then, do not support, but clearly reject, Dr. Tyndall's notion. Nor is the evidence of the rocks from which he supposes that masses have been "rooted away" less distinctly against him. How could these masses be broken away without angular surfaces being left behind? and how is it that in those places where glacier-action has been most powerful angular surfaces are most wanting? Dr. Tyndall appeals to the magnitude of the old glaciers, and to the enormous pressure which they exerted upon their beds, to explain his "rooting-away," as confidently as if his case was completely proved thereby. Yet, in those places where glaciers are and have been the greatest, and where their pressure has been the most tremendous, and exerted for the greatest length of time, we find the rocks which have been worked upon are the most highly polished, the most flat in contour, and the most devoid of all angularity whatsoever!

It is clear, therefore, that the theory of "soft places," as applied by Dr. Tyndall, cannot be sustained, and does not in the least assist us to determine how far glaciers are competent to excavate valleys. The idea is plausible that soft rocks must suffer under the grinding of glaciers more rapidly than hard ones, and may be admitted; but it will be shown presently that there are things to be said upon the other side. The notion that glaciers root away