ening might arise from the tendency to "heap-up." The "unusual thickness" by which he gets his "extra erosive power," is entirely conjectural, and, judging by the glaciers of the present time, it is very doubtful if it had any existence whatever. If the Professor could point to a single glacier which is doubled in thickness through retardation, he would materially fortify his argument; but, in the absence of any such evidence, we may be permitted to doubt if there is much force in his idea.[1]
Secondly, the great basins which Professor Ramsay believes were excavated by glaciers,[2] are assumed to have been scooped out of areas filled by especially soft strata, which were removed with comparative facility, and at a rapid rate. Very eminent geologists disbelieve in the existence of these especially soft areas. [3] Others, again, offer evidence which leads us to believe that some of the great Alpine lake-basins existed before the glacial period.[4] But let us suppose that they are all wrong, and that the Professor is right. Let us suppose, too, that retardation actually doubled the thickness of the glaciers. Taking all this for granted, it is still incomprehensible how the ancient glacier of the Rhone managed to excavate the bed of the Lake of Geneva to the depth of 984 feet (opposite to Evian), when it was unable to remove a tenth part of that amount from the valley of the Ehone (say between Sion and Sierre); for it was working for a greater
- ↑ No one can consult the excellent map which accompanies Martins' and Gastaldi's Terrains Superficiels without seeing in a moment, from the disposition of the moraines, that the great glacier of Aosta spread itself out directly it arrived upon the plain. Hence, any material thickening through retardation was impossible. It can readily be shown that this spreading-out frequently occurs to the glaciers of the present time, when they pass from confined places on to open spaces (places where the valleys widen).
- ↑ The basins of the lakes of Geneva, Neuchatel, Thun, Zug, Lucerne, Zurich, Constance, etc. etc.
- ↑ For example, see the remarks of Prof. Favre upon the Lake of Geneva, in Phil. Mag., March 1865.
- ↑ Sir Charles Lyell, for example. In regard to the lakes of Zurich, etc., see his Antiquity of Man, 3d ed., pp. 314-16.
