Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/461

 Fig. 2. — Diagram of Le Bateau.

P. Precipice of Le Rateau. P'. Rocky Spurs with precipices towards Glacier, S. Steep snow slopes. G. Glacier. --> Snow-basin leading to Glacier du Mont de Lans.

If, then, it be conceded that the neve of a glacier can settle down so fast that the uppermost mile or two of its bed shall be almost a cliff compared with the remainder of the stream, and we thus account for the configuration of such valleys as those above named, and, on a smaller scale, those in which lie the Brenva, Miage, and Argentiere glaciers near Mont Blanc, the Unter-Grindelwald and Lauter Aar glaciers in the Oberland, the Trift glacier near Zermatt, and dozens more which could be easily named in all parts of the Alps, how are we to explain such contradictions as the Mont de Lans, the Theodule, the Gorner (between Monte Rosa and the Strahlhorn), and the Titlis glaciers ? or such anomalies as the low opening of the Ampezzo Pass (about 5000 feet) among the towering summits of the Drei Zinnen, Cristallo, and Geiselstein * ? Surely it is far safer to suppose that the glen, by whatever cause fashioned, gave rise to the glacier, rather than the glacier to the glen.

But perhaps it will be urged that the greater steepness of the heads of the valleys may be explained by the fact that, in the gradual retreat of the ice-streams since the glacial epoch, they have been exposed to erosive action for a longer time than the lower parts ; and so the glaciers, in comparatively recent periods, have steepened the slope of their upper glens. The suggestion is plausible, and might be supported by an appeal to tarns like those of the Lago Bianco and Nero on the Bernina Pass, and by occasional flat


 * All about 10,000 feet above the sea.

z 2