where,—above as well as below. I contend that if the entire valley had been excavated by glaciers, the surface of the rocks would have been as smooth as glass, from one end to the other, when the ice retired.[1] Now, I have frankly admitted (note to p. 323) that, given sufficient time, sun, frost, and water, are capable of destroying highly glaciated surfaces; but I will not admit the possibility of such perfection of glaciation as I have just indicated being completely effaced (say, at heights exceeding 9000 feet), while a few yards lower down ice-marks are seen, and seen everywhere. For it is well known to all who have scrambled amongst the Alps, that those mountains are not glaciated from summit to base. The marks of the great glaciers of the olden time extend up to a certain height, and then they cease. This is the case throughout the Alps generally. The limit of glaciation is usually placed at about 9000 feet. Above this limit the mountains are more or less rugged and angular. Below it, the traces of the glacial period are more or less apparent. Above it, you seek in vain for glacier-eroded rocks.[2] Below it, they are found almost everywhere. Here is the evidence of Agassiz upon this point:—
"Every mountain-side in the Alps is inscribed with these ancient characters, recording the level of the ice in past times. . . . Thousands of feet above the present level of the glacier, far up towards their summits, we find the sides of the mountains furrowed, scratched, and polished, in exactly the same manner as the surfaces over which the glaciers pass at present. These marks are as legible and clear to one who is familiar with glacial traces as are hieroglyphics to the Egyptian scholar; indeed, more so,—for he not only recognizes their presence, but reads their meaning at a glance. Above the line at which these indications cease, the edges of the rocks are sharp and angular, the surface of the mountain rough, unpolished, and absolutely devoid of
- ↑ See p. 152.
- ↑ It is not, of course, meant that there are no traces of glacier-action above 9000 feet, upon rocks bounding, or surrounded by, the existing glaciers. There are, for example, many islands of rock in the Alps, surrounded by glacier, at elevations considerably exceeding 9000 feet, which are highly glaciated. I refer to those mountains which are away from the existing glaciers, and which have never been influenced by them.
