Page:Popular Science Monthly Volume 44.djvu/807

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789
THE ICE AGE AND ITS WORK.

gravel in places from three to four hundred feet higher than the beds of limestone rock which are from two to ten miles off. Débris of red sandstone is also found much higher than the parent rock. Bowlders of Shap granite, Mr. Kendal tells us, have passed over Stainmoor by tens of thousands, and in doing so have been carried about two hundred feet above their source; and the curious Permian rock, "Brockram," has been carried in the same direction no less than a thousand feet higher than its highest point of origin.[1] In Scandinavia there are still more striking examples, erratic blocks having been found at an elevation of forty-five hundred feet which could not possibly have come from any place higher than eighteen hundred feet.[2] We thus find clear and absolute demonstration of glacier ice moving up-hill and dragging with it rocks from lower levels to elevations varying from two hundred to twenty-seven hundred feet above their origin. In Switzerland we have proof of the same general fact in the terminal moraine of the northern branch of the Rhone glacier being about two hundred feet higher than the Lake of Geneva, with very much higher intervening ground. As it is universally admitted that the glacier of the Rhone did extend to beyond Soleure, all the a priori objections to the various cases of rocks carried much higher than their origin, in America, the British Isles, and Scandinavia, fall to the ground. We must either deny the existence of the ice-sheet in the great Swiss valley, and find some other means of accounting for the traveled blocks on the Jura between Geneva and Soleure, or admit that the lower strata of a great glacier can travel up-hill and over hill and valley, and that the ice-sheets of the British Isles, of Scandinavia, and of North America merely exhibit the very same characteristics as those of Switzerland, but sometimes on a larger scale. We may not be yet able to explain fully how it thus moves, or what slope of the upper surface is required in order that the bottom of the ice may move up a given ascent, but the fact of such motion can not any longer be denied.

The facts thus established render it more easy for us to accept one of the latest conclusions of British glacialists. A great submergence of a large portion of the British Isles during the Glacial period, or in the interval between successive phases of the Glacial period, has long been accepted by geologists, and maps have been often published showing the small group of islands to which our country was then reduced, the supposed subsidence being about fourteen hundred feet. The evidence for this is the occurrence, at a few spots, of glacial gravels containing marine


  1. Wright's Man and the Glacial Period, p. 154.
  2. James Geikie's Great Ice Age, second edition, p. 404.