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326 all those marks resulting from glacial action. On the Alps these traces are visible to a height of nine thousand feet."—Atlantic Monthly, Feb. 1864. If these facts mean anything, they mean that the great glaciers of the glacial period did not extend above this limit. For I cannot suppose that Dr. Tyndall is a believer in the childish notion of the late Dollfus-Ausset, that glaciers are, and were, permanently frozen to the rocks at heights exceeding 9000 feet, and therefore do not, and did not, erode them! If that idea is correct, why are there any crevasses at heights exceeding 9000 feet? In what manner is the continuity of the glaciers maintained, if their lower portions move down, whilst their upper ones are immovable? Dr. Tyndall is far too well acquainted with glaciers to believe any such absurdity. I maintain that this evidence (although scarcely so conclusive as that which has preceded it) affords strong grounds for believing that the valleys of the Alps were never completely filled by glaciers, and therefore that the valleys were not excavated by glaciers.

The evidence from the mouths of the valleys of the Alps is not less hostile to Dr. Tyndall's theory. For, observe, 1. The glaciers existed for a briefer period at the mouths of the valleys than at their upper portions. 2. The glaciers must have moved there, as a rule, at a slower rate than at the upper portions; because, as a rule, the gradients at the mouths were more moderate, and frequently (as in the case of the Valley of Aosta), there was a dead level. 3. The glaciers had usually received, before arriving at the mouths of the valleys, the whole of their most important affluents, and must have been rapidly diminishing in volume. The conclusion which is inevitable from these considerations is, that the glaciers must have exercised less erosion at the mouths of the valleys than at their upper portions; and this conclusion agrees very well with that arrived at by Dr. Tyndall himself, namely—"Lower still the elevations diminish and the slopes become more gentle; the cutting