Specimen of a Gorge, 3000 to 4000 feet high, scooped out by "rain, frost, and running water," according to the geological creed of "Modern Causes." To face page 96. thin layer of boulders and gravel, the product of ancient and modern glacier moraines. Yet we know that in places where weathering (whose influence no geologist will underrate) is going on to a great extent, as on the sides and summit of the Matterhorn, an exceptionally fissile mountain, a vast pile of debris at its foot proclaims the action of frost and thaw, which ceases not during the whole summer. Not that we find in this instance "the missing strata have been carried away grain by grain," 1 for the geologist who uses this expression need scarcely be reminded that frost and weather do not act in this fashion, but by working into the crannies of rocks, by detaching flakes and fragments, and even after the expiration of ages small traces of granulation are perceptible, so as to enable the debris in any quantity to be washed away by rivers. But mountain peaks and ridges by their very shape proclaim their hardness and power of resisting the weather. Yet how is it credible that these colossal obelisks were originally imbedded in an uniform matrix of solid rock, the bulk of which was liable to be washed out while they were left standing? How came the sides of valleys to stand, while the centres were swept away, and have vanished? 1 Geikie, Scenery of Scotland, p. 9. H We know that weather acts equably upon all rock-surfaces exposed to it, consisting of similar strata, and placed under the same conditions of exposure. Sir Charles Lyell1 has too readily taken for granted that the largest and deepest valleys are in rocks which yield most readily to the atmosphere. The reverse is so often the case as to be a strong argument against erosion. The very deep valley of the Dee, in Aberdeenshire, is riven through granite, and that of Chamounix, the deepest in Europe, in rocks of the hardest crystalline texture. Where then are we to seek for an explanation which will relieve geology from these discordant improbabilities? The only one we can offer is that real denudation, which effected such astonishing revolutions on the earth, was no imperceptible "feeble process," was a power quite different from the puny everyday causes now in action, and one infinitely surpassing them in energy and intensity. We see in it the results of the phenomena accompanying the transition of our earth from a globe in great part crusted over with thick ice to its present habitable condition that state of glaciation having probably been the climax of the cooling down of our planet which produced the first breaking up of its crust, which we have already attempted to describe.2 1 Antiquity of Man, p. 36. 2 See Chapter IV. CHAPTER VIII. EFFECTS OF SUDDEN OF DENUDATION BY GLACIATION- COATING. THE existence of glaciers in primæval times, not merely in the heads of the highest valleys, as at present, but filling them entirely, radiating from the mountain chains, and overspreading large parts of the existing continents, was first discovered amidst the Alps, but it has been since traced to distant corners of the globe. Mount Sinai, Lebanon, Norway, the Himalayas, and New Zealand, alike proclaim in their old moraines, grooved and mamillated rock-surfaces and boulders, the widespread presence, at one time, of an icy crust. Greenland, a country equal to Germany in area, exists at the present day in that state of glaciation. There the valleys are scarcely to be distinguished from mountains, so completely is the surface equalised by the burthen of snow and ice. Investigations among the Alps have detected, at heights of 6000 and 7000 feet above the sea, |