Silurian and the deposition of the Red Conglomerate of Mell Fell, ushering in the great Carboniferous period. For these Lower Carboniferous rocks (Mell Fell Conglomerate, etc.) are deposited across the denuded edges of all the older formations; at one place they lie upon Upper Silurian, at another upon rocks of the Volcanic Series, and at yet another upon the Skiddaw Slates. Thus there cannot be the shadow of a doubt as to the length of time which must have elapsed between the close of the Upper Silurian and the commencement of the Carboniferous period, and of the greatness of the work accomplished in that time.

"It is to the earlier part of this lengthy period, when the Skiddaw Slates were buried at their deepest, and internal commotions began to be displayed, that I would assign the formation of the various granitic centres. I have already treated of the probable pressure under which they were respectively formed, and called attention to the fact-in the Survey Memoir (p. 74)—that an axial line of the most intense metamorphism runs parallel with the main axis of upheaval. That there was a disposition at this period towards volcanic outburst I do not doubt, and that the mass of Shap Granite came nearest to establishing a volcanic connection with the surface I have hinted before; but we have no evidence that the granitic roots were ever continuous, in this district, with volcanic vents, though, having no deposits of the true Old Red age (Lower Old Red) in the district, it would be unsafe positively to say that there were not volcanic eruptions within this area in Old

Red times, or that the Shap Granite, for example, does not represent the root of such an Old Red volcano. Of the three principal granitic centres the Skiddaw Granite occurs only in connection with the Skiddaw Slate, which is extensively metamorphosed around, but the granite, where we now see it, is undoubtedly intrusive; the Eskdale Granite ranges for a distance of more than fourteen miles through the Volcanic Series, and is surrounded by an extensive zone of altered volcanic rocks; while the Shap Granite has altered both volcanic rocks and the Coniston Series. We have, in fact, in these three masses, granite consolidated at various depths, or the potential roots of volcanoes exposed at different stages."

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CHAPTER II.

THE ORIGIN OF MOUNTAIN AND HILL SCENERY.

Different Shapes of our Hills and Mountains-Mountains not upheaved into their Present Forms-Physical Geography of the Highlands-How the Highlands were formed-Sections across Mountain Ranges—Valleys produced by Denudation— Result of Denudation of Hard and Soft Rocks-Origin of Plains, Fens, Marshes, &c.-Valleys on Mountain Summits— "Cheese-wrings," how they were formed-Débris on Mountain Sides-How Passes, Gorges, and Ravines have been formed-Minor Scenery of Hilly Districts-Rounded HillsEvidence of Former Ice-action-Evidence of Continental Ice Conditions-Ancient Glaciers among our British Mountains -Origin of Lakes, Tarns, &c.--Perched Blocks, Ancient Moraines, &c., of our Mountains-Eskers, Kaimes, &c.— Rev. J. Clifton-Ward on Glaciation of the Cumberland Mountains.

THIS part of our subject naturally grows out of that just discussed. To many people it may sound strange to hear the origin of scenery debated, for they have, perhaps, always entertained the idea that the present scenery of the globe was created just as we now see it. No mistake could be greater. Our physical scenery is the result of certain conditions and natural processes, all of which can be easily understood. The different shapes of our various hills and mountains, the gorges which seam their flanks, the passes which cross mountain-chains, the valleys which separate hill from hill, the tarns scattered among their quietest and

most solemn recesses, and the peaceful lakes which repose at their feet and reflect their loftiest summits -all these characteristic features have been formed by certain operations, which it is the duty of the physical geologist and geographer to elucidate.

The first idea, in endeavouring to explain the origin of mountains, is to suppose they were upheaved into their present forms. There is just sufficient truth in this to lead a student wrong. It is true that all mountain-masses occupy areas of elevation, but it is not correct to conclude that the individual hills and mountains owe their shapes to mere elevation. Let us take the Highlands of Scotland as an example and illustration of the origin of mountains generally. If we could get a straight-edge long enough to extend across the entire region we should find it would nearly touch the tops of all the mountains it stretched across. We should then see the idea is here, at least, perfectly correct, that mountains owe their shapes entirely to the valleys which have been scooped out of them. This Highland region was once a lofty table-land, an elevated plain of marine denudation. In the long ages which have elapsed since the plain was elevated, the atmosphere has been wearing and tearing its surface. Rains, rills, and rivers have eaten into it, the softest rocks have weathered the quickest, and the hardest the slowest. Consequently, after this almost infinite wear-and-tear, we have now the present billowy arrangement of hills and mountains. The valleys occur, as a rule, where the rocks are softest, and the highest mountains are where the rocks of the once

highly elevated table-land were hardest. Hence, as Prof. Ramsay has well remarked, "Just as a railway navigator leaves pillars of earth in a railway-cutting to mark how much he has removed, so the great excavator, Time, has left these mountain land-marks to record the greatness of his operations."

Section across a Mountain-Chain, showing the Highest Points occupied by Hard Gneissose Rocks.

Thus we are brought face to face with the wonderful fact that every mountain owes its existing shape solely to the sculpturing agencies of the atmosphere. Hence our oldest mountains are composed of the hardest rocks, and of the latter we shall invariably find the hardest of all, such as granite or gneiss, forming the loftiest peaks and summits. The common idea is, that if we were to cut a section across a

Section across a Hilly Range, formed of the same Formation, showing how Valleys are produced by Denudation.

mountain-chain we should find the rocks lying against each flank, and going over like a saddle, to form the ridge. This is very seldom, if ever, the case. It is true that strata have been often crumpled and folded in the neighbourhood of mountains, for unless such a process had taken place there would have been none