Here, then, we have a valley, not cut out by the working of any streams which now appear; and we may therefore make trial of the hypothesis of a _debacle_. This, however, will afford us no assistance; because, if we suppose what is now hollow to have been once occupied by the same kind of rock which is on either side, no force of torrents can have suddenly loosened and removed from its place a body of such vast magnitude. A greater column of water, than one having for its base a transverse section of the valley, could not act against it, and this would have to overcome the cohesion and inertia of a column of rock of the same section, and of the length of sixty-two miles. It is not hazarding much to affirm, that no velocity which could be communicated to water, not even that which it could acquire by falling from an infinite height, could give to it a force in any degree adequate to this great effect. The explanation of this valley, which appears to me the most probable, is the following. It will be shown hereafter, that there is good reason to suppose, that, in most parts of our island, the relative level of the sea and land has been in past ages considerably higher than it is at present. In such circumstances, this valley may have been under the surface of the sea, the highest part of it being scarcely 100 feet above that level at present. It may have been a kind of sound, therefore, or strait, which connected the German Sea with the Atlantic; and the strong currents, which, on account of the different times of high water in these two seas, must have run alternately up and down this strait, may have produced that flatness of the bottom, and straightness of the sides, and that widening at the extremities, which are mentioned above. In this way, too, some difficulties are removed relative to Loch Ness, which is so deep as hardly to be consistent with the indefinite length of the period of waste that must be ascribed to the mountains on each side of it. Its depth is said, where greatest, not to be less than 180 fathoms. According to this hypothesis, it may, at no very distant period, have been a part of the bottom of the sea.] 363. They who maintain the existence of the _debacle_, will no doubt allege, that though these valleys were not cut out by means of it, yet others may. But it must be recollected, that if some of the greatest and deepest valleys on the face of the earth, such as that just mentioned, on the east side of Mont Blanc, are thus shown to be the work of the daily wasting of the surface, what other inequalities can be great enough to require the interposition of a more powerful cause? If a _dignus vindice nodus_ does not exist here, in what part of the natural history of the earth is it likely to be found?