Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/374

 on a set of terraces, the sides of which held an unequally angular direction to its current, render such a supposition untenable. It is not less an argument against this notion, that they are found entering into both the smaller and larger lateral glens and into the furrows of the hill torrents, which should have protected the terraces, had such existed in these situations, from the influence of any current or river running through the valley. The only appearance of argument on which this hypothesis rests is, that the lowest line of Glen Roy is found continuous with a large terrace at its upper end. It has indeed been said that all the lines terminated in terraces in the same place, a mistake which the ample description that I have given at the beginning of this paper will rectify. But, admitting the whole of this postulate, the existence of terraces in the course of this valley and the coincidence of some of them with the lowest line, is no proof that the lines have been produced by the same species of action which produces terraces in the course of other rivers. Another and equally satisfactory explanation of the formation of these terraces will be given hereafter, since it is chiefly connected with the third hypothesis not yet considered, but the appearances must be briefly noticed in this place. Two sets of them are to be seen in Glen Roy. Numerous low ones of different elevations skirt the banks of the river through all that part of the valley which is marked by a flat alluvial bottom, or which has the appearance of a strath. It is plain that these are the almost daily consequences of the action of the present river, and that they are in all respects similar to those terraces which are nearly the invariable companions of the rivers that flow in straths. But another and a distinct order of them is to be found at a greater elevation, which however perhaps common in their origin with the former, or rather the parents and progenitors of these smaller ones,