Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/371

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on Glen Spean and Glen Gloy. If the solitary line of Glen Spean was produced by the action of a current, it is difficult to conceive that of the three separate lines marked in Glen Roy by one common to both glens, only a portion of the lowest, and that for a short space, should be visible in Glen Spean.

The case of Glen Gloy is still more difficult. I have shown that the head of this valley, by which it communicates with Glen Roy, is obstructed by such a rise as to exclude a free communication at this junction, of the whole of the lines of the latter. No current could therefore pass from Glen Roy into Glen Gloy, since its bottom, as I have also shown, is of ancient and hard rock, not a recent formation. If then there was a current common to both these vallies, the communication must have been formed by the opening of Glen Gloy through the intervention of Loch Lochy. A stream of water must therefore have run from a point where it had either a free exit, or at least a wide space in which to diffuse itself, to one whence there was no exit, and with a velocity as great in the most difficult as in the most easy circumstances, since the lines of Glen Gloy, wherever they exist, are at least as deeply impressed as those of Glen Roy.

The last inquiry to be made on the supposition that these lines are the consequences of a deluge, is, into the origin of the water which flowed through the valley, a subject on which I was compelled in some measure to enter at the beginning of this argument, but of which the whole difficulty could not be appreciated without including Loch Laggan in the investigation; a tract of which the importance could not then have been so readily understood. The views which I have formerly given of the level of this lake, and of that of Glen Spean, show that this supposed point must be removed far to the eastward, without which the waters could not have flowed