Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/339

 unnecessary to pursue the course of this glen further, as it adds no illustration to the subject; but it is necessary to remark, that not only at the angles and curvatures of these lateral glens, but at the turns which the principal valley Glen Roy itself makes, the breadth and form of the lines is equal every where, as well below as above the curvature. The breadth of the bottom of the valley here has been for some time reduced to an angle; and the strath, or alluvial flat, which characterized its upper part, has ceased. The hills on the left hand side descend with various curvatures and irregularities, but the three lines continue well marked on them as far as Glen Glastric, on the north side of which they turn up for a short space, and then disappear. Below Glen Fintec all the three are visible as far as a stream which enters the Roy nearly opposite Glen Glastric, and here the uppermost disappears. The rapid fall of the Roy has now increased the distance between the lowermost line and the foot of the glen, as the section will show. A material alteration here takes place in the aspect of the sides of the glen, but most particularly on the right. A great range of deep alluvium is seen between Glen Fintec and Glen Glastric, the upper surface of which is not far below the lower line, bearing marks of a level once continuous, though now much interrupted. This waste is owing to the action of mountain streams, which have ploughed it deeply to the very river, forming a great range of semiconoidal hillocks, similar to those which I mentioned as occurring in the upper part of the glen, but much more remarkable.

It is here necessary to notice that the alluvium at the top of the glen which covers the sides of the hills, consists of sharp fragments with a mixture of clay, a bed precisely similar to that which occurs so generally on the declivities of mountains, and which, from the