This circumstance also renders this part of the glen the most striking, particularly as it is seen from the south, or looking upwards; while the beauty of the picture is much enhanced by the picturesque disposition of this part of the valley. It is easy to account for this regu larity, by the evenness both of the curvature and inclina tion of the slope of the hill on which they are marked, as well as by the form of its summit, which diverts the wa ter courses in such a direction as to preserve this part of the bill from their action. This equality is an important feature ; because it proves that the causes which produced these different lines have been similar and equal, and that the irregularities which occasionally occur are the result, not of irregularities in the action of the power by which they are produced, but of irregularities in the capacity of the ground on which that has acted.
At this place an elevated glen opens into Glen Roy on the right. No water enters from this glen, but thc junc tion is formed by a dry plain, extending for some space, which, declining gradually in the opposite direction, car ries its waters towards Glen Gloy, with which it also com municates. As the bottom of this glen is, at its entrance, at a higher level than the lowest of the lines, this latter is here interrupted ; but the two upper ones enter it on each hand, and are continued for some way along its sides. It is unnecessary to pursue the course of this glen farther, as it adds no illustration to the subject ; but it is proper to remark that, not only at the angles and curvatures of 3hese lateral glens, but at the turns which the principal valley itself makes, the breadth and form of the lines is equal and similar everywhere, as well below as above the curvature.
A bout this place, the breadth of the bottom of Glen .Roy has been for some time reduced to an angle; the strath or alluvial flat, which characterized the upper part, having changed its character. The hills on the left side descend with various curvatures and irregularities, but the three lines continue well marked on them as far a's Glen Glastric, on the north side of which they turn up for a short space, and then disappear. Below Glen Fintcc, all the three arc visible, as far as a stream which enters the Roy nearly opposite to Glen Glastric, and here the uppermost one disappears. The rapid fall of the Roy has now materially increased the vertical distance between the lowest line and the bottom of the glen. A material al
teration also here takes place on the aspect of the sides of the glen, or of the including hills, and particularly on the right. A great range of deep alluvium is seen be tween Glen Fintec and Glen Glastric, the upper surface of which is not far beneath the lowest line, having marks of a level area continuous, but now much interrupted. This waste is owing to the action of mountain streams which have ploughed it deeply to the very river, produc ing a great range of semi-conoidal hillocks, similar to those mentioned as occurring in the upper part of the valley, but far more remarkable.
It is now necessary to say, that the alluvium at the top of the hill, which covers the sides of the hills, consist of sharp fragments, with a mixture of clay, precisely similar to that which occurs so generally on the declivities of mountains, and which, from the uneven nature of the fragments, and their identity with the rocks above, seems evidently to have resulted from the wearing down of the summits. But the terraces that are at the top of the glen vary in their materials; and, though often composed of the same kind of sharp fragments that cover the general declivities, they also contain, as might easily be expected, various rolled and transported substances. The conoidal hillocks above-mentioned, and most of the terraces and hillocks that occupy positions much inferior to this, all along the course of the Spean, consist almost purely of transported materials. They exhibit, in their casual sec tions, deposits of sand, gravel, clay, and rolled stones, dispersed in a manner irregularly stratified, and inclining to the horizontal position, as is usual in similar cases else where.
No traces of the lines are visible on the left hand, from Glen Glastric down the course of the valley, although no particular reasons for this deficiency can be observed, either in the form or nature of the ground ; unless the gentleness of its shape may have had some share in this effect. There are no streams to which their destruction could be attributed ; nor, indeed, can we properly consi der the slope as the cause, as the very same lines occur again lower down, where the form and condition of the ground are exactly the same. Were it not that these lines occur at this lower point, we should, at first, be led to suppose that the action of the efficient cause had here terminated.