We must regret that we are unable to accompany the following description with such maps or plates as are almost indispensable to a due understanding of the phenomena ; but as the great number of those that would be wanted renders this impossible, we must be content with refer ring such of our readers as may be at a loss on the sub ject, to the papers formerly mentioned, where all the re quisite illustrations will be found. Those who are pos sessed of a map of Scotland, may, however, easily trace the courses and positions of the rivers fand valleys which are the seats of these appearances.
All our readers know that the great glen of Scotland through which the Caledonian Canal is conducted, ex tends in a straight line from Fort William to Inverness, containing the connected chain of lakes, Loch Ness, Loch Oich, and Loch Lochy. The greatest height of this valley is only 94 feet above the level of the sea ; and its bottom, wherever it is accessible, is alluvial, so as to have led to the not very improbable opinion that the west ern and northern seas once communicated through it, and that the north-western region of Scotland was a distinct island.
Between the southern extremity of Loch Lochy and Fort William, is found a wide opening, bounded on one hand by the skirts of Ben Nevis, and, on the other, by the hills near llighbridge, which separate Glen Roy from Glen Gloy. This latter glen opens into Loch Lochy at it more northern point, and extends, in a somewhat tortuous course, to the middle of Glen Roy, with whidlt it commu nicates at a high level. But the wider opening forms two principal ramifications—the one into Glen Roy, and the other into Glen Spean, which, in its prolongation, is now the scat of Loch Laggan. From Glen Spean different small valleys branch off, giving access to the mountain streams that flow into the Spean. These are, however, little concerned with the phenomena in question ; with the exception of that valley which leads to Loch Treig, and conducts its waters to the Spean below.
Where Glen Roy branches away from Glen Spean, it first holdsa course somewhat to the northward, and then turns off to the east, where, after a course of about eleven or twelve miles, it appears to terminate. This may be called the Lower Glen ; as, after suddenly rising to a higher level, it continues to hold its course eastward for about four miles, till it nearly reaches Loch Spey, on an elevation which here forms the highest water level of the country, and from which the rivers separate to the east ward and westward. We need not describe here the mi
nor valleys that open into Glen Roy, as we could not convey a just idea of them, and as they will hereafter be noticed wherever they arc required for the description of the phenomena under review.
In this whole system of associated valleys, the parallel roads, as they are called, may be traced with more or less of distinctness and continuity. But they are far more perfect and numerous in some places than in others, while in many they are altogether invisible. As they are most complete in Glen Roy, and as their effect there is far more impressive, while their origin can at the same time be more satisfactorily found, we shall commence with the description of that valley. The others will require comparatively little notice; and we shall here only pre mise that we have substituted the term lines for roads, the latter name conveying improper notions of their na ture.
Commencing at the uppermost or western extremity of Glen Roy, we find a low granite hill skirting the boundary between Loch Spey, which is the source of the river Spey, and the upper valley of the glen in question. The water from the loch runs slowly eastward through a boggy plain ; till, meeting with numerous other streams, it holds its way into Badenoch, and forms the noble river which finally terminates at Speymouth. The western end of this plain stretches for a few hundred yards beyond the head of Loch Spey, and then descends by a sudden step into the upper valley of Glen Roy. This valley is of an oval form, about four miles in length, as we just remark ed, and one or more in breadth, being bounded on two op posite sides by high mountains. From these descend two streams, which unite about the middle of the valley to form the Roy. After this junction, the united streams flow with a moderate velocity for a space of two miles, when the glen suddenly contracts, and terminates in a rocky hill of no great elevation. The water, forcing its way for some distance through a narrow pass between ap proaching rocks, enters into a second glen, or into Lower Glen Roy, where the principal appearances under review are found.