We need not trace the details of this line more nicely, as they convey no useful information. The only remain ing point of importance is, to inquire respecting the height of the line of Glen Cloy, which, on a general view, would be esteemed to correspond with the upper one in Glen Roy. From the fact, that all the levels of Glen Roy, Glen Spean, Loch Trcig, and the smaller communicating valleys, are continuous, it would be a natural conclusion that the same rule held good for Glen Gloy, and that all these valleys had originally formed part of one lake. This is, however, doubtful, or MOM. By our own barometri cal measurements, it appears that the line of Glen Gloy is 12 feet higher than the upperipost of Glen Roy, and we had no opportunity of examining it by the level. Mr. Maclean's measurement, however, by the level, gave ex actly the same difference; so that, however inclined to think otherwise, we are perhaps bound to believe our own observations, thus confirmed. It will hereafter be seen how much depends on their truth or falsehood.
We have thus described, at sufficient length, all the chief details which relate to the forms of these glens, their communications, and the disposition of the lines; but it is now necessary to give some account of their nature. This is the more requisite, as the idle question respect ing their artificial origin depends very much on their form and construction.
Their extreme breadth may safely be taken at seventy feet, or a little more, and their most general one lies be tween that and fifty. They seldom exceed the former, or fall short of the latter dimensions. The most remarkable exceptions of this nature have been mentioned in de scribing the upper part of the glen ; and our readers will recollect, that they were said to be always least marked on the most rocky ground. In these situations, indeed, they cannot, with the least propriety, be called roads, since they are absolutely invisible to a person standing on them.
In no case is their surface level ; but it lies at various angles with the horizon, from thirty degrees and upwards, to ten or twelve. This is the reason that they are so often invisible, or difficult to see; their own inclination coin ciding so nearly with that of the slopes of the hills on which they lie. Both the interior and the exterior angles are very much rounded, and the surfaces are marked by considerable inequalities, from the fall of stones, and the partial accumulation of plants and recent soil. If we were to describe their relations to the sides of the hills without the aid of figures, we would say that they resembled the sections of parallel layers applied in succession to their declivities. In only one instance «e observed a slope, or superior rains, which was visible for about half a mile ; but no marks of an inferior one were observed, as should happen if they had been roads formed by digging in the alltnial covering. As to their materials, they necessai ily
consist of the alluvia that happen to be present, wnether these be sharp or round ; and this is, therefore, a part of their history which can prove nothing respecting their causes as some have vainly imagined, since, whether the produce of nature or art, they must have been formed out of I he materials that were present.
It remains yet to say a lew words respecting the com munications of these glens with the surrounding country and with the sea, a subject on which we only touched at the beginning of this description We remarked that the wide valley which forms the joint opening of the glens of the Spean and the Roy into the great Caledonian valley, was marked by an irregular bottom, interspersed with low hills, not rising to the height of the line which is con tinued on both sides of it. It would have been more cor rect to say, that there are some trifling exceptions to this rule, as we determined by levelling. The Spean falls into the Lochy through a deep ravine, well known by the wild scenery about Highbridge; but there are no other streams of any note in this tract. The opening of Glen Gloy is narrow, and its communication with the Caledonian valley is at a level somewhat higher than that of the former, as it falls into Loch Lochy.
The highest level of the Great Valley, already said to be 94 and 90 feet from the two seas which it joins, is at Loch Oich. This valley receives various other streams at different places ; from Eoch Eil, Loch Arkeig, and nu merous smaller glens ; while, on the north-eastern de clivity, it is the receptacle of the waters of Loch Garry, Glen Morison, Fyers, Glen Urquhart, and others of less note. Thus its highest level is inferior by 886 feet to the lowest line of Glen Roy and Glen Spean, and to the up permost, by 1180 ; taking the height of this above the sea at 1262 feet, as determined, for want of better means, by the barometer. The glens which communicate with this great valley are chiefly seated on the western side, and the principal ones are, Glen Morison, Glen Urquhart, Glen Garry, and the valley of Loch Eil Though we have no means of determining this point properly, we have reason to think that the four first of these branches rise at their western ends to levels higher than those of the lines in Glen Roy It is lortunate, how ever, that this point is not a material one in considering the phenomena of Glen Roy, as these would have been nearly the same, though these valleys had never existed. But the glen of Loch Eil requires some further notice, as it is probably implicated in the consequences which follow one of the theories that has been proposed for the explana tion of these appearances.