for removing the boundary of the lake of Glen Roy beyond Dalchully, the two greatest elevations west of this point and between it and Glen Roy, which I have already shown to be lower than the highest line, bear no marks at present of having ever had a higher elevation, or of being now subject to causes of waste. Instead of this there is a plain at the elevation of Loch Spey, and a second in upper Glen Roy before the point at which the river enters this valley, amounting collectively to about a thousand yards in length, through which no water runs. This portion of the present boundary and division of the east and west rivers, so far from being in the act of waste, is gradually increased in height by the sliding alluvium of the sides of the hills which bound it, and by the formation of peat moss; an increase which is producing a visible diminution of Loch Spey, and which will, as in the case of numerous other highland lakes, at some future time, obliterate it altogether. If we examine next the nature of the present boundary at Loch Laggan, we shall find that it consists of a ridge of rock, and that it affords passage to no river. The river, on the contrary, which runs into Loch Laggan has its source at a distance, and flows in a parallel direction to it, while that which drains its eastern side into the Spey, passes it in a similarly parallel course. That all hills are subject to other causes of waste is undoubted, but this ridge affords at any rate an example of an elevation of which the wasting causes are at least trifling.
Independently of the consequences I have attempted to deduce from the supposition that an ancient lake was the cause of the lines in Glen Roy, other geological inferences of no small importance may be made from these phenomena, without the necessity of considering the precise nature of the action which produced them; or even with the admission that either of the two rejected hypotheses is the true one.
