386 Dr. Mac Culloch on the Parallel Roads of Glen Roy. 



for removing the boundary of the lake of Glen Roy beyond Dal- 

 chully, 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. In- 

 stead 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 pre- 

 sent 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 nume- 

 rous other highland lakes, at some future time, obliterate it alto- 

 gether. 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 1 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 con- 

 sidering 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. 



