

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



on a set of terraces, the sides of which held an unequally angular 

 direction to its current, render such a supposition untenable. It is 

 not less an argument against this notion, that they are found entering 

 into both the smaller and larger lateral glens and into the furrows of 

 the hill torrents, which should have protected the terraces, had such 

 existed in these situations, from the influence of any current or river 

 running through the valley. The only appearance of argument on 

 which this hypothesis rests is, that the lowest line of Glen Roy is 

 found continuous with a large terrace at its upper end.* It has 

 indeed been said that all the lines terminated in terraces in the same 

 place, a mistake which the ample description that I have given at 

 the beginning of this paper will rectify. But, admitting the whole 

 of this postulate, the existence of terraces in the course of this valley 

 and the coincidence of some of them with the lowest line, is no proof 

 that the lines have been produced by the same species of action which 

 produces terraces in the course of other rivers. Another and equally 

 satisfactory explanation of the formation of these terraces will be 

 given hereafter, since it is chiefly connected with the third hypo- 

 thesis not yet considered, but the appearances must be briefly no- 

 ticed in this place. Two sets of them are to be seen in Glen Roy. 

 Numerous low ones of different elevations skirt the banks of the river 

 through all that part of the valley which is marked by a flat alluvial 

 bottom, or which has the appearance of a strath. \ It is plain that 

 these are the almost daily consequences of the action of the present 

 river, and that they are in all respects similar to those terraces which 

 are nearly the invariable companions of the rivers that flow in straths. 

 But another and a distinct order of them is to be found at a greater 

 elevation, which however perhaps common in their origin with the 

 former, or rather the parents and progenitors of these smaller ones, 



* Plate 15. Plate 21. Sect. L. t PI. 14, 15. PI. 21. Sects. K, L. 





