Dr. Mac Culloch on the Parallel Roads of Glen Roy. 325 



segments on the faces of the hill, and appearing to be the remains 

 of more regular terraces furrowed and destroyed by the mountain 

 torrents. Although the two upper lines are to be traced at the 

 salient angle opposite to Glen Turk, they are interrupted and ob- 

 scure to the very top of the valley. It is important to remark that 

 the glen here takes a turn, * forming a considerable angle, the 

 opening of Glen Turit being not far from the re-entering one. 

 At the salient angle the lowermost line is first seen, as on the right 

 side it first is found at the entrance of Glen Turit, into the wide 

 opening of which it runs, together with the upper ones, for a very 

 short space ; the whole of them speedily disappearing on this side 

 of that glen, while on the contrary side the upper one runs well 

 marked until its course is suspended by the gradual rise of the 

 bottom of the valley. 



Having, at this part of Glen Roy arrived at the point where 

 three lines on each side are visible, it is time to observe that there 

 is a perfect correspondence of level between the opposite pairs 

 wherever they are found. Numerous trials with the spirit level 

 confirm the universality of this rule, and from this point of the 

 glen downwards to its junction with Glen Spean, I did not observe 

 that any one instance occurred of even the little anomalous curva- 

 tures which I have already mentioned as happening in the upper 

 part of the valley. They are in many places entirely wanting, as 

 the plan will show, and as will be mentioned hereafter, but where- 

 ever they are present they obey the law. It is to this circumstance 

 they owe that aspect of parallelism from which they have derived a 

 part of their name, but which evidently can be a parallelism only 

 in the vertical plane. The varying slope of the hills prevents all 



* PI. 18. 



Vol. iv. 2 t 



