Dr. Mac Culloch on the Parallel Roads of Glen Roy. 329 



unnecessary to pursue the course of this glen further, as it adds no 

 illustration to the subject ; but it is necessary to remark, that not 

 only at the angles and curvatures of these lateral glens, but at the 

 turns which the principal valley Glen Roy itself makes, the breadth 

 and form of the lines is equal every where, as well below as above 

 the curvature. The breadth of the bottom of the valley here has 

 been for some time reduced to an angle ;* and the strath, or allu- 

 vial flat, which characterized its upper part, has ceased. The hills 

 on the left hand side descend with various curvatures and irregu- 

 larities, but the three lines continue well marked on them as far as 

 Glen Glastric, on the north side of which they turn up for a short 

 space, and then disappear. Below Glen Fintec all the three are 

 visible as far as a stream which enters the Roy nearly opposite Glen 

 Glastric, and here the uppermost disappears. The rapid fall of 

 the Roy has now increased the distance between the lowermost line 

 and the foot of the glen, as the section will show, j" A material al- 

 teration here takes place in the aspect of the sides of the glen, but 

 most particularly on the right. A great range of deep alluvium 

 is seen between Glen Fintec and Glen Glastric, the upper surface 

 of which is not far below the lower line, bearing marks of a level 

 once continuous, though now much interrupted, if This waste is 

 owing to the action of mountain streams, which have ploughed it 

 deeply to the very river, forming a great range of semiconoidal 

 hillocks, similar to those which I mentioned as occurring in the 

 upper part of the glen, but much more remarkable. 



It is here necessary to notice that the alluvium at the top of the 

 glen which covers the sides of the hills, consists of sharp fragments 

 with a mixture of clay, a bed precisely similar to that which occurs 

 so generally on the declivities of mountains, and which, from the 



* PI. 21. Sect. F. + PI. 21. Sect. E. J Vide Horizontal Section, E.F. PI. 21. 



