Dr. M^c Culloch on the Parallel Roads of Glen Roy. 006 



This is among the best marked of those which are any where 

 to be found, its breadth being not less than 70 feet and its inclination 

 among the least of those which I measured. It is important to no- 

 tice that the opposite sides of Glen Turit are very little dissimilar 

 either in shape or composition, although they do not exhibit equal 

 traces of the lines ; and it is still more essential to remark that the 

 bottom of this glen is of solid rock and not of alluvial formation ; 

 since in the course of the examination it will be important to 

 remember that the operation of ordinary causes is to diminish, not 

 to augment its elevation. 



Where this solitary line disappears in consequence of the rise of 

 the glen, a level space occurs without a stream, but in no long 

 time it produces one, which running westward forms the water of 

 Gloy and enters Loch Lochy beyond Lowbridge. 



When I said that the upper line which is prolonged so far into this 

 glen is stopped by the rising of its bottom, I did not intend to 

 speak precisely : it ceases in fact for some space before, but evi- 

 dently from the sliding of the face of the hill into the stream. 

 That which it is important to note is, that if it had been prolonged 

 it would have met the bottom of the glen, which may be con- 

 sidered as there forming an intermediate hill between Glen Gloy 

 and Glen Roy, and thus interrupting the continuous level which 

 should take place between them at the height of the upper line. 

 It is this part of the fact alone which is important, and important 

 in more views than one, as will appear when I shall attempt to in- 

 vestigate the cause of these lines. I may remark that these alti- 

 tudes are not estimated, but were observed by the spirit level. 



I have reason to regret that a tempestuous season prevented me 

 from examining Glen Gloy with the same care which I had be- 

 stowed on Glen Roy. The requisite observations, attended with 

 Vol. iv. 2 u 



