Dr. Mac Culloch on the Parallel Roads of Glen Roy. 367 



first and highest line is to be seen in the upper Glen Roy within a 

 very short distance of the source of the Spey, and at an elevation of 

 some yards above the point whence the waters of this great river are 

 directed eastwards. It is not easy to comprehend under what pos- 

 sible circumstances a river capable of exerting the actions required 

 under this hypothesis, should have run towards the west. No river 

 exists at present in the vicinity of this portion of the upper line ; 

 and even where the Roy first appears, at a place far below the posi- 

 tion of this line t it is a feeble stream incapable of the powerful effects 

 which must be assigned to it on this supposition. 



In adducing these arguments against the present hypothesis, I may 

 further remark, that I have given it every possible advantage by 

 limiting the question to Glen Roy. It is easy to see that if Glen 

 Spean and Glen Gloy, both bearing the marks of the water lines y 

 are taken into the account, the difficulties become still more glaring. 



I shall now proceed to inquire into the probabilities which attend 

 the third and only other supposition, under which the lines of Glen 

 Roy can be referred to the action of water. I am aware that diffi- 

 culties of no trifling magnitude attend this supposition also ; but 

 none of them amount, or even approach, to physical impossibility. 

 It is equally certain that no very direct proofs can be produced in 

 favour of it, and that in defect of such there is nothing to offer but 

 a set of analogies. But the strongest evidence is perhaps founded 

 on the dilemma (to use the word in its vulgar sense) to which the 

 whole question is reduced, in the review of the former hypotheses. 

 At the same time it must have been apparent that the chief argu- 

 ments which refer to this hypothesis have already been anticU 

 pated, since they were unavoidably implicated in the consideration 

 of those which were used to invalidate the other two. Little there- 



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