354 Dr. Mac Culloch on the Parallel Roads of Glen Roy, 



west to the east, or from the present lowest level of the country to 

 the highest one, it will be seen in the course of the argument, that 

 many of the facts bear equally against the possibility of this suppo- 

 sition ; to such an extent indeed as to render it quite unnecessary 

 to enter into a formal refutation of it. 



The cause of such a deluge or torrent as is here supposed, is 

 generally assumed to be an elevation of a portion of land, elevating 

 at the same time the superincumbent waters. I shall as far as pos- 

 sible simplify the phenomena, and thus give all the assistance I 

 can to this hypothesis by supposing that with one line only, no 

 other valley but Glen Roy exhibited that appearance. A single 

 elevation of the site of Loch Spey would therefore be the only 

 change required to produce the effect. But the fall of the country 

 to the east, and the present course of the Spey show, that a wave 

 produced by this cause must have equally tended to flow in the 

 contrary direction or into the present valley of the Spey, and con- 

 sequently to leave its impressions to the eastward as well as to the 

 westward of its origin, on the supposition that the form of the 

 surface was then similar to its present one. But no such impressions 

 exist, although the form of the present valley of the Spey is fully 

 as capable of receiving them as that of the Roy ; and there are no 

 reasons to suppose any material changes in the shape and disposition 

 of that valley. No water courses either antient or recent, nor any 

 agents are to be seen, capable of destroying these remains if they 

 ever existedo Nor is it possible to comprehend by what means a 

 wave produced at the present elevation of Loch Spey could have 

 formed the first line which is visible in the upper Glen Roy. It is 

 evident that the quantity of water carried by the assumed wave 

 must have been sufficient to have filled the whole of Glen Roy for 

 a course of twenty miles or upwards. It must have consequently 



