6 On the Shelves of Lochabcr. 



the country so as to make it present its existing aspect, by 

 the means which nature has phiced at his command, seems 

 to me an utter impossibility. There never could have been 

 any means consistent with his theory, other than the waters 

 issuing from the district. The Great Glen which is supposed 

 to have been filled along with the others, presents a special 

 difficulty in the great depth of its lakes. How this glen, and 

 the basins of the lakes were cleared out, Mr Milne leaves us 

 to conjecture. Until they were cleared out, there was no- 

 thing to direct us to the point where the Lochaber streams 

 might have reached the sea ; and their courses are not un- 

 important to his theory. If we suppose the clearing of the 

 Great Glen to have been accomplished as far as its present 

 relative position to the level of the sea, it would still remain 

 to shovel out the detritus from its lake basins, to the depth 

 of some six or seven hundred feet ; to a depth, indeed, ex- 

 ceeding that of the Noi'th Sea. 



The foundation of Mr Milne's theory does not admit of 

 barriers placed here and there as occasion might require. 

 The whole was filled with detritus to the height of the high- 

 est shelf, which must have been the highest level of the sup- 

 posed lake ; and if we admit of lakes at all, the water in them 

 must have been retained by a fall or slope of tlie great mass 

 covering the whole country. Let us, however, imagine a 

 barrier extending a mile or two across a valley, and of breadth 

 proportioned to its height. Tlie operation of a stream, such 

 as that of the Roy, commencing its work at the top of the 

 barrier, would be to cut from the edge of the outer slope 

 backwards. After the cutting had proceeded to a certain 

 depth, the sides would fall in, giving the stream additional 

 laboiu- to perform. This would, in course of time, be repeat- 

 ed, till the slope of the sides became sufficiently low to pre- 

 vent their falling in. Following out, then, the simple me- 

 chanical operation of water on masses of loose matter, and 

 considering the immense amount of such matter assumed by 

 Mr Milne, we must conclude that some ti'aces of that accu- 

 mulation, and some unequivocal marks of the progress of the 

 streams should have remained to this day, as well as the 

 shelves. No such traces or marks appear ; and I deny the 



