On the Shelves of Lochabcr, 5 



however, v/ould find its Wcay to whatever point of the com- 

 pass the surface might lean, and however tortuous tlie course. 



Every one who has observed tlie action of rivers on loose 

 materials knows that when a stream flows over an extended 

 surface, it cuts but little away, until it comes to an edge or 

 slope ; and then it cuts backwards, throwing before it such 

 loose matter as it has power to move. This process is in- 

 compatible with the formation of a lake. To form a shelf, 

 there must have been a considerable depth of water under 

 the line of surface where it was to be shaped out ; but in the 

 case before us there could be no such thing. 



Such, I conceive, to be the simple mechanical result of Mr 

 Milne's filling the valleys with detritus. He makes no pro- 

 vision for hollows to form lake? ; but he evidently assumes 

 them, though inconsistently with \\\q statement with which 

 he sets out. But I am not disposed thus to limit the theory 

 in question. I Avill admit that there were hollows left free 

 when the detritus filled the rest of the country. I will take 

 Glen-Roy as an example, and suppose that the detritus ex- 

 tended but a little way up the Glen, all the rest being empty. 



Now, while the land was submerged, according to Mr 

 Milne's hypothesis, what is now Glen-Eoy must have formed 

 part of the bottom of the sea ; and we cannot doubt that, in 

 such a case, it would be inhabited by marine animals com- 

 mon to the latitude. It is obvious that when the land rose 

 above the level of the sea, Glen-Roy would be, at first, a salt 

 water lake, and the creatures inhabiting it would be caught, 

 as it were, in a trap. The fresh water running into this 

 lake w^ould gradually free it from salt, and the animals would 

 perish. As the process of emptying the lakes is supposed 

 by Mr Milne to have been gradual, the remains of these ani- 

 mals, bones and shells, being uninjured and undisturbed, 

 ought to have been left behind in sufficient quantity to indi- 

 cate the catastrophe that had befallen them, just as Ave find 

 such exuvite in what are called elevated sea-beaches. No- 

 thing of the kind has hitherto been observed. 



The chief difficulty which to me appears to meet Mr Milne's 

 theory is, howtogctridoftlieenormous mass of materials which 

 he ha.s accunmiulated. For, to produce the shelves, to clear 



