1862.] JAMIESON GLACIATION OP SCOTLAND. 175 



is very remarkable, the largest and most angular blocks are more 

 numerous high up on the very brow of the hill, at a level of from 

 130 to 400 feet from the top, than they are further down. Thus, one 

 measuring 12 feet long, by 9 broad, and 6 high, lay 130 feet lower 

 than the summit of the hill ; a few yards from it was another 9x6x4; 

 and at a level of about 400 feet below the top, or 1700 feet above 

 the sea, was a magnificent block, 15 feet long, by 10 broad, and 6 

 high : this was the largest, and, from its conspicuous position on the 

 bare brow of the hiU, may be seen at a great distance, being visible 

 with the naked eye from the Bridge of Eoy Inn, four miles off. 



This is another very striking example of boulders being carried up 

 far above the source from whence they were derived ; and I have 

 little doubt that these granite blocks have come from the patch of that 

 rock in the bottom of the valley to the eastward ; for no mineral 

 mass of the same kind is known elsewhere in the neighbourhood, nor 

 did I see any of it on the sides of Loch Treig, where, by the by, 

 there is an absence of these fragments also. It has been suggested 

 by Mr. Darwin that such cases might be explained by supposing the 

 boulders to have been frozen into coast-ice and carried upwards 

 during a period of submergence, when the land was gradually sink- 

 ing ; and it is also found to be the case that even the sea-waves, un- 

 aided by ice, can during a heavy swell throw up boulders upon the 

 rocks out of deep water. But neither of these explanations will, I 

 think, suffice for the phenomena on Craig Dhu ; for, in the first place, 

 there are no water-rolled pebbles accompanying these boulders ; and 

 in the second place, the repeated stranding of the blocks by coast-ice 

 or a heavy surf would, as Darwin admits, have rounded and reduced 

 them to smaller size the farther up they were carried, whereas we 

 see here that those most conspicuous for size and angularity are 

 highest up on the very brow of the hill. I may also point out that 

 the submergence of an isolated hill, like Craig Dhu, would have left 

 its top but a little round speck of an island, where coast-ice would 

 have had no shelter and been readily driven away. The scoring 

 also of the subjacent rock, if caused by the stranding of the boulders 

 either by coast-ice or waves, would not have been so horizontal and 

 so steadily in one direction ; we should have rather found scores run- 

 ning uphill, from the blocks being driven on it by the surf. 



The extraordinary profusion of these granitic boulders aU about 

 the valley, the manner in which such immense blocks are piled up 

 one over another on the surface of heaps of moraine-like debris, and 

 the way they have been elbowed up the slope of the hill opposite the 

 gorge of Loch Treig, together with the strong scoring and polish on 

 the rocks, — all seem to me to speak an unmistakeable language ; for 

 I know of no agency, except that of a great glacier-stream, that could 

 have effected all this. 



The granite boulders have been carried westward past Craig Dhu, 

 for I found some of them on the top of Bohuntine — a hill on the west 

 side of Glen Roy, nearly 2000 feet high, and of a remarkably rounded 

 outline, as if it had been moulded by the passage of ice. In an oppo- 

 site direction they have been carried towards Loch Laggan, affording 



VOL. XVIII. PAET I. N 



