1863.] JAMIESON PARALLEL ROADS OP GLEN ROY. 241 



level, as is well seen along the western side of the valley, from the 

 Gap np to Glen Turrit ; where, however, the valley is wide, and has 

 been exposed to the westerly gales, the terraces are broader, ruder, 

 and more shelving. This is seen on Tom Brahn, and in the Spean 

 valley above Tiendrish, for example. 



The general appearance then of the Roads did not, at first sight, 

 exhibit that erosion which I should have expected from a coast- 

 line. There is a marked absence of well-rounded shingle, less of it 

 indeed than I have observed along the margin of existing fresh- 

 water lakes. This absence of any strong erosion has been generally 

 admitted ; but there is at one place a certain amount of rounded 

 rock, upon which the author of the marine theory built a good deal, 

 as evincing an amount of abrasion that no mere freshwater lake 

 could have accomplished. This is near the entrance to Loch Treig, 

 where the lower line only occurs ; and this was one of the points Mr. 

 Darwin wished me particularly to attend to. 



But the rounding of the rocks here I found to be clearly due to 

 glacier- action. This, indeed, Mr. Darwin himself had begun to 

 suspect. It extends, as I have shown in another paper, for many 

 hundred feet up the hill on both sides of the entrance ; the line 

 here, and around Tom-na-fersit, being formed by a thick terrace of 

 gravelly debris abutting against the ice-worn rocks. Until, however, 

 the contingency of ice-action in Britain was thought of, it was, of 

 course, almost unavoidable to attribute this effect to water. Some 

 rounded rocks occur also at the gorge near the head of Glen Boy, 

 owing to the same cause, the scoring being in many places quite 

 visible. On the flank of Craig Dhu the glacial markings are often 

 very finely displayed close above and below, and even on the very line 

 itself. But I nowhere found any decided notching or cliff that I 

 could assign to the action of the old lake. 



There was another feature that seemed to bear against the pre- 

 sence of the sea. This was the state of the deltas in the upper part 

 of Glen Boy. The fine preservation of these is very remarkable. 

 One upon the east side of the glen, below the shooting-lodge of 

 Dalriach, is especially worth notice. Its surface comes up to the 

 level of the lowest line, and it protrudes from the little ravine that 

 gave it birth nearly halfway across Glen Boy, bulging out like an 

 artificial mound, compact and clear in outline as when first formed, 

 save that the stream from which it was originally deposited has now 

 cut a great gash through its midst. The fan-shaped margin shows 

 that the water it dropped into had no strong set or current, either 

 up or down the glen. If it had, the debris would have curved more 

 or less up or down the valley ; whereas it has disposed itself almost 

 equally all round the mouth of the little stream, the tendency being, 

 if any way, down the glen. Now it seems to me that the continual 

 swaying up and down of a sea-loch subject to the tides, is incom- 

 patible with all this. So far as I have observed, delta-matter car- 

 ried into the sea, or into a salt-water lake, is levelled and spread 

 out to a much greater degree. Its bearing upon the notion of a 

 deluge sweeping up the glen is still more obvious. There is a fine 



