252 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 21, 



Roads to have been formed by freshwater lakes, I was now anxious 

 to ascertain what relation in time these lakes bore to the great sub- 

 mergence that seems to have overspread so much of Britain and 

 Ireland during what has been called the Drift-period. The preser- 

 vation of the deltas in the upper part of Glen Hoy, and the way in 

 which the pebbles lie on the water- worn ledges of the outlet east from 

 Makoul, just where the eddying outflow of the lake seems to have 

 left them, appeared to me to show that neither the sea nor any 

 diluvial catastrophe had, since the time of these lakes, approached the 

 level of the lower line, which, in round numbers, we may call 850 feet 

 above the present tide -mark. 



Seeing that Glen Nevis opens upon the head of Loch Eil, which is 

 now an arm of the sea, I thought an examination of it would afford 

 some further light upon this question. If Lochaber partook in the 

 submergence, and if this submergence occurred after the glaciers had 

 finally disappeared, then some trace of the sea's presence should be 

 found in Glen Nevis, either in the shape of marine strata, or in the 

 moraine-hillocks being levelled by the inroad of the waters. Even 

 supposing no shell-beds could be detected, yet some shingle beaches 

 or stratified beds of clay and sand might be looked for. 



It was, therefore, with a good deal of curiosity that I walked up 

 the Glen some five or six miles to try this point. The result was 

 that I found nothing to show that the sea had ever occupied the 

 glen since the glacier left it. The moraine-hillocks, even near the 

 mouth of the glen, have all their original roughness, and are dotted 

 w T ith boulders just as they are in the Larig Leachach. There are no 

 high terraces of silt or gravel, no beds of brick-clay ; but there are 

 irregular mounds of debris covered with big stones, and the torrents 

 that scar the steep sides of Ben Nevis are still pouring down their 

 shoals of gravel. The stream in the bottom has likewise accumulated 

 a slight depth of alluvial loam in the flatter parts of the valley; but 

 of the sea's presence I saw no trace. 



The same remarks will, I think, apply to the lower part of Glen 

 Arkaig, judging from what I saw during my hasty visit to that locality. 



Both Mr. Darwin and Professor Ramsay have expressed their 

 opinion that in "Wales the glaciers made a considerable advance after 

 the great submergence which left the shells on Moel Tryfan, and 

 these later glaciers, they maintain, have swept the marine drift out 

 of many of the valleys there. Adopting this opinion, we might 

 suppose some such re -extension of the glaciers to have swept all 

 trace of the sea out of Glen Nevis. 



If the glacier-lakes of Lochaber were not formed during the 

 shrinking of the great ice- covering which preceded the submergence, 

 we may suppose them also to belong to this later period. The un- 

 disturbed horizontality of the Parallel Roads is in favour of this view, 

 for we should hardly have expected them to be so perfect had they 

 shared in all the ups and downs of the later Pliocene period. This 

 second advance of the ice would also account w T ell for the absence of 

 all high-lying beds of marine shells in the more mountainous parts 

 of Scotland. If, therefore, the Parallel Roads arc the beaches of 



