164 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 26, 



unobserved, or are ascribed to the retiring or encroaching of the sea. 

 We may suppose, therefore, that in times comparatively recent a small 

 movement of elevation or depression of the land has taken place, 

 sufficient to have brought the rocks in question within this wasting 

 action of the sea. 



3. On the Ice-woen Kocks of Scotland. 

 By T. F. Jamieson, Esq., F.G.S. 



Contents. 



1. Erosion of the rocks beneath the Drift. 



2. Ice-action compared with torrent-action. — Case of the latter at Crinan. 



3. Keasons for thinking the erosion of the rocks in Scotland to be due chiefly to 



land-ice, and not to water-borne ice. 



4. Eemarkable instances at Loch Treig and Glen Spean. — Boulders lifted up 



far above the parent rock. — Glen Koy. 



5. Example of ice-action at Knapdale. — Motion uphill. 



6. Probable solution of the phenomena. — Eeference to Greenland. 



7. Difficulty as to climate. — Eossil-eyidence. — Probable period of elevation. 



8. Proofs of great submergence subsequent to period of elevation. 



9. Criteria for distinguishing action of land-ice from that of floating ice. 



1 0. Denudation. — Probable geological date of the great land-glaciation of Scotland . 



§ 1. At the bottom of all the Drift-beds there is in our northern 

 latitudes a phenomenon which, if rightly understood, would dispel 

 much of the obscurity that still envelopes the history of that period ; 

 I mean that curious scoring and polishing of the rocky bed on which 

 the Drift is found so frequently reposing. Saussure, in his Alpine 

 journeys, had often remarked those rounded masses which he called 

 roches moutonnees, and also did not omit to note the polishing of the 

 rocky surface ; curiously enough, however, although so familiar with 

 glaciers, he did not refer these appearances to their true cause, but 

 attributed this scoring of the rocks to the passage over them of 

 boulders hurried along by a rush of water. Colonel Imrie, also, and 

 Sir James Hall, who in 1812 both described the same appearances 

 in Scotland, sought to explain them in a similar manner. As this 

 theory of their origin has found favour with several geologists, I am 

 induced to describe here a case of some interest which came under 

 my notice, and was peculiarly fitted to test the sufficiency of a 

 powerful torrent, carrying with it great boulders and stony debris, 

 to affect the rocks in the manner under consideration. 



§ 2. In the county of Argyle an artificial channel was cut, a good 

 many years ago, between the Sound of Jura and Loch Fyne, called 

 the Crinan Canal ; it is about 9 miles long, and lies in an E. and W. 

 direction, or rather S.E. and N.W. Sloping up from the south side 

 of this canal there is a range of hilly ground, where there are a 

 few small lakes that have been converted into reservoirs for regu- 

 lating the supply of water, and which are situated at a height of 

 about 700 feet above the canal. Three of these lakes, each of them 

 covering an area of about thiity acres, have been connected, and the 

 depth of their waters increased by artificial embankments. But in 

 Febiniary 1859, owing to heavy floods or some other cause, the 



