416 Dugald Bell — Glacial Mound in Glen Fruin. 



requires ; and (2) by what possible main currents of the ocean, 

 whicb alone could move them, they could be brought to these 

 localities and positions. For these and other reasons, it seems more 

 probable that such boulders owe their transport to a great sheet of 

 land-ice which once filled the glen from side to side, proceeding 

 from the Argyleshire mountains on the north-west, and overflowing 

 the neck or col at the bend of the glen as also that at the head of 

 the Gareloch, between it and Lochlong.^ 



This view is strongly corroborated by the phenomenon we have 

 now to describe, viz. a remarkable mound of detritus which occurs 

 about half a mile farther up the glen than the large boulder referred 

 to, and extends for a considerable distance in a winding line across the 

 hill-side in a direction from S.W. to N.E., i.e. transverse to the glen. 

 It is most conspicuous on the eastern side of the glen, where it runs 

 from 300 to about 500 feet above the sea, " tailing out " on the 

 hill-side towards Lochlomond at a still greater elevation ; but it can 

 be traced on the western side also, in the same general direction, 

 though there the ground is lower, and not so favourable for its 

 preservation. It is composed of typical moraine matter — large and 

 small stones, sand and gravel, confusedly mixed together ; many of 

 the stones being distinctly striated. Some are sandstones from the 

 immediate neighbourhood ; others, schists and quartzes, from greater 

 distances. 



The mound varies from 10 to 20 or 25 feet in height, and from 

 20 to 30 feet in breadth. In some parts it resembles a row of 

 hummocks of varying height ; in others it rises from the surrounding 

 moor, distinct and continuous as a railway embankment. A number 

 of boulders, some of considerable size, are perched on its sides or 

 summit, and strewn along its base. 



There can be little doubt this is a " terminal moraine " of the great 

 ice-sheet which once occupied the glen; and we may add it is one 

 of the most notable and characteristic which we have seen in the 

 West of Scotland. 



A number of detached mounds of considerable size occur at lower 

 levels, beyond the opening of the glen towards Lochlomond, and 

 may be relics of still older moraines. 



Meantime the one we have described suggests the following 

 inferences : 



1. There has been no submergence to this point since the mound 

 was deposited. Its rough, undressed, unstratified condition — its very 

 existence as a distinct mound — proves this. Had there been a sub- 

 mergence of as much as 500 feet since it was deposited, such a loose 

 earthwork would soon have been demolished and effaced by the 

 currents sweeping across this low neck of land between Lochlomond 

 and the Clyde. 



2. For the same reason, there could be no submergence to that 

 extent wTiile the mound was being deposited. Some geologists hold 

 that the ice-sheet reached the sea as the land rose (assuming a sub- 

 mergence) and laid down such mounds along the sea-margin. In 



1 As noticed many years ago by C. Maclaren ; Edin. New Phil. Journ. vol. xi. 



