MR DAVID MILNE HOME ON THE BOULDER-CLAY OF EUROPE. 685 



and striated by the action of ice. Thus, for example, the late Mr Maclaren points 

 out that the ridge which divides the Gareloch from Loch Long, about 450 feet 

 above the sea, as also two other ridges to the eastward, the one 700 feet, and the 

 other about 1700 feet above the sea, present rocks the surfaces of which are 

 " smoothed and rounded off." Mr Maclaren remarks upon this fact — " A glacier 

 lodged within the valley would grind off the asperities of the rocks at its bottom ; 

 but what smoothed the very tops of the ridges ? Is it not probable that it was 

 icebergs? "* 



The Duke of Argyle was struck with the same appearances on the ridge of 

 hills dividing Loch Fine and Loch Awe, and at a height of about 1800 feet above 

 the sea. In a letter addressed to the late Principal FoRBES,f His Grace observes, 

 " In this case glacier action is impossible. Even if this hill had been the seat of 

 a glacier, it could only have been snow, so near the summit. The only explana- 

 tion which seems to me possible is, that this peak, when subject to the grinding 

 force, was a rocky islet above the surface of a glacial sea, and that floating ice- 

 bergs drifting from the N.E. were constantly grinding upon its sides." 



In Arran, as Dr Boog Watson points out, there are several ridges between 

 adjoining valleys which are smoothed in a like remarkable manner. He has no 

 doubt that they were smoothed by ice ; but he leans to the opinion that glaciers 

 may have produced the effect, by overflowing the sides of the valleys in which 

 they were formed. 



(4.) Another remarkable phenomenon is the position of isolated boulders on 

 narrow ridges of hills, or ledges of rock, from which to all appearance the slightest 

 force could dislodge them. The wonder is how these boulders could have been 

 placed in such precarious positions. 



The Duke of Argyle takes notice of a number of these boulders as being on 

 the hills about Loch Fine and Loch Awe, adding, that it is much less difficult to 

 account for their transportation on the supposition of floating ice than of glaciers. 



Professor Ramsay, in his "Ancient Glaciers of Wales," gives a representation 

 of several of these boulders perched on the very edges of cliffs ; and I can, from 

 personal observation, as well as sketches made by myself in Wales, confirm Pro- 

 fessor Ramsay's account of the singular appearance which some of these "blocs 

 perces " present. One of these boulders, of angular shape (being 27 feet long, 15 

 feet high, and 6 feet broad), and weighing about 1 80 tons, is stated by Professor 

 Ramsay as beings " on the very crest of the slaty ridge of" a mountain, about 

 2000 feet above the sea. " The parent rock is at least a mile distant." What 

 says Professor Ramsay to the question, how this boulder was transported ? " I 

 am aware it has not been customary to consider accumulations at so great an 



* Edin. New Phil. Jonrn. for 1846, vol. xl. p. 141. 

 f Proceedings Roy. Soc. Edin. vol. iii. p. 461. 

 % Ancient Glaciers of Wales, p. 80. 



