460 



which currents of water, whether bearing ice or stony matter, or 

 both, would naturally take, if guided in any degree by the existing 

 configuration of the surface. 



What appears to me to be the peculiarity of the " Roche 

 Moutonnee" I am now about to describe, is its position, forcing us 

 to seek for its explanation in causes with which the physical geo- 

 graphy of the country can have had comparatively little to do. 



In a communication to the Geological Society of London which I 

 made about three years ago, with reference to another subject, I 

 gave a general description of the structure of the ridges which 

 separate the valley of Loch Fyne from that of Loch Awe. This 

 line of hills, taken from the point where it is traversed by Glenaray, 

 runs in a south-westerly direction about twenty miles, till it falls 

 into the transverse valley behind Lochgilphead, along which the 

 Crinan Canal is carried from Loch Fyne to the Western Sea. It 

 is of moderate elevation as compared with the great group of 

 mountains which lies to the N.E. But these mountains, closing 

 round the upper end of Loch Awe, terminate in Ben Cruachan, 

 opposite to the point which I have taken as the commencement of 

 the ridge referred to ; and beyond that point the remainder of the 

 northern shores of Loch Awe, and the whole district of country ex- 

 tending from it towards Oban, is of much lower elevation, so that, 

 standing on the higher points of the range of hills to which I refer, 

 there is an uninterrupted view to the channels which wind among the 

 larger Hebrides to the mountains of Jura, Colonsay, Mull, and up 

 the Linnhe Loch to the entrance of the great valley of the Caledonian 

 Canal. 



It was on going to one of these points — the highest on the ridge 

 for some miles, and probably about 1800 feet above the level of 

 the sea — during last autumn, that I was sui-prised to observe 

 close to the summit so remarkable an example of a well-rounded 

 surface of rock as to attract my attention from a considerable 

 distance. It is the more remarkable, from the contrast it presents 

 with the generally sharp and broken edges of the strata, which are 

 there composed of hard qnartzose beds, at a high inclination, and 

 with steep escarpments. The direction from which the abrading 

 force has acted is about N.N.E. It has passed over a lower 

 shoulder in its way — lower by about 100 feet ; but the effect is 

 strongest upon the rocks of the main peak itself, and especially 



