151 



ing the hills themselves, and the intermediate spaces, marked glacially, 

 and the glacial striae, and the lengths of the hills and intermediate 

 hollows, all conformable in direction, the author of the paper thinks 

 it probable that ice, not water, will yet be concluded to have bee^ the 

 cause of this notable example of the phenomenon of Denudation ; and, 

 consequently, of many others where its operations have not as yet 

 been suspected. 



It is in the midst of this district of old red sandstone mountains, 

 that the author discovered the traces of local glaciers passing through 

 the vale of Loch Assynt, and that containing the estuary of Kyle 

 Skew. These consisted of moraines damming up lakes in the high 

 grounds, — smoothed hummoqks and ridges of rock in the valleys, 

 with the exposed side towards the supposed sources of the glaciers, 

 and trains of brown debris in the opposite direction, — and blocks of 

 the gneissic platform of the country carried in the latter direction 

 over the crust of old red sandstone on the coast. The direction of 

 the striation in these instances, is different from that above described, 

 and at one place, on the skirts of Canisp mountain, above a valley 

 containing many moraines, the normal striation from the north-west 

 is crossed, like the chequers of cloth, by another system traceable to 

 an agent which has passed right down hill. 



The author considers these facts as indicating that there has 

 heen,Jlrst, a general sweeping of the surface in that district by some 

 icy agent, wliich has come from the north-west, and been all but 

 wholly indifferent to the inequalities of the ground ; and, second, 

 systems of local glaciers -which have passed over certain portions of 

 the ground, substituting their own peculiar set of tracings and me- 

 morials for those of the previous movement. And thus he considers 

 himself as having obtained a key to much that was perplexing in 

 the glacial phenomena of the southern portions of the Highlands. 

 Having in Lochaber, — where Mr Maclaren had found in the valleys 

 traces of a westerly movement, — seen on the higher grounds the clearest 

 memorials of one to the south-eastward and eastward, he believes that 

 the former instances are merely results of later and more local gla- 

 ciation, the direction of which was of course determined by the de- 

 scent of the valleys; while it remains true of this, as of the more 

 northern districts, that a general sweeping of the surface, irrespective 

 of hill and valley, had taken place at an earlier period. The author 

 conceives that the smoothings of valleys still more to the southward, 



