ICE-EROSION IN THE CUILLIN HILLS, SKYE. 251 



hio-her corries of the Cuillins. These have not the character of screes resulting from 

 modern subaerial waste; and indeed, despite an increased elevation amounting to 100 

 feet, the actual waste under existing conditions is exceedingly small.* Certainly it 

 is inadequate to account for more than a very small fraction of the material which 

 chokes the heads of many of the glens. 



While the great taluses, composed mainly of blocks of gabbro and the associated 

 rocks, on the slopes and much of the debris on the floors of the corries have clearly 

 reached their present situations by falling, rolling, and sliding, probably assisted in 

 part by snow-slopes, it is often impossible to divide these accumulations from the 

 similar material farther down-stream, which has doubtless been ice-borne, probably on 

 the tail of a dwindling glacier. A good instance of this difficulty is seen in An G-arbh- 

 choire. the glen to the south of the Sgurr Dubh ridge. The whole length of the 

 valley, about a mile, is rendered almost impassable by the blocks, great and small, here 

 chiefly of peridotites, by which it is covered. These cannot be separated distinctly 

 from the more scattered blocks over the little plateau between the mouth of the glen 

 and Allt a' Chaoich. In the lower part of the valley the peridotite blocks must have 

 travelled down, for the slopes on both sides are of gabbro ; but the higher part of the 

 accumulation is merely a great talus streaming down from the steep main ridge. 

 Something of the same kind is seen in Coireachan Ruadha, where the taluses of gabbro 

 and peridotite blocks are on a large scale. Among the outer corries of the Cuillins, 

 Coire Labain is a good example of the large amount of material detached from the 

 ridges by frost- weathering at a late epoch. On the slopes round its head are three or 

 four large taluses, more or less confluent, the one from the gap between Sgiirr Alaisdair 

 and Ssrurr Tearlach coming down some 1200 or 1300 feet to the floor of the corrie. 



It is perhaps significant that Coir' a' Grhrunnda, which lies in the heart of the 

 highest mountains, and at a considerably higher level than its neighbours, has com- 

 paratively little talus. We have seen that this valley differs from the others in having 

 below it a large and well developed crescentic moraine. We may conjecture that the 

 upper part of the Coir' a' Ghrunnda glacier survived after the heads of the neighbouring 

 glens had been vacated, and that the moraine in this case corresponds with the taluses 

 in the other corries. 



In conclusion, it should be remarked that frost and other subaerial agents have had 

 no share in developing the characteristic forms of the mountains and valleys as described 

 in the foregoing section ; their effect has often been to undo in some measure the work 

 of ice-erosion, viewed from the standpoint of topographic forms. The slopes which hem 

 in the cirques, for instance, have the familiar 'glaciated' surface far up towards the 

 summit ridges, and it is these latter which have suffered from later destructive action. 

 The boldly salient form and unbroken character of the ridges must have been more 

 remarkable when they first emerged from the declining ice-cap than they are at the 

 present time. 



* See Geol. Mag. 1899, pp. 485-491. 



