198 



A. Harker — Glaciated Valleys in 8kye. 



(vi) In longitudinal profile the floor of a valley often consists 

 of two or three stretches of relatively gentle slope separated by 

 precipitous drops (Fig, 2). These features are not related to 

 anything in the geological structure of the ground, and the levels 

 are not the same in adjacent valleys. 



(vii) A tributary valley debouches at a considerably higher level 

 than the floor of the main valley, so that it terminates in a pre- 

 cipitous drop. This is true not only of the smaller tributary valleys 

 but also of glens of considerable size (e.g. Tairneilear at its junction 

 "with Coir' a' Mhadaidh). The point sometimes comes out more 

 clearly if we regard the lines of ice-drainage instead of the present 

 watercourses. Thus the stream from Garbh-choire, the lower part 

 of which is shown in Fig. 3, turns eastward to fall into the sea in 



Fig. 3. — Section down the lower part of Garbh-choire and across Loch Coruisk at 

 its deepest part. 



Loch Scavaig, but in one stage of the glaciation the ice-drainage was 

 partly over the low watershed into Coruisk. 



Other features might be enumerated, but they appear to arise 

 merely from the co-operation of the several conditions implied in 

 the preceding paragraphs. Thus we find circular amphitheatres 

 enclosed by steep slopes and isolated by precipitous drops from the 

 valleys into which they drain. Where such a corrie occurs at the 

 head of an important valley (e.g. Coir' a' Ghrundda), it falls under 

 the heads (iii) and (vi). Where it overlooks the side of a main 

 valley (e.g. Coir' an Lochain, Fig. 4), it falls under (iii) and (vii). 



Fig. 4. — Section down Coir' an Lochain (from the Bealach from Coir' a' Ghrundda) 

 through the tarn and down to the Coruisk valley. 



In like manner other scenic features of the district are found to 

 resolve themselves into the elementary forms already set forth 

 above, and these seem therefore to embody all that is characteristic 

 of a glaciated valley-system in its simplest development. If so, 

 they afibrd at the same time the tests by which any synthetic theory 

 of the mechanics of ice-erosion must be tried, but such theory is. as 

 has been remarked, still a desideratum. McGee's treatment of the 

 problem, referred to above, labours under the drawback that it top 



