J. G. Goodchild — On the Origin of Coums. 489 



inclined Carboniferous conglomerates belonging to the Calciferous 

 Sandstone Series; and variously inclined beds of Lower Carboni- 

 ferous rocks of the ordinary Dale District type. Yet the general 

 regularity of form and the uniformity of curvature of the crater-like 

 recess that all the rocks have been ground into is particularly 

 striking when one is aware of the nature and the lie of the rocks 

 that form the walls of the amphitheatre. This instance is one of 

 many others in the neighbourhood, all of which are remarkable for 

 their sweeping outlines and general regularity of form. 



In regard to the position of these coums no very general rule 

 can be laid down. They seem, howevei*, to occur with greatest 

 frequency in the neighbourhood of the highest ground, especially 

 where there is much diversity in the directions taken by the larger 

 valleys. Not a few coums occur at the heads of valleys, of which 

 the Snaizholme Coum may be taken as a very good type. They 

 are, however, by no means confined to such situations, but occur 

 almost as commonly on the sides of valleys, far removed from the 

 source of the stream. In a few instances such recesses are found 

 in considerable perfection on the sides of a main valley opposite 

 the point where this is joined by a tributary of .considerable size. 

 Good examples of such are to be found in the Coum wherein 

 Bolton Castle in Wensleydale stands, just opposite where the Yore 

 valley is joined by the large branch dales of Waldendale and 

 Bishopsdale ; at Bampton near Shap, where the valley of the 

 Lowther is joined by the Hawes Water valley ; and again at 

 Lowther Park, where Heltondale and the Lowther valley join. 

 Many similar cases to these might easily be pointed out if there 

 were further need to do so. In some of these instances the most 

 regularly curved outlines are found only within a small vertical 

 extent of the hollow where they occur; in other instances the 

 curvature is so slight that, on the ground, it seems almost imper- 

 ceptible ; but a reference to the beautiful one-inch maps of the 

 Ordnance Survey shows that these seemingly unimportant curves 

 are in reality but parts of curved surfaces of much greater extent, 

 whose real nature can only be seen by looking at them from a 

 considerable distance, from which point the curve is often seen to 

 inclose an arc of sixty, eighty, or even a greater number of 

 degrees. The three coums referred to above are shaped out of 

 a series of alternations of hard beds with others comparatively soft 

 in regard to their capacity to resist mechanical erosion, and. the 

 rocks they occur in are more or less inclined from the horizontal ; 

 yet the resulting terraces in each case are equally well developed 

 at one point as at another. In the case of the Lowther recesses the 

 rocks and their terraced outcrops incline inwards towards the high 

 ground ; yet, although there is in this instance a combination of 

 circumstances mo'st favourable for the retention of rock debris 

 detached by subaerial agencies, hardly a fragment of any of the 

 harder rocks is to be found loose at the surface, which seems as 

 if it had been swept clean from one end to the other ; except where 

 a thin coating of drift has been left by the melting of the ice-sheet. 



