74 J. G. GOODCHILD ON THE GLACIAL PHENOMENA OP THE 



of curvature, thus plainly enough pointing to the oneness of their 

 origin. We can also see why it is that these curved lines of scar 

 are so frequently opposite to the mouth of some large branch dale, 

 the ice from which compelled the main stream to curve against the 

 opposite bank. 



If now we turn to those parts of the dales where the ice has 

 flowed up the cross valleys and across the lines of outcrop of the 

 beds, instead of the terraces and scars observable in other parts of 

 the dales, we find the hill- sides ground into smooth slopes, with 

 nothing at the surface to mark the diversity in lithological character 

 of the rocks beneath. In the case of the dales on the south side of 

 "Wensleydale above Hawse, wherein Snaizholme Beck, Widdale Beck, 

 and Duerly Beck flow, we have some instances of regularly curved 

 hollows just at those points where the form and direction of each 

 dale would cause the ice from the high ground to the north to take 

 a slight curvilinear motion, which resulted in the grinding-down of 

 preexisting irregularities into sweeping curves. Looking at the 

 beautiful " coum " at the head of Snaizholme Beck, one cannot help 

 being convinced that nothing but ice could produce such a result. 

 Springs, as before pointed out, tend rather to cut the rock back into 

 notches ; and, moreover, in the dale rocks they act only along cer- 

 tain definite lines. Streams act still more powerfully in forming 

 ravines, quite unlike any of the smooth concave hollows here re- 

 ferred to. And, lastly, the ordinary action of the weather tends to 

 encumber such slopes with the ruin of the higher rocks. But in the 

 instances here referred to comparatively little weathered material 

 lies on the hill-sides ; and in the case of the Snaizholme coum the 

 slopes are nearly bare, except where a thin covering of drift clings 

 to them and hides the rock. 



Many other instances of similar coums could be adduced ; but one 

 other instance from the Dale district will suffice. It was pointed 

 out above that the ice-sheet crossed Dentdale in a south-westerly 

 direction in flowing towards Lunedale. Part of this stream, as the 

 ice-markings show, passed in a south-south-westerly direction up Dib- 

 dale. At the head of the dale the stream divided against the Nab, 

 one branch going off to the south-west and turning against Gragreth, 

 the other taking a south-south-easterly course and curving against 

 Whernside. The result is that we have two coums which, if not so 

 striking as the Snaizholme coum, show a greater height of curved 

 surface. That on the west side of Whernside can be traced upwards 

 for at least 1000 feet — the curves opening with great regularity, from 

 one of a radius of about a quarter of a mile near the bottom, to the 

 curved line of grit scar, at the top of which the radius is about a 

 mile. 



When we compare these coums with the other rock-features of 

 the district, there is seen to be a perfect gradation from a nearly 

 straight line of scar, through others more and more curved, to such 

 a coum as that at the head of Snaizholme Beck. 



In many other places where the form of the ground has caused 

 the ice-stream to turn in its course we find more or less perfect 



