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were left at nearly the original elevation, corresponding to a part 
of the Third, or Subcretaceous Plain; while the soft beds sank into 
a hollow ranging all along from Penrith to Wreay. So it came 
about that the waters of the Petteril gradually changed their course 
there also, and were turned into the new channel that they occupy 
at the present moment. In this case, as in the other, the deserted 
part of the river course remains as a col or pass cutting across the 
escarpment of the Penrith Sandstone. 
This instance of the severance of a river, which is afforded by 
the Petteril, is only one out of many that have come under my 
notice in England. There are numerous other examples of the 
same nature abroad in various parts of the world. I believe that 
the explanation above given will apply to nearly all cases of inoscu- 
lating valleys, and that the severance of a stream into two, which 
eventually flow in opposite directions, is almost a necessary conse- 
quence of the subaerial denudation of a river valley whose rocks 
differ so much in their relative durability, that subaerial waste 
lowers one part faster than the river itself frets its way across the 
outcrop of the harder beds at a lower point. 
ICE WORK. 
The last great change that has taken place here is one that, did 
time permit, I should be glad to dwell upon at considerable length. 
I refer to the Glacial period. I have elsewhere* given my reasons 
for believing that the whole of Edenside was once completely filled 
with ice, which ice attained a thickness of over two thousand feet 
at one period. This ice was propelled up the valley, from Carlisle 
towards Stainmoor, not from the mountain land of Stainmoor 
towards the low ground of the Solway, as it would seem natural 
it should do. Why it so moved it would take too long to discuss 
now, and I refer to the subject at all only because the effects of 
the ice action upon the rock surfaces around us cannot be passed 
over without some kind of notice. Subaerial denudation had 
* «Quarterly Journal of the Geological Society,” Vol. xxxi. (1874), and 
again in my paper on ‘‘ Ice Work in Edenside,” published in our Transactions 
g Yeu P 
for 1887. 
