156 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 7, 



over part of these Carboniferous strata, they must have thinned 

 away to a feather edge before the Oolitic escarpment began to be 

 formed. 



Taken as a whole, from the great escarpment of Carboniferous 

 Limestone that overlooks the vale of Eden on the east, all the 

 Carboniferous strata thence to the German Ocean have a gentle 

 eastern dip — so gentle, indeed, that, on Mallerstang and other high 

 hills overlooking the vale of Eden, outlying patches of the Lower 

 Coal-measures or Gannister beds still remain to tell that once the 

 whole of the Coal-measures spread across the country as far as the 

 edge of the vale of Eden, and even far beyond, in pre-Permian 

 times. These gentle eastern and south-eastern dips, caused by up- 

 heaval of the strata on the west and north-west, gave the initial 

 tendency of all the rivers of the region to flow east and south-east ; 

 and thus it happens that the Tees, the Wear, the Derwent, the 

 Tyne, the Blyth, the Coquet, and the Alne have found their way to 

 the German Ocean, cutting and deepening their channels as they ran. 

 The sides of these valleys, widened by time and subaerial degradation, 

 now rise high above the rivers in the regions west of the Coal-measures, 

 in a succession of terraces of limestone bands, tier above tier, as it 

 were in great steps, till on the tops of the hills we reach the Mill- 

 stone-grit itself. 



We now turn to the western rivers of England, about which there 

 is far less to be said. 



First the Eden. This river flows through the whole length of 

 the beautiful valley of that name, through Permian rocks, for nearly 

 forty miles. At the mouth of the valley, at and near Carlisle, a 

 patch of New Red Marl lies on the Permian Sandstones ; and on the 

 Marl rests the Lias. Whether the whole length of the Permian 

 strata of the Yale of Eden was once covered by these rocks, it is 

 impossible to determine ; but I believe that it must have been so to 

 some extent, and also that the Lias was probably covered by Oolitic 

 strata. As these were denuded away by time, the Eden began to 

 establish itself, and now runs through rocks in a faulted hollow in 

 the manner shown in fig. 5 (p. 154). What is the precise date of the 

 formation of this great valley and its river-course I am un- 

 able to say ; but I believe that it may approximately be of the same 

 age as the valleys last described. And so with the other rivers of 

 the west of England, the Lune, the Eibble, the Mersey, and the 

 Weaver — unless, indeed, some of these rivers, including the Dee, 

 had their Aveslern courses determined by that western tilting of the 

 strata that I believe originally established the greater part of the 

 channel of the Severn. 



I have already said that the rivers of Wales, the sources of the 

 Severn, and all the other rivers that flow through the high Palaeo- 

 zoic rocks are difficult to treat of in a definite manner ; so highly 

 disturbed are most of the rocks, and so ancient are those disturb- 

 ances. The mountains there are, to say the least, pre-Permian, 

 though it does not therefore follow that the present valleys date 

 from that venerable age. The great tableland of South Wales, in 



