EDEN VALLEY AND YORKSHIRE- DALE DISTRICT. 95 



in any section of far-derived drift. There seems, too, to be some 

 reason for thinking that this intermingling would be still further 

 brought about by the occasional upforcing of some of the strata 

 of the ice-sheet in places where, so to speak, the ice was closely 

 hemmed in on all sides, as it must have been at the foot of JStain- 

 moor. 



When the great ice-sheet began to melt, the stones that were 

 nearest the bottom of the ice, and which, from their position, must 

 have undergone the greatest amount of glaciation, began to be de- 

 posited on the floor of glaciated rock, or on patches of the true 

 moraine jorofonde, where these existed. The water resulting from 

 the melting of the bottom ice would find its way here and there 

 towards the sea along channels in the slowly thickening deposit of 

 till. Where such ridges of rock existed as resulted from the un- 

 equal wear of hard and soft beds, the water would be more likely to 

 flow along the intervening hollows than to pass along or across the 

 higher ridges ; so that in this way it must often have happened that 

 the deposition of till went on over preexisting rock-ridges, while 

 the intervening hollows were kept clear by the water that flowed 

 in them. It is obvious that the further the point from the head of 

 the valley the greater would be the quantity of water flowing 

 beneath the ice. It should be borne in mind that there would be 

 not only the water resulting from the melting of a great thickness 

 of ice, but the rainfall of the period to be carried off in some way 

 towards the sea. We can therefore understand how it is that the 

 drift-materials that were slowly melting out of the ice sheet, 

 became more and more waterworn in proportion to the distance from 

 the head of the valley. As the currents shifted they must have 

 allowed till to accumulate in parts where previously nothing but 

 sand and gravel had been laid down ; while, on the other hand, they 

 must frequently have cut into banks of till, and afterwards filled the 

 denuded hollows with waterworn materials as their course slowly 

 changed. In this way there can be little doubt that the drift in 

 the lower parts of the Eden valley must frequently have been re- 

 moved soon after deposition, and the materials re-sorted and further 

 waterworn, and afterwards redistributed in some protected spot 

 further down the valley. 



Here and there waterworn materials must have found their way 

 down through crevasses to the bottom of the ice, so that nests of 

 undisturbed sand and occasional patches of gravel would accumulate 

 where, for some distance around, nothing but till was being left by 

 the ice. In the quiet spots amongst the till, out of the reach of the 

 subglacial streams, runlets of water charged with fine glacial mud 

 must have flowed over the irregularities of the till, depositing sheet 

 upon sheet of fine clay until some of the inclined sheets of gutta- 

 percha clays were accumulated. It would be very difficult to give 

 any satisfactory explanation of their origin besides the one here ad- 

 vanced. If the clays were deposited under water, they would not 

 fail to be spread out in perfectly horizontal sheets ; at any rate it is 

 quite impossible that they could be thrown down at angles of from 



