EDEN VALLEY AND Y0RKSB IRE -DALE DISTRICT. 97 



Before concluding, it will perhaps be well to refer to one or two 

 other glacial phenomena this theory of the origin of drift seems 

 to throw light upon. 



In many places in the Dale district, beyond a radius of ten or 

 twelve miles from the principal centre of dispersal of the ice, great 

 heaps and ridges of un stratified drift, with very little clay and almost 

 no scratched stones, but charged throughout with angular blocks, 

 occur here and there on the higher ground. It seems mostly to lie 

 on the lee side of prominent ridges which the ice must have swept 

 over at the time when it attained its greatest thickness. Most of it 

 has a very morainic look, which is rendered still more striking by 

 the irregularly moundy character of its surface. As a rule, the in- 

 cluded blocks seem to indicate that the bulk of the drift was derived 

 from the higher-lying rocks of the district, fragments of beds below 

 the upper division of the dale -rocks being seldom met with. Had 

 it not been that these highest beds referred to are largely made up 

 of shales and soft beds of a similar nature, to the extent of fully half 

 the whole bulk of the rocks, the origin of these mounds could have 

 been easily enough accounted for ; but the absence of any noticeable 

 proportion of clay or of shale -fragments renders it extremely unlikely 

 that the moundy-surfaced drift represents either the lateral or the 

 terminal moraine of any part of the great ice sheet as it receded up 

 the dales. The detritus scraped off from ridges that the ice was 

 crossing at high levels must very frequently have found its way into 

 the main stream at nearly the same level, and, as a consequence, 

 must very rarely have got low enough to undergo any great amount 

 of glaciation by being forced over other high-lying rocky surfaces 

 that might help to round and scratch any of the blocks imbedded in 

 the ice. All the soft beds that entered the ice along with the harder 

 blocks would soon be either decomposed or crushed into clay, which 

 would sooner find its way to the bottom of the ice than any of the 

 stones that entered with it. A sheet of ice charged in this way must 

 always have had the greatest proportion of worn stones and clay near 

 its base, and the most angular and least clayey detritus at the top. 

 When such a sheet of ice flowed across many valleys, it can hardly 

 be doubted that in the majority of cases it was the upper part only 

 of the ice that would cross the next opposing ridge ; and in this way 

 the materials of the till would be sorted out again and again from 

 the angular drift. As the ice melted, it deposited this angular drift 

 in exactly the same way as it did the till at lower levels, the 

 difference being that in the case of this moraine-like drift little or 

 no clay and hardly any scratched stones were imbedded in the ice 

 to be deposited along with the angular drift, while nearly all the 

 clay was left in the till. 



The heaping-up of masses of drift at the main-valley end of the 

 dividing ridge between two tributary dales, pointed out in Mr. 

 Dakyns's paper " On the Glacial Phenomena of the Yorkshire Up- 

 lands"*, is to be accounted for in the same way as the shaping of the 

 drumlins. The water resulting from the melting of the ice must 



* Quart. Journ. Gksol. Soc. vol. xxviii. (1872) p. 384. 

 Q.J.G.S. No. 121. h 



