lxviil PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [vol. lxxvi,. 



the country. This, added to the previous fraction, raises the pro- 

 portion of our land shaped wholly out of the drifts to rather over 

 a quarter. 



In the rest of England and Wales within the bounds reached 

 by the ice-sheets, the drifts play a subordinate, though still often 

 a conspicuous, part in the landscape ; of which, however, the main 

 features are under the control of the solid rocks. We may reckon 

 that there is about 20,000 square miles of glacially-modified 

 country of this kind, or well over a third of the total land-area. 



There remains rather over a third of England, mostly lying 

 south of the line drawn from the head of the Bristol Channel to 

 the estuary of the Thames, which appears to have escaped 

 glaciation. During the Glacial Period this tract was perhaps more 

 drastically affected by denudation and erosion than any other part 

 of the land ; but the agents were of the normal subaerial kind, and 

 their general effect was only to accentuate the proper features of 

 the solid rocks. 



Some Drift-Features and their Origin. 



With respect to the shape of the drift-covered country, it is to 

 be noted that one of the many attractive qualities of the Glacial 

 deposits is the infinite diversity of their outward form, so different 

 from the regular structural features prevalent in the rocks beneath 

 them. This diversity constantly challenges interpretation, and is 

 generally found to be explicable by a consideration of the local 

 circumstances associating the original features of the land with 

 the direction of ice-movement during the glaciation. I can now 

 only refer, of course, in general terms to the drumlins, moraines, 

 eskers, out-wash plains, and other such features, which would 

 require full local discussion for their elucidation. But there are 

 some broader matters, affecting the distribution of the English 

 drifts as a whole, which lend themselves to treatment in mass ; 

 and it is with these that I propose mainly to deal. 



One of these matters is, as to the source of the great mass of 

 material contained in the drifts. In the higher hill-regions and 

 on some of the bordering low ground we can usually be sure, from 

 the composition of the deposits, that the material has been almost 

 entirely derived from the waste of the neighbouring uplands ; and 

 sometimes such streams of local detritus may be traced on the low 

 ground for long distances. But the greater part of the big spreads 

 of drift shown on my map have been carried by ice-sheets which 



