On British Drifts and the Interglacial Problem. 361 



In considering this factor it is also especially interesting to 

 find that Captain R. F. Scott is of opinion that the great 

 shrinkage in the Antarctic land ice, of which he obtained such 

 convincing evidence during the recent expedition, is due to the 

 present excessive coldness, and consequent dryness, of the 

 climate ; and he assigns the former extension of the southern 

 ice-sheets to a period of warmer and moister conditions.* It 

 would have been easy, had time permitted, to bring together 

 numerous illustrations from Polar lands to show how strongly 

 localised in many places are the conditions of existing glacia- 

 tions ; and such conditions must have been still more eflfectiv e 

 at lower latitudes. Hence we can readily imagine that, during 

 the Glacial Period, differential growth and shrinkage might be 

 brought about concurrently in areas not very wide apart, by 

 local circumstances. 



Waning Ice-sheets. — So far as the eastern side of England is 

 concerned, I think that the epoch of maximum glaciation was 

 reached, not when the East British lobe pressed farther west- 

 ward, but when the Pennine and North British ice advanced 

 southward along its receding flank ; and this stage is, I presume, 

 equivalent to the ' Polandian Glacial Epoch ' of Professor 

 Geikie's classification. It was at this time that the ice lapped 

 highest around the slopes of the Jurassic and Cretaceous 

 uplands of Yorkshire, causing that radical diversion ot the 

 surface-drainage which produced the remarkable eff"ects first 

 made known to us by the brilliant researches of Professor P. F. 

 Kendall in Cleveland, t and since traced by him and his fellow- 

 workers at intervals wherever the margins of the ice-sheets 

 have abutted against the slope of the land. 



Farther southward this ice, augmented by the snowfall on 

 its own broad surface, appears to have spread over the lower 

 ground far beyond the bounds of the former invasion, covering 

 most of East Anglia and the East Midland counties with a 

 moving ice-cap, beneath which the Chalky boulder-clay was 

 accumulated. The Upper boulder-clay of Yorkshire I consider 

 to be the product of the same ice-sheet at its waning. 



This final waning of the British ice-sheets, as I have else- 

 where attempted to show, \ must have been accompanied bv 



* 'Results of the National Antarctic Expedition.' Geograpli. Jonni.y 

 vol. XXV. (1905), p. 306. 



t 'A System of Glacier-Lakes in the Cleveland Hills.' Quart. Jotini. 

 Geol. Soc, vol. Iviii (1902), pp. 471-571. 



X 'The Geolog-y of the Isle of Man.' Mem. Geol. Stt/-vey (1904), pp. 

 395-7- 



1906 October i. 



2 A 



