PRESIDENTIAL ADDRESS. 551 



ostwcoda they contain are generally of a boreal or arctic cbaracter ; and my 

 colleague, Mr. H. B. Woodward, after extensive field-experience of these deposits, 

 concludes that they are inseparable from tlie associated drifts acknowledged to 

 be of glacial origin, and tbat their curiously mixed assemblage of shells does not 

 represent a contemporaneous fauna.' These beds form part of the ' Helvetian ' 

 interglacials of Professor Geikie's scheme. 



Midland Counties.— In the North Midlands, Mr. R. M. Deeley,^ in classifying 

 the complex drifts of the Trent Basin, has sought to explain these deposits as the 

 product of several successive glacial and interglacial epochs, but the correlation of 

 these supposed epochs with those of Professor Geikie is found difficult.^ All ex- 

 cept the latest of the deposits classed as interglacial are unfossiliferous ; and the 

 evidence for glaciation later than tliis fossiliferous deposit— an ancient river-gravel 

 of the Der-went containing mammalian remains (hippopotamus, rhinoceros, and 

 elephant) *— is verv questionable.' The recent work of the Geological Survey in 

 the district, in which I am taking part, confirms Mr. Deeley's opinion that the 

 basin was invaded by ice-lobes from different quarters, which attained their maxima 

 at difterent times. It is also found that there are areas which apparently lay 

 beyond the reach of these lobes, and remained unglaciated." In these circum- 

 stances, the simplest explanation of the facts seems to be that the marginal area 

 was sometimes exposed and sometimes ice-covered by the different flows in their 

 oscillations during a single prolonged period of glacial conditions. There is no 

 evidence of marine submergence in the district, though the whole of it lies much 

 below tlie level attained by the shelly ' middle glacial ' stratified drifts of the 

 country to the westward. 



Farther south, Mr. "VV. Jerome Harrison, after a lengthy investigation of a wide 

 area centring around Birmingham, finds that the drifts were the product of three 

 great ice-lobes— the ' Arenig Glacier,' the ' Irish Sea Glacier,' and the ' North 

 Sea Glacier ' ; and he concludes that there has been no marine submergence and 

 that ' the district affords no proof of any " interglacial " period.' ^ 



N'orth-western Counties.— The glacial deposits of West Lancashire, Cheshire, 

 and North W^ales are essentially analogous to those of the Isle of Man. The sup- 

 posed ' middle glacial ' submergence has figured largely in the voluminous litera- 

 ture of this part of the country ; and Professor Geikie, by supposing tbat certain 

 Welsh and Yorkshire cave deposits of doubtful age are interglacial, and that an 

 undefined part of the glacial sands and gravels indicates interglacial submergence, 

 is able to picture a ' Saxonian ' glaciation, a ' Helvetian ' mild interglacial epoch 

 with a wide land surface succeeded by marine conditions, and then a later ' Polan- 

 dian ' glaciation from the same quarter as the first.* But the investigators who 

 have studied this district most closely are agreed that the interstratification of tlie 

 boulder-clay with the sands and gravels is so intimate and so many times repeated 

 that the deposits must have been practically contemporaneous and of common 

 origin ; and the differences of opinion tliat have arisen are on the question whether 

 these drifts as a whole have been deposited by the sea or by land-ice." The case 



' 'The Glacial Drifts of Norfolk.'. Proc. Oeol. Assoc, vol. ix. (1837), pp. 111-129. 

 "^ ' The Pleistocene Succession in the Trent Basin.' Quart. Journ. Gcol. Soc, vol. 

 Xlii. (1886), pp. 437-480. 



» ' The Glacial Succession.' Geol. Mag., dec. iii., vol. x. (1 893), pp. 31-35. 



* H. H. Arnold-Bemrose and R. M. Deelcy, ' Mammalian Remains in Derwent 

 River Gravels.' Qiuirt. Journ. Geol. Soc, vol. Iii. (1896), pp. 497-510. 



* C. Fox Strangways, Mem. Geol. Survey ; ' Country between Derby,' &c. (1905), 

 p. 41. 



" Summary of Progress of Gcol. Surrey for 1905. 



' ' The Ancient Glaciers of the Midland Counties.' Proc. Geol. Assoc, vol. xv. 

 (1898), pp. 400-108. 



* Great Ice Age, 3rd ed., pp. 367-374. 



9 e.g.:—C. E. De Ranee, Rej). Brit. Assoc for 189.3, p. 779; A. Stralian. Quart, 

 Journ. Geol. Soc, vol. xlii. (1886), p. 383 ; T. Mellard Reade, Quart. Journ- Geol. Soc, 

 vol. XXX. (1874), pp. 35-37 ; and ibid., vol. x.xxix, (1883), pp. 123-127. 



