364 Oil British Drifts ami the Iiifcrffldcuif Problem. 



which the ice-sheet shrank away from the hills, which were 

 never ag"ain covered. Owing- to local circumstances that are 

 readily recog^nisable, the recession of its marg-in was relatively 

 accelerated in the northern part of the island, so that a broad 

 hollow was formed there between the hills and the ice-border ; 

 and in this hollow a mass of stratified drift was deposited. 

 From its terraced aspect and the occurrence of scattered shells, 

 I thoug-ht at first that this deposit mig^ht be of marine orig-in ; 

 but examination in detail convinced me, as it had previously 

 convinced Professor P. F. Kendall," that the phenomena could 

 only be explained by regarding the stratified material as marginal 

 'overwash ' from the ice-front. As in Yorkshire, the association 

 of the boulder-clays with the stratified drift is in most places so 

 intimate that again the evidence for the continuous presence of 

 the ice-sheet in the surrounding basin seems irrefragable. 



Following closely upon this local deposition of stratified 

 drift, there appears to have been a limited re-advance of the ice, 

 which brought about the accumulation of an upper boulder-clay 

 on parts of the low ground. But, unlike the Upper Clay of 

 Yorkshire, this bed lies well within the limits of the lower clays, 

 both in extent and elevation ; and it seems to denote only a 

 slight augmentation of the persisting ice-sheet, which was thus 

 enabled to close in again upon the lower flanks of the hills. 



The end of the glacial invasion was marked by similar 

 conditions to those found in Holderness. Great fans of flood- 

 gravel were spread out around the mouths of the upland glens ; 

 and the hollows in the drift-plain were occupied by lakelets, 

 now mostly obliterated by an infilling of marly and peaty 

 sediments. Among the plants found in a bed near the base of 

 one of these hollows is a northern willow {Salix herbacca), 

 along with the remains of a minute arctic freshwater crustacean 

 [Lepiiiiinis glacialis) ; and similar remains were also found in a 

 peaty layer interbedded with the flood-gravels. 



Here, then, is another area in which the drifts arc fully 

 developed and magnificently exposed in clifl' sections, but still 

 yield no proof of the supposed interglacial epochs or of the 

 marine submergence. 



I Mr. Lamplugh next shows that analogous results were 

 obtained from four separate areas in Ireland which he had 

 personally in\estigated ; and he then proceeds to discuss the 



' On the Glacial Gi-ului^y oflhi- Isli' (if Man.' ) '// I.icti'- Miuiiiinui^h, 

 vol. i. |)t. ij. pp. 397-438. 



Naturalist, 



