548 TRANSACTIONS OF SECTION C. 



shrank away from the hills, which were never again covered. Owing to local 

 circumstances that are readily recognisable, the recession of its margin 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 thought at first that this deposit might be of marine origin ; 

 but examination in detail convinced me, as it had previously convinced Prof. P. F. 

 Kendall,' that the phenomena could only be explamed 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 readvance 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 {Saliv kerbacea), along with the remains of a minute arctic 

 freshwater crustacean {Lepidimis 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 are fully developed and 

 magnificently exposed in cliff sections, but still yield no proof of the supposed 

 interglacial epochs or of the marine submergence. 



Ikish Drifts. — During recent years, while attached to the staff of the 

 Geological Survey in Ireland, I had occasion systematically to examine the drifts 

 of four separate and typical areas. With my colleagues of the Irish staff, the 

 mapping of the superficial deposits was carried out in the country around the 

 cities of Dublin, Belfast, Cork, and Limerick. The results, which have been fully 

 stated in recent publications of the Survey,^ differ only in detail from those already 

 dealt with, and need not detain us long. 



Cork IMstrict. — In the south of Ireland, the infra-glacial beach, with its 

 associated cliff and shore-line, discovered by Messrs. H. B. Muff and W. B. 

 Wright,^ is essentially similar to the buried cliff at Sewerby and at almost 

 exactly the same level. The presence of the old beach-line within the submerged 

 valleys or rias of this coast proves that the valleys were excavated during some 

 earlier stage of elevation. In its eastward extension the beach, with its covering 

 of sub-aerial land-waste or ' head,' is overlain by the shelly boulder-clay of the 

 West British ice-lobe ; but in the south-west of Ireland, where the glaciation was 

 from landward, this boulder-clay is absent, and its place is taken by a till of more 

 local origin. The Cork district appears to have lain not far within the southerly 

 bounds of the ice-sheets, and its valleys were filled to the brim almost entirely 

 with ice from the interior of Ireland. Where the products of this ice are seen 

 in contact with the shelly drift, as in the vicinity of Youghal, the latter lies 



' ' On the Glacial Geology of the Isle of Man.' Yn Lioar Manninagli, vol. i. 

 pt. 12, pp. 397-438. 



' Jtlems. Geol. Survey: 'The Geology of the Country around Dublin' (1903); 

 ' The Geology of the Country around Belfast ' (1901) ; ' The Geology of the Country 

 around Cork and Cork Harbour' (1905); 'The Geology of the Country around 

 Limerick' (in press). 



^ Wright and MuflE, ' The Pre-glacial Raised Beach of the South Coast of Ireland.^ 

 Sc. Proc. Hoy. Duilin Soc, N.S., vol. x. pt. U (1901), pp. 250-324. 



