272 Scientific Proceedings, Royal Dublin Society. 



of a previous cycle of subaerial denudation ("peneplain"), the 

 deep trenching of the rivers indicates an uplift of the plain above 

 its former level. 



The next movement it is possible to record is a depression of 

 the land to the level at which the raised beach was formed ; i.e., 

 about 12 feet below its present level. This small discrepancy 

 between recent and pre-glaoial sea-levels cannot but be regarded 

 as remarkable, when one considers the long and varied succession 

 of events which are known to have taken place in the interval. 



An uplift of the land again occurred when the blown sand 

 and lower head were accumulated. It has been pointed out that 

 this uplift need not have been more than 10 or 20 feet above 

 present level, though it may have been greater. 



The lower head is overlaid by boulder-clay deposited by land- 

 ice, which originated in more than one centre, as already explained. 



The succession of events subsequent to the formation of the 

 old plain may thus be summarised 1 : — 



1. Land higher than at present — erosion of valleys now sub- 



merged. 



2. Land depressed to about 12 feet below present level — forma- 



tion of raised beach. 



3. Land again elevated to an unknown extent above its 



present level — accumulation of blown sand and lower 

 head. 



4. Advance of Irish Sea ice-sheet from the north-east and east, 



and deposition of marly boulder-clay. Advance of ice 

 from the West Cork Mountains and from the Central 

 Plain contemporaneous with the above, and also at a 

 later stage, advancing over ground formerly occupied by 

 the Irish Sea ice-sheet. 



5. Accumulation of the upper head. 



The outline of the pre-glacial coast-line of the south of Ireland 

 at the period of the raised beach was, as a whole and in many of its 

 details, similar to that of the present coast-line. Even where the 

 platform and its overlying deposits have been removed by the 

 recent encroachments of the sea, the peculiar rounding off at the 



1 For possible dates of these events, see Croll, E. Ball, and others. 



