02 The Irish Naturalist. April, 



glacier of the Irish Sea basin. ^ In the districts north of 

 Dubhn the facts as known up to the present rather tend 

 to support the opinion that the deposits of the Irish Sea Ice 

 have been largely swept away by a later advance of the 

 ice from the centre of Ireland towards the south-east. The 

 successive movements in time and space of ice-sheets, are 

 of course extremely hard to prove, but up to the present 

 we may safely say that there is no evidence which supports 

 an inter-glacial period in Ireland of the type known to have 

 taken place in the European Alps during the Ice Age. 



The origin of the sands and gravels has yet to be faced. 

 The submergence theory was clearly not satisfactory and has 

 been abandoned. That the sands and gravels had their 

 origin during the later stages of the individual ice-sheets 

 may be assumed. The number of sections where the sands 

 and gravels obviously overlie the boulder-clay are so 

 numerous as to place this beyond question. It must also 

 be assumed that the Irish Sea Glacier had reached its 

 maximum development and that as a result of an ameliora- 

 tion of climate, decay was already setting in. The ice was 

 charged with the debris of the ground over which it had 

 passed, and as the melting of the ice proceeded great 

 quantities of sand and gravel were released. The assumption 

 has also to be made that the ice-sheet became stagnant over 

 practically the whole Irish Sea basin, and then melted where 

 it stood, and that the agents of destruction were at w^ork 

 simultaneously over all the area occupied by the ice. As 

 decay proceeded the higher ground of the mountains in the 

 Irish Sea basin became uncovered and then accelerated 

 differential melting took place, both by the direct melting 

 of the ice along the landward margin of the ice-sheet and 

 by the effects produced by the streams of running water just 

 above freezing point, when they left the ice-free land and 

 came in contact with the stagnant ice-sheet. In these 

 streams, flowing both from the ice-free land and across the 

 glacier, the sand and gravels would be sw^ept into the tem- 

 porary lakes which had been formed between the margins 

 of the ice-sheets and the higher levels of the land. By this 



* G. W. Lamplugh, " British Drifts and the Intcrglacial Problem," 

 British Assoc. Report, pp. 545-5^0 York, iyo6. 



