262 Scientific Proceedings, Royal Dublin Society. 



hills also are glaciated up to 1000 feet, so that the Irish glacial 

 system must have attained important proportions. 



South-easterly striae abound on the east coast of the county of 

 Down, and some bearing northward occur on Rathlin Island. It 

 is therefore obvious that the central snowfield extended at least to 

 the coast line of Antrim, perhaps beyond it, towards the Scottish 

 coast opposite. And it would seem, judging from the directions 

 of striae in Fermanagh and Donegal, that a spur or projection from 

 the central snowneld extended westward to the head of Donegal 

 Bay. 



Relative Ages. — It remains to consider the Irish and Scottish 

 systems of glaciation with, reference to their relative ages. It is 

 reasonable to suppose that a very considerable accumulation of snow 

 and ice obtained in the Irish area during the period of intensest 

 cold, while the Scottish, system was gathering maximum strength ; 

 and that an ice-movement outward was concomitant with this 

 accumulation. Such a movement would obviously be northerly in 

 Ulster, and would maintain this general direction until the Scottish 

 ice-sheet invaded this area, to move westward uninterruptedly. 

 Previously- formed striae would thus be to a large extent effaced, 

 and replaced by those bearing westward. Some might remain, but 

 would obviously be very few. Striae bearing northward are, how- 

 ever, by far the most numerous, and may be seen to form the more 

 recent set also, where observed in proximity to those bearing west- 

 ward. From this we conclude that during decline, or possibly after 

 decline and subdued revival of glacial conditions, an independent 

 mer de glace flowed northward and southward, finding its axis of 

 movement in the great central snowfield. 



