58 TJic IrisJi Nattiralist. April, 



Anglese\^ and at Moel-Tryfaen, in gravel deposits at 

 1,350 feet above sea-level, both erratics and arctic shells 

 have been found in great abundance. The great pebble 

 ridge at Aberystwyth in Cardigan Bay, yields many large 

 boulders of Ailsa Craig riebeckite and chalk-flints, and 

 Prof. Fleure, of University College, Aber3'stwyth, considers 

 that these northern erratics have been derived from glacial 

 deposits recently destroyed by the action of the sea. At 

 St. David's Head, in Pembrokeshire, there is evidence of 

 the passage of the Irish Sea Glacier, and as far south as the 

 Scilly Isles deposits with erratics occur, which may be 

 derived from the ground-moraine of the Irish Sea Glacier, 

 although G. Barrow, of the Geological Survey, inclines 

 towards the view that floating ice from the north was the 

 agency by which these deposits w^ere brought to their 

 present position. 



Having traced the advance of the Irish Sea Glacier along 

 the eastern coast of the Irish Sea basin, the progress of the 

 ice-sheet ma}- now be followed south from Wicklow. Here 

 the ice-sheet relieved from the restriction imposed by the 

 mountain-ranges on both sides of the Irish Sea, began to 

 fan out towards the south-west. The widely-spread 

 series of deposits known as the Wexford Beds are the result 

 of this fanning out, and prove that having extended inland 

 in north Wexford up to heights of from 200 to 250 feet above 

 sea-level, the ice-sheet travelled south-westward across 

 south Wexford and Waterford into east Cork as far as Power 

 Head, outside Cork Harbour. These widely-spread deposits 

 of marly boulder-clay with overlying gravels have lately 

 ,bccn investigated by Prof. Cole and T. Hallissy, and in 

 addition to the numerous arctic and Pliocene mollusca 

 already known to occur, the authors report an extraordinary 

 series of erratics. Anthracite and bituminous coal, lignite 

 and chalk flints occur in such abundance that the authors 

 consider that they have been derived from submarine 

 deposits out in the neighbouring sea to the east.^ An 

 interesting fact about the marly boulder-clay of the Irish 



* G. A. J. Cole and T. Hallissy, "The Wexford Gravels and their 

 bearing on Interglacial Cieology." Geol. Mag., n.s., decade \i., vol. i., 

 Pi). 498-509 (^ov. 1914)- 



