54 The Irish Naturalist. April, 



the alleged movements of the Irish Sea Glacier would require 

 an elevated ice-cap, l3ang over the northern parts of the 

 British Isles, to explain its advance, and there is very little 

 evidence to support the existence of this ice-cap. Now it 

 has been pointed out by G. W. Lamplugh that a great 

 glacier, deployed in the direction of the maximum precipita- 

 tion, might grow so quickly by deposition of snow upon the 

 surface of its outer margin that eventually the ice-sheet 

 would begin to create its own local climatic conditions and 

 methods of growth, so that finally breaking loose from the 

 control of the hills and the control of local gravity, it would 

 move forward with very little regard for the lesser contours 

 of the ground over which it passed.^ 



The application of this speculation to the ice of the 

 Clyde area and afterwards to the Irish Sea Glacier would 

 help us out of some of the difficulties, and the recent in- 

 vestigations of Nansen and Scott in Greenland and Antarc- 

 tica appear to lend support to the theory. 



The Irish Sea Glacier during its development and decay 

 created glacial deposits on both sides of the Irish Sea and 

 on the south coast of Ireland, and b}^ these deposits, with 

 arctic shells and northern erratics, we are able to trace the 

 progress of the ice-sheet from district to district. Over a 

 considerable part of Antrim and Down the northern ice- 

 sheet passed, laying down the boulder-clay and gravels, 

 with the typical Scottish erratics and arctic shells. These 

 glacial deposits of north-east Ulster are widely developed, 

 as far west as the Bann, and have been investigated by 

 S. A. Stewart and Joseph Wright, and later by Madame 

 Christen. Both S. A. Stewart and Joseph Wright have 

 always been staunch upholders of that earlier theory of 

 submergence which has been recently challenged, but we 

 cannot withhold a tribute to the great accuracy of their 

 field-work and the notable contributions which they have 

 made to Irish glacial geology. 



The next important locality where the deposits of the 

 Irish Sea Glacier are extensively developed is the Isle of 

 Man, where Lamplugh and Kendall have proved that the 



^ Glacialista' Mag., vol. i., no. ii, p. 231 (1894). 



