Kilroe — On Directions of Ice-flow in the North of Ireland. 261 



western seaboard. These caii alone be attributable to the move- 

 ment of an iee-sbeet continuous with a mass which blocked up the 

 adjacent oceanic area, and moved outward to the open waters of the 

 Atlantic. Confirmatory evidence of such a movement is to be found 

 in the occurrence of chalk-flints in the drift of Inishowen ; also in 

 the absence of granite boulders from the lower boulder clay of 

 Glen Swilly, 1 and from that which rests on the granite and schist 

 at the north entrance to Barnesmore Gap. 



Hence we have strong reasons for believing that the ice-sheet 

 which passed off the Wigton and Ayrshire coast, moving westward, 

 flowed on to Irish soil, and urged its way across Ulster to escape 

 on the western coast by the various bays of Donegal, Sligo, Mayo, 

 and Galway. Dr. Hull considers that a glacial system, centred in 

 the Mourne Mountains, diverted the flow of this ice-sheet south- 

 ward, which would account for the absence of westward striae south 

 of the Galway Bay and Strangford Lough line. 



The Irish Glacial System. — Much has been done by the Rev. 

 M. Close towards the elucidation of glacial phenomena in the Irish 

 area, 2 and his map of the glaciation of Iarconnaught, prepared in 

 conjunction with Mr. G. H. Kinahan, and published in 1872, has 

 furnished important aid in the preparation of the maps accompany- 

 ing this Paper. Dr. Hull, in his Physical Geology of Ireland, has 

 described the glaciation of the country in considerable detail ; and 

 on his maps, 3 indicates an axis of glacial movement coincident 

 with a great central snow-field, which sentjits flows northward and 

 southward. This the author represents as stretching north-east- 

 ward between the counties of Galway and Antrim ; and it is 

 satisfactory to be able to state that all the evidence brought to li«-ht 

 since the publication of his book in 1878 tends to the establish- 

 ment of his conclusions. 



It has been stated in the commencement of this Paper that the 

 prevailing direction of one set of glacial striae in the North of Ire- 

 land is northerly. South of the axis of glaciation the flow has 

 been south-easterly over the central plain of Ireland, and towards 

 the Irish Sea, even across the Mourne Mountains ; the Fermanagh 



1 As observed by Mr. M 'Henry. 



2 Paper on tbe General Glaciation of Ireland, with map, Jour. Roy. Geol. Soc. Ire I. 

 vol. i., new series, p. 207. 



3 Loc. cit., page 211. 



