260 Scientific Proceedings, Royal Dublin Society. 



country with uninterrupted flow, and proceed to show that such 

 an ice-sheet crossed the North Channel from the central Highlands 

 of Scotland, forming a portion of what we may speak of as Thk 

 Scottish Glacial System. That an ice-flow has invaded the east 

 of Antrim from seaward has been fully established by my 

 colleagues, Messrs Symes and M'Henry, by striatial evidence, and 

 the occurrence in the drift of blocks of chalk and Fair Head basalt, 

 which must have travelled westward from their original site. 

 Blocks of schist from Cantire also bestrew the surface of Eathlin 

 Island. 



On the published Government maps of Ayrshire and Wigton 

 numerous striae are indicated, some bearing northward, and several 

 westward, precisely as they occur in Ulster. The latter set evi- 

 dently indicates an outward flow towards the Irish Coast, which, 

 it cannot be doubted, was continuous with that which moved land- 

 ward over the counties of Antrim and Down. 



Extension of the Scottish Ice-sheet. — Dr. A. Greikie has supplied 

 us with numerous interesting data, 1 and deductions therefrom, as 

 to the extension of the mer de glace, which centred in the Scottish 

 Highlands. Eastward it coalesced with the great Scandinavian 

 ice-sheet, and south-westward with that which covered Ireland ; so 

 that a vast glacier probably extended from Cape Clear to North 

 Cape — a distance of 1500 miles. 



In considering the movements of this vast mass of ice, as it 

 spread itself outward to reach the open ocean, and its immense 

 thickness 2 in Scotland, it is easy to comprehend how it crossed the 

 Minch, and overflowed the outer Hebrides, to a height of 1600 

 feet at least 3 in North Harris. I observed striae bearing westward 

 in the Nephin group at the 1100 feet contour line, in the course of 

 my survey work in Mayo, in 1878. Dr. A. Greikie records strife 

 on Ben Lomond at 2250 feet above datum. We are, therefore, 

 justified in concluding that the ice-sheet in the North Channel was 

 of sufficient thickness to overtop the Antrim coast-line by perhaps 

 1000 feet. Striae have been observed bearing westward from the 

 entrance to Lough Foyle throughout the county of Donegal, to the 



1 Scenery of Scotland, by A. Geikie, LL.D., F.R. S., 2nd ed., pp. 251, et scq. 



2 In parts attaining 3000 feet, Great lee Age, p. 100. 



3 Paper by James Geikie, LL.D., F.R.S., Jour. Geol. Soc, vol. xxsiv., p. 832. 



