IN THE NORTH OP IRELAND. 829 



we must conceive the passage of an ice-sheet of vast thickness 

 across the country with uninterrupted flow. 



We proceed to show that an ice-sheet crossed the North Channel 

 from the Scottish coast opposite, forming a portion of the Mer de 

 glace which originated in the Central Highlands, and which we may 

 for this reason speak of as " The Scottish Glacial System " (see 

 Map, fig. 1). That an ice-flow has invaded the east of Antrim from 

 seaward has been fully established by my colleagues Messrs. Symes 

 and M*^Henry, who were engaged on the Survey of that part of 

 Ulster, and who have indicated on the Government maps several 

 instances of striae in this direction. Confirmatory evidence of this 

 westerly movement is found in the occurrence of blocks of the cha- 

 racteristic columnar basalt of Pair Head, westward of their original 

 site, included in the drift which overlies the schist and Carboniferous- 

 Limestone areas near Ballycastle. Mr. Symes informs me that he 

 found blocks of chalk in Carnlough Glen, due west of Glenarm, 

 400 feet above the sea-level, and resting upon basalt one mile within 

 its boundary, which must obviously have travelled westward and 

 upward from their parent mass. Blocks of schist from Cantire 

 bestrew the surface of Rathlin Island, where striae also are nume- 

 rous, most of which indicate a westerly ice-movement. 



In Ayrshire and Wigton numerous striae are represented on the 

 Goverment published maps, which seem separable into two distinct 

 sets, as in the case of those in the North of Ireland, the directions 

 moreover being strikingly similar to those maintained by the two 

 sets in the Irish area. It will at once be seen that those bearing 

 westward indicate an outward flow towards the Irish coast, and 

 strongly suggest the connexion of this flow with that which moved 

 landward from the North Channel over the counties of Antrim and 

 Down. The small map published by Dr. Geikie in his ' Scenery of 

 Scotland ' *, showing the glaciation of that country, clearly suggests 

 the theory we maintain, and has supplied matter for the prepa- 

 ration of the small map (fig. 1) accompanying this paper. This 

 author has likewise given us numerous interesting data, with deduc- 

 tions therefrom, as to the vast extension of the Mer de glace which 

 centred in the Scottish Highlands. Eastward it coalesced with the 

 Great Scandinavian ice-sheet, and south-westward united with the 

 Irish Glacial system, so as to form a vast glacier, probably extending 

 from Cape Clear to the North Cape, a distance of 1500 miles. 



Considering the movements of this ice-sheet, as it spread itself 

 outward to reach the open ocean. Dr. Geikie informs us that part of 

 it moved southward along the floor and over the shores of the 

 German Ocean. We also know that part moved northward and 

 north-westward over the Orkney Group t, and that westward it 

 crossed the Minch and Outer Hebrides i, to fill the contiguous 



* Pp. 251 et seq. 



t Paper and map by Messrs. Peach and Home, Quart. Journ. Geol. See. 

 vol. xxxvi. 



I Paper by Jas. Greikie, LL.D., F.E.S., Quart. Journ. Geol. Soc. toI. xxxiv. 



Q.J.G.S. No. 176. 3 1 



