74 



[Proc. B.N.F.C, 



Above the Chalk and resting upon it with marked uncon- 

 formity is to be seen the Tertiary basalt, which, owing to its 

 frequently columnar structure, the massive hills and bold head- 

 lands which it produces, and its strong colour contrast with the 

 underlying Chalk, is responsible for the grandest scenery of this 

 remarkable region. Covering, as it does, nearly the whole of 

 Antrim, and extending into the highest peaks of that county, its 

 scenic importance will be readily appreciated. 



The basalt rests on a denuded surface of Chalk, the hollows 

 in which contained flint gravels prior to the extrusion of the 

 igneous rock, the heat from which burnt many of the flint nodules 

 to a bright red colour. 



With the basalt flows are intercalated numerous intrusive 

 sheets of dolerite, and it was suggested that the columnar basalts 

 of the Giant's Causeway and other parts of the district might have 

 had a similar origin. 



The glaciation of the country is of great interest, the principal 

 factor having been the great Firth of Clyde glacier, which over- 

 rode the whole of the Antrim plateau and also affected the coast 

 area as far as, and probably beyond, Londonderry. 



Erratics characteristic of this ice-sheet are : — (i) Riebeckite- 

 eurite of Ailsa Craig ; (2) Quartz porphyry of Drumadoon Point, 

 Arran ; and (3) Granite of Goatfell, Arran. 



Dr. Dwerryhouse stated that he had found these rocks up to 

 a height of 1,000 feet near Ballycastle, and that up to the present 

 he had been unable to find any evidence of a northward travel of 

 erratics in any part of the Antrim plateau, with the exception of 

 boulders of basalt which had been carried from Trostan down 

 Glen Dun and some neighbouring valleys for a distance of a few 

 miles. 



Other evidence of glaciation is to be found in the gravel 

 delta-terraces produced in glacier-dammed lakes and the deserted 

 overflow channels cut by the waters of these lakes, many of which 

 are of large size and form conspicuous features. 



