352 . MAJOE A. E. DWEBEYHOtJSE ON THE [vol. Ixxix, 



15. The Glaciation of Noeth-Eastebn Ieeeand. By Major 

 Aethttb Richaed Dwebbyhouse, T;D., D.Sc, M.R.I. A., 

 F.G.S. (Read June 28th, 1922.) 



[Plates XXIII & XXIV.] 



Contents. 



Page 



I. Introduction 352 



II. The Northern Part of the Antrim Plateau 355 



III. The East Coast of County Antrim 364 



IV. The Belfast Valley 374 



V. The Area between Slieve Gallion (Tyrone) and the Belfast 



Valley 375 



VI. The Central Depression north of Lough Neagh 383 



VII. County Down -. 394 



VIII. The Carlingford Mountains and the Slieve Gullion Area . . . 405 



IX. Summary and Conclusions 415 



I. Inteodtjction. 



The region to be described covers the counties of Antrim and 

 Down, with parts of Armagh, Londonderry, Tyrone, Monaghan, 

 and Louth, in all about 3200 square miles, and is included in 

 sheets 6, 7, 8, 12, 13, 14, 18, 19, 20, 21, 26, 27, 28, 29, 34, 35, 

 36, 37, 47, 48, 49, 59, 60, 61, 70, and 71, of the maps of the 

 Ordnance Survey of Ireland on the scale of 1 inch to the mile. 



The area is also covered by Bartholomew's ' Quarter-inch to the 

 mile map of Ireland ', Sheet 2, which contains most of the place- 

 names used in this paper. 



References to the previous papers on the subject are collected 

 in a ' Bibliography of Irish Glacial & Post-Glacial Geology ' by 

 R. LI. Praeger, Proc. Belfast Nat. Field-Club, App. (1896), 

 and in a Summarv of Recent Glacial Investigations by the 

 B.N.F.C., ibid. App. vii (1905-1906). 



The area is naturally divided into four geographical units — 

 the basaltic plateau of County Antrim, the Trias-filled valley of 

 Belfast, the undulating Palaeozoic area of Down and Monaghan, 

 and the igneous areas of the Mourne Mountains, Slieve Croob, and 

 Carlingford. 



(1) The Basalt-Plateau. 



The great plateau of County Antrim is formed of Tertiary 

 basalts lying unconformably upon various older rocks, including 

 Dalradian schists, Carboniferous, Triassic, Liassic, and Cretaceous 

 rocks. The present surface of the basalt country forms a trough 

 with its axis running north and south. The central valley is 

 occupied by Lough Neagh, the waters of which stand at 52 feet 

 above, and the lowest portion of its floor at 50 feet below, sea- 



