part 3] GLACIATIOX OF >'OB,TII-EASTEJEtN IRELAND. 353 



level, and by the lower course of the River Bann and the valley 

 of the River Main. The eastern and western portions of the 

 plateau rise into extensive uplands. 



The western margin, extending from Magilligan Strand, at the 

 mouth of Lough Foyle, to the western shores of Lough Neagh, 

 forms in its northern part the bold escarpment of Binevena and 

 Benbradagh, which overlooks the valley of the Roe and the towns 

 of Limavaddy and Dungiven in the rolling country formed by the 

 Dalradian schists and gneisses and the Carboniferous rocks which 

 overlie them on the northern flank of the Sperrin Mountains. 



Farther south, where the basalts come into contact with the 

 great schistose mass of the Sperrins, the escarpment is not so 

 marked, owing to the greater height of the land on the west. 

 South of the general line of the Sperrins the level of the plateau 

 falls towards the basin of Lough Neagh, and the escarpment, 

 although still present, does not form a conspicuous feature of the 

 landscape where it passes from the neighbourhood of Magherafelt 

 to Moneymore, and onwards in the direction of Coalisland. 



The eastern escarpment of the plateau runs along the sea-coast 

 from Benmore (Fair Head) on the north, to the head of Belfast 

 Lough, and thence by Cave Hill, Black Mountain, and Colin to 

 the neighbourhood of Hamiltonsbawn in County Armagh. South 

 of this point the basalt is represented by outliers at Markethill 

 and Poyntzpass, but these do not form marked features. 



The country inland from the eastern cliffs is very hilly, and 

 culminates in the rounded dome of Trostan (1817 feet O.D.), 

 while farther south the peaks of Sliemish (1437 feet) and Divis 

 (1567 feet) form the dominant elevations. 



The eastern escarpment has been deeply scored by streams which 

 flow down its steep face into the North Channel, giving rise to the 

 famous Glens of Antrim. These, in succession from the north, 

 are Glen Dun, Glen Aan, Glenballyemon, Glenariff, Carnlough 

 Glen, Glenarm, the valley of the Larne Water, and the smaller 

 glens along the face of the Belfast Hills. 



In the extreme north-east of the area, in the neighbourhood of 

 Ballycastle, the basalts with the underlying Chalk and Trias have 

 been removed by denudation, laying bare the Dalradian schists 

 and gneisses below ; but there are several outliers indicating the 

 former extension of the basalts over the whole area. Chief among 

 these northern outliers is the great dome of Knocklayde, which 

 forms the most conspicuous feature in the Ballycastle district, and 

 is separated from the main mass of the plateau by a deep valley 

 that played an important part in the drainage of the country 

 during the Glacial Period. 



East and west respectively of Knocklayde lie the valleys of 

 Glenshesk and of the River Tow, the latter being the pre-Glacial 

 outlet of the Bush River. 



The central low-lying portion of the basalt-plateau is occupied by 

 the valley of the Bann, and by that of the almost parallel stream, 

 the River Main. The Bann leaves the northern end of Lough Neagh 



