Wkight — Palcvosoic Floor of North-East Ireland. 



635 



are brought up against the Ordovician rocks of the Southern Uplands, and of 

 counties Down, Monaghan, and Cavan is also remarkably straight where 

 visible. The gap, where it is concealed beneath the sea and beneath the 

 Mesozoic and Cainozoic rocks of Antrim, extends from the coast of Scotland 

 to the neighbourhood of Armagh, and is much greater than iu the case of 

 the northern boundary. The continuation to the south-west of Armagh is, 

 however, a line of remarkable straightness, which can be projected into the 

 concealed area with a fair amount of confidence. 



Exposed Coalfields. 



Conjectural Coal- basins 

 concealed beneath the 

 Mesazoic cover c the Sea. 

 Area covered by 

 Sfesazojc& Tertiary 

 roots 



■Limits of direct 

 Synclinal troughs. 



Exposed Coalfields. 



A. Fife Lothian 



B. Lanarkshire. 



C. Ayrshire 



D. Dungannon. 



E. Lough Allen. 



F. Ba//ycastle. 



G. Machrihanish 



Limits of transverse 



Synclinal troughs. 



We are enabled, therefore, to lay off the limits of the trough-valley beneath 

 the sea and the basalt plateau with some approach to accuracy, and the 

 Palasozoic floor between these limits may reasonably be expected to be com- 

 posed, as it is in Scotland, on the one hand, and Ireland on the other, largely 

 of Carboniferous and Old Eed Sandstone strata. "When we come to consider, 

 however, what portions of this floor are most likely to contain coal-bearing 

 strata, we find it necessary to further restrict the limits, for it will be seen 

 from the 25-mile map that a wide belt along the north-western side of the 

 trough, in the Lowlands of Scotland and in Co. Tyrone, is occupied by Old 



