Geological Features of the North-east of Ireland. 127 



Sd System of Mountains. 'The Basaltic Group. 



This group may be more accurately described as separated into 

 two chains, bounding on the east and west the trough or valley 

 through which the river Bann flows from Lough Neagh to the 

 ocean. 



The eastern chain lies in the county of Antrim, being compre- 

 hended between the valley of the Bann and the Northern Channel. 

 It presents an abrupt declivity towards the east, falling with a gentle 

 slope towards the west, in which direction the beds composing its 

 mass dip. 



The hills of which it is composed are generally detached and 

 distinct, but yet so closely grouped together that there can be no 

 impropriety in considering them as parts of a single chain. 



According to Dr. Berger's measurement Kock-lead in the north- 

 secondary and primitive formations seems to pass near the southern extremity of the 

 Peninsula of Cantire, where a small secondary district, containing, like that of Arran, 

 some indications of coal occurs near Campbelltown. See Jameson Mineral of Scottish 

 isles, vol. 1. p. 134. 



Whether any connection can be traced between the floetz trap of Ulster and the 

 extensive deposits of similar rocks in the islands of Sky, Egg and Mull, is a question 

 which will be examined with greater advantage when the geology of these islands 

 has been further elucidated by the able descriptions of Dr. Mac CuUoch. It should appear 

 that in these islands strata of shell limestone containing belemnites and ammonites, and 

 appearing to be of more recent formation than those associated with the coal fields of the 

 main land, occur; hence we may perhaps be led to expect that they will be found to exhibit 

 a still nearer approach to the structure of the hills which constitute our third system. 

 Towards the west, the limestones and sandstones associated with the coal formation extend 

 from the banks of Lough Neagh to those of Loch Corrib in Connaught, passing by Lough 

 Erne and Lou^h Allen ; but the overlying trap is confined to the district described in this 

 paper, with one trifling exception which is presented by the Corliew mountains in 

 Roscommon, two miles to the north of Boyle, where the sandstone is covered by a cap of 

 greystone : the structure of these hills, therefore, agrees still more nearly with the trap 

 ranges of Scotland than does that of the great Ulster group. 



