Geological Features of the North-east of Ireland. 125 



It Is highly worthy of observation that the points of the coast of 

 Scotland immediately opposite the Peninsula of Ardes, where the 

 greywacke terminates abruptly on the Irish side of the North 

 Channel, present in the neighbourhood of Port Patrick and through 

 the greater part of the Mull of Galloway, a resumption of the 

 same formation ; nor is the analogy in the structure of the two 

 countries confined to this one point. The hills of the Mull of • 

 Galloway are a branch of the great chain of mountains which 

 under the name of the Lead hills and other local titles, traverses 

 the whole of Scotland on the south reaching from sea to sea, and 

 the composition of this chain agrees through its entire extent with 

 that of the mountainous tract just described, the transition rocks 

 forming its predominating constituent, enveloped by which several 

 small districts of granite occur, as in the hills of Cairnsmuir and 

 Griffel ; while the whole is distinguished from the great northern 

 chain of mountains or Grampians, by the rare occurrence or total 

 absence of mica slate, which in the latter is remarkably prevalent. 



On the north of the Mourne Mountains rise the Bann one of 

 the tributary streams of Lough Neagh, and the Lagan which flows 

 into the estuary of Belfast ; and on the south several small rivulets 

 which run Immediately into the sea, the base of the mountains 

 being in that direction washed by the Irish Channel. 



2d System, Primitive Chain of Londonderry . 



The mountain group which I have thus designated, rises at the 

 distance of about 50 miles to the N.N.W. of the external chains of 

 the first system. 



It forms a large mountainous tract comprehended between the 

 river Roe and the Strabane, partly situated in Derry and partly In 

 Tyrone. Q 2 



