344 [ pr0c - B.N.F.C., 



and the metamorphic rocks, which include a great variety, supposed 

 to have been altered by volcanic, hydro-thermal, or chemical 

 agencies. But the real distinction between these rocks has not 

 been clearly settled by geologists. On this point they are divided 

 into two schools — one holding that our granites, dolerites, and 

 their associated greenstones, and even our schistose rocks, are of 

 plutonic origin ; while the other school claims for all these rocks, 

 and even for granite, an aqueous origin. Mr. Gray reviewed the 

 arguments for and against both theories, and explained that we 

 have in the North three varieties of granite — first, the Slieve Croob 

 granite, supposed by some to be a truly metamorphic granite, 

 because it appears to pass from the typical granite, through 

 schistose varieties, into unaltered Silurian Shales ; second, the 

 Mourne granite, an undoubted intrusive plutonic rock ; third, the 

 Carlingford granite, like the Mourne, manifestly plutonic. In 

 addition to these we have the metamorphic rocks of Antrim, Derry, 

 Tyrone, and Donegal, affording examples from which to study the 

 debated question of metamorphic action. In studying the origin 

 of the crystalline rocks we can be materially assisted by a careful 

 examination of the basaltic rocks of the North of Ireland. We 

 have thus two remarkable groups of rocks — the granites and the 

 basalts — and both associated with a variety of the sedimentary 

 rocks, ranging from the Cambrian to the Chalk. Mr. Gray de- 

 scribed the basalt and its central zone of iron ore, with the associated 

 bauxite clays, and lignite beds, and the very remarkable plant 

 remains found in the iron ore, bauxite clays, and carbonaceous 

 shales. The late meeting of the British Association gave a grant 

 towards the expense of exploring these beds. 



Of the several papers read before the British Association 

 having reference to our district, one of the most suggestive was a 

 paper by Mr. Traill, of the Geological Survey, on the " Rocks of 

 Ulster as a Source of Water Supply." In reference to this paper, 

 it might be stated that in the opinion of Mr. Traill, the water- 



