Kinahan — On Granite and Metamorphic Rocks. 217 



Silurian rocks are altered ; in the other counties they are not so. 

 In places the basal euryte of the Mweelrea beds, Co. Mayo, is 

 replaced by quartz-rock of a nearly similar nature to that men- 

 tioned above, as occurring at the base of the Carboniferous rocks in 

 Munster. 



In north-west Galway some of the bedded eurytes can be traced 

 downwards by dykes to bosses of elvan and granite, in the Arenig 

 rocks of Lugnanoon, south of the Kylemore valley. 



Carboniferous Granites (?) El vans (?) Whinstones (?) Eurytes (?) 

 and Felstones (?). — It cannot be shown that any of the exotic rocks 

 are certainly of Carboniferous age. In Mayo, to the S.W. of 

 Croagh Patrick, are the Corvockbrack granites, coming up through, 

 and altering, the Silurian rocks; they may, possibly, be of Car- 

 boniferous age ; but one kind of elvan, that seems to be an adjunct 

 of it, graduates into a uralitic gabbro, which may render this sup- 

 position questionable. 



In West Galway, Mayo, Sligo, and Donegal, there are mela- 

 phyres, eurytes, and felstones, newer than the Silurians. These are 

 very like those elsewhere that are known to be of Carboniferous 

 age ; but in West Galway, associated with them, there are dolerytes 

 identical with those of Antrim. However, there are apparently, 

 hereabouts, two systems of whinstone dykes of different periods. 



[In connexion with the Corvockbrack granite is a tract of metamorphic Silurians. 

 The exact time during which the metamorphism took place is uncertain ; it is possible 

 that it took place near the end of the Silurian or in the Devonian time, and that the 

 interbedded eurytes in the Fintona beds (Cos. Fermanagh and Tyrone) are products of 

 this metamorphism ; but these rocks are similar to, if not identical with, the Bundor- 

 ragha eurytes at the base of the Mweelrea beds (Co. Mayo), and consequently they are 

 probably older than this granite. Furthermore, the granite is very similar to that 

 elsewhere, which is supposed to be of Carboniferous age ; and, if this is allowed, the 

 metamorphic action must have taken place during the Carboniferous period. The 

 above-mentioned Lugnanoon granite and elvan, south of the Kylemore Valley, are 

 positively the root rocks of the Silurian eurytes, and are quite different from, and, as 

 I believe, much older than, the Corvockbrack granite. If this is correct, the latter 

 must be post-Silurian.] 



Triassic Granites (?) Elvans (?) Whinstones (?) Eurytes (?) 

 and Felstones (?) — Doleryte occurs associated with the Triassic in 

 Co. Tyrone. In North Mayo there are post- Carboniferous exotic 

 rocks, some of which are probably of Triassic age. 



Eocene Elvans, Whinstones, and Trachites. — In Antrim and 



8CIEN. PK0C. R.D.S. VOL. VI., FT. IV. S 



