8 G. U. Kinahan — Irish Metamorphic Hocks. 



follows : — 1st, Boylagh and Kilmacrenan, Co. Donegal ; 2nd, Tirhugb, 

 Co. Donegal ; 3rd, Erris, Co. Mayo ; 4th, Slievegamp and Ox 

 Mountain, Cos. Mayo, Sligo, and Leitrim ; 5th, Cbarlestown district, 

 Co. Mayo ; 6th, Slievegallion or Pomeroy district, Cos. Tyrone and 

 Derry ; 7th, Cary or Ballycastle district, Co. Antrim ; 8th, Yar- 

 Connaught or West Galway ; 9th, Croaghankinshella, Cos. Wicklow 

 and Wexford ; and 10th, Carnsore, Co. Wexford. 



Boylagh and Kilmacrenan. — These are the northern baixmies in the 

 county of Donegal, across which obliquely a tract of granitic rocks 

 extends, having outlying patches inKossgnll and Fanad, in the latter 

 barony. In connection with the gneiss there are some remarkable 

 peculiarities which as yet have not been explained ; but as the country 

 has still to be completely explored, it seems expedient only to say 

 that the Americans seem to consider the gneiss and associated schists 

 of Lackagh valley to be lithologically identical with the American 

 rocks of Mt. Alban series (Hitchcock) or Hudson River series (Dana), 

 as seen in the vale of the Schuyllkill river, Pennsylvania ; and these 

 American rocks they consider to be the equivalents of the English 

 Ordovician or Lower Silurian. Immediately south of the gneissoid 

 rocks supposed to be Laurentians, there is a long tract of rocks 

 which lithologically are identical with some of the Ontario 

 Laurentians, much more so than any of the gneissose rocks ; they, 

 however, have been ignored. To the main tract of gneiss in the 

 bavony of Kilmacreenan, in any place, either along the north-west 

 or south-east of its limits, there are no hard boundaries to indicate an 

 unconformability or fault boundary, as along these boundaries the 

 gneiss graduates into schists, and the latter into submetamorphic roclcs ; 

 to the south-east, however, the graduation is, in general, more rapid 

 than to the north-west. 



Tirhugh. — This tract is situated to the N.W. of Pettigo, in the 

 south portion of the Co. Donegal. The rocks partake very much of 

 the lithological characters of some of the Ontario Huronians and 

 Laurentians, but up to the present time they have not been claimed 

 as Irish Laurentians. In former writings I have suggested that they 

 are probably the representatives, either of the Passage beds between 

 the Ordovicians and the Cambrian, or of the Upper Cambrians. 



Erris. — This is a portion of North-west Mayo. The gneissose 

 rocks have no well-defined boundaries ; neither has there been found 

 in connection with them an overlying unconformable conglomerate, 

 as has been believed by some, on account of the wording of their 

 published descriptions. In former papers (Royal Geol. Soc. Ireland) 

 I have suggested that these rocks are metamorphosed Cambrians, 

 but no positive statement can be made as to their age ; lithologically 

 they are similar to the metamorphosed Cambrians of the Co. Wexford, 

 but they are also very like some of the American Laurentians. 



Slieve Gamp and Ox Mountains. — These rocks occupy a long 

 narrow strip which extends from north-east Mayo, across Sligo into 

 the county of Leitrim. Some of the rocks are peculiar, as they occur, 

 similarly to the Norians of the Province of Quebec, as intrusive masses, 

 into which a coarse foliation has been subsequently introduced. The 



