G. R. Kinahan — Archcean Bocks, 505' 



ence to them, or any other tract of English metamorphic rocks, would 

 be much more cautiously given. With respect to the Irish metamorphic 

 rocks, however, statements can be more confidently made, and to 

 him it would appear that no rocks in that island are the representatives 

 of the American ArchcBan, or even of the at present unnamed, or un- 

 recognized, " Fassage Beds " between the Archceans and tlie Primordial. 



Prior to 1878, as has been pointed out in papers published by 

 the Eoyal Dublin Society and the Koyal Geological Society of Ireland, 

 first Jukes and Sterry Hunt, and afterwards Murchison and the 

 writer, pointed out that the equivalents of the Laurentian rocks might 

 exist in places in the provinces of Connaught and Ulster (Cos. 

 Antrim, Tyrone, Donegal, Leitrim, Sligo and Mayo). Subsequently 

 Hicks suggested that my supposed Cambrians in Tyrone (Slieve 

 Gallion District) were more probably of Archaean age ; while still 

 more recently Drs. Callaway and Hull have stated that they have 

 proved the existence of Archaean rocks in different places. But 

 none of the tracts so exalted have the characteristics considered 

 essential by Dana, Le Conte, etc., as nowhere in Ireland are there 

 records of a great lapse of time between the accumulation of the strata 

 said to be ArchcBan and those of Cambrian or Ordovician ages. 



As to the rocks at Greenore and Kilmore, Co. Wexford, said to be 

 Archsean, the firt-t are evidently a metamorphic protrude of exotic 

 rocks, and the second are interstratified with their fellows; the 

 rocks in both cases being so intimately intermingled that it is 

 absurd to attempt to separate them ; here therefore there is no 

 record of a vast lapse of time between the Archeeans and Primordials, 



In North-west Ireland, that is, the portions of the Provinces of 

 Connaught and Ulster, between Galway Bay and the eastern boun- 

 daries of the Cos. Londonderi'y and Tyrone, there was one large 

 tract of metamorphic rocks. This has now on it, in places, patches 

 of Silurian and Carboniferous rocks, thus dividing it up into subor- 

 dinate tracts ; yet the connection between all of them is very 

 conspicuous and can be easily traced out. 



In Ulster there is an unconformability in these metamorphic 

 rocks; but some of the strata above and below this unconformability 

 have general characters so similar that it is disputed by some ; the 

 so-called Archgean are a portion only of the rocks below the uncon- 

 formability. In places both in Ulster and Connaught portions of 

 both the older and later rocks are unaltered, and contain fossils or 

 markings that are considered to be fossils. 



In North-west Galway and South-west Mayo, in the unaltered 

 portions of these rock-tracts, there are fossils of Llandeilo 

 types, and after tracing the equivalents of these fossiliferous rocks 

 northward and north-eastward through North-east Mayo, Sligo, 

 and Leitrim, into Donegal, Tyrone, and Londonderry, it induced 

 the opinion, published some years ago (1878), that the later rocks in 

 Ulster, that is, those above the unconformability, represented the 

 upper portion of the Irish Ordovicians (Volcanic and Slate Series), 

 and perhaps in part the Llandovery [Passage Beds between the 

 Ordovicians and Silurians) ; while the strata below the unconformability 



