TRANSACTIONS OF SECTION C. 609 



The following Papers were read : — 



1. On the Laurentian Beds of Donegal and of other parts of Ireland. By 

 Professor Edward Hull, LL.D., F.B.S., Director of the Geological 

 Survey of Ireland. 



After a perusal of tlie writings of previous authors, and a personal examination 

 made in the spring of 1881, in company with two of his colleagues of the Geo- 

 logical Survej', Mr. R. G. Symes, F.G.S., and ISIr. S. B. Wilkinson, the author had 

 arrived at the following conclusions. 



1st. That the Gueissose series of Donegal, sometimes called ' Donegal Granite,' 

 is unconformably overlain by the metamorphosed quartzites, schists, and limestones 

 which Professor Harkness had shown to be the representatives of the Lower 

 Silurian beds of Scotland (' Quart. Journ. Geol. Soc' vol. xvii., p. 256). This 

 unconformity is especially noticeable in the district of Lough Salt near Glen. 



2nd. That the Gneissose series is similar in character and identical in position 

 and age with the ' Fundamental Gneiss ' (Murchisou) of parts of Sutherlandshire 

 and ilossshire, and is, therefore, like the latter, presumably of Laurentian age. 

 That the formation is a metamorphosed series of sedimentary beds, has been 

 shown by Dr. Haughton and Mr. 11. H. Scott. 



3rd. That the north-western boundary of the Donegal Gneiss is a large fault 

 between the Laurentian Gneiss and the metamorphosed Lower Silurian beds, 

 ■owing to which the older rocks have been elevated, and by denudation have been 

 -exposed at the surface. 



4th. That the Cambrian formation of Scotland is not represented in Donegal, 

 and that the unconformity above referred to represents a double hiatus, and is of 

 the same character as that which occurs in Sutherlandshire, in the district of 

 Foinaven and Ben Arkle, where the Lower Silurian beds rest directly on the 

 Laurentian Gneiss. 



5th. That Laurentian rocks may be recognised in other parts of Ireland, as in 

 the Slieve Gamph and Ox Mountains of Mayo and Sligo, at BelmuUet, and in 

 West Galway north of Gal way Bay, where the rocks consist of red gneiss, horn- 

 blende rock, and schist, &c., similar to those in Donegal ; also possibly in Co. Tyrone, 

 as suggested by Mr. Kinahan. 



■2. On the Laurentian Bodes in Ireland.^ By G. H. Kinahan, M.R.I.A., ^c. 



The writer first mentioned that Cainozoic and Mesozoic rocks only occurred in 

 the province of Ulster, while in the rest of the island there was a nearly continuous 

 sequence of Palaeozoic rocks, from the Coal-Measures down to the Cambrian, 

 proved by the work of Griffith, Jukes, and their subordinates. He then pointed 

 out that a recent attempt had been made to try and disturb their natural order, 

 but that the new theory was founded solely on assertions that would not bear 

 investigation. 



He proceeded to observe that the geologists of the Pre-Cambrian school ap- 

 peared to lay more weight on lithological evidence than that to which it was 

 entitled, and in continuation he gave the localities for the oldest rocks in Ireland, 

 with the reasons for and against the rocks being Laurentian. The localities are 

 Carnsore or S.E. Wexford, where it was shown that although the rocks were 

 lithologically similar to the I-aurentians, yet they contained Cambrian fossils — Gal- 

 liuiy, S^E. Mai/o, Sliffo, and L'iitrim —rock* that, from their lithological cliaracters, 

 were said to be Laurentian by Murchison, who recanted his statement when 

 Harkness showed that stratigraphically this was an impossibility. These rocks 

 •occur on two zones, those on the highest being now said to be Laurentian — Erris, 

 N. W. Mayo — very old rocks, about which nothing can be positively said, except 

 that they are older than the associated metamorphic rocks, which arf> iilsn of nncer- 

 tain age. Donegal, Londonderry, and Tyrone — the Laurentian age of some <if these, 



' A paper on the subject of this abstract appeared i:i tie Geol. Mag., for Sej^t. 1S81, 

 p. 427. 



1881. E K 



