Cole — The Problem of the Bray Series. 5 



In a notice of the memoir of 1903, i' I expressed my frank opinion of 

 M'Henry's proposition, unsupported by palseontological evidence, as to the 

 Gotlandian age of both the Bray Series and the greater series of shaly rocks 

 flanking the Leinster chain on either side. The possible continuity of these 

 two series, which was suggested by Lamplugh, left another problem still 

 unsolved. Why is the Bray Series in the counties of Dublin and Wicklow 

 not invaded by the Leinster granite, while the Ordovician shales have 

 yielded a conspicuous marginal belt, where abundant veins of granite and 

 eurite penetrate an aureole of mica-schist ? 



SoUas,"' with characteristic ingenuity, suggested in 1893 that the granitic 

 mass was a laccolitic intrusion, with an Ordovician cover and the Bray Series 

 as a floor. The gneisses of Carnsore, in the south of the county of Wexford, 

 appear, however, to be of composite origin, and to result from the intrusion 

 of granite into slates of the Cambrian series. Sollas's explanation might 

 none the less hold good for the main field of intrusion. 



Is not, however, the solution to be found in the horizontal movements 

 that Sollas recognized in Howth ? J. F. Blalfe" and other authors have 

 emphasized the resemblance of the Bray Series to the rocks near Holyhead, 

 in Anglesey. E. Greenly, in describing the " Gwna Group " in his fine and 

 recent memoir,'" recognizes these beds in llowth, and regards them, with 

 Blake, as pre-Cambrian. 0. A. Matley-' has shown how the green rocks of 

 what Greenly now styles the Mona complex override Ordovician strata as the 

 result of thrusting. The thrusts do not affect the Carboniferous beds." 

 Matley states that they occurred between Upper Ordovician and Upper Old 

 Eed Sandstone times; they are thus, with extreme probability, of Caledonian 

 age. Matley,"' again, indicates similar thrusts and inversions of older rocks 

 on Llandilo strata at Mynydd Garn, in N.- W. Anglesey : and Greenly presents 

 a large body of detailed evidence, bringing his experience of mapping in the 

 Scottish highlands to bear on his twenty years' work on the Mona complex 

 and its environment. When it again becomes possible to carry on systematic 

 field-work in southern Ireland, the solution of the relations of the Bray 

 Series to the rocks that flank the Leinster granite will probably be found on 

 the lines indicated by Matley for the rocks across the Channel. 



" Irish Naturalist, vol. xii, p. 119 (1903). 



'*Proc. Geol, Assoc, vol. xiii, p. 104. 



'""The Moiiian System of Rocks," Quart. Journ. Geol. Soc. London, vol. xliv, 

 p. 534 (1888.) See also R. I. Murchison, ' ' Siluria," p. 165 (1854). 



=» " Geology of Anglesey," p. 896 (1919). 



2'" The Geology of Northern Anglesey," Quart. Journ. Geol. Soc. London, vol. Iv, 

 p. 636 (1899). 



22 76id., p. 667. 



-'3 " The Geology of Mynydd Garn," ibid., vol Ivii, p. 20 (1901). 



