4 Proceedings of the Royal Irish Academy. 



G. H. Kinahan," from his experience over a wide area, supported tlie view 

 of a o-eiieral nnconformitj- ; but he pointed out the absence of basal con- 

 o-lomerates in tlie counties of Dublin and Wicklow, except at Moneystown 

 Hill, where the evidence is none too clear. He records a basal Ordovician 

 cong-lomerate lying on the upturned edges of the altered rocks near Greeuore, 

 south-east of Wexford town, and two other instances on the south coast of 

 the county of Wexford. In other cases, he speaks of the Ordovician shales as 

 " plastered against " protrusions of the older rocks. Though the statement 

 is not distinctly made, this suggests the occurrence of Cambrian bosses as 

 horsts among Ordovician strata. 



The conception of a general unconformity at the upper limit of the Bray 

 Series was adopted by myself'^ and by W. J. Sollas.'^ In the present paper I 

 venture to urge that the evidence of it has been destroyed in the counties of 

 Dublin and Wicklow by thrusting of post-Ordovician and possibly of 

 Armorican date. 



In the Geological Survey memoir on " The Geology of the country around 

 Dublin " (1903), which includes a revision of that previously published on 

 sheet 112 (102 and 112), G. W. Lamplugh'" cast, as it seems to me, un- 

 necessary doubt on the stratigraphical value of the oi-ganisms of the Bray 

 Series. At the same time he published A. M'Heury's views on the absence 

 of an unconformity between that series and the Ordovician shales. M'Henry 

 at that time urged that the Bray Series was of younger age than the 

 Ordovician, and was in reality Gotlaudian (Upper Silurian of the Survey). 

 F. W. Egan is cited as an adherent of the same opinion ; but those who 

 followed contemporaneously the " Silurian revision " undertaken at that time 

 by the Geological Survey in Ireland will remember that a zeal for sweeping 

 changes, and a particular affection for the Llandovery Series, were apt to 

 outrun the evidence that could be established in the field. Lamplugh showed 

 much hesitation as to M'Henry's views ; he was willing, however, to discard 

 the unconformity, and to place (p. 8) the grey slates of Ireland's Eye with 

 the Bray Series. He aptly compared the latter with the lower part of the 

 Skiddaw Slates Series of the Isle of Man, which lies in the same geographical 

 province. On p. 74 of the Memoir of 1903, M'Henry remarks on the close 

 resemblance of the slates of Ireland's Eye, which were held by Jukes to be 

 Ordovician, with those associated with the Bray Series in the counties of 

 Wicklow and Wexford. 



'^ " On Geological Unconformalities," Journ. R. Geol. Soc. Ireland, vol. vii, p. 218 

 (1889). 



" " County Dublin," Irisli Naturalist, vol. i, p. 32 (1892). 



'» "Geology of Dublin," Proo. Geol. Assoc, vol. xiii, p. 99 (1895). 



"^Meni. of 1903, p. 7. 



