Prof. Cole cO T. Hallissy—The Wexford Gravels. 507 



which so closely resembles that of Wexford, effervesces when touched 

 with acid, while the matiix of the Upper Boulder-loam gives no 

 reaction. 



Mr. W. D. Haigh, A.R C.Sc.I., has made the following deter- 

 minations for us in the laboratory of the Geological Survey of Ireland : — 



Percentage of Calcium Carbonate in Chocolate Clay. 



Greenore Point, Co. Wexford 9-83 



Eosslare, Co. Wexford 12-97 



Killiney, Co. Dublin 11-15 



10-56 



Kill of the Grange, Co. Dublin 11-80 



Eochestown Avenue, near Cabinteely, Co. Dublin . . . 9-76 



The continuous sections in the county of Wexford are more 

 imposing than those of Dublin ; but enough is still seen at Killiney 

 to justify a comparison, and, we believe, an accurate correlation. 



We thus find ourselves in disagreement with Kinahan, who denies 

 the existence of an Upper Boulder-clay at Killiney^; in agreement 

 with Lamplugh, who accepts an Upper and a Lower Boulder-clay 

 with gravels between them ; but in disagreement with Lamplugh and 

 Kilroe,^ when they minimize the importance of the lower clay and 

 regard it as a mere interlamination in the gravel series. Nor can we 

 agree with Kilroe that the red colour of this clay is due merely to 

 'progressive weathering'. The sections in the county of Wexford 

 produce a very different impression. 



It is noteworthy that the clay brought from the North Sea over 

 the east of England by the great extension of ice from Scandinavia is 

 characteristically of a reddish buff colour.^ This may be the colour 

 of submarine sediments that became incorporated in the ice-sheet, 

 though 0. B. Biiggild* states that a brown tint is very rare in such 

 deposits if they are of terrigenous origin. Boggild regards the brown 

 colour of such sediments as due to an oxidizing action of the sea on 

 deposits that would ordinarily be grey or blue or green. Fritz Heim,* 

 in his examination of specimens from the Atlantic, concludes that 

 red clays are not necessarily derived from the clays of other tints 

 that underlie them, but represent a stage when the area happens to 

 be far from land. He suggests that a difference of colour in the 

 deposits at any one spot indicates a tectonic change. Hans 

 Spethmann*^ states that in the Baltic, off south-eastern Sweden, 

 a chocolate colour is associated with a high percentage (some 13 per 

 cent) of calcium carbonate ; but his tables do not bear this out for 

 other areas. 



1 " Middle Gravels (?), Ireland " : Geol. Mag., 1872, p. 265. 



2 Mem. to Sheet 112, 1903, pp. 40, 104. 



^ P. G. H. Boswell, "On the occurrence of the North Sea Drift": Proe. 

 Geol. Assoc., vol. xxv, p. 150, 1914. 



■* " Memoire sur les sediments sous-marins " : Crosiere oceanographique de 

 la Belgica dans la Mer du Gronland (Bruxelles, 1907), p. 6. Also Keport on 

 the Danish Oceanographical Expeditions 1908-10 to the Mediterranean, p. 259. 



* " Bericht liber die Grundproben " : Zeitscb. Ges. Erdk. Berlin, 1912, No. 2. 



® " Studien uber die Bodenzusammensetzung der baltiscben Depression": 

 Wissen. Meeresuntersuchungen, Kiel, Bd. xii, p. 313, 1910. 



