506 Prof. Cole & T. Hallissy — TJie Wexford Gravels. 



We may now compare the "Wexford Series with that in Co. Dublin, 

 on which Harkness ^ and Hull - so largely based their threefold 

 division of the Irish drifts. 



III. COMPAKISON OF THE WeXFORD DeIFTS WITH THOSE NEAE 



Dublin. 



Mainly in consequence of the work of Gr. W. Lamplugh,^ the 

 shelly gravels near Dublin are now regarded as the product of local 

 melting of glacier ice, and of the consequent washing away of the 

 finer particles as the englacial matter was set free. The shells in 

 them have been carried, with the Lower Boulder-clay, to their present 

 sites by movements of the ice. Maxwell H. Close, while holding 

 that the gravels represented a submergence, was wont to say that 

 the molluscs had certainly not lived in the beds in which tliey now 

 are found. They are, in fact, concentrated from a shelly boulder- 

 clay, that is, from the englacial burden brought in by the Scottish 

 ice from the Irish Sea. 



The unwashed boulder-clay of this Scottish ice is typically seen in 

 the brick-pits at Kill of the Urange, 1 mile south-west of Kingstown. 

 This deposit and its shelly contents have been fully described by 

 Sollas & Praeger,* who state (p. 327) that, though it rests on 

 granite, only one pebble of granite was found among 129 stones 

 collected. A northern origin is assigned to this deposit. J. R. 

 Kilroe in the Survey memoir on the country around Dublin states ^ 

 that the Kill of the Grange clay is older than the Killiney sands and 

 gravels, and than the layers of boulder-clay interstratified with them. 



The Kill boulder-clay, which is also well seen in pits nearer to 

 Cabinteely, is greyish to chocolate brown, and strikingly recalls the 

 lower ' marl ' or boulder-clay laid down by the Irish Channel ice in 

 Wexford. The fact that it similarly efi'ervesces with acid has not, 

 we believe, been previously noticed. Lignite occurs in it in fair 

 abundance, doubtless from some source now covered by the sea. 



Such very different statements have been made about the 

 neighbouring section in the sea-cliff below Killiney station that Ave 

 might well hesitate to express an opinion here. But we find a marked 

 difference between the chocolate clay, containing few stones, which is 

 revealed at the base towards the south end of the section, and the 

 boulder-clay with large blocks of local granite that overlies the 

 gravels.^ An overthrust, probably due to the pressure of ice lying 

 somewhere towards Bray, and slipping northward during the epoch 

 of melting, has pushed up the chocolate clay over a portion of the 

 stratified gravels ; but the three deposits seem to us sufficiently 

 distinctive, and to support the triple classification long ago advocated 

 by Hull. It cannot be a matter of accident that the chocolate clay, 



^ " On the Middle Pleistocene Deposits " : Geol. Mag., 1869, p. 542. 

 - Op. cit., Geol. Mag., 1871, p. 294. 

 =* Mem. to Sheet 112, 2nd ed., 1903, p. 45. 

 ■• Op. cit., Irish Naturalist, 1895, p. 321. 

 ^ Mem. to Sheet 112, 2nd ed., 1903, p. 108. 



^ Hull's view that this is a true boulder-clay (letter in Geol. Mag., 1872, 

 p. 335) has been supported by all recent writers. 



