G. S. Kinahan — Re-arranged Glacial Drift. 113 



up to 300 feet. 1 found one shell in the Esker at Maryboro', Queen's 

 CO. ; while Messrs. Bryce and Hyndman have found them near 

 Belfast up to a height of 150 feet. All these localities, except, 

 perhaps, those of Messrs. Bryce and Hyndman, are probably in 

 gravel or sands belonging to the " Esker sea period," and the great 

 height at which some of them are found will be hereafter referred to. 

 From the above it is seen that although as a general rule the " Esker 

 sea period " gravels are without fossils, yet in some places these do 

 occur ; and this peculiarity may be due to the conditions under which 

 the drift was formed. As in places these gravels contain fossils, and as 

 they occur at an elevation very similar to that of the shelly drifts of the 

 CO. Wexford, it does not appear unreasonable to suppose that all were 

 formed simultaneously ; and in support of this idea it should be 

 mentioned that to the south-west, and north-west, the Wexford shelly 

 drift seems to graduate into unfossiliferous accumulations, while in 

 both localities they seem to merge into the " Esker sea period " 

 gravels : from the first, through the valleys of the Suir, the Nore, 

 and the Barrow ; and from the latter, through the valley of the 

 Slaney : while in places, both on the Esker gravels of the central 

 plain, and on the Wexford shelly drift, there are perched 

 erratics that seem to have been dropped from icebergs. If 

 this suggestion is correct, the drifts of Wexford and south-east 

 Wicklow must have accumulated under conditions more favourable 

 than the other " Esker sea period " gravels to the growth and pre- 

 servation of the shells now found in thera.^ 



It was at one time suggested that the ridges or eskers of the 

 central plain of Ireland were the remains of a central gravelly 

 member of the glacial drift, and that it had once been covered by a 

 newer Boulder-clay. If such had been the case, it is scarcely 

 possible but that in that portion of the island a part of the Upper 

 Boulder-clay would have remained, to record its former existence. 

 This suggestion, however, had to be abandoned, as the Officers of the 

 Geological Survey in no place could find the remains of this Upper 

 Boulder-clay, but, on the contrary, found that the " Esker sea 

 period " gravels were always the highest member, whether the 

 subjacent drift be the older Boulder-clay drift or the newer Moraine 

 drift, the Esker-gravels stretching continuously over both. In the 

 S.E. of Ireland, in the counties Wicklow and Wexford, over the 

 shelly drifts is found in places a drift that sometimes contains ice- 

 dressed blocks and fragments, and in places graduates into true 

 glacial-drift.^ This Glacialoid (or glacial -like) drift, however, also 

 graduates into, and is interstratified with, the shelly gravels, marls, 

 and clays, and does not always contain the ice-dressed blocks and 



^ Sir H. James records shells at a height of 400 feet on the Forth Mountains, 

 CO. Wexford. There would, however, seem to be a mistake in the figures, as Mr. 

 "Wyley, during his survey, did not observe them, but states they are not to be found 

 above 250 or 300 feet, and the drift on the higher portions of those hills is a rock 

 detritus in which shells could scarcely occur. 



^ On the borders of the counties Limerick and Tipperary, fringing the high land 

 [Slieve Phelim], Glacialoid drift is found capping and interstratified with the Esker- 

 period gravels. 



DECADE n. — VOL. I. NO. III. . 8 



