September 1898] THE ESKERS IN IRELAND 173 



300 feet from the existing level. The old sea-margins are pointed 

 to in proof of the depression — lines of beach, and notches cut into 

 the hill-sides ; but, as will appear further on, such evidence is by 

 no means conclusive of marine action. 



" The low country," continues Jukes, " is largely covered by a 

 widely-spread mass of drift, consisting of dark sandy boulder-clay, 

 with pebbles and blocks, and occasional beds of sand and gravel, 

 sometimes very regularly stratified." In a footnote he adds: — 

 " This seems to be the equivalent of the Scottish Till, at least in 

 its upper part." The gravel, it may be remarked, extends through- 

 out wide areas and to considerable depth, without any apparent 

 mingling of clay, but consisting wholly, or almost so, of sand and 

 pebbles. " The great majority of the pebbles are rounded fragments 

 of Carboniferous Limestone, whence the deposit usually goes by the 

 name of the limestone gravel. This deposit rests not only on the 

 limestone but sweeps up on the flanks of the hills, both those that 

 are made of the lower palaeozoic rocks and those formed of the 

 Coal-measures. In each case the limestone gravel becomes largely 

 mingled with detritus of the rocks of which the hills are made, and 

 sometimes to such an extent that the local rocks assume a decided 

 preponderance and occasionally compose almost the whole of the 

 deposit." 



That these superficial deposits were formed under the sea, Jukes 

 entertains no doubt, just as Professor Eamsay holds that the drift of 

 North "Wales is of marine origin. Kinahan agrees with Jukes. The 

 only ground, according to these able writers, for a contrary opinion 

 is supplied by the unfossiliferous character of the deposits. But the 

 circumstances would not be in favour of the preservation of shells 

 (save those embedded in the limestone) in a mass of materials, which 

 presumably have been subjected to much agitation and trituration. 

 Against these, however, we have the very decided opinion of 

 Dr James Geikie, as to the analogous order of things in Scot- 

 land : — " It seems most reasonable to conclude that neither the 

 water-worn and stratified drift, nor the loose angular debris, nor 

 yet the erratics that lie scattered over the low grounds of Scotland, 

 give any indications of a former submergence of the land below the 

 sea. The loose angular debris or moraine matter and erratics have 

 been carried down and dropt over the terminal front of the ice- 

 sheet, or have stranded upon the mountain-slope and hillside, or have 

 been left lying in what once formed the bed of the old ice-sheet. 

 The sand and gravel drifts have been produced by the 

 action of water escaping from the melting ice-sheet which 

 re-arranged the morainic debris, &c, heaping it up in banks 

 or spreading it out in undulating flats" (" The Great Ice Age," 

 p. 244 of 2nd Ed.). 



