116 G. H. Kinahan — Re-arranged Glacial Drift. 



apparent ; but it may have been due to a sudden change in the level 

 of the land, or, what seems more probable, to the formation of sand 

 banks that dammed up portions of the slobs, causing the water on 

 them suddenly to become brackish or even fresh. 



These sunken and submarine bogs are as yet unexplored, con- 

 sequently their depth beneath the level of the sea is unknown. Peat, 

 however, from 10 to 16 feet deep, has been sounded in places off the 

 south and west coast, below low water of spring tides ; while during the 

 works carried on for the reclamation of the estuary muds of Wexford 

 Harbour, peat about 5 feet thick was found under 16 feet of the mud, 

 the lowest portion being 21 feet below the surface ; and these muds, 

 before they were reclaimed, were covered at half-tide. It may also 

 be mentioned that in places off the mouth of Wexford Harbour there 

 are now tidal islands in places, which in the ancient charts were 

 marked as " dangerous shoals." 



A resume has now been given of the movements that are known 

 to have changed the level of the country, and a short description of 

 the drifts and other deposits accumulated during these recent periods^ ^ 

 w^e may therefore return to the Olacialoid drift; and as we believe it 

 is not a true glacial drift, we will give suggestions, as to how it may 

 have been formed, illustrating these by facts that can be observed at 

 the present day. 



The Glacialoid drift of south-east Ireland occurs over or interstrati- 

 fied with shelly drifts, while under the latter are typical glacial 

 drifts. Beginning to the northward at Killiney-hill, co. Dublin, 

 there is a shelly gravel overlying a Boulder-clay. The latter drift can 

 be traced southward from that hill along the sea-cliff to Bray river, 

 it appearing at the base of the cliff under the shelly drifts. It is 

 nearly continuous all the way.; but as the drifts have been moved np 

 and down by recent faults, in a few places, where it has been let 

 down below the sea-level, it is hidden from view. Over this Boulder- 

 clay the drift may be sand, gravel, in a few places a shingle, or marl 

 or clay, often a good brick clay ; and all except the last are more 

 or less shelly. There is also a sandy clayey accumulation, which in 

 places contains subangular or rounded blocks and fragments, some of 

 which are partially ice-dressed. The latter variety only occurs in very 

 subordinate quantities, and always graduates into the gravels or clays, 

 generally the latter. The division between the shelly drift and the 

 Boulder-clay is in general well marked, and the change from one to 

 another abrupt ; but in a few places it is not so, one being a little 

 southward of Shanganagh river, where near the base of the former 

 there is a thin subordinate bed of Boulder-clay. Inland, in the country 

 between Kingstown and Bray, similar varieties of the upper drift occur, 

 with apparently the same relations to one another ; while where the 

 Boulder-clay drift is exposed, they always appear to lie on it.^ In 



1 The ^olian drift or blowing sand has not been mentioned in connexion with 

 these accumulations, as such sands may be of any age, some being as old as the later 

 part of the Glacial Period, having been formed while the moraine drift was accumu- 

 lating, while portions are forming at the present day. 



2 There is a section exposed in the old sea-clifF at Dunleary Harbour, east of the 

 Salt-hill Hotel, iu which, as seen from the railway, a Eoulder-clay-like drift overlies 



