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Vol. III. AUGUST, 1894. No. 8. 



NOTES ON GLACIAL DEPOSITS IN IRELAND. 



BY PROFESSOR W. J. SOU, AS, F.R.S., AND R. LLOYD PRAEGER, B.E, 



I. — The Bray River. 

 The progress in the discovery of the history of the last great 

 glacial period advances like the glaciers themselves — so 

 slowly, that a sceptic might be pardoned for doubting whether 

 any advance is being made at all ; nor, considering the 

 extent, complication, and fragmentary nature of glacial 

 deposits, and the number, variety, and contradictoriness of 

 glacial theories, is this in any way surprising. Facts, and the 

 analysis of facts appear to be even still requisite before the 

 subject can be regarded as ripe for synthetic treatment. 

 In the series of notes of which this is the first, we will confine 

 ourselves to a detailed description of the deposits as they are 

 found in some localities in Ireland where we have had an 

 opportunity of studying them, drawing only immediate 

 inferences, and leaving generalization to a later period. 



An account has already 1 been given of the succession and 

 character of the glacial deposits as seen in the fine section on 

 the shore between Bray and Killiney ; we will now trace 

 their extension inland, availing ourselves of the numerous 

 sections which occur on both sides of the Bray River. 



The Bray River, which flows eastward into the Irish Sea 

 some ten miles south of Dublin, is formed by the confluence of 

 the Dargle and Cookstown Rivers, which are made up of 

 numerous tributaries, having their sources among the granite 

 hills (1,000-2,000 feet) of the Leinster chain. Descending 

 from the granite, these feeders flow over Ordovician slates, and 

 micaceous and other schists produced by contact alteration of 

 the slates. The Bray River itself flows chiefly over Cambrian 

 rocks, down a wide valley thickly filled with drift, through 

 which the stream has cut a deep channel. The Carboniferous 



1 Irish Naturalist, Vol, III., 1894, pp. 13-18. 



