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Vol. III. JUNE, 1894. No. 6. 



THE HIGH AND LOW-LEVEL SHELLY DRIFTS 

 AROUND DUBLIN AND BRAY. 



BY T. MEU<ARD READE, F.G.S. 



There has of late years been a great revival of interest in 

 Glacial Geology, more especially as relates to our own 

 country. The high-level shelly gravels have given enthu- 

 siastic glacialists both joy and tribulation. Joy where the 

 facts fit in with one's favourite theories, and tribulation when 

 we discover further and unthought-of difficulties in applying 

 the pet hypothesis of the hour. Personally, my endeavour 

 has been to preserve a philosophic calm befitting so difficult a 

 subject, but whether it has been successful or not must be left 

 to others to decide. 



Very few geologists are aware of the great development of 

 shelly drift extending from sea-level up to 1200 feet which 

 exists in the neighbourhood of Dublin and Bray. Before I 

 examined the district under the experienced guidance of the 

 Rev. Maxwell Close, I was under the impression that all I 

 should see at the higher levels would be sporadic patches of 

 shelly sands and gravels. I was agreeably disappointed ; for 

 the continuity, extent, and bulk of the shelly deposits exceed 

 any of those in the classic regions of England and Wales. 

 These I had previously explored in a rather careful way, but 

 the deposits in Ireland supplement and help to explain the 

 better known deposits in England and Wales in some most 

 important respects. 



All that one can pretend to give in these few pages is a 

 general conception of the high-level shelly drift, and its inter- 

 mediate relations with the drift of the coastal margin ; and to 

 do this, the natural way is to describe the coastal deposits, 

 and trace them up to the higher levels. 



Beginning at the Hill of Howth, shelly sands and gravels 

 are seen in considerable development from Howth to the 

 Bailey lighthouse. They extend to 300 feet above the sea- 



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