December, 1921 The Irish Naturalist, 



f37 



THE ESKERS OF IRELAND. 



BY J. DE W. HINCH. 



The Eskers of Ireland have always attracted attention 

 on account of their singular appearance in the great central 

 plain, and the suggestions recently put forward by Prof. 

 Gregory of Glasgow' to account for their origin have aroused 

 considerable interest among those geologists who are con- 

 versant with the subject. 



A satisfactory definition of an Esker is difficult to agree 

 upon, as deposits w^hich are merely irregular mounds of 

 angular rocky material have been included in the term, 

 and many of the older geologists applied the word Esker 

 to any ridge of postglacial sand and gravel which showed 

 signs of stratification. It is, however, in Ireland, usual 

 to restrict the term to the winding steep-sloped ridges of 

 water-worn sand and gravel which stretch for such con- 

 siderable distances across the central plain, the most noted 

 being the Esker Riada, the old boundary line between 

 northern and southern Ireland. In form and linear distri- 

 bution the Eskers vary greatly, and while some of the 

 Eskers having the Esker Riada structure can be traced 

 across country for considerable distances in a fairly straight 

 line, there are on the other .hand many hundreds of small 

 Eskers with very little claim to definite form at all and whose 

 longer axes show no connected general trend. 



The Eskers are related to the great glacial deposits of 

 straliied sands and gravels and must be regarded as the 

 very latest of the late glacial series ; in fact the formation 

 of the Eskers must be considered as the closing episode 

 of the Great Ice Age. Concerning the origin of Eskers 

 there has been much discussion, and it must be said that 

 the question still remains unsolved, and especially as regard 

 the details. G. H. Kinahan regarded them as shoals and 

 s mdbanks formed by the tides and currents of the sea 

 resulting from a postglacial submergence of the central 

 plain, and showed much ingenuity in separating them into 

 Fringe Eskers, Barrier Eskers, and Shoal Eskers, but his 

 most enduring contribution to the subject is his recognition 



^ Gregory, J. W. ' The Irish Eskers," Phil. Trans. Roy, Soc. 

 Section B., vol. ccx., 1920 -21. 



