86 G. H. Kinahan — Asar^ Esker., or Kaims. 



V. — Asar, Esker, or Kaims. 

 By G. H. Kinahan, M.R.I.A., etc. 



AS I have paid some attention to the Eskexs of Ireland, perhaps I 

 may he allowed to make a few notes on the papers of Mr. F. 

 J. Jamieson recently read before the Geological Society of London, 

 and the letter of M. Jespersen that appeared in the Geol. Mag. 

 for December, 1874. These observers put forward the theory (if I 

 understand them rightly) that these peculiar ridges of shingle, 

 gravel, and sand may be in part glacial, they having been accumu- 

 lated as marginal fringes to the different stages of the ice-cap that 

 at one time covered the northern portion of the Continent of Europe, 

 as it intermittingly retreated. This suggestion seems worthy of 

 consideration, as possibly, if the ice^cap had an intermittent retro- 

 gression, there would be fringes or ridges of shingle, gravel, and 

 sand marking each rest, formed of the detritus from each successive 

 portion of the iee that disappeared ; but such accumulations should 

 be at different altitudes, and being carried by water off the ice, and 

 deposited successively at its edge, should be stratified outwards, — 

 or if the margin was retreating, they would be jumbled together. 



Gravel ridges answering these requirements may occur in places ; 

 but if we examine into the facts connected with the great systems 

 of eskers in Ireland, such a theory will not answer the requirements. 

 The data connected with this phenomenon I have explained on 

 former occasions, 1 and from those notes the following generaliza- 

 tions may be extracted. 



First. The Esker ridges are usually stratified more or less in con- 

 formity with the slopes of both their sides ; the stratification evidently 

 being due to currents coming in different directions. Second. The well- 

 marked eskers usually occur on ground between the 100 and 350 

 contour-lines. Third. When the eskers run on to ground above the 

 850 contour-line, they break into shoals or irregular mounds or accu- 

 mulations, while the shingle, gravel, and sand graduates into the 

 drift of the country; let the underlying drift be normal Boulder-clay- 

 drift, Moraine drift, or the Glacialoid stratified drift. Fourth. The 

 eskers or ridges occur in such places as it might be expected that 

 tidal or other currents met ; either in open seas, in straits, in bays, or 

 estuaries. Fifth. The eskers or ridges may be divided into three 

 kinds, namely: Fringe-eskers, margining high ground; Bar-eskers, 

 stretching from one high ground to another ; and Shoal-eskers, com- 

 posed of short ridges and hillocks mixed irregularly together. While 

 Sixth. From the charts we learn that nearly similar fringes, bars, and 

 shoals are now being formed in the shallow seas, the straits, bays, 

 and estuaries, by tidal and other currents. 



If the great system of eskers in Ireland was due to detritus 



1 On the Eskers of the Central Plain of Ireland, Dublin Quart. Journ. Science, 

 vol. iv. p. 109, and Dublin Geol. Soc. Journ., vol. x. Notes on some of the Drift in 

 Ireland, Dublin Quart. Journ. Science, vol. vi. p. 249, and Journ. Royal Geol. Soc. 

 Ireland, vol. i. pt. iii. 



