551.33(41.5) 243 



III 



The Eskers of Ireland 



Part II. 



TT^HE various theories which have been advanced to account for 

 -L eskers may, I think, be reduced to two classes — 



The first class will contain those held by geologists who, while 

 differing in matters of detail, agree that the eskers result from 

 marine agency — tides and currents. 



The second class will contain those propounded by writers who 

 see their way to dispense with marine action, and who find in the 

 agency of glacier-ice the origin of all manner of drift deposits. 



The Neptunists — a term which will serve to indicate the 

 upholders of the marine agency theory — are well represented by 

 .1 ukes and Kinahan, who have the advantage, as regards the 

 eskers, of minute practical acquaintance with the geology of 

 Ireland. 



The Glacialists are represented by Hummel and Geikie — the 

 former belonging to the Geological Survey of Sweden, and the latter 

 to the Geological Survey of Scotland. 



I begin with J. Beete Jukes, who was for many years, prior to 

 his death in 1869, connected with the Geological Survey of Ireland. 

 In his opinion the ' ridges ' "seem to have been formed by the piling 

 action of two opposing currents, or to have been heaped up in the 

 eddy at the margin of the currents running in different directions." 



But it is in this ' piling-up action ' that the difficulty lies. 

 Irregular heaps or mounds of sand, gravel, or shingle may have 

 been got together in this way, although it would not be so easy to 

 account for the stratification observable in the true eskers. But 

 when we come to consider the long narrow ridges of the railway 

 embankment type the difficulty becomes really formidable. I have 

 no doubt that Jukes is correct in saying that " many of the eskers 

 were perhaps similar to harbour-bars in their mode of formation, 

 and may be directly related in this way to the valleys running into 

 the neighbouring hills, which must, of course, have formed bays or 

 harbours during some part of the last slow rising of the land above 

 the sea." 



In Geikie's edition of "Jukes' Manual " of Geoloyv, there is a note 

 on p. 712, citing, as an excellent example of an old ' harbour-bar,' 



