1898] THE ESKEBS OF IRELAND 247 



inti; between the Silvermines ami the Slieve Boughta mountains behind 

 Portumna. Last, not least, the great group of drift ridges and hills 

 at Esker College, Athenry, is situated near the mouth of the great 

 strait which occupied the valley of Gort and Lough Cooter between 

 the mountains of South Galway and those of North Clare. 



Dr James Geikie remarks that Mr Kinahan was the first to 

 point out the relation between these groups of post-glacial mounds 

 and ridges with the openings of valleys branching off from the great 

 central plain ; and the circumstance is further noteworthy as form- 

 ing (accidentally, I think) a connecting link between the two sets of 

 theories represented by Kinahan and Geikie respectively. While 

 Kinahan looks to the 'colliding' or dividing of flow-tide currents, 

 (ieikie finds all that is necessary in the melting away of 'confluent 

 glaciers.' The latter regards the explanation which Mr David 

 Hummel gives of the asar of Sweden as applicable to the drift for- 

 mations of Scotland and (as he believes) to the analogous formations 

 of Ireland, including, of course, the eskers. 



From the observations made by him on the asar and other 

 drifts of Sweden, Hummel concludes that the facts indicate the 

 agency of running water, and the direct action of glacier-ice ; and 

 he comes to the conclusion that the asar have been formed in 

 tunnels underneath the dissolving ice by running water introduced 

 through crevasses, etc., acting on the ground moraines of the great 

 confluent glaciers which covered Sweden during the glacial period. 

 ( ieikie adopts a similar explanation of the kames of Scotland, and 

 remarks that the theory to some extent resembles Mr Goodchild's 

 view of the origin of drift deposits in general. 



Dr N. 0. Hoist has proposed another explanation of asar, which 

 he supposes to have been deposited in superficial channels licked out 

 of the ice-sheet by the water derived from the melting of the inland 

 ice. The materials were, as he believes, derived from the melting 

 ice in which they had lain embedded. Geikie rejects the explanation 

 for these reasons : — 



(1) Because asar, eskers, and ridgy kames are not so continuous 

 as they must have been had they been formed in superficial river 

 channels ; and 



(2) Because we have no reason to believe that the ice of the 

 old extinct glaciers was more thickly charged with debris than the 

 present ice-sheets of arctic and antarctic regions. 



Moreover, it occurs to me that, while it is by no means im- 

 possible that morainic matter may have collected in such grooves, it 

 is very unlikely that it would come to terra firma without disturb- 

 ance of stratification. The groove would be narrower at bottom 

 than at top, the reverse of what we find in the esker. 



Hummel's theory, as adapted by Geikie, while open to a share 



