252 NATURAL SCIENCE [October 1898- 



the ' causeways ' have a preponderance of pebble and shingle, that 

 is owing to the circumstance that the shore in question is thickly- 

 strewn with granitic boulders. 



It is not necessary, I think, to point out that I do not advance 

 these remarks as a solution of the esker question. At the same 

 time, I submit that the circumstances are deserving of some attention 

 when the question is as to the way or ways in which the typical 

 eskers have been formed. However much we may feel inclined to- 

 prefer the explanations offered by Hummel and Geikie, we cannot,. 

 I fancy, yet afford to discard in its entirety the principle so ably 

 worked out by Kinahan. That there is a ridge-forming power in 

 the flow-tide action of the great ocean — when the current meets- 

 some object sufficient to part it in the shallower waters near the 

 coast — we can see for ourselves in such instances as I have just 

 cited. That the eskers, properly so-called, are mainly confined to 

 the zone which may be regarded as a continuation of Galway Bay 

 is, to my mind, a circumstance more easily reconcilable with 

 Kinahan's than with Geikie's later theory. Yet I do not regard 

 this aspect of the question as by any means fatal to the principle 

 propounded by the latter. If we have not typical eskers outside the 

 midland zone we have at least their ruins, and these in plenty, in 

 the counties of Monaghan, Tyrone, Fermanagh, Mayo, etc. ; that is r 

 we have such heaps, mounds, and flats as would be produced by the- 

 partial dispersion of a true esker ridge. In whatever way we may 

 suppose the ridge to have been produced we can see that there were 

 many chances against survival in the perfect form. That so many 

 have withstood ' the shocks of time and chance ' is rather wonder- 

 ful ; for hardly less curious or less puzzling than their origin is the 

 question as to the conservation of so many eskers in Ireland and of 

 corresponding ridges in other countries. 



Thomas Fitzpatkick.. 



St Ignatius' College, 

 Galway. 



