252 NATURAL SCIENCE [October 189% 
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, { 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 im 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, 
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 FITZPATRICK. 
St Ienatius’ CoLLEGcRE, 
GALWAY. 
