638 Scientific Proceedings, Royal Dublin Society. 



"Foot hills" has not as yet been satisfactorily explained; it is, 

 however, evident that they are adjuncts of rivers from an alpine 

 region- They die out as the lower open valley is reached, while 

 elsewhere they are connected with greater or less flats. As their 

 different characteristics are common both to the present Canadian 

 and these ancient Irish river valleys, it seems not improbable that 

 the terraces in both had a common origin. 



It may be pointed out that the term "Esker gravel" seems 

 to be getting very mixed. " Esker gravel " — proper — is the 

 gravel due to the action of the "Esker sea" that once occupied 

 the central plain of Ireland. Now, however, both in Ireland 

 and America the term is being applied to all gravels if heaped up 

 in ridges. This in one sense is correct, as all are " eskers," i.e. 

 ridges; but the term ought to be restricted to marine gravels. 

 This is not the case in the Co. Fermanagh, or in different places 

 in the United States of America, where drift called eskers or 

 kams is evidently either of fluvial or glacial origin. Such, it 

 would appear, was the origin of most of the gravels of Fermanagh 

 and western Tyrone. But in south-east Tyrone it would appear 

 as if the " Esker sea" came into some, at least, of the valleys, thus 

 causing a blending of the Esker sea and the glacial gravels. A 

 similar phenomenon may possibly also have taken place in the 

 lower levels in the Co. Fermanagh, as the surface of Lower 

 Lough Erne is about 150 feet over ordinary low water in Donegal 

 Bay. 



