36 Hie Irish Nahtralist March, 1922'. 



run for miles in lines so even and straight as to suggest rule measurement ! 

 And this condition is what one should expect on a level plain where the 

 face of the glacier should have an even and uniform shape, and deposit 

 its burden correspondingly, 



James G- Butler. 

 Garryhill, Bagnaisto^^n. 



The note by Mr. Butler on the Eskers in the neighbourhood of Mullingar, 

 Tullamore, and other localities in the central plain is a welcome indication 

 of interest in this complicated question, and his statement that alter 

 having had these deposits under observation for 15 years, he has not 

 found a shell fragment is m.ost important. It is v.ell known to those 

 who have done work in this direction, that the local conditions frr successful 

 collecting of Glacial mollusca vary very quickly, and that a good collecting 

 ground may be destroyed or overgrown in the space of a few years, and 

 that therefore continuous observation of the sections available, is of 

 primary importance. 



With certain other conclusions of Mr. Butler I do not find myself in 

 agreement. It is true that many books on the Ice Age contain maps 

 which show north-western Europe covered with an ice-cap radiating 

 from Scandinavia and extending from Cracow in the south-east to the 

 Atlantic ocean in the west. This map is a generalized statement of fact, 

 but while we may agree that Scandinavian ice reached south-east almost 

 to the Carpathians, it has to be borne in mind that the British Isles and 

 Ireland produced their own local ice-cap ; and that while the eastern 

 coast of England was invaded by Scandinavian ice, no Scandinavian ice 

 reached either Wales or Ireland. 



Regarding the proposal by Mr. Butler to consider the Eskers as the 

 Terminal Moraines of the melting ice-sheet, it m.ay be pointed out that 

 the terms " Esker " and " Moraine " are both well defined terms in 

 geology, and that it will only lead to confusion to regard them as inter- 

 changeable, and that while a few Eskers have been mistakenly classed 

 as Moraines and a few Moraines classed as Eskers, the number which 

 have to be transferred in either case is not great, and does not effect the 

 general bread division. It should also be remembered that any theory 

 of the origin of Eskers does not effect the relation, in the field, of Eskers 

 to Terminal Moraines, and that when high-pitched ridges of sand and 

 gravel trend at right angles or nearly right angles to the Terminal Moraine 

 they should be regarded as Eskers. If in any locality there are ridges 

 called Eskers, but composed to any marked extent of angular rocky 

 material, the view that they are Moraines rather than Eskers may be 

 reasonably held, and the relation of these ridges to the undoubted Eskers 

 should then be examined. 



J. DE W. HiNCH. 



Geological Survey, Dublin. 



