34 The Irish Naturalist. 



" rudder, which Professor Hull regards as interglacial, yield 

 11 abundant specimens of a fauna as arctic in character as any 

 "portion of the boulder clay." It is interesting also to find 

 that such a fragile shell as Lcda pygmcea is frequently found in 

 the boulder clay in a perfect state, with valves united, and 

 that in spite of the great number of shell fragments, perfect 

 specimens are frequently found under such conditions as pre- 

 clude the idea of transportation or re-deposition. 



The search for "foreign" rocks in the deposits is in itself of 

 surpassing interest, and the glacial geologist spends many 

 delightful hours in this exciting pursuit. We are watching 

 keenly for Scottish fragments, especially for the unique Ailsa 

 Craig eurite, which has been found at Greenore and Killiney 

 by Professor Cole, and at Greystones by Professor Sollas. It 

 is, however, possible that as the coalescence of British and 

 Scandinavian ice in the North Sea allowed Scandinavian erra- 

 tics to be found in Yorkshire and southwards, but not, as yet, 

 in Scotland, so the supposed meeting of Scotch and Irish ice- 

 sheets in the Irish Sea may have shunted the Scottish stream 

 south-eastwards, so that fragments from Ailsa may not have 

 reached our district — a suggestion which their presence in the 

 Moel Tryfaen deposits seems to favour; it is one of the problems 

 of modern glacial geology to account satisfactorily for the 

 transport of these fragments from their parent rock to their 

 Welsh resting-place, fully a thousand feet higher. 



Remembering that where we now find the greatest rainfall, 

 the glacial period was also most severe, we see in Ireland an 

 admirable field for inquiry, and in the Irish Naturalist a valu- 

 able medium for recording and publishing the results obtained. 

 Nor can we doubt that from lack of such a publication in 

 former times facts remained unrecorded, and important obser- 

 vations were lost to science (we must earnestly hope not irre- 

 trievably), that may now be given to its readers. Many un- 

 published glacial observations must exist that were made 

 incidentally by members of the Geological Survey, as well as 

 by individual geologists, perhaps working at other questions, 

 which we may surely hope to see gradually collected in these 

 pages, so that our Irish magazine may be the means of contri- 

 buting to the scientific world valuable information, and casting 

 new light upon the, as yet, unsolved problems of Glacial Geology. 



