66 



The Irish Naturalist. 



April, 



evidence of floating ice. The fact that none has been 

 observed in Ireland may be due to defective observation, 

 to complete removal by denudation or to the fact that it 

 now hes below sea -level. At any rate it has not been found, 

 and we are left with a mere presumption that the post- 

 Neolithic warping only represents in part the total post- 

 Glacial warping. 



We can get an idea of the total amount of post -Glacial 

 warping which might reasonably be expected, in this way. 

 In Scandinavia the late Glacial and Early Neolithic shore- 

 lines are well known. Let us take a place which in its 

 position relatively to the Scandinavian centre of glaciation 

 corresponds roughly with that of Lough Neagh to the 

 Scottish centre. Christiania or Stockholm would do equally 

 well. At these places the gradient of the late Glacial 

 shoreline is about two and a half times that of the Neolithic 

 or Littorina-Tapes shoreline. Applying this ratio to the 

 case of Lough Neagh we get a gradient of five inches to 

 the mile for the total post -Glacial warping, and this would 

 correspond to a submergence of five feet at the southern end 

 of the lake. We are clearly still a long, wa}^ from Canon 

 Lett's figure, but it is interesting to see that the amount 

 of post -Glacial warping recorded on the shores of Lough 

 Neagh ought to be considerably greater than that which 

 can be seen to affect the Early Neolithic raised beach around 

 our coasts. 



It would be easy to apply a test to Lough Neagh to see 

 if its basin has really been affected by post -Glacial warping. 

 It is found that if we join up the points where the Neolithic 

 beach has the same altitude above high -water mark through- 

 out Ireland, England, and Scotland, we obtain elliptical 

 curves circling round the south-western Highlands of Scot- 

 land, i.e., round the most powerful centre of glaciation in 

 later Glacial times. These are called isobases, and it is 

 obvious that the isobase which passes through the outlet 

 of Lough Neagh ought, if it crosses the lake, to divide it 

 into two portions, one of which, to the north of the line, 

 ought to show traces of emergence of the land, and the other, 

 to the south, only submergence. This isobase separates off 

 Antrim Bay from the rest of the lake. One would therefore 



