August, 1 92 1 



The Irish N aturalist. 



85 



THE POST-GLACIAL CLIMATIC OPTIMUM IN 

 IRELAND. 



BY J. DE W. HINCH. 



When it was decided to arrange the palaeontological col- 

 lections of the Geological Survey of Ireland on more modern 

 museum lines, the Estuarine Clays of the north-east of- 

 Ireland were among the first sections to be dealt with. Apart 

 from the decision to give them a more definite representation 

 in the succession of the geological deposits of Ireland, a 

 representation to which they are undoubtedly entitled in 

 the opinion of every geologist who has seriously studied 

 them, it was thought desirable to bring out as clearly as 

 possible the fact that the present distribution of the marine 

 mollusca contained in the clays, points to a warmer climate 

 at the time of their formation, than that existing in the same 

 locality at the present day. The present paper is a pre- 

 liminary and tentative effort in this direction. 



The shells from the Estuarine Clays have long been 

 famous among conchoiogists on account of the very perfect 

 condition in which they are found ; the material in which 

 they are buried, a fine tenacious clay, having preserved the 

 colour, glaze and sculpturing to such an extent that it is 

 often almost impossible to distinguish many of the Estuarine 

 Clay fossils from modern specimens collected on the sea- 

 shore. These Estuarine Clays have been studied from time 

 to time by conchoiogists, among others by Grainger, Thomp- 

 son, Hyndman and Stewart, and more especially by Stewart, 

 but the most definite contribution made regarding their 

 geological importance occurs in two papers, written in 1892^ 

 and 1896^ by R. LI. Praeger, better known to the scientific 

 world as a botanist, the author of " Irish Topographical 

 Botany " than as a geologist. 



^R. LI. Praeger : The Estuarine Clays of N.E. of Ireland, Proc. Roy. 

 Irish Acad., Series 3, vol. ii, 189 1-3. 



2R. LI. Praeger : The Raised Beaches of N.E. of Ireland, with special 

 reference to their fauna, Proc. Roy. Irish Acad., Ser. 3, vol. iv, i8c6-8. 



