192 1. HiNCH — Post-Glacial Climatic Optimum in Ireland. 87 



contains the results of the studies of European and American 

 botanists and geologists on the post-Glacial fluctuations of 

 climate, and the evidence derived from many divisions of 

 the animal and plant world is there collected and discussed. 

 In the British contribution on the subject the attitude is 

 taken up that the evidence of fluctuation of climate since 

 the close of the Ice Age is so confused and unequal in quality 

 that an explanation may be found in local changes of 

 physiography, and the effect of the strength and directions 

 of the prevailing winds, rather than in a great secular 

 change effecting considerable areas of the world, and that 

 on the whole the post-Glacial deposits have been accumulated 

 during a progressing improvement of climate. The only 

 works mentioned in the British contribution are those of 

 James Geikie and F. J. Lewis on the forest-beds in Scotland 

 and northern England, and as there appears to be consider- 

 able difference of opinion as to the value to be assigned to 

 this particular type of evidence, it is a very great pity that 

 the marine mollusca of the Estuarine Clays of the north- 

 east of Ireland were not also mentioned, and the reasonable 

 deductions from the then more northern distribution of 

 many southern species, of a post-Glacial improvement of 

 climate, discussed. It will be desirable now to give in a 

 very general way the results collected by the Executive 

 Committee of the Eleventh Geological Congress regarding 

 the post-Glacial rise in temperature, or, to use the more 

 official phrase, the post-Glacial Climatic Optimum. 



In this work the most important investigations and 

 contributions have been made by Scandinavian scientific 

 men, and the predominent position occupied hy the geolo- 

 gists and botanists of Norway and Sweden, and to a lesser 

 extent by those of Denmark, in the study of these post- 

 Glacial phenomena is easily explained by a consideration 

 of the geological formation of these countries. In Norway 

 and Sweden especially, the attention of scientific students 

 can only be directed to two considerable geological epochs^ — 

 the ancient floor formed of Archean and very early Palaeozoic 

 rocks, and the over-tying cover of the Pleistocene series, 

 consisting of boulder-clays, glacial sands, gravels, and silts, 



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