494 Proceedings of the Royal Irish Academy. 



at Kew Gardens they are obliged to winter tte collection in frames, 

 thus exposing them to a higher temperature than what at present 

 obtains in the British Islands. It seems to me probable, therefore, 

 that the extensive migrations of Alpine and Arctic plants, which un- 

 doubtedly took place in past ages, did occur long before the Glacial 

 Period, during a milder and more equable epocli, and that they have 

 since become adapted to live in countries where they receive sufficient 

 moisture during summer and are protected from severe frost in the 

 winter by a cover of snow. 



I believe that neither the animals nor the plants which have 

 been discovered in British Pleistocene strata indicate the presence 

 of an Arctic climate in the British Islands during the so-called 

 •'Ice Age." The theory of a general glaciation of these islands — 

 the south of England excepted — has, however, been so universally 

 accepted by geologists, that it has almost passed the stage of con- 

 troversy, and is more generally regarded as an established fact. I 

 am not sure whether even those who are in favour of the view 

 of the marine origin of the boulder-clay, disbelieve in a previous 

 general glaciation. Yet it is not long ago that the generally 

 accepted view was that all the plienomena now attributed to land- 

 ice had been produced by the action of floating icebergs, Tbe 

 rock-scorings, " crag and tail," boulder-clay, scratched stones and 

 drumlins were all believed to be due to the action of the sea 

 assisted by floating ice. 



I will not, however, venture to discuss this extremely intricate 

 subject of land ice versus floating ice, and hope that geologists may 

 t hink fit to reconsider their final verdict in the light of the con- 

 clusions I arrived at from a study of the geograpliical distribution 

 of animals. 



There is one factor of importance in connexion with this theory 

 of an ice-sheet, which may throw some light on the subject, and 

 that is, the configxiration of Ireland during the Glacial Period. Mr. 

 Close remarks (17, p. 241): "Some sufficient increase of relative 

 height towards the west or "W. S. ^ ., with a corresponding extension 

 of the land in that direction, is required, if we are to account for 

 the general glaciation of Ireland by the movements of a univer- 

 sal ice-covering formed upon her own surface"; whilst Prof. Bonney 

 seems to think that the coast margin in the earlier part of the 

 Glacial Period may have roughly corresponded with the present 

 hundred-fathom Line {10 a p. 194). The land-connexion between 

 Scandinavia, Scotland, and Ireland formed, as we have seen, a 



