I9I2. ScHARFF. — Britannic Flora and Glacial Epoch. 107 



sank beneath the sea, till the depth of water over the 

 eastern coast of England was fully 500 feet, and over the 

 western nearly 1,400 feet, from which depression it slowly 

 recovered. After this statement, Professor Bonney dwells 

 on the difficulties involved in accepting either of these two 

 theories, and finally comes to the conclusion that while 

 the objections to the first or land-ice hypothesis are more 

 serious, he cannot as yet declare the other one to be satis- 

 factorily established. 



No one who has read Professor Bonney' s able address 

 can remain in a moment's doubt that the \dews represented 

 by Mr. Clement Reid of the nature of the Ice Age are highly 

 hypothetical. Hence the whole of the superstructure of 

 Mr. Reid's theory regarding the origin of the plant popu- 

 lation of the British Isles rests on an insecure foundation. 

 If the land-ice hypothesis is only the less probable of two 

 theories, what becomes of Mr. Reid's view^s of the Glacial 

 climate and the almost total destruction of the flora ? 

 If we had only local mountain glaciers and a subsequent 

 submergence instead of a vast mantle of ice and snow, no 

 wholesale destruction of the flora need have taken place. 

 It is conceivable even that under such conditions many pre- 

 Glacial plants could have survived the Ice Age in Ireland, 

 especially so in situations exposed to the influence of the 

 Gulf Stream on the western coasts. If the submergence 

 extended over all the western parts, the plants in low-lying 

 districts no doubt w^ould have been destroyed, whereas 

 they would have had a chance of surviving here and there 

 in the more elevated parts which had then become islands. 



To Mr. Reid, however, only one theory is possible, and 

 that is the prevalence during the Ice Age of an arctic 

 climate. It seems to him evident (p. 204) that a temperate 

 flora could not have survived the cold in Ireland. He does 

 not produce any botanical evidence in favour of this belief, 

 but in support of his contention that an arctic climate 

 prevailed over the British Islands, he directs attention to 

 the south of England, where leaves of the dwarf Arctic 



Bonney, T. G. : — Presidential Address. Report of British Association 

 Meeting at Sheffield in 1910, London, 191 ^ PP- 3-34- 



A 2 



