io6 The hish Natu7'alist. June, 



of our flowering plants — except in the case of a few arctic 

 and alpine species — must have been indeed impossible. 

 But are geologists really so unanimous in their opinion that 

 all Scotland and Ireland were buried under snow and ice 

 during the Glacial Epoch ? It has been truly remarked 

 that in all controversies, as time goes on, hypotheses are 

 apt to masquerade as facts. And this is a case in point. 

 The hypothesis of the destructive influence of the Glacial 

 Epoch or Ice Age is regarded by Mr. Reid and his followers 

 as no longer a mere theory, but a well-established fact. 

 Mr. Reid does not tell us that there is any doubt about 

 Ireland having been buried under vast masses of ice and snow 

 during the Ice Age, so that practically all vegetation was 

 wiped out of existence. 



And yet only a year before he opened this memorable 

 discussion at the British Association, the same illustrious 

 assembly listened to an eloquent Presidential Address which 

 ought to have had the effect of warning Mr. Reid that his 

 views of the Ice Age are altogether hypothetical. I am 

 alluding to Professor Bonney's address. Professor Bonney 

 was chosen President of the British Association at Sheffield 

 in 1910 on account of his distinguished services in the field 

 of geology. And since he made his reputation principally 

 by his contributions to Glacial geology, surely his opinions 

 are worthy of serious consideration. The main interest in 

 his address lies in the fact that it is devoted to the dis- 

 cussion of the origin of the Glacial deposits. 



There are only two theories, according to Professor 

 Bonney, which interpret all the phenomena involved. 

 One asserts that throughout the Glacial Epoch the British 

 Isles generally stood at a level higher than at present, so 

 that the ice which almost buried them flowed out on to 

 the beds of the North and Irish Seas. The boulder-clays 

 represent its moraines. The stratified sand and gravels 

 were deposited in lakes formed by the rivers w^hich were 

 dammed up by the ice -sheets. 



The other theory recognises the presence of glaciers in 

 the mountain regions, but maintains that the land, which 

 at the outset was rather above its present level, gradually 



