0)i British Drifts and the Interghwial Problem. 309 



part of the North Sea basin just before the g-reat g-laciation ; 

 and they therefore enable us without interruption to continue 

 the history beg'un in East Anglia. 



The old chflf of chalk and the marine beach at its foot which 

 lie buried at Sewerby, on the southern side of F"laniborouifh 

 Head, under sheets of boulder-clay and g-ravel, prove to us that 

 at the very beg-inning- of glacial times the North Sea still held 

 possession of its basin, and with a surprisingly slig'ht difference 

 from its present level. A few far-transported stones in the old 

 beach denote that ice-floes sometimes drifted southward into 

 Holderness Bay ; while the bones of animals in the shingle, 

 and in the blown sand which overlies it, prove that amongf 

 the denizens of the neighbouring land were the elephant 

 {E. antiqniis), rhinoceros {R. leptorhinus), hippopotamus 

 {H. ainphibius), and bison. This fauna is frequently considered 

 to be proof of mild conditions of climate ; but from the mode of 

 its occurrence in this and other places, I can find no reason 

 to doubt that these animals inhabited the country, perhaps as 

 seasonal migrants, until the time that it was actually covered 

 by the encroaching ice-sheets. 



And here I may note my opinion, that throughout the 

 discussion of our glacial deposits too much weight has been 

 allowed to the deductions regarding- climate based upon scanty 

 indications afforded by the ancient fauna and flora. We know 

 little regarding the range of adaptability possessed by the forms 

 in the past, and can judge only from their present habitat, 

 which is generally g-overned by many other factors besides 

 climate ; moreover, it is granted that species already estab- 

 lished when subjected to gradual change, will persist for long- 

 under circumstances that would have effectively barred their 

 introduction. In the Upper Zambesi Valley last year I was 

 more impressed with the cold of the nights than with the heat 

 of the days ; and even at that latitude the sturdy hippopotamus 

 in his noctural raids must experience a temperature occasionally 

 descending below freezing-point. 



It took us long to break away from the established convic- 

 tion that the fossil elephant and rhinoceros could not have 

 existed in a cold climate ; and the same conviction still lingers 

 with respect to their companion, the hippopotamus. But the 

 far-travelled stones in the Sewerby beach and in the beaches of 

 the same age in the south of Ireland are evidence that the 

 British seas were already cold enough to carry ice-floes while 

 these large mammals still tenanted the land. 



1906 September i. 



