James Geikie — On Changes of Climate. 165 



this conclusion appears inevitable, for, as Sir John Lubbock remarks, 

 " Even if protected by fur, as Mr. Prestwich supposes, the animal 

 could never live in a country where the rivers were frozen over. ' 

 I shall therefore not attempt to discuss this hypothesis further, but 

 will confine v/hat remarks I have to make to the two theories referred 

 to above. The latter of these — that, namely, which supposes a period 

 of strongly contrasted summers and winters to have prevailed during 

 the deposition of the English valley -gravels and cave-accumulations 

 — has lately been ably advocated by Mr. Dawkins, who has brought 

 to the task a wide knowledge of the subject. His case is stated 

 with great clearness, and he seems to have employed all the argu- 

 ments that can be adduced in its favour. Yet I cannot see my way 

 to accept his conclusions. Had these conclusions followed from a 

 consideration of palesontological evidence alone, I should hardly 

 have ventured to dispute the position maintained by one who has 

 devoted so much time to this special study ; the question, however, 

 is one chiefly of climate and physical conditions. 



By noting all the localities where our superficial deposits have 

 yielded remains of the Quaternary mammalia, he has shown ^ that 

 these fossils are confined to the low-lying districts of England ; and 

 he accounts for their absence from the Post-giacial beds of Wales, 

 the north of England, and Scotland by supposing that these regions 

 were covered with ice at the time that the mammalia were in full 

 occupation of Central and Eastern England. At this period Britain 

 was connected across the bed of the German Ocean and the English 

 Channel with the Continent, and he explains the intermingling in 

 the same deposits of hippopotamus and other southern forms with 

 those of an Arctic fauna, by supposing that in " summer-time the 

 animals now only found in the warmer regions migrated north- 

 wards, and in winter-time those now found in the Arctic regions 

 went southwards." Sir Charles Lyell had previously suggested that 

 the hippopotamus might have been a summer visitant only; and 

 this, Mr, Dawkins says, is the only " hypothesis that satisfies all the 

 conditions of the problem." 



But does it really do so? What kind of climate, let us ask, would 

 be likely to result were Scotland and the mountainous districts of 

 England and Ireland to be covered with snow and ice ? Mr. Daw- 

 kins thinks that it would be " somewhat similar to that of the vast 

 plains of Siberia extending from the Altai Mountains to the Arctic 

 Sea, or to that offered by the iuland climate of North America. In 

 Siberia," he continues, " we meet with every gradation in climate, 

 from the temperate down to that in which the cold is too severe to 

 allow of the growth of trees, which gradually decrease in size as the 

 traveller passes northwards, and are replaced by the grey mosses 

 and lichens of the low marshy tundras. Throughout the north the 

 winter cold is intense, and in the southern portion is almost com- 



1 Quart. Journ. Ge&l. Soc.^, vol. xxv., p. 192. Mr. Dawkins has fui-tlier explained 

 and illiistrated his views in a paper, " On Pleistocene Climate and the Relation of 

 the Pleistocene Mammalia to the Glacial Period." — Popular Science Review for 

 October, 1871. 



