216 James Geikie — On Changes of Climate. 



where are their remains ? and where in Scotland do we meet with 

 deposits like those of the Thames and other English valleys ? The 

 Scottish post-glacial deposits have yielded relics only of Arctic and 

 northern species, and these, as we trace the drift-beds upwards into 

 recent accumulations, gradually give place to the present fauna. The 

 condition of Scotland after the re-elevation of the land in post-glacial 

 times became suited to the wants of reindeer and their northern 

 associates, but certainly not to those of the hippopotamus and his 

 congeners. Nor can it be for one moment supposed that while 

 Arctic conditions obtained in Scotland, a mild and genial climate 

 characterized England. 



I might therefore rest the case simply upon this question of post- 

 glacial climate, — the presence of hippopotamus betokens a mild and 

 genial winter : no such genial climate has intervened since the close 

 of the Glacial epoch ; therefore the hippopotamus cannot possibly 

 have lived in Britain in post-glacial times. But the purely geological 

 evidence seems not only not against but positively in favour of this 

 conclusion. The mere intermingling of Arctic and southern forms 

 in the same river-deposit cannot be considered a difficulty. No one 

 who has studied the formation of river sands and gravels will fail 

 to see how fossils entombed at widely-separated intervals may come 

 to occupy the same level. Kivers are constantly cutting down 

 through their own deposits, and again filling up the excavations 

 they make. In this way gravel and sand are banked against similar 

 beds" which may belong to a much greater antiquity ; and the line 

 of junction it is often impossible to determine — the one deposit 

 seeming to shade into the other. 



Nor need the absence of the mammalia from the interglacial beds 

 of the north-west and east of England surprise us. For, in the first 

 place, these beds are of marine formation, and every one knows how 

 rarely remains of land animals occur in such deposits ; and, in the 

 second place, it is unlikely that the marine interglacial beds referred 

 to were laid down at a time when the large mammalia inhabited 

 Britain. When the cold of any particular Arctic period had reached 

 its climax, and a thick sheet of ice overflowed Scotland and a great 

 part of England, it is quite impossible that any portion of Britain 

 could have been tenanted by the large mammalia. Even the 

 tichorhine rhinoceros and the mammoth must have gone south. 

 Again, when the cold had passed away, and the climate was getting 

 temperate, our country could only have become populated by means 

 of a land communication with the continent. It may, therefore, be 

 inferred that during the warm interglacial period or periods, when 

 the hippopotamus and its southern associates visited these latitudes, 

 our country formed part of the continent, and consequently that the 

 marine deposits then thrown down are even yet covered by the 

 waters of the ocean.^ The records of past time are preserved chiefly 



1 This conclusion receives strong support from the views advocated by Adhemar, 

 CroU, and others, concerning the effect likely to be produced upon the level of the 

 ocean in our hemisphere by the presence of a great ice-cap at the antipodes. During 

 a cold period in the southern hemisphere there would be a tendency to an increase 

 of land-surface here — an increase, however, which we have at present no certain 

 means of estimating. 



