170 James Geikie — On Changes of Climate. 



When we come to ask wliy our cave-deposits have so frequently 

 been relegated to Post-glacial times, we get no satisfactory answer. 

 If we put out of consideration the upper layers in certain cave- 

 deposits, there is really nothing in the bone-earths and breccias to 

 limit the age of these accumulations to such a recent period. Ac- 

 cordingly, many geologists have been of opinion that the mammalian 

 remains occurring in the caverns were introduced at various epochs, 

 and may belong to Pre-glacial equally with Post-glacial times. 

 Buckland thought that tlie great mammals existed in Britain before 

 the period of the Diluvium or Drift, and his belief is shared by 

 Mr. Godwin-Austen and some of our leading geologists. Professor 

 Eamsay is decidedly of opinion that "caves such as those in which 

 mammalian remains occur must have existed in Pre-glacial times, 

 and therefore it would be strange," he adds, '' if none of those ex- 

 plored contained Pre-glacial remains." But between Pre-glacial and 

 Post-glacial times there intervened several mild inter-glacial periods, 

 during which, as I have showti, the climate in Scotland was suited 

 to the wants of the mammoth, the reindeer, the Irish deer, the urus, 

 and the horse ;^ and I have also pointed out that, so far as geological 

 evidence is concerned, there is nothing to show that some inter- 

 glacial periods may not have been warm enough to cause all the 

 snow and ice to vanish from Britain. If such was the case as 

 regards Scotland, England must have been characterized by similar 

 climatal conditions. It is therefore not necessary to suppose that 

 any large portion of the bone-deposits was Pre-glacial ; for during 

 inter-glacial periods the caves would form dens for wild beasts, just 

 as they must have done in pre-glacial times. To some such mild 

 and genial inter-glacial period or periods I would refer the hippo- 

 potamus and the other southern forms met with in English caves. 

 The conditions under which these animals lived need not have been 

 comparable to those that characterize the tropics. All that we are 

 entitled to infer is that the winter temperature of Britain during 

 certain inter-glacial periods must have been mild and genial. It is 

 by no means necessary to suppose, however, that the summers were 

 much warmer than they are now. An equable and genial climate, 

 with no great difference between the seasons, would nourish an 

 abundant vegetation, and render the country habitable for a prolific 

 mammalian fauna. 



But it will be objected to this view that the species just referred 

 to occur also in the river-gravels of England. After carefully con- 

 sidering the evidence, however, there seems to me not only no 

 proof that all these older river-gravels are of Post-glacial age, but, 

 on the contrary, many considerations induce to the belief that such 

 is almost a physical impossibility. 



1 Remains of the Irist deer and the horse were obtained in the inter-glacial beds 

 at Crofthead, -which yielded the skull of urus. Besides these fossils there were 

 other fragments of bone, which my friend, Professor Young, has under examination. 



( To be continued in our next number.) 



