Changes in Geography and Climate. 45 



deep freezing. This led to enormous and rapid denudation, 

 over areas where the rain now sinks in and is slowly given 

 out as springs. Masses of loose flint and chalk debris were 

 swept off the South Downs and spread out in a wide sheet 

 extending several miles over the lowlands, and over the 

 Interglacial deposits already described. Even in Cornwall 

 the rubbly drift known as ' head ' seems to have marked a 

 similar stage. It is difficult to believe that anything but a 

 poor Arctic vegetation could have withstood these condi- 

 tions, and the Arctic plants of Devon may belong to this 

 cold epoch, rather than to the older one represented by the 

 erratics of Sussex and the Boulder Clay near London. 

 The Arctic mammals found near Salisbury may belong to 

 the same stage, they are migratory or else Steppe species. 



The stage that follows — the transition from the 

 Palaeolithic to the Neolithic — is unfortunately one of the 

 most obscure, and I can only suggest that the break is 

 more apparent than real, and that one follows the other in 

 close succession. No doubt there is generally a marked 

 difference between deposits of Palaeolithic and those of 

 Neolithic age, the older series occupying terraces far above 

 the reach of any flood, while the more recent series lie in 

 the bottoms, or below the bottoms, of existing valleys. It 

 may prove, however, that the climatic change and the 

 difference in the position of the deposits are related as cause 

 and effect, little change having really occurred in the 

 contours of the country. As soon as the climate amelio- 

 rated, frozen soil would no longer cause erosion and 

 deposition to act in the peculiar way above described. 

 The older deposits would be left stranded at all elevations, 

 and denudation and deposition would at once change to 

 the ordinary types caused by river action in a Temperate 

 climate. With the climate, the fauna and flora would also 

 change; and at the same time the race of hunters would 



