140 PREHISTORIC EUROPE. 



5. During the prevalence of cold climatic conditions the 

 erosion of valleys would proceed at a more rapid rate than is 

 the case in our latitude at present, and any calculation of the 

 antiquity of Pleistocene fluviatile deposits which should be based 

 upon the rate of denudation now in progress would most pro- 

 bably be exaggerated, not necessarily to such an extent, however, 

 as might at first sight appear ; for, during the milder periods, or 

 period when hippopotamuses lived in the north of England, de- 

 nudation would proceed less rapidly than when the climate 

 was arctic, and thus the one rate might to a certain extent 

 balance the other. 



But while it may be admitted that the views so ably ex- 

 pounded by Mr. Prestwich are capable of a wide application, 

 and will explain the phenomena presented by the Pleistocene 

 valley-gravels throughout Europe generally, yet they fail to 

 account for the origin of certain gravelly accumulations which 

 have yielded both mammalian remains and Palaeolithic imple- 

 ments. I refer to those sheets of coarse gravel and detritus 

 which spread often continuously over wide districts in Southern 

 England. They are not confined to valley- slopes, but sweep up 

 and over hill- tops, valley -partings, and watersheds ; extend 

 across plateaux and platforms between separate valleys ; and, in 

 short, bear little or no relation to the present drainage-systems 

 of the country. It is not possible that those gravels could have 

 been laid down by rivers in the process of deepening their 

 valleys, — their distribution and general appearance show that 

 the surface had already received much of its present contour 

 before the deposits were scattered broadcast over the country. 

 I should mention that the deposits in question are frequently 

 very coarse and rudely bedded. They often show a confused 

 and tumbled appearance, consisting of sand, grit, angular debris 

 and blocks, and well-rounded stones, promiscuously heaped and 

 jumbled together. And what is particularly noteworthy, many 

 of the stones are often standing on end, and not lying in the 

 position they might have been expected to assume had they 

 been laid down by ordinary river-action. 



