176 THE BOOK OF NATURE STUDY 



In the south the Arun and Ouse are gaining on the Adur, while 

 the Cuckmere has been reduced to little more than a single trans- 

 verse stream. The balance between even the north-flowing and 

 south-flowing streams does not appear to have been yet reached, 

 for to the south the Arun seems to be gaining at the expense of 

 the Wey and Mole, and to the north the Medway at the expense 

 of the Ouse and Cuckmere. 



Some such process of river development, dating back to the first 

 making of the arch and the emergence of it from the sea in which the 

 Chalk was formed, seems to account for the principal facts of the 

 case ; the outward radiation of the rivers, their neglect of the 

 now easy path in the great valleys, their passage through the 

 hard rock ranges, the gorges which they cut through them, their 

 low head-waters, and the fact that the ranges attain a greater 

 altitude than the present height of Crowborough and its associates. 



