208 ENGLISH CUALK DOWNS. 



tho wealden clays and sands that lie under its 

 bottom. Owing to this extraordinary denuding 

 action, the chalk ceases abruptly at the escarp- 

 ment of the North Downs, and reappears again 

 only near Brighton, having been worn away over 

 the entire intervening region by the gradual 

 power of the rain and streams. But once upon 

 a time the chalk must have spread uninterruptedly 

 from the one range of downs to the other across 

 what is now the deep valley of the Weald of 

 Sussex. 



It is to the same cause that we owe the very 

 peculiar rounded conformation of our existing 

 chalk downs. Indeed, the whole set of actions here 

 described is not something that once took place in 

 the remote past, but something that is still slowly 

 taking place everywhere around us at the present 

 moment. The chalk downs are still being per- 

 petually attacked and disintegrated by the rain, 

 and are still being everywhere unbuilt and lowered 

 and cut back farther and farther before our very 

 faces. Every shower that falls upon the chalk 

 slopes carries down in its drops carbonic acid in 

 solution; and the carbonic acid thus introduced 

 helps to dissolve the lime which forms the chalk, 

 rendering the water excessively "hard," as we 

 say of all water with an excessive quantity of 

 lime dissolved in it. The water and the lime 

 sink together down through the chalk, and come 



