Mr. Cowham's Address 289 



other evidences of still mightier internal 

 forces already observed but not specially 

 mentioned: the tilting of the successive 

 rock forms already passed — Chalk, Green- 

 sand, Gault, Folkestone and Hythe beds, 

 the uplifting of the Chalk mass from the 

 oceanic bed to 1000 feet above sea-level — 

 these evidences of movement are recalled, 

 and all are associated with one and the same 

 cause, viz. that of the shrinking of the 

 earth crust and consequent development of 

 heat and the expenditure of internal force. 



2. The view from Tilburstow Hill over the Weald and 



the distant view of the South Downs stimu- 

 late the imagination to bridge over the area 

 with those successive masses of rock strata 

 which have been slowly but surely removed 

 by surface weathering. The successive rock 

 forms passed over in the walk from Cater- 

 ham may be found at the base of the South 

 Down in Sussex. They face each other still ; 

 though thirty miles of Weald to-day separ- 

 ate them, they were originally connected; 

 every year they become removed farther 

 apart. These are the reflections which ob- 

 servation stimulates. 



3. An attempt is now made to solve one of those 



difficulties which thirty years ago perplexed 

 the writers of our physical geographies. The 

 rivers Kennet, Mole, and Medvvay, rising in 

 the Weald, appear to break through the 

 North Downs on their way to join the 

 Thames. We were told that they dashed 



