^pp 



the Weald. 345 



certain fragmentary outliers described by Professor 

 Prestwich. These by some persons have been supposed 

 to be outliers of the Lower Eocene strata, called the 

 Woolwich and Keading beds, but Professor Prestwich 

 considers them to belong to part of the Crag. The 

 physical evidence seems to me to be in favour of the 

 former. 



If they belong to any part of the Eocene series, 

 then, as they lie as it were accidentally conformably 

 on the Chalk, they were evidently affected by the dis- 

 turbance that raised the Wealden into an anticlinal curve, 

 and depressed the Chalk and overlying Eocene beds 

 into the now divided synclinal curves of the London 

 and Hampshire basins, and therefore, the beginning of 

 the chief denudation of the Weald, by which it gradually 

 assumed its present form, was post-Eocene. Under 

 these circumstances it is probable that the Eocene beds 

 themselves were cut across during the gradual formation 

 of the plain of marine denudation. On the other hand, 

 if the outliers on the' Chalk escarpment west of Folke- 

 stone be parts of the Crag beds, then it is possible that 

 strata of the Crag may have been deposited upon that 

 plain, and found their way into those isolated petty pot- 

 holes in which the fossils were found, and in that case 

 the bay-like denudation of the Weald has probably 

 taken place since that epoch, implying a lapse of 

 time so long, that by natural processes alone, nearly 

 half the marine mollusca, and probably nearly all the 

 terrestrial species of mammalia of the world, have dis- 

 appeared and been slowly replaced by others. This 

 may mean little to those who still believe in the 

 sudden extinction of whole races of life ; but to me 

 it signifies a period analogous to the distance of a 

 half-resolved nebula, the elements as yet being wanting 



