the Weald. 337 



Chalk rises in bold escarpments, forming what are 

 known as the North and South Downs. On the east 

 it is bounded by the sea. There can be no doubt that 

 the Chalk and the underlying formations of Upper 

 Greensand, Gault, Lower Greensand, and Weald Clay 

 originally extended across all the area of the Weald for 

 a breadth of from twenty to forty miles from north to 

 south, and nearly eighty from east to west (figs. 7 1 and 73). 

 This vast mass, many hundreds of feet thick, has been 

 swept away, according to an opinion formerly universal 

 among geologists, by the wasting power of the sea, but., 

 I believe, chiefly by atmospheric agencies ; so much so, 

 indeed, that I am convinced that all the present de- 

 tails, great and small, of the form of the ground, are due 

 to the latter. The result is, that great oval escarpments 

 of Lower Greensand, and outside of that of Chalk sur- 

 rounding the Wealden area, rise steeply above the 

 nearest plain, which is composed of the Weald Clay, 

 from beneath which the Hastings Sands crop out, form- 

 ing a central nucleus of hilly ground, in the manner 

 shown in the following diagram, the height of which is 

 purposely exaggerated so as to bring the features pro- 

 minently before the eye. 



N FIG. 71. s 



a a Upper Cretaceous strata, chiefly Chalk, forming the North 

 and South Downs ; b b escarpment of Lower Greensand with a 

 valley between it and the Chalk ; c c Weald Clay, forming 

 plains ; d hills formed of Hastings Sand and Clay. The Chalk, 

 &c. once spread across the country, as shown in the dotted 

 lines. 



Let us endeavour to realise how such a result may 

 z 



