296 EOCENE PERIOD. [Ch. XXI. 



is often entirely wanting on the surface of the clay at the foot 

 of the chalk escarpment, and no traces of chalk flint have ever 

 been found in the alluvium of the central c v 'net, or Forest 

 ridge. It is rare, indeed, to see any wreck 01 the chalk, even 

 at the distance of two or three miles from the escarpments of 

 the North and South Downs. To this general rule, however, 

 an exception occurs near Barcombe, about three miles to the 

 north of Lewes., where we obtain the accompanying section *. 



No. /I. 



Section from the North escarpment of the South Downs to Barcombe, 



1, Gravel composed of partially-rounded chalk flints. 



2, Chalk with and without flints. 



3, Lowest chalk or chalk marl (upper green-sand wanting). 

 4 ; Gault. 5, Lower green-sand. (j, "Weald clay. 



It will be seen that the valley at the foot of the escarpment 

 extends, in this case, not only over the gault, but over the 

 4 lower green-sand'' to the Weald clay. On this clay a thick 

 bed of flints, evidently derived from the waste of chalk, re- 

 mains in the position above described. 



We say that there is no detritus of the chalk and its flints on 

 the central ridge of the Weald. I have sought in vain for a 

 vestige of such fragments, and Mr. Mantell, who has had 

 greater opportunities of minute investigation, assures me that 

 he has never been able to detect any. Now whether we embrace 

 or reject the theory of the former continuity of the chalk and 

 other groups over the whole space intervening between the 

 North and South Downs, we cannot certainly imagine that 

 any transient and tumultuous rush of waters could have swept 

 over this country, which should not have left some fragments 



* The author visited this locality with Mr. Mantell, to whom he is indebted for 

 this section. 



