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 district, or Forest 
ridge. It is rare, indeed, to see any wreck of 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. 71. 
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. 6, 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 
'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 
thia section. 
