372 WEALD, WHEN DENUDED. [Ch. XIX, 



It was long ago observed by Dr. Mantell that no vestige of the 

 chalk and its flints has been seen on the central ridge of the "Weald or 

 on the Hastings Sands, but merely gravel and loam derived from the 

 rocks in situ in the neighborhood. This distribution of alluvium, 

 especially the absence of chalk-flints in the central district, agrees 

 well with the theory of denudation before set forth ; for by referring 

 to fig. 356 (p. 358), the reader will see that had the chalk (No. 2) 

 been once continuous, and covered everywhere with flint-gravel, 

 this gravel would be the first to be carried away from the highest part 

 of the dome long before any of the gault (No. 3) was laid bare. 

 Now, if some ruins of the chalk remain at first on the gault, these 

 would be, in a great degree, cleared away before any part of the lower 

 greensand (No. 4) is denuded. Thus in proportion to the number 

 and thickness of the groups removed in succession, is the probability 

 lessened of our finding any remnants of the highest groups strewed 

 over the bared surface of the lowest. 



But it is objected, that, had the sea at one or several periods been 

 the agent of denudation, we should have found ancient sea-beaches 

 at the foot of the escarpments, and other signs of oceanic erosion. 

 As a general rule, the wreck of the white chalk and its flints can 

 only be traced to slight distances from the escarpments of the North 

 and South Downs. Even where exceptions occur, and where flints 

 are seen two or three miles from the nearest chalk, they are so angular 

 as to be regarded by many as indicating fluviatile rather than marine 

 denudation. Without wishing to gainsay the doctrine that many of 

 the last superficial changes of the Weald may have been due to rain 

 and rivers, combined with successive upheaval and depression of land, 

 I may, nevertheless, remind the reader that, in the absence of organic 

 remains, it is often impossible to distinguish between gravel formed 

 in the bed of a river and that which accumulates on a sea-beach. 

 For if we examine the broken flints at the base of a cliff, in places 

 where they are not peculiarly exposed to the continuous and violent 

 action of the waves, we may observe that they retain much angularity. 

 This may be seen between the Old Harry rocks in Dorsetshire and 

 Christchurch in Hampshire. Throughout the greater part of that 

 line of coast the cliffs are composed of tertiary strata, capped by a 

 dense covering of gravel formed of flints slightly abraded. As the 

 waste of the cliffs is rapid, the old materials are gradually changed for 

 new ones on the beach ; nevertheless we have here an example of 

 angles being retained after two periods of attrition ; first, that during 

 which the gravel was spread originally over the Eocene deposits ; and 

 secondly, when the Eocene sands and clays were undermined and the 

 modern cliff and sea-beach formed. As to the angularity of the flints, 

 it has been thought by some authorities to imply great violence in 



in Post-pliocene times, availing myself of the maps and memoirs of Mr. Trimmer, 

 Mr. Godwin- Austen, and others. 



