260 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 21, 



for the remarkable freedom from all admixture of pebbles of the older 

 rocks* in the enormous flint-pebble beds of the Lower Tertiaries. It 

 is to be observed also that we have no chert-pebbles, which may arise 

 from its more splintery structure, or from the sea not having en- 

 croached so far on the land as to have reached the cherty beds of the 

 lower greensand. 



Thus the changes in the remarkable area of the Weald appear to 

 date back to a period possibly far anterior to that even of the lowest 

 tertiaries. While, however, I am inclined to extend the action of the 

 subterranean forces acting along that axis to an epoch antecedent to 

 that at present assigned to it, I at the same time consider, with many 

 other geologists, that the chief disturbances are of comparatively re- 

 cent date. I cannot think that that denudation of the Weald which 

 tended to give it the present form, or even its main features, was co- 

 eval with a gradual elevation during the London Clay period, and that 

 the debris of the Wealden clays drifted out during this prolonged 

 denudation supplied the materials for this more important eocene 

 deposit. The denudation, or denudations, resulting in the present 

 peculiar structure of the Weald, I would rather place in the newer 

 pliocene and the post-pliocene periods f. Still, as before mentioned, I 

 believe that a portion of the Weald was elevated at the commence- 

 ment of the tertiary period, and that there was a long-continued and 

 gradual action of the sea on that coast (during probably a very slight 

 progressive subsidence), unaccompanied by the operation of any large 

 rivers from the land ; for the spread of the Thanet Sands appears to 

 have been eifected more by marine currents and tidal action than by 

 river transport, if we can judge by the facts stated above, that no 

 distinct fluviatile beds have yet been found in them, and that their 

 marine character is preserved over their entire area. Small streams 

 must necessarily have existed, but none of power sufficient to accu- 

 mulate distinct and independent groups of strata. 



The changes, therefore, which took place in the Weald during this 

 tertiary period were, I conceive, confined to the planing down of the 

 chalk and part of the greensand, whereby a large mass of strata was 

 removed from this area, — an operation which must have greatly faci- 

 litated the further changes which, at a later period, ended in pro- 

 ducing the existing striking configuration of the surface. 



These views with respect to the distribution of land and water at 

 this geological epoch are in some measure corroborated by the evi- 

 dence of organic remains, for it is curious that the fauna of the 

 Thanet Sands seems to indicate that the temperature of the sea in 

 this district was rather lower than at the subsequent period of the 

 London Clay. We cannot of course argue conclusively upon this 

 point, but, merely viewing the question generally, the limited number of 



differ from those of cbalk-flints around London. I hope he will shortly make 

 public the result of his researches on this subject. 



* Except a very few quartz-pebbles which may have come out of the chalk. 



t T do not here enter into the general question of the elevation of the Weald, 

 as that will form part of a paper on the " Drift " of the South of England, which 

 I hope at a future period to lay before the Society. 



