the London and Hampshire Basins. 169 



that country, and he will be satisfied that drift of the real diluvial 

 character is not wanting to this, the barest part of the Wealden. 



The presence of these detrital masses, and the absence of the 

 remains of the higher strata on these elevated ridges, ought to 

 be received as corroborative proof of the community of character, 

 and the one and indivisible nature of these drifts of denudation. 

 It is to be remembered that thousands of feet of greensand, 

 chalk, and tertiary beds have been cast off from these elevated 

 ridges, and it is only wonderful that any fragments of their ruins 

 are still to be found in their vicinity. I venture to reassert, 

 then, my conviction, that a large and comprehensive view of the 

 arrangement of drift in concentric zones is agreeable to nature 

 and fact, from the patches of eocene to be found on the Hamp- 

 shire chalk down to the lowest beds of Hastings and Winchelsea ; 

 with such exceptions only as tend to confirm the rule. 



Of the absence of the usual mammal bones in the Wealden 

 zone of drift, I infer but little, but that little is of the affirmative 

 character. All the upper beds being removed, the greater the 

 chance that with them would be removed the remains of the 

 animals which died a natural death on the original surface of the 

 country, or of the surrounding countries, or which perished in 

 the catastrophe we contemplate. 



]\Iuch remains to be said in reference to the local arrange- 

 ments of drift ; the involved and tumultuous admixture of sands 

 and clays, the manufacture of brick-earths and loams on the 

 spot on which they are found, and the quasi stratified beds* 

 of sand and gravel,' and of the boulder clays which have been 

 swept into the great synclinals on either side ; but it is most 

 convenient to confine our attention at present to the central 

 and most simple, as well as the most illustrative part of our 

 subject. Of the fossil or diluvial wood, and trunks of trees 

 in situ amongst the gravel beds of Surrey, below the chalk, 

 spoken of by Sir Pt. Murchison (on the authority of Mr. Austen) 

 in attestation of " a true terrestrial surface " after the commence- 

 ment of the denuding sera, I cannot say that they do not exist ; 

 but I have looked into many gravel-pits there, and in the cor- 

 res])onding districts under the South Downs, and I have never 

 seen any wood in drift which was not of the most modern de- 



* I believe that man}' of these dihivial beds contain organic remains 

 derived from the latest tertiaries, broken up tempore denudationis. Such 

 rcinyins are supposed to be of pleiocene date, as assimilating to, or even 

 identical with, existing species. 



Specimens ol" this sort were shown to me by Mr. Mackie from the drift at 

 l"'oli<stone, and it was from some such semi-stratified deposit near Bognor, 

 I Huspect, that Lady Murchison took the shells spoken of by Sir Roderick. 

 (Jouru. Geol. Soc. vol. vii. p. .'571.) 



Phil. May. S. 1. Vol. 7. No. 41. March 1854. N 



