1854.] AUSTEN — LAND-SITRFACES BENEATH DRIFT. 113 



old surface, — and that it was in mud and silt of this age that the 

 nearly perfect skeleton was found on the Pease Marsh, as was also 

 the other of the parallel valley of the River Mole. As the great end 

 to which geological inquiry is now tending is that of the past physi- 

 cal conditions which the earth's surface has undergone, and as the 

 value of such inferences is wholly dependent on the accuracy with 

 which observed facts may have been described, I am desirous of 

 adding to the instances I before adduced respecting this ancient ter- 

 restrial surface, more particularly as the facts referred to have been 

 represented in another way by Mr. P. J. Martin, in his "Additional 

 Observations on the Anticlinal Line of the London and Hampshire 

 Basins," published in the Philosophical Magazine, March 1854. 



With reference to the phaenomena of the Wealden area, considered 

 physically, Mr. Martin is of opinion that ** the key to the whole is in 

 the conception of the cotemporaneity of upheaval and denudation," 

 and that '* there is no drift that is not of the age of the denudation." 

 The circumstance that there should occur marl-beds, showing tranquil 

 accumulations for long periods, — peat-bogs in old valleys, with trees 

 of large growth, — and all now overlaid and preserved by this very 

 covering of drift-gravel, proves that an external configuration of the 

 surface somewhat the same as is presented now existed before the 

 Drift, and that the two phaenomena of denudation and drift-beds cannot 

 be coupled as cause and effect. 



Mr. Martin therefore observes, " Of the fossil or diluvial wood and 

 trunks of trees in situ amongst [? beneath] the gravel-beds of Surrey, 

 below the chalk, spoken of by Sir R. Murchison"^ (on the authority 

 of Mr. Austen) in attestation of ' a true terrestrial surface,' after 

 the commencement of the denuding aera [subsequent to the comple- 

 tion of the process of denudation?], I cannot say that they do not 

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

 responding districts under the South Downs, and I have never seen 

 any wood in drift which was not of the most modern description, such 

 as would till lately have been called mere 'alluvium.' Carbonized 

 trunks of trees are to be found in all the bogs and swamps, especially 

 in the alluvium of the river-courses, as noticed in my early memoir on 

 Western Sussex. On the banks of the Mole and the Wey, and of 

 their affluents, I doubt not such prostrate and uprooted trees may be 

 detected; — they are post-diluvial." 



The " diluvial " has ceased to be a definite geological period for 

 the last ten years or more ; and it may seem to some that it was not 

 necessary to notice such objections, more particularly as they were 

 accompanied by such other representations as that " the raised beach 

 at Brighton belongs to the Eocene asra." 



The supposition that the terrestrial surfaces referred to truly 

 formed part of the most modern or present period was altogether 

 unnecessary, inasmuch as these peaty and alluvial accumulations 

 were distinguished f from the older ones both by position and in 

 the different assemblage of animal remains. 



* Quart. Journ. Geol. Soc. vol. viii p. 375, &c. f Ibid. vol. vii. p. 281. 



