Geological Society. 421 



gitudinal valleys on the south side of the central axis of the 

 Wealden elevation, namely, the Arun, Adur, Ouse and Cuckmere 

 rivers; whilst five gorges in the escarpments of the North Downs 

 give exit to five rivers formed in longitudinal valleys on the north 

 side of the same central axis of the Weald, namely, the Wey, the 

 Mole, the Darent, the Medway, and the Stour. 



An objection has been sometimes raised to the theory which at- 

 tributes the existing position of inclined strata to elevation, grounded 

 on an assumption that the same relative positions of the strata in moun- 

 tains and the valleys adjacent to them may have been caused by the 

 subsidence of the lower parts of the strata into the basins, as by the 

 elevatioti of those portions which now occupy the highest place ; but 

 these objections are overruled by mechanical and mathematical 

 reasons, arising from observation of the relative positions of the dis- 

 located strata on each side of the " upcast dykes" or faults that 

 run parallel to these assumed lines of elevation ; namely, that the 

 dislocated strata, in almost all cases, occupy the place which an up- 

 ward movement would have given to them respectively on each 

 side of the fault, and which they could not have received from a 

 downward movement under any process of depression *. 



Mr. Martin, of Pulborough, has also resumed his consideration 

 of the structure of Western Sussex, and of the anticlinal lines of 

 the London and Hampshire Basins published in 1828 and 1829, 

 with a paper on the relative connection of the eastern and western 

 chalk denudations ; in which he traces westward, from the Wealden 

 district of Sussex, a system of six nearly parallel anticlinal lines, 

 across the high table-land of chalk in Hants, Wilts, and Dorset ; 

 three of these lines of elevation proceed westward from the Wealden 

 district, and three penetrate the chalk in an easterly direction from 

 the valleys of Wardour, Warminster, and Pewsey. The continuity 

 of these lines is occasionally interrupted for considerable intervals, 



• It is due to the memory of Mr. Farey, the cotemporary and fellow- 

 labourer of Mr. Wm. Smith, that we should here notice the fact of his 

 having many years ago presented to this Society an unpublished section 

 across the Weald of Sussex, along the road from London to Brighton, to 

 which due credit was not then attached. In this section, together with 

 the general direction of the component strata of the district, as given in 

 the sections of Mr. Mautcll and Dr. Fitton, he introduces a series of 

 faults, twenty-five in number, between Rycgate Hill upon the North Downs 

 and Clayton Hill on the South Downs, representing minor movements and 

 longitudinal fractures parallel to the great escarpments that bound the area 

 of the Weald ; many of these faults have been recognised where ho had 

 placed them by Mr. Ho))kins. Mr. Farey also, in his " View of the Agri- 

 culture and Minerals of Dc'rbyshirc," 181.5, has given an account of great 

 systems of faults and denudations in Derbyshire and five adjacent counties; 

 together with the coloured figures before alluded to explanatory of the na- 

 ture of faults and dislocations, or tilts of the strata, and the subseijuent 

 effects of denudation upon them ; which, though not confirmed in all their 

 details by modern observations, show him to have been a most ingenious 

 original oljserver, whose merits in this department have not been suffi- 

 ciently appreciated. 



