Wealden District and the Bas Boulonnais. 35 



our theory, that the elevatory force acted with greater general intensity in the former 

 than in the latter part of the district. It is also concluded, that the intensity of the 

 elevatory force, throughout the district of greater geological elevation, so far at least 

 approximated to uniformity, that its variation was generally much less rapid in 

 passing from one point to another within the boundary of this portion of the whole 

 tract, than in passing from a point within to another without that boundary. 



The hypothesis of a single elevatory movement introduced, as above stated, for 

 the greater distinctness of elucidation, is not essential to this reasoning. If we 

 suppose the whole elevation to have been produced by successive movements, we 

 must then apply the conclusion of the preceding paragraph more especially to that 

 particular decisive effort of the elevatory force to which we refer the characteristic 

 phfenomena of the district. 



5. The next point in the application of this theory is the determination of the 

 boundary of the district which may have been simultaneously disturbed. This 

 must be effected by ascertaining the area throughout which the phsenomena of 

 elevation are distinctly characterized by the same laws. Thus in the case with 

 which we are immediately concerned, we observe that, in the western portion of 

 the Wealden district, the longitudinal lines of elevation run approximately east 

 and west ; and such is also known to be the case in the Vale of Pewsey, and again 

 in the Vale of Wardour. The great dislocation likewise of the Isle of Wight and 

 the Isle of Purbeck preserves a parallel direction ; and, although the evidence may 

 not be so determinate as in the Weald, Mr. Martin has lately shown that interme- 

 diate lines, some of which may be regarded as continuations of those from the 

 Weald into the great Wiltshire plateau of chalk, approximate to the same general 

 law of parallelism. Hence I conclude that the boundary of the tract subjected 

 to the simultaneous action of the elevatory forces is exterior to, and not remote 

 from, the chalk escarpment of the Bas Boulonnais ; and, after passing across the 

 Channel from the north of Wisant to the east of Folkstone, that it is continued in 

 like manner exterior to the chalk escarpment of Kent and Surrey, till it comes to 

 the north of the Hog's Back and Farnham, whence I conceive it to be continued 

 westward parallel to the general direction of the valley of the Thames, and pro- 

 bably not far from it (as shown by the discontinuous line in the map), as far at 

 least as the Vale of Pewsey. On the south I consider this tract to be bounded by 

 a line south of the southern coast of this country (see map), the exact position of 

 which we have not the means of ascertaining ; and on the west there is also some 

 indeterminateness, arising partly from the absence of more detailed observations, 

 and partly from the interference of other systems of dislocation which may have 

 originated in independent elevatory movements in the south-western portion of 

 this country. If all the strata removed by denudation were replaced, the above 



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