Wealden District and the Bas Boulonnais. 23 



the escarpment becomes extremely bold and abrupt till we come beyond Pluckley, a 

 village five or six miles from Ashford. About Sutton and Ulcomb it begins to 

 approximate to the chalk escarpment, and its general dip must be somewhat greater. 

 Opposite Ashford we find another great break in the range, which, further south, no 

 longer preserves by its elevation the distinct character which it generally possesses. 



The springs along this escarpment are not nearly so frequent as in those of Leith 

 Hill and Seven Oaks, where the indications of disturbance are much greater ; and 

 we may particularly remark, that between the Medway and Sutton Valence, the 

 Ordnance Map does not indicate the existence of a single rivulet flowing from the 

 escarpment, and resembling those always formed elsewhere by the springs I have de- 

 scribed. Now this part of the escarpment, from its altitude and verticahty, would 

 be particularly favourable to the formation of springs in cases where the water, 

 arrested in its descent from the upper surface by some impervious stratum, would 

 be compelled to seek a horizontal outlet, probably that which the nearest valley or 

 escarpment would afford. Such springs however seldom occur in escarpments 

 from which there is any considerable dip ; and on this account the escarpments 

 previously mentioned would be less favourable to the production of springs than 

 that now spoken of. The comparative absence of springs in this escarpment is 

 probably due to an absence of those dislocations in which perennial springs so fre- 

 quently originate. This conclusion is in perfect harmony with the undisturbed 

 character of this portion of the district. In the escarpment east of Sutton there 

 are two or three large springs which I attribute to fractures ; there is also reason 

 to believe that the disturbance has there been somewhat greater. 



River-courses through the Chalk Escarpment. — One of the most curious circum- 

 stances connected with the geological structure of the Wealden district is its trans- 

 verse drainage through the apparently insurmountable barrier of the surrounding 

 chalk hills. The river-courses through these hills are far more striking than similar 

 instances already mentioned in the interior of the district, because, in the first 

 place, the barrier broken through is of far greater strength and massiveness, and 

 secondly, the continuous lateral longitudinal valleys seem to present scarcely the 

 smallest impediment to a totally different drainage, by which the whole water of 

 the district might have been carried along those valleys under the chalk escarp- 

 ment, or that of the greensand, and discharged into the channel by Folkstone or 

 Beachy Head. The most obvious solution of the difficulty which the existence of 

 the transverse river-courses under such circumstances presents to us, is in the 

 hypothesis of their having originated, as in other cases, in transverse dislocation, 

 and I have been desirous of verifying the truth of this hypothesis by the discovery 

 of indications of disruption along the transverse valleys through the chalk. I 

 have not, however, in these instances been very successful. The amount of the 



