Martin's Geological Memoir on Western Sussex, 45 



^ 



" The principal transverse fissures, some of which were destined to 

 become river-channels, have a remarkable correspondence on each 

 side of the valley, particularly in the chalk, and in several instances 

 are directly opposed to each other ; which could not have happened 

 without a simultaneous action and common consent and continuity 

 of parts. The direction of a rent would be ruled by the density and 

 tenacity of the different parts of the stratum ; occasionally deviating 

 from the straight line, it might be lost in one part, and taken up 

 and carried on by another, giving less resistance. The coincidence 

 is therefore the more remarkable, and proves not only the continuity 

 of the chalk strata at the moment of convulsion, but also their uni- 

 form density and strength. Of the valleys thus opposed to each 

 other by the continuity of the greater transverse fissures, the most 

 remarkable are, — the defiles of the Arun in the South, and the Wey 

 in the North Downs ; the vale of Leatherhead, or the Mole, and 

 that of Findon, or the Worthing road ; of the Adur and Smitham- 

 bottom, or the pass of Merstham and Croydon. The Ouse is also 

 opposed to the Darent, and the Cuckmere to the Medway. 



" But it must not be supposed that this simple transverse fissure is 

 the only appearance of displacement exhibited by the chalk strata. 

 They have suffered in common with the other rocky strata, that 

 adjustment of parts which might be expected from the nature of the 

 material on which they rest. If the fissile character of the stony 

 strata determine their division in straight and broad lines, it would 

 also be the character of the wealden formation to be torn and con- 

 torted in a manner widely different. For a stratum of clay of great 

 thickness, carrying stone barely sufficient to give it stability, would 

 tear rather than split in the act of displacement; and such a diver- 

 gence of the fissures as might be expected in so tenacious a mass, 

 can be readily traced in every part of the weald surface. This di- 

 vergence and laceration has therefore modified the disposition of 

 the stony strata still superincumbent upon the clay ; and the subsi- 

 dence, elevation, and contortion consequent thereon, are every- 

 where visible in the dip and variable bearings of all their masses. 

 In appreciating the evidence of these acts of laceration and fracture, 

 it must not be forgotten also, that strata of various structure far 

 below these under review, have suffered the same disruption; and 

 by the variable nature of their fracturings have operated to modify, 

 and in some cases to obscure, a great part of the direct testimony 

 of the order here described. The pressure of superincumbent strata 

 of unknown thickness and kind must also be taken into account; 

 and it will not be thought wonderful that, diluvian action and the 

 operation of more modern causes apart, there should be so little 

 direct evidence of fissure upon the surface. 



"The divergence or distribution of the transverse fissures is to be 

 traced in the upper stony strata, as well as in the minuter divisions 

 of the clay districts. If a fissure of this sort be followed from its 

 termination in any of the hilly counties, it will be found to present, 

 first a little coomb, into which the stone inclines on both sides, and 

 at first carrying no water. By-and-bye springs burst forth, (the 



natural 



