Martin's Geological Memoir on Western Sussex, 43 



Bignor-farm, under Bedham Hill, Buckfold, Parkhurst, Lickfold, 

 and within half a mile of Blackdown, near Lurgershall, where there 

 is a fine bank of it exposed at Northhurst-farm. Eastward it runs 

 by Willets and Spear Hill, and crosses the Worthing road, at Win- 

 caves ; from whence its course is a good deal disturbed by the 

 disruption of the Vale of Greenhurst ; but it is found at Jessups, and 

 again a little north of Henfield*." 



The first course of the well-known concrete of fossil shells of He- 

 lix or Vivipara, called Sussex marble, is followed by another suc- 

 cession of clays, of much less depth than either of the former ; and to 

 this follows a second bed of sand more micaceous and of a deeper 

 brown, with less admixture of clay, and carrying Horsham grit. 

 Next succeeds the thickest and finest bed of Sussex marble : there 

 are then beds of blue and red clay, and a third course of fawn- 

 coloured micaceous sand. 



" Immediately below this course of sand, a thick bed of red clay 

 succeeds, and then the calcareous grit, sand-stone, and clays of 

 what has generally been considered the * forest range' of the weald. 



" By this sketch of the contents of this part of the weald, it will 

 be seen that there are two distinct beds of sand above the Sussex 

 marble, the highest of which has all the character of the * Hastings- 

 sand,' and the second carries Horsham grit. 



" There is therefore no line of demarcation to distinguish the 

 weald from the Hastings-sands and -clays, except a slight elevation 

 of the line of country, a more stony structure, and greater sterility." 



To the " District Survey" succeeds the " Theory of Derangement 

 and Denudation," which is certainly the most important part of the 

 work. But we find it difficult to convey an adequate idea of this 

 theory by extracts. Those which we subjoin, however, will impart 

 some idea of it. 



After stating that the Weald-denudation is understood to be 

 bounded on each side by what are called the chalk-basins of Lon- 

 don and Hampshire, the author observes, that, although the con- 

 tents of these basins have been carefully examined and described, 

 no satisfactory explanation of the mechanism or mode of formation 

 of the basins themselves has yet been given. — He then proceeds to 

 give his own theory, and partly in the following manner: 



" The strata which compose these basins, then, previously in a hori- 

 zontal position, suffered disruption; and in the act qfbasining (whether 

 by the elevation of the sides, or the subsidence of the central parts, is 

 not now material), all their parts were deeply and extensively fissured, 

 in an order correspondent with that act; — producing, with the help of 

 diluvian action, a system of longitudinal and transverse valleys answer- 

 ing to the double inclination (the dip and lateral bearings, or obliquity 

 of the plane) of their fractured masses, and a consequent removal of 

 the broken materials brought within the range of the denuding force. 



" The effect of raising from the horizontal position, or in any other 



* " The irregularity of the denudation between Warminghurst and Hen- 

 field, seems to have left outliers of this sand, as well as of the upper bed of 

 weald-clay, out of the usual course in that line of country." 



G2 way 



