42 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Bill, the coast-line lies due E. and W., so that there intervenes a tract 

 between the chalk-range and the sea, which ultimately acquires a 

 width of ten miles, as from Lavant to Selsea ; this tract is low and 

 level, and presents the series of superficial accumulations which will 

 be here described. 



The escarpment of the chalk-range which overlooks the Weald is 

 very abrupt ; the outward or south slopes are also steep. The rivers 

 which pass through the range, such as the Arun, the Adur, the Ouse, 

 and the Cuckmere, have very little fall in the lower portions of their 

 courses, so that the country at the base of the inner slopes of the 

 chalk-range, as along the Rother, is but little higher than the tract 

 outside ; a very slight depression, such as would submerge the area 

 south of the chalk, would cause the same mass of waters to occupy 

 the transverse valleys and their ramifications beyond. 



The tract south of the chalk-range consists of accumulations which 

 have a thickness of from 30 to 35 feet at most ; these rest on a 

 surface of chalk or else of nummulitic strata, which have expe- 

 rienced a uniform levelling at some former period, a counterpart of 

 what is being produced at present by sea-action ; as around the island 

 of Heligoland,* and other coast- lines. The chalk comes to the 

 surface about South and North Berstead, Shrapley, and Poole Farms 

 at Felpham, and in the parish of Siddlesham. 



The higher levels of the chalk- range, which rise to the edge of the 

 escarpment, present a clear surface, free from detritus ; remains of 

 lower tertiary deposits are also wanting ; in which respects the Downs 

 on the south of the Weald differ from those on the north. 



Patches of lower tertiary strata occur between High Down Hill 

 (north of Little Hampton) and the main line of the chalk, as also 

 near Brighton ; there is again the well-known outUer of Castle Hill, 

 near Newhaven, where the lower fluvio-marine beds (plastic clay, or 

 Woolwich and Reading Series) are covered, as on the North Downs, 

 with gravel. Further west blue and mottled clays of the same series 

 occur close up to the base of the chalk-hills near Goodwood. 



The line of coast from Beachey Head to Folkestone need not now 

 be noticed, as the phsenomena connected with it belong to changes, 

 and to a condition of the English Channel of much later date than 

 that indicated by the newer tertiary deposits of Selsea. The manner 

 in which the beds of this series are cut off by the present coast-line 

 suggests that at one time a like condition of surface with that of the 

 Sussex levels extended along the whole range of the chalk, not only 

 as far as Beachey Head, but even across from the Chalk Downs of 

 Sussex to those of the south limit of the Boulonnais, before the sub- 

 sidence of the land of that interval had taken place. 



The rate of removal along the line of the deposits of the Sussex 

 levels is so rapid, as to assure us that the present breadth of that 

 tract is no indication of what its extent has been, even within his- 

 torical timesf , still less of what it was at yet earlier periods. 



* Ueber die geognostischen Verhaltnisse von Heligoland, t. 2. Von Dr. G. H. 

 Otto Volger. 

 t See Mantell, Dixon, and the Volumes of the Sussex Archaeological Society. 



