134 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 19, 



3. On some Geological Features of the Country between the South 

 Downs and the Sussex Coast. By P. J. Martin, Esq., F.G.S. 



The object of this paper is not so much to give a minute descrip- 

 tion of the district I am about to review, as to promote a discussion 

 amongst the members of the Society here present on some of its 

 phsenomena, which seem to be singularly illustrative of the super- 

 ficial changes that have been eifected in the south of England by 

 dynamic forces of comparatively modern date. 



The district is to be found in the ninth section of the Ordnance 

 Map, and extends from near Portsmouth to Shoreham, or that flat 

 country which is to be seen from any part of the tops of the South 

 Downs from Portsdown Hill eastward to the Shoreham River. 



If time serve, we may perhaps be induced to extend our views as 

 far as Brighton. The cliffs of Brighton and its raised beach have 

 been so often described, have given rise to so much discussion, and 

 so little new can be said about them, that I have in my own 

 mind set them down, and the beach in particular, as amongst those 

 specialties (like terrestrial surfaces, patches of modern, or recent, 

 or post-pliocene deposits with correspondent fossils) which cannot 

 be ignored, but which I hope some day to see brought into harmony 

 with the simpler actions of consentaneous elevation and denudation, 

 which I, and much abler geologists than myself, have endeavoured 

 to expound. 



The first remarkable feature of this tract of country which I pro- 

 pose for your notice, and which brings it into the same category with 

 all the disturbed districts of the south-eastern part of our island, is 

 an anticlinal line of chalk-elevation, extending from Portsdown Hill 

 into the sea at or near Worthing. Portsdown is on its northern 

 slope ; its ridge, or line of culmination, runs by Emsworth and West 

 Thorney to Donnington and Hunston, south of Chichester (here 

 much obscured by drift), and then less obscurely by Climping and 

 Ford to the Arun. From thence it passes between Leominster and 

 the hamlet of Wick, and rises suddenly on its northern slope, like 

 Portsdown, in another, but smaller, eminence called High Down*. 

 From thence, I believe, it goes out to sea and is lost, unless it ap- 

 proximates to the South Downs east of the Ouse, and produces the 

 synclinal tertiaries of Newhaven and Seaford. 



This anticlinal brings up at Hunston and elsewhere along its range, 

 a portion of the white chalk, characterized by Marsupites, which I 

 regard as higher in stratigraphical position than the so-called "upper 

 chalk " of the south-eastern counties of England. This uppermost 

 chalk is soft and marly, and without flints; it is called "free-chalk *' 

 or " marl " ; and is dug for manure at Stoke and Lavant. It appears 

 also along the base of the chalk-escarpment at Halnaker and a few 

 other places in West Sussex, but does not occur on the Downs, which 

 have lost this upper member of the chalk-series by denudation. 



North and south of this chalk-elevation are two synclinals or 



* These eminences were described as " outliers by protrusion " in Mr. Martin's 

 ' Geological Memoir on a part of West Sussex,' 1828. 



