BLUE CHALK MARL. 81 



where uncultivated is covered by rushes and other plants, that affect a 

 moist and clayey soil. 



This deposit seldom exceeds 100 feet in thickness. It may be traced 

 with but Httle difficulty, from near Laughton Place, six miles N. E. from 

 Lewes, through Kingmer, Harasey, Offham, Plumpton, near Ditchling, 

 Clayton, New Timber, &c. to Seeding. West of the Adur, its place is 

 occvipied by a compact argillaceous limestone, provincially called Malm 

 Rock ; and which, from the observations of Mr. Hawkins, there can be no 

 doubt is a contemporaneous formation. This malm rock continues along 

 the foot of the Downs, near Sullington, Storrington, Amberley, Bignor, 

 &c. to Petersfield in Hampshire. 



On the south-eastern margin of the county, the blue marl disappears, 

 and the grey marl reposes immediately upon the green sand ; this cir- 

 cumstance is clearly shewn by the section of the cliffs near Eastbourne. 



The identity of this bed with the blue marl of Folkestone*, the gait 

 of Cambridgeshire, and the malm of Surrey f, cannot for a moment be 

 doubted; not only is there a perfect agreement in their physical characters, 

 but also in their geological position, and organic remains. The marl of 

 Folkestone is said, by ]\Ir. Phillips, to contain 30 per cent, of carbonate of 

 lime ; and that of Eingmer, upon being submitted to the action of acids, 

 indicated a like proportion. In the absence of natural sections, an exa- 

 mination of the wells sunk in different parts of its course, are the only 

 means we possess of obtaining a knowledge of the structure, and organic 

 remains of this deposit. Availing myself of this source of information, I 



* The blue marl of Folkestone has been ably described by Mr. W. Phillips. Folkestone 

 is built upon the green sand, and the cliffs on the east of the town are from 80 to 90 feet high, 

 the upper part of which, for a considerable distance from theu' termination at Copt Point, 

 consists of the blue marl. Crystallized sulphate of lime occurs in this bed, and nimierous re- 

 mains of shells with their pearly lustre still preserved. There can be no doubt that this deposit 

 is altogether analogous to that, underlying the chalk at Mailing in Kent, in Cambridgeshire 

 and Oxfordshire, and which, in the latter counties, is provincially termed Gait. {Geological 

 Transactio7is, Vol. 5, page 37.) _ 



f At the foot of the chalk hills near Godstone and Bletchingley, the blue marl rises from 

 beneath the grey marl ; and I have collected from these localities precisely the same species of 

 ammonites, belemnites, nuculte, &c. as those which occur at Ringmer and Laughton. 



