438 EOCENE. 



render it desirable to retain the distinctive term of Bognor Beds, 

 a name which was employed by Prof. Prestwich.^ Casts of fossils 

 are met with, which are sometimes converted into crystallized 

 carbonate of lime. The species include Dentaliiim, Solarium 

 bistriatian, Cyprina planata, Pectiinailus breviroslns. Pinna affinis, 

 Modiola elegans, Osirea gigantica, Lingula tenuis, Venue f us Bognor- 

 iensis, etc. The total thickness of the Bognor Beds is estimated 

 at 2 go feet. 



Chichester is situated on the London Clay, and this formation 

 occurs near Southampton, Romsey, Wimborne Minster, and south- 

 westwards towards Dorchester. (See p. 433.) 



In the Isle of Wight the junction with the Woolwich and 

 Reading Beds is sharp and well defined, and both in Alum and 

 Whitecliff Bays the division is indicated by a band of flint-pebbles 

 • — the basement-bed of Mr. Prestwich. At about thirty-five feet 

 above this bed there is a zone of Panopcca intert)iedia, and Phola- 

 domya margaritacea ; at fifty feet a band of Ditrupa plana ; and at 

 about eighty feet a band of Cardita occurs. (See Fig. 73, p. 428.)'^ 

 The total thickness of the London Clay is about 300 feet at White- 

 cliff Bay, and 220 feet at Alum Bay. At the former locality the 

 beds are vertical and in places slightly reversed.^ 



Economic products, etc., of the London Clay. 



Fossil copal (Copaline) or Highgate resin was discovered during the excavations 

 for the Highgate Archway. Pyrites has been procured on the Sussex coast, also 

 at Sheppey, for the manufacture of sulphuric acid, etc.* 



Septaria or Cement-stones have been largely used in the manufacture of Roman, 

 Portland, or Parker's cement. For this purpose they have been dredged in 

 Chichester Harbour, and off the coast of Hampshire : they have also been 

 collected at Sheppey, near Southend, and at Harwich.^ Medina cement is made 

 in the Isle of Wight. Stucco is also manufactured : a material extensively 

 employed to obscure inferior bricks. 



An analysis of Cement-stone from Sheppey showed the following composition : — 



Carbonate of lime 64 "oo 



Silica 1775 



Alumina 675 



Magnesia 0"50 



Oxide of iron 6"oo 



Oxide of manganese i -oo 



Water 3 -oo 



Loss I -oo 



^ P. Geol. Assoc, ii. 76. See also Prestwich, Q. J. iii. 362, x. 418 ; Dixon, 

 Geol. Sussex, ed. 2 ; C. J. A. Meyer, Q, J. xxvii. 74; and J. W. Elwes, G. 

 Mag. 1S84, p. 548 (Southampton). 



~ Prestwich, Q. J. ii. 223, x. 409; Bristow, Geol. I, of Wight, p. 35 ; J. S. 

 Bowerbank, T. G. S. (2), vi. 169. 



^ Whitaker, G. Mag. 1864, p. 69. 



^ P. Geol. Assoc, iv. 321. 



5 Webster, T. G. S. ii. 190. 



