THE WEALDEN DEPOSIT. 



they seem to represent a part of 

 the neocomian (or Shanklin) for- 

 mation. In the Pyrenees the lay- 

 ers are often of a deep colour, 

 and separated by argilla'ceous 

 schists, which seems to make 

 them a part of the transition for- 

 mation ; but, on the contrary, in 

 the north part of the basin of 

 the Gironde, they belong to the 

 chalk. 



5. The neocomian, which was 

 not at first distinguished from 

 other parts of the chalk forma- 

 tion, is now recognized in a 



Fig. l&.-Spkernli i^ otnirtcota, or, 



RadioLi' te.-- lurbiiiu ta. 



Fig. 123. Nummuli'tes from the chalk. 



great part of France, Switzerland, and different parts of Gerro tiy, 

 Poland, and even to the Crimea. Here and there deposits of <yp- 

 sum of greater or less extent are met with, sometimes isolated, and 

 sometimes associated with crystalline rocks. 



6. The WEALDEN DEPOSIT. We frequently meet in the tirst 

 deposits of the chalk formation the remains of organized bodies, 

 which appear to belong to paludi'nae, clearly showing there was 

 here and there an afflux of fresh water to those seas in which 

 these remains accumulated. We also find in the same situations 

 deposits of combustibles, which have always been known under 

 the name of lignite (from the Latin, lignum, wood), probably form- 

 ed from con'ifers (as dicotyledons did not then exist), which 

 were doubtlessly carried by rivers : such are those in the environs 

 of Orthez, in the department of Landes ; of Bellesta and of 

 Saint-G irons, in the department of Ariege ; of Irun, in Guipuscoa 

 (Spain), &c. But all these local deposits are nothing compared to 

 those which have long been described in England, in parts of the 

 counties of Kent, Surrey, and Sussex, under the name of wealds 

 from which is derived the term wealden formation. 



5. What is the Neocomian deposit? What is its extent' 



6. What is meant by Wealden formation ? Why is it so called ? 



