S8 CRETACEOUS GROUP. 



comparatively free from them. This character, however 

 con-ect for the south of England, is not constant over a 

 wide area ; for the lower chalk of Yorkshire contains an 

 abundance of flint nodules, and the same fact is remarked 

 in the neighbourhood of Havre, and elsewhere. The Lower 

 Chalk and Chalk Marl consist of greyish earthy or yellowish 

 marly chalk, sometimes indurated. In Dorset and Devon- 

 shire, a bed with numerous fossUs occurs towards the base 

 of the Chalk, which is composed of chalk with green par- 

 ticles and minute grains of quartz, and we find, also, 

 towards the base of the chalk in Norfolk and Yorkshire, a 

 stratum of red chalk which may be considered to repre- 

 sent the gault of the southern counties. 



The Upper Green Sand consists of a sUicious sand, or 

 of a marly calcareous sand with green grains and mica ; 

 the celebrated firestone of Merstham belongs to this divi- 

 sion. The Gault next succeeds in a descending order and 

 is a blueish tenacious clay, sometimes marly and with 

 indurated argillaceous concretions. The Lower Green 

 Sand is chiefly an arenaceous deposit, formed of sands, and 

 indurated and ferruginous sandstones, with beds of clay 

 and clayey sand, and containing, in some localities, bands 

 of limestone (Kentish Eag), and regular seams of chert, 

 and sometimes a coarse and highly ferruginous conglome- 

 rate, as near CaLne, &c. The Kentish Kag is largely 

 quaiTied near Maidstone, and is used extensively as a 

 building stone in Kent and the adjoining counties ; it was 

 in one of these quarries that the fine specimen of the 

 Iguanodon, now in the British Museum, was discovered 

 by ]\Ir. Bensted. The calcareous matter appears to have 

 been developed towards the eastern part of this formation, 

 (Kent, &c.), for in the Isle of Wight there is scarcely any 

 trace of it, and certainly no masses of thick-bedded lime- 

 stone ; the best Fuller's earth is obtained from this divi- 

 sion, as at Nutfield, Surrey ; Woburn, Bedford. Dr. 



