of the South-east Part of England. 67 



trough of Poole, and at the bottom of the blue clay in many 

 parts of the London basin. An imperfect coal, or lignite, also 

 frequently occurs in it. This formation corresponds to the French 

 plastic clay, which lies over their chalk. 



Ctialk with Flints. — This formation in England extends from 

 Flamboroiigh-head in Yorkshire to a little beyond Lyme Regis 

 in Devonshire [Dorsetshire] ; and, where ii is not covered by the 

 beds above, forms chalk-hills or downs. It is distinguished by 

 the regular layers of flint nodules. 



Chalk without Flints. — The inferior bed of chalk in the south- 

 east part of England is always vvitliout flints. When the chalk 

 with flints is wanting, it forms the surface. The relations of 

 both maybe seen at the Culver and Compton Bay in the Isle of 

 Wight, Handfast-point, Beach vhead, Guildford, Dorking, &c. 

 It diflfers from the former only in the absence of flints, in the 

 beds being thicker, and the chalk being sometimes a little 

 harder. 



Chalk Marl. — This bed consists of chalk and an intimate mix- 

 ture of clay. It is ahvavs found below the two last strata. It 

 may be readily distinguished from chalk, by its falling to pieces 

 on being wetted and dried again. Some varieties of it, when 

 burnt, form an excellent cement for building. It is also a valu- 

 able manure. 



Green Sand-stone. — The formation to which I have given this 

 name, consists of siliceous sand united by calcareous matter, 

 and contains also mica and green earth. From the variety in 

 the proportion of the latter ingredient, it is by some divided into 

 the green sand and gravsand ; a distinction which cannot always 

 be made, since these alternate, and pass into each other. It is 

 found in the wealds of Kent and Sussex, at the foot of the 

 chalk downs, and is dug at Rygate and Mearsham for fircstone. 

 It is seen also at Folkstone, Beachyhead, the Culver and Comp- 

 ton Bay in tlie Isle of White, Pewsey in Wiltshire, &c. Al-^ 

 teraating with it are often beds of limestone, as at Maidstone 

 in Kent, where they are called Kentish rag ; also in the Under- 

 cliff. Isle of Wight, beds of chert occur in it. It abounds in 

 organic remains. 



Blue Marl. — This bed may be seen under the former very di- 

 ^incily in the Isle of Wight ; as at Sandown Bay, many parts of 

 the Undercliff, Niton, and Compton. It contains very few 

 fossils. 



Ferruginous Sand. — This denomination is given also to an 

 alternating series of siliceous sandstone^ t-'hiy, and limestone : the 

 eandstone contains alwavs more or less oxide of iron, sometimes 

 in such quantity, as in the wealds of Kent and Sussex, that it 

 was formerly [and still occasionallv at Ashbuniham] employed as 



E2" ' an 



