TIIK KOCKNK SK1IIK> 



of tlu- Woolwich Sands is a mass of pebble* in a sandy 

 matrix, taking the place of the Oldhaven Beds and often called 

 ,. -kheath Beds. 



Tlic Hlarkheath Beds do not extend west of Croydon, and are 

 not found along the northern edge of the London basin. The 

 pebbles composing them area-U well-worn and rounded flints without 

 any sulvingiil;ir pebbles such as occur on our shingle beaches ; henee 

 Mr. Whitaker concludes that they were not laid down in beaches, but 

 were deposited by strong currents at some little distance from the 

 shore, and his view is confirmed by the frequency of current bedding. 



Beds of mottled plastic clay begin to appear in West Kent near 

 tin- ba>e, and these increase westward through Surrey, the shell- 

 bearing beds gradually dying out, till in Hampshire and Berkshire 

 they consist entirely of mottled clays, in tints of red, yellow, grey, 

 purple, and green, associated with beds of red, yellow, and white 

 sand. These are known as the Reading Beds, and marine fossils 

 only occur in the basement-l>ed, the only fossils in the clays being 

 leaves of plants. Near Reading the group consists of : 



Feet 



Mottled clays 40 to 50 



Yellow and white sands . . . . . 20 to 30 

 Bottom bed with marine fossils . . . 5 to 8 



Beds of the same (Reading) type range along the northern lip of 

 the basin through Herts and Essex, but include some pebble beds 

 which are occasionally concreted into the kind of conglomerate 

 known as " plum-pudding stone." 



They recur in the Hampshire basin, where they consist almost 

 entirely of bright red and white mottled clays with several layers 

 of brown sand, one of these being at the base and resting on the 

 Chalk, No fossils except fragments of plants have yet been found 

 in these clays, and they do not therefore seem to be of marine 

 origin. Their thickness in Whitecliff Bay is 163 feet, at Alum 

 Bay 84 feet, and they are still from 70 to 80 feet thick in Dorset 

 near Bere Regis. Near Dorchester they include beds of sand and 

 of subangular gravel consisting of Cretaceous Hints and cherts. 



The London Clay occupies broad areas both on the north 

 and south side of the Thames Valley. It is of much more 

 uniform composition than the lower group, the mass of it consist- 

 ing of stiff bluish clay with layers of septarian nodules The 

 sin face colour of the clay is generally brown, but this is due to the 

 oxidation of the iron it contains by exposure to the weather ; its 

 normal tint in deep wells and borings is a bluish-grey colour. 



The basement-bed is of a different character to the rest, con- 

 si-ting of brown, grey, or greenish sand and sandy clay, in which 



