16 THE ORIGIN OF SOILS [chap. 



of London and in East Kent were probably laid down 

 either by floods on the river meadows or in quiet bays 

 and lagoons of an estuary. 



Over a great part of Britain north of the Thames, 

 especially in the midlands and the eastern counties, 

 the surface of the land is covered with beds of clay 

 and sand which owe their origin to glacial ice. In 

 Scotland, the north of England, and Wales, these beds 

 are full of ice-scratched stones, and clearly represent 

 material that has been ground down by a moving 

 glacier : but the origin of the glacial drift of the eastern 

 counties is more obscure, for water seems to have played 

 some part in its formation. These glacial drifts are 

 often described as " boulder clays," but they are not 

 necessarily very heavy or clayey in character from an 

 agricultural point of view. Indeed in Norfolk, as over 

 a great part of northern Europe, they may be of the 

 lightest sandy type, and again in Cheshire, Stafford, etc., 

 where over large areas they are derived from the New 

 Red Sandstone they do not differ greatly from the light 

 sedentary soils originating from the same formation. 

 When the glacial drift is derived from primitive and 

 crystalline rocks the soils are marked by the pre- 

 dominance of angular fragments, "rock dust," which 

 have undergone but little decomposition compared 

 with the similar fragments present in soils originating 

 from sedentary rocks. Such soils, found in North 

 Wales and Scotland, in which the quartz particles are 

 unrounded and the felspar particles are but little 

 kaolinised, differ from the more normal soils both in 

 their chemical behaviour and in their response to 

 cultivation operations. 



