

ENGLISH AGRICULTURE. 55 



this country succeed each other in a remarkably orderly 

 manner. 



Without going minutely into the matter, let me remind my 

 reader that the crust of the earth is composed of a large series 

 of rocks, superimposed upon each other in orderly succession. 



We know, for example, that London is situate upon the 

 London clay. The London clay forms " the London basin." 

 Chalk hills rise to the south, and chalk hills rise to the north 

 of it. The Kentish Downs or the North Downs rise south 

 of London, and the hills of Saint Albans or Hertfordshire 

 rise on its north. The chalk, again, is divided into upper and 

 lower chalk. Under the chalk is the upper and the lower 

 greensand. Notice that these likewise form a part of what 

 is called the London basin. Next in inferior position is the 

 Weald clay, which, however, is restricted to a well-known 

 district. The Weald clay occupies an important position in 

 the counties of Sussex and of Kent. It is often spoken of 

 as a clay soil, but it is not invariably so, there being a great 

 deal of light land in the Weald. After that, in descending 

 series, there are the upper oolites ushered in by the Purbeck 

 beds, the Portland beds, and finally by the Kimmeridge clay. 

 Next the middle oolite, and the lower oolite, then the lias, 

 the new red sandstone, the magnesian limestone, the coal 

 measures, the mountain limestone, and the old red sandstone 

 at a vast depth beneath the surface. Such is briefly the 

 geological staircase. If a well could be sunk in Trafalgar 

 Square the boring would in turn penetrate these formations. 

 They are superimposed upon each other in the order in which 

 they were originally deposited, and if we examine a geological 

 section of England we shall find that the above is the order 

 of succession of these rocks. But the point which I wish 

 to call attention to is, that each of these rocks in turn occu- 

 pies the surface of the country, and it is not altogether 

 easy for a student of agriculture who has not attended 



