Feather stonhaugh^s Geological Report. 



57 



prepare the surface, where this rock prevails, for wheat, 

 always called corn in England. In Yorkshire the sandstones, 

 shales, and seams of coal repeated, are subjacent to this stra- 

 tum, and are conceded to be the equivalents of Mr. Murchi- 

 son's coal seams of Brora, in the oolitic group of Scotland, 

 which he first described. 



The Oxford clay is a dense, blue, argillo-calcareous mass, 

 including stony beds called Kelloway rock. This is an exten- 

 sive deposite, as well on the continent as in England, where, 

 with its associate members of the oolitic series, it describes an 

 incurved line through the kingdom, following the course of the 

 lias. 



The coral rag is an oolitic rock, lying between an upper 

 and lower calcareous grit in the north of England. The ovula 

 are frequently as large as peas, which has occasioned the rock 

 in certain localities to be called pisolite. This deposite is re- 

 markable in some localities for its abundance of coral structure, 

 and deserves notice as separating those two great argillo-cal- 

 careous deposites betwixt which it lies. 



The Kimmeridge clay is a calcareous clay, of a blue color, 

 which, like the other great argillaceous deposites, contains 

 septaria, besides lignites. 



The Portland oolite is the bed which produces the fine free- 

 stone called in England Portland stone ; it is found both com- 

 pact and oolitic, is disposed to be cherty, and contains, towards 

 the bottom, green sandy beds. 



The Purbeck limestone is superincumbent to the oolitic 

 series ; its general structure is clays, embracing beds of lime- 

 stone with ironstone. 



The Hastings sand consists of various colored sands and 

 sandstones, containing lignites and coarse grits. 



The weald clay^ so denominated from the weald of Sussex, 

 is a stiff, slaty clay, containing ironstone, alternating towards 

 the bottom with sands, and embracing beds of fresh-water lime- 

 stone. 



