Kaolin and other Clays. 609 



and the other ingredients of granite, it forms natural 

 beds of clay. This is dug out, and the clay is trans- 

 ported chiefly to the district of the Potteries in North 

 Staffordshire. The same process is sometimes secured 

 by art, when the decomposed granite being dug out, 

 is washed by artificial processes, and the more alumi- 

 nous matter is separated from the quartz with which it 

 was originally associated. Then, in the Potteries, it is 

 turned into all sorts of vessels fine porcelain, stone- 

 ware, and common-ware in every variety of size, and 

 form, and texture. 



In the Eocene tertiary beds, in the neighbourhood of 

 Poole, there are large lenticular beds of pipe-clay, in- 

 terstratified with the Bagshot Sand. Great quantities 

 of this clay are exported into the Pottery districts to be 

 made into the coarser kind of earthenware, and they 

 are also mixed with the finer materials from Devon and 

 Cornwall, to make intermediate qualities of stone-ware 

 and china. 



But in addition to clay, the chalk is brought into 

 requisition to furnish its quota of material for this 

 manufacture. The flints that are found embedded in 

 the chalk, chiefly in layers, are also transported to the 

 Potteries, and ground up with the aluminous portions 

 of the clay, since it is sometimes necessary to use a 

 certain proportion of silica in the manufacture of 

 porcelain. 



Many other formations, such as the Old and New 

 Red Marls, are also of use when clay is required for the 

 manufacture of bricks. The Oolitic and Liassic strata 

 are to a great extent composed of clay, such as Lias 

 Clay, Fullers' Earth Clay, Oxford and Kimeridge 

 Clay ; there is also the Weald Clay, and the Gault lies 

 in the middle of the Cretaceous strata. The Boulder- 



