If the objects to be thrown on the wheel are of ordinary earthenware, the clay may be "ball" clay. This clay is found in Dorsetshire, and is used in its natural state without further preparation. If the articles are of fine china or porcelain, the clay is specially prepared. Kaolin, or china clay, is found in Cornwall, and is produced by the decomposition of a variety of granite called pegmatite. In the manufacture of porcelain, this clay may be mixed with calcined bones, flint, etc. These materials are weighed and measured, and placed in large vats filled with water, in which they are thoroughly stirred up and mixed together. The mixture is then run into troughs and passed through fine sieves of lawn, and afterwards left till the superfluous moisture has evaporated. It is then "wedged," or repeatedly cut up, and it is then ready for the thrower.