Page:Cornwall; Cambridge county geographies.djvu/101

 MINERALS AND MINING 85 white mica. In 1817 the amount shipped for manu- facturing pottery was comparatively small, but of late years it has grown, and employs over 3000 persons. The china-clay is the same as the Chinese Kaolin ; its value was discovered by a Plymouth Quaker, Mr Cookworthy, in 1745. Porcelain was introduced into Europe from the East in 1518, when it acquired the name of China. For a long time it was supposed that the kaolin or fine white clay of which it is composed, was found only in the Celestial Empire, and specimens of this brought to Europe fetched a high price. At the beginning of the eighteenth century it was discovered in Saxony in an odd way. A merchant named Schnerr, being on a journey, was struck with the whiteness of some clay near Schneeburg, and collecting some of it used it for powdering his wig. It succeeded, but had this disadvantage, that wigs dressed with this new powder were very heavy. An apothecary named Botcher noticed the increased weight of the wig, analysed the powder, and discovered that it was identical with Chinese kaolin. He began to make Dresden China in 1709, and the process was carried on with the greatest secrecy, the exportation of the earth being forbidden under heavy penalties. In 1 748 Cookworthy discovered kaolin on Tregonning Hill, more was found at Boconnoc, and Cookworthy and Thomas Pett began to make china in 1768. At present St Austell is the great seat of this industry, and the produce is shipped at Charlestown and Polmear. The important slate-quarries of the Duchy, of which