P0RCELA1N-EARTH. *** violet colours from gold precipitated by tin and silver, certain green colours by copper, precipitated from its so lutions in the acids by alkalies; red colours from oxides of iron ; blue from zaffre ; yellow from diaphoretic an timony, mixed with glass of 1 lead ; brown and black co lours from iron-filings and zaffre ; and the finest green tints from oxide of chrome. It is said that the art of making porcelain was disco vered in the year 1703. by Bdtticher in Dresden. Observations. This mineral is distinguished from the other Clays, by the fineness of its particles, its soiling strongly, and its fine but meagre feel. 4. Common Clay. • Tins species is divided into the following subspecies, viz. toam, Potters-Clay, Variegated Clay, and Slate-Clay. first Subspecies. Loam. Leim, Werner. Magerer Thon, Karsten, Tabel. s. 28—Leimcn, Hah. s. 4^. Id. Steffens, b. i. s. 197- W. Lenz, b. ii. s. 549- Id- Oken, h. i. s. 370. External Characters. Its colour is yellowish-grey, sometimes inclining to greenish-grey, and is spotted yellow and brow n.
