POTTERY. 29 



coating one surface (the inner, if hollow) with a silvering 

 liquid (see Hydrometallurgy), and then cutting or otherwise 

 ornamenting the outer surface. (Thomson and Varnish, in 

 Lond. Journ. xxxvii. Aug.) 



2. Semivitrification, 



Or the making of brick, earthen-ware, stone-ware, fine 

 pottery, and porcelain. The basis of these arts is clay, which 

 is often unmixed for brick ; consists of finer and coarser clays 

 for earthen-ware ; of still better for stone-ware ; of the best 

 clays, quartz, and feldspar, for fine pottery and porcelain. 

 The materials for all these wares, except brick, are ground 

 fine, made into a slip with water, partially dried to a plastic 

 state, in which state they are formed, by pressing, throwing 

 and moulding, into the endless varieties of forms wdiich we 

 daily witness. A glaze is given to the surface by covering it 

 with red lead, for common ware ; with a fusible flux or glass 

 containing lead, for the better wares ; and with a glaze chiefly 

 composed of feldspar, for porcelain. A very high heat is 

 given to common earthen-ware, and a much higher to por- 

 celain, sufficient to cause the ware to undergo incipient fusion. 

 The subject presents a wide field for improvement by the 

 application of chemical principles, although at the present 

 time we need more of sound practice in the United States, 

 especially in the finer kinds of clay-ware. Our common and 

 fire bricks, and common earthen-ware and stone-ware, are al- 

 ready of excelle^it quality, and our black-lead crucibles are 

 superior to the German, the best being made at Taunton, 

 Mass., and Jersey City, opposite New York. We employ 

 pots from both establishments at the United States Mint, and 

 melt in them about 2500 oz. gold at once. Although the 

 quality is not uniform, they are generally excellent. 



Some attempts have been made to produce fine pottery 



(Faience, Liverpool-ware), but few have met with success : and 



among the latter we may mention the Pottery Company at 



Jersey City, and the Spring Garden Pottery, Philadelphia. 



c2 



