Uses and Statistica.—The e,ommon kinds are used in the manufacture of porc,elain, and the fine qualities are c,onsumed by the tobace,o-pipe makers. The annual export from Asia Minor is said to reach 8000 to 10,000 boxes, representing a money value of about 100,000/., principally to "Vienna and German towns.
Arerrnair., MEER8CHAUM.-A cheap artificial imitation of meerschaum is made from gypsum, hardened, treat,ed with stearie acid or paraffin, polished, and c,oloured by a solution of gamboge and " dragon's blood." Meerschaum pipes are said to be now manufacttuod in Frane,e from potatoee. The latter are peeled, and placed in a mixture of 8 parts sulphuric acid and 100 parts water, for 36 hours, whereby they become black. They are next drie,c1 by blotting-paper, and submitted to pressure, becoming thereby a material which can be easily carved. The e,ounterfeit is said to be excellent.
Pipe-clay.—This is another variety of fine, plastic clay, so named from its application to the manufacture of tobacco-pipes. It is found in the counties of Cornwall, Devon, and Dorset, whence some few thousand tons are annually exported to Frane,e, Belgium, Holland, &e., besides that for home consumption. The composition of pipe-clay resembles that of china-clay, except that there is a preponderance of silica ; it may be approximately stated as 54 ; alumina, 32 ; water, 12; oxide of iron, lime, and magnesia, traces. The analysis of a light and a dark coloured sample from
Dorset gave respectively :—Silica, 65-49, 72-23 ; alumina, 21-28, 23-25; oxide of iron, 1 -26, 2-54; alkaline earths, 7-25, 1-78 ; sulphate of lime, 4-72, trace.
Pottery-clay.—The distiibution of clays suited for the manufacture of earthenware or pottery is very wide, and their origin is very various. They elways occur in more or less superficial beds, with but a slight thickness of earthy or gravelly covering, consisting of fine laminated silts of the Glacial period, or old estuary deposila, as well as river-valley accumulations, and re-formations from the waste and wash of the Boulder-clay. Their composition varies exceedingly ; e. g.:—Silica, 44 to 58; alumina, 24 to 38 ; oxide of iron, 1 to 7 ; water, 10 to 15 per cent. ; with traecs of magnesia and lime. Tbe e,oarser qualities approach briek-clay ; the finer, china-clay. The requisite properties are plasticity, colour, and the absence of proportions of iron or alkalies which might be prejudicial to the burning proeess. They are worked by ahallow pita, and are "ripened," ground, and washed, as the other clays.
(See Alum; Alumina; Cotton Manufactures ; Crucibles ; Paper ; Pottery.)