74? PORCELAIN CLAY. 
1 1 8. PORCELAIN CLA Y is generally of white or reddish 
while colour, sometimes inclining to yellowish or grey. When 
dry, it absorbs moisture rapidly ; and it becomes very tenacious 
when kneaded. 
It is known from the other clays by the fineness of its par- 
tides, its .wiling thejingers much uhcn handled, and its fine 
but meagre feel. 
The usual distinction betwixt earthen ware and por- 
celain is, that the former is opaque, and the latter semi- 
transparent. In the manufacture of porcelain the clay 
is sometimes -used alone, and sometimes intermixed 
with other earths, or with felspar (110). The earliest 
manufacture of porcelain is supposed to have been that 
in China and Japan. The quantity produced in China 
must formerly have been extremely great ; as not only 
a considerable portion of the eastern parts of the world, 
but almost the whole of Europe, was supplied with it. 
la a single province it is said that nearly a million of 
persons were at one time emplo} r ed in this manufacture. 
The manufactory at Sevres, in France, has long been 
celebrated both for the excellence and elegance of its 
porcelain. There are well-known manufactories of por- 
celain at Meissen in Saxony, at Berlin, and in Austria; 
but none of these are at present superior to our own, in 
Worcestershire and Staffordshire. 
Porcelain clay occurs chiefly in countries which 
abound with granite (251) and gneiss (255). It is found 
in small quantity in Cornwall, and other granite districts 
of England, as well as in those of Scotland and Ireland. 
But the most valuable kinds of this clay are found in 
China and Japan. 
The mineral is not used in the state in which it is 
found in the earth ; but is previously washed several 
times to free it from impurities. After the process 
of washing, only about fifteen parts of pure clay re- 
main : this is the kaolin of the Chinese. To form the 
composition of the porcelain, this clay is mixed, in cer- 
tain proportions, with quartz (76), flint, gypsum (192), 
