90 
Clay in common is best characterized when wet and 
soft, in which state it is most generally found below the 
common surface of the Earth. It is known by its plastic 
qualities, and fitness to be formed into any shape. Thus 
specimens of common Clay are scarcely to be described by 
their fracture, and, being generally gathered in a moist state, 
have the marks of the tool, and are frequently made into 
balls or squares. Their tenacity, however, gives them a 
raggedness in breaking, rather peculiar to themselves, 
smoothest on the sides, and somewhat roughish or earthy ; 
but when dry it varies much, according to circumstances, 
and is sometimes a little conchoidal. It is chosen as white 
as possible for pipe-making, and for the finer purposes, and 
certain proportions of different kinds are used to suit the 
intention of the potter. For making tobacco-pipes it is 
burnt or baked so as to stick to the tongue or lips, but 
is sometimes polished. In making china it is generally 
more baked and smoother, which adds to its hardness. 
This is said to be the best Clay for glass-house melting- 
pots. It is often used in the composition of artificial stone, 
and for cleaning cloth, wool and leather. 
Pure Clay is said to have been found at Halle, in Saxony, 
but some doubts have arisen as to its being natural. This, 
according to Fourcroy, is composed of 
ieee ot eee 
Sulphateof Lime . . 924 
NWAtEL 7. ys enmag oem 
Silica anda Muriate . 4 
