MINERAL RESOURCES OF DEVON AND CORNWALL. 203 
able china clay from 5 to 10 tons of useless matter, in the shape 
of overburden-—rocks, stones, gravel-sand, mica, and shine, have 
to be handled at considerable cost. At the Lee Moor Works this 
cost is considerably abated by the utilization of much of the sand, 
mica, and coarse clay in the manufacture of large quantities of a 
very superior fire-brick, which has deservedly obtained a very high 
reputation, not only in this country, but also on the Continent. In 
some localities in Cornwall where water is scarce, the water run off 
from the clay is pumped back again to the higher level for use over 
again. In other localities where it is abundant it is a question 
whether great economy in labour would not be effected by the 
adoption of the Californian hydraulicing system, by which the 
clay might be washed out without the labour of digging. 
The large quantities of refuse Mica deserve consideration as to 
the feasibility of application to some useful purpose. It consists 
principally of silica and alumina, with from 8 to 14 per cent. 
potash. If by some economical process this potash could be set 
free, it would be a valuable agricultural material. 
China stone is principally raised in the neighbourhood of St. 
Austell. It consists principally of quartz and silica, with felspar 
and little, if any, mica. It is used for the manufacture of glaze for 
china, the china clay being reserved for the production of the body 
or biscuit ware. ‘The principal localities of consumption of china 
clay are the Potteries in Staffordshire, and the cotton mills of 
Lancashire. It is used principally in the production of earthen- 
ware and china, but is also employed in the manufacture of alum, 
of ultramarine, of paper, and what is technically termed bleach in 
the production of cotton cloth, on which it is pasted for the purpose 
of producing body and colour. It has a limited consumption also 
in the manufacture of paper hangings. 
It is largely exported to the Continent—to France, Germany, 
and Russia—and also to the United States. 
It is said to have been at one time used in this country in the 
adulteration of flour. I have reason to suspect that on the Continent 
it is still used for this nefarious purpose, as some time since, 
amongst other samples of mineral offered me for sale by a German 
house was one which, under the denomination of Pierre Mort, I 
found to be china clay, and the use of which I found on inquiry 
was for the manufacture of ship biscuits. 
The value of the 216,000 tons of china clay and china stone 
