504 
Cornish China Clay . 
[October, 
No generally accepted conclusion has yet been arrived at 
as to the direcft causes of formation of the kaolin, or china 
clay. Mr. Collins is of opinion that it is formed through 
the adtion of fluorine, because fissures which invariably 
contain minerals (tourmaline and mica) of which fluorine is 
an essential ingredient are always present in the clay. Tin, 
too, is frequently found in connection with kaolin, which 
some geologists believe is brought there by the agency of 
fluorine. To this theory of formation we are strongly dis- 
posed to incline. Mr. Collins has himself adted upon 
granite with dilute hydrofluoric acid, and, without otherwise 
altering its appearance changed it into kaolin. It may be 
mentioned that most of the kaolin found in Europe consists, 
with slight variations, of Al 2 0 3 , 2 SiQ 2 -}- 2 H 2 0 .* 
The other principal materials used in the preparation of 
porcelain are bones and flint, the latter being employed for 
hardening the ware.f Inferior descriptions of clay used in 
the Potteries are obtained from the counties of Devon and 
Dorset, especially from the neighbourhod of Teignmouth, 
where the much-used ball clay is found. At present there 
are 117 china clay works in Cornwall leased or rented from 
the freeholders of the land, and it has been roughly calcu- 
lated that about 1600 working hands altogether are em- 
ployed. In Devonshire there are eight different clay works, 
all in the vicinity of Lee Moor. 
The method of raising the china clay in Cornwall is inte- 
resting. With the exception of a few modern improvements 
it is very similar to that pursued for many hundreds of years 
past by the Chinese clay raisers. And indeed many of the 
plans in clay raising and pottery manufacture invented and 
adopted by Europeans are merely unconscious repetitions of 
those practised long before by the workers in China and 
Japan. The clay is worked in open cuttings, which at some 
of the principal works are of very considerable extent and 
* No very great amount, indeed, of scientific inquiry has yet been brought 
to bear upon the subject of the kaolin formation ; nor does any chemical work 
to which we have been able to gain access bestow much attention on the point. 
Watts’s Dictionary of Chemistry, vol. i., says “ It (kaolin) may be supposed 
to be formed from orthoclase, or K 2 0Al 4 0 3 6Si0 2 , by the abstraction of the 
whole of potash and § silica, and addition of 2 at. water,” but offers no sug- 
gestion as to how this may by nature be brought about. Watts also says “ the 
averagecomposition (of kaolin as naturally found) is Al 4 0 3 ,2Si0 2 + 2 Aq,” but 
Ure’s, Tomlinson’s, and other scientific cyclopaedias agree with the formula 
Al 2 0 3 2Si0 2 + 2 Aq, which latter is the most correct, so far as the major quantity 
of kaolin found is concerned. 
f Pegmatite, a substance found rarely, but which deserves more attention 
from geologists than has hitherto been bestowed upon it, is said to contain in 
its natural state all the necessary ingredients for porcelain.— See Tomlinson’s 
Cyclopaedia of Useful Aits, 
