ON THE CHINA-BTONE AND CHINA-CLAYS OF CORNWALL. 2( >0 



In drab ware, — Caen marl, 32 ; Dorset clay, 22 ; China-stone, 45 ; 



and nickel, 1 part. 

 In jasper, — barytes, 32 ; kaolin, 15 ; Dorset clay, 15 ; stone, 33 ; 



and of lead, 3 parts. 



The glaze commonly used for the cream-coloured ware consists of 

 varying proportions of white lead and China-stone, or, as these may 

 craze, a frit of the following materials is often employed : — 



Of China-stone, 30 ; flint, 16 ; red lead, 25 ; soda, 12 ; and borax, 

 17 parts ; 26 parts of this are then mixed with 15 of China-stone, 

 10 of flint glass, 9 of flint, aud 40 of white lead ; which consti- 

 tutes the fritted glaze. 



The composition of most of the bodies and clays now used is a secret 

 confined to the walls of the mixing room, so that it is extremely diffi- 

 cult to ascertain, with any degree of accuracy, the influence of an excess 

 of ingredients ; thereby entailing a co-existent difficulty on the part of 

 the producer, in his endeavour to form or prepare a substitute for these 

 articles. 



- The China-clay or kaolin of Cornwall was first brought into notice 

 at a very late period, though the material itself has been long used ; in 

 fact, not only were the Chinese well acquainted with it, both in a raw 

 and a manufactured state, from the most remote ages, but it is also 

 probable, from the interesting evidences brought to light, through the 

 industrious exertions of Air. Layard, and from other sources, that the 

 Egyptians knew somewhat of its uses. 



When obtained by Mr. Cookworthy, in 1768, from the Lescrowse 

 and Trethose clay works, in the parish of St. Stephens a large supply 

 was at once demanded for the Staffordshire potteries, which has gradually 

 increased till the present time. 



A considerable amount of crude kaolin has been exported to every 

 pottery on the Continent, and also to those of our inquiring American 

 brethren, while a small portion has been used for bleaching. 



Kaolin is found intermixed with quartz and scales of mica, in most 

 valleys contiguous to the decomposing hills of the primary strata of our 

 county, and is not, as far as is at present known with regard to China 

 stone, confined to any particular district, being now obtained or obtain- 

 able, though of different qualities, on the south-western sides of either 

 of the granite districts ; yet, of course, poorest near those beds of China 

 stone which I before described as free from most deteriorating substances, 

 as in the parish of St. Stephens. 



It exists in these beds or stopes, as they are designated, as an 

 amorphous whitish-blue opaque powder ; which from the softening 

 influence and rainy character of the south- westerly winds, are most 

 frequent in valleys situated on the same aspect ; often lying on the con- 

 tiguous borders of the granite and killas, clay-slate, grawacke or transi- 



