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POPULAR SCIENCE REVIEW. 
dazzling white clay, which never fails to attract the attention of 
tourists. 
The object of the present paper is to describe the salient 
features of this industry. Most people know that u china ” was 
first brought by the Portuguese from China — hence the name. 
It was called by them a porzellano,” because it was supposed to 
be fabricated from sea shells : hence the term u porcelain ; ” but 
no real knowledge was obtained of the materials used until the 
publication of the reports of the Jesuit Father D’Entrecolles, 
in 1712, and of Count Reaumur, in 1729. These reports led 
to the establishment of the manufactories at Dresden, Sevres, 
and Plymouth — the last-named having been established in 1733. 
Up to 1745, the fine porcelain materials used in the Plymouth 
works were imported ; but soon after that time, Mr. Cookworthy, 
the founder of the works, discovered 66 kaolin ” (which he calls 
grow an clay , now called china clay), and the “ petuntze ” 
(called by him growan or moorstone , and now known as china 
stone) similar to or identical with that used by the Chinese, 
in several parts of Cornwall in great abundance. In conjunc- 
tion with Lord Camelford, he took out a patent for the use of 
these materials in 1768. How these materials are used in the 
manufacture of porcelain, earthenware, and more recently in 
many other British manufactures, forms no part of the subject 
of the present paper — this is limited to a description of the 
modes of occurrence and of preparation of the china clay and 
china stone. 
China clay is prepared by washing a peculiarly white decom- 
posed granite, which occurs very largely in the granite district, 
north of St. Austell, as well as in many other parts of Cornwall 
— and also in Devon. This natural china clay rock, which has 
been elsewhere called “ Carclazyte,” is simply a granite com- 
posed of white or pale smoky quartz, white mica (lepidolite), 
sometimes a little greenish-yellow gilbertite, and white felspar, 
in which the latter is partly or completely metamorphosed 
into kaolin. This modification of granite occurs in areas of 
irregular form, generally much elongated in one direction, and 
extending to an unknown depth. It is in the West of England 
universally associated with quartzose and schorlaceous veins — 
evidently of later origin than the rock itself — which sometimes 
also contain oxide of tin. The greatest extension of the decom- 
posed granite coincides with the 66 run ” or “ bearing ” of the 
veins, and is more complete as the vein is followed downwards 
in depth.* 
• In a paper read before the Royal Geological Society of Cornwall in 1876, 
I have given my reasons for believing that the decomposition has been pro- 
duced in situ by fluids circulating within the fissures, joints, and shrinkage 
