1814.] On the Porcelain Earth of Cornwall. 181 



I. Steatite* which is found at Cape Lizard in what are described 

 as veins t that traverse rocks of serpentine. 2, Granite, the felspar 

 of which is in a disintesfrated state. 3. Porcelam earth. Ihe 

 object of this paper is to describe the mode of preparing the two 

 last-mentioned substances for exportation. 



It is not improbable that porcelain earth, or, as it is denominated 

 by the workmen, « China clay," may be found in several parts of 

 Cornwall ; but the prei)aration of it for the manufacturer was, when 

 I visited that country in IbOJ, confined to the parishes ot St. Ste- 

 phen and St. Denys, in the neighbourhood of St. Austle. There 

 were at that time seven different works, viz. : two at Hendra, m 

 tlie parish of St. Denys; and in that of St. Stephen, two at Tre- 

 viscoe, and one respectively at Gonnemarris, Goonvean, and Tre- 

 thorsa. These were carried on by manufacturing companies of 

 Staffordshire and other places, for their own consumption ; and I 

 believe in one instance by a company at Plymouth, who prepared 

 the clay and sold it to manufacturers who had not works of their 



own. 



b LJ. . 



The country around the works is a wild and barren moor; the 

 ground being in general uninclosed, and of very little value for the 

 purposes of agriculture. The rock which forms its basis is granite, 

 consisting of a large proportion of felspar in a disintegrated state, 

 with little mica and quartz, and some specks of a greenish sub- 

 stance, probal)ly steatite. 



To each of the works for the preparation of the porcelain earth 

 there is annexed a " quarry," where the granite itself is extracted, 

 in a solid form, for the use of the manufacturer. It is detached 

 from the rock by means of blasting and wedges, and then broken 

 into pieces of a convenient form for exportation, the hardest of 

 which are preferred, on account of their more easy carriage. These 

 pieces, as well as the prepared " China clay," are conveyed in carts 

 to St. Austle and to Charlestown, in the neighbourhood ot that 

 place ; from whence the greater part, if not the whole, is shipped 

 for Plymouth, and thence to the potteries, where the granite is 

 subsequently prepared for the manufacturer by grinding and washing. 



The " clay pits," as the jilaces are called where the porcelain 

 earth is dug, are all situated in " bottoms," in the course of valhes 

 or ravines which traverse the surface of the country ; the accumu- 

 lation of tliis earth appearing to have arisen from the detritus of the 

 granite brought down by water from the more elevated ground. 

 The " clay," as might have been expected from its apparent mode 

 of deposition, is found at various distances from the surface ; in 

 some places close to it, in others several feet below. Immediately 



• The names of minerals employed in this paper are those of Mr. Jameson's 

 8)*lein iif .MiiK'rul(i(;y. . .c i • 



t Or. Tlwiiiiioii, however, mpposes the steatite at the Lizard to be mcreiy » 

 poriii-u of ihe s.rpei.iine itself, altered by the action of wat«r, or some oiiui: 

 «4u«c.'" — AnnuU uj i'hUotoyliij, vol. ii. j>. '^>' , 



