ON THE CHINA-STONE AND CHINA-CLAYS OF CORNWALL. 203 



. Until a very late period pottery manufacture was comparatively un- 

 known in England ; in the eighteenth century we were indebted entirely 

 to the Chinese for our best, and to the continental potteries for our com- 

 moner wares ; a century has but elapsed, and to the credit of the 

 industrious, the persevering, the indefatigably speculating, Englishman, 

 be it added, that from pole to pole, under any portion of the Globe's 

 equator, wherever the traveller may roam in search of adventure, no 

 less than through the length and breadth of his happy little island home, 

 he ■will find, in his cup, his plate, or his dish, a never-dying testimonial 

 to the enterprising character of the Englishman. 



In porcelain or China and the coarser variety termed pottery, the 

 ingredients are so combined as to act chemically on each other, the 

 decomposed felspar consisting of a fusible glass of silicate of alumina 

 and potash, more opaque than that formed by the fused silex in which 

 it is disseminated ; and when the body is formed of China-clay, infusible 

 at the highest temperature, in the process of vitrifaction, it is so acted 

 on, as to form a substance uniformly opaque, having a vitreous, waxy 

 fracture, aud when coloured by some metallic base is termed stone-ware. 

 There are two kinds of China or porcelain ; the one termed the hard 

 China was formerly imported from France, though, of late years, it has 

 been altogether superseded by the second variety, or soft China. The 

 body of hard China may be conveniently formed by a mixture of in- 

 gredients in the following proportions : — 



Kaolin, or China-clay 70 parts 



Felspar 14 „ 



Sand 12 „ 



Selenite 4 „ 



which calcined, forms the biscuit : this, after being dipped in a mixture 

 of potash and felspar, is again heated, when vitrifaction ensues, the 

 article possessing a homogenous translucent structure and not a mere 

 glaze or coat as found on the common earthenware. In making soft 

 China the English potters fully vitrify the ware by the first application 

 of heat, the shape of the article being kept by ground flint, removable 

 with ease after it is taken from the oven, and the glaze, being subse- 

 quently applied, is vitrified at a lower temperature than that used in the 

 formation of the biscuit of soft China, the ingredients used to form 

 which, are,— 



Bone 46 parts 



Kaolin 31 „ 



China-stone... 23 „ 



In making the glaze, a frit is first formed, which renders the glaze more 

 easily applicable to the surface of the biscuit, by calcining a mixture 

 similar to the following : — 



China-stone.... 25 parts 



Soda 6 „ 



Borax 3 „ 



Nitre 1 „ 



