+--------------------------------------------------------------------------+ | Pastes. |Silica.|Alumina.| Oxide |Lime.|Magnesia.|Potash.|Soda.| | | | |of Iron.| | | | | |--------------------------------------------------------------------------| |China, 1st quality|69.00 |23.60 |1.20 |0.30 |0.02 |3.30 |2.90 | |China, 2d quality |70.00 |22.20 |1.30 |0.80 |traces |3.60 |2.70 | |China, 3d quality |73.80 |19.30 |2.00 |0.60 |traces |2.50 |2.30 | |China, 4th quality|68.94 |21.30 |3.48 |1.14 |traces |3.42 |1.78 | |Meissen |58.50 |35.10 |0.80 |0.30 |traces |5.00 |.... | |Vienna |59.60 |34.20 |0.80 |1.70 |1.40 |2.00 |.... | |Berlin |64.30 |29.00 |0.60 |0.30 |0.45 |3.65 |.... | |Limoges |70.20 |24.00 |0.70 |0.70 |0.10 |4.30 |.... | |Sèvres |58.00 |34.50 |.... |4.50 |.... |3.00 |.... | |Sèvres (sculpture)|64.10 |30.24 |.... |2.82 |traces |2.80 |.... | |Worcester |82.00 |9.10 |..... |1.30 |7.40 |.... |.... | |Paris |71.20 |22.00 |0.80 |0.80 |.... |4.50 |.... | +--------------------------------------------------------------------------+ The English artificial porcelain differs from the natural paste of China and the European continent chiefly in one particular. At first the compound used was white clay, white sand, and glass, the latter being employed to impart the necessary transparency. More recently bone came largely into use, and is now one of the distinctive ingredients of English paste. The phosphoric acid of that material was found to produce, in combination with the other materials, a clear, translucent body, of less strength than natural paste, but less liable to sink. The following may be taken as the mean composition: Bone, 47; kaolin, 34; felspar, 19. The kaolin is found in Cornwall, where a very large tract is formed chiefly of decomposed granite. The purest rock having been selected, it is placed on an inclined plane, upon which water can be turned. It is washed down into a trench, and thence into a catch-pit, and again into lower pits, in which successively the impure ingredients are retained, the water laden with the finer particles running into tanks, and there depositing its fine silt. The clay is partially dried, and cut into blocks, and in that shape reaches the potters. The manner in which the kaolin is prepared bears a very close resemblance to that adopted by the Chinese, as previously described. The glaze is composed of felspar, carbonate of lime, borax, and white-lead. Sometimes the kaolin is mixed with the bone and felspar in the proportions above specified, and sometimes the bone is made, in combination with silex and pearlash, into a frit.