There are three different sorts of porcelain: 1. The Chinese and Japanese, with which may be assimilated the German and French, all of them made of kaolin and felspar, sometimes with an addition of quartz. The principal seat of this manufacture is now in France, with Limoges for its centre. 2. The soft porcelain, of which the most perfect type is the old SA"vres, includes those of Chelsea, Bow, Worcester, and Derby. In all these the transparency, which is the distinctive feature of porcelain, is secured by the introduction of _fritt_, a mixture of sand and alkaline materials thoroughly vitrified, ground and made workable by an addition of plastic clay. The calcareous marl used at SA"vres gave to the French works a superiority over the English, who could only use the clays from our southern counties. The manufacture of the soft porcelain, on account of its difficulties, is almost abandoned. 3. The English porcelain, the body of which is made, like the hard, from kaolin and Cornish stone, but differing from it by the addition of a large proportion of calcined bones. This kind is exclusively English. For the hard porcelain, the glaze is made from felspar containing a variable quantity of quartz, or, as in Germany, from quartz vitrified by an addition of gypsum, the melting of which in both cases requires a very high temperature. For the glazing of the two other classes of porcelain, a soft, vitreous mixture containing silicate of lead and borates is used, the temperature necessary to melt these being much inferior to that required for firing the biscuit. The most ancient porcelain is, as everyone knows, the Chinese, which, relying on the few authorities that have written on this subject, may have been in existence for two thousand years, and is said to have reached its greatest perfection towards the eleventh century of our era. The Portuguese have the credit of having been the first to introduce it in Europe, in 1520; but it is not improbable that, before they doubled the Cape of Good Hope, some specimens were brought to Europe through India and Persia. This may be inferred from the mention by ancient historians of some extraordinary white vessels, which could hardly correspond to any other kind of ware. The Portuguese and the Dutch, who were the first to explore the Chinese seas, seem to have derived a good trade from the importation of the porcelain into Europe, and, since then, the reproduction of that refined pottery was the ambition of many alchemists, who pursued their experiments in that direction with an eagerness almost equal to that wasted in the search for the philosopher's stone. For a long time, in consequence of the imperfection of their chemical knowledge, their efforts ended in failure. The only successful attempt was that of Francis II., one of the Medicis, who produced a few pieces of soft porcelain recognizable by their mark, representing the dome of Florence.