METHOD OF MAKING POTTERY

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would be pervious to fluids. Ordinary pottery is glazed with asemi-vitreous oxid of lead, or by throwing common salt over itin the furnace.

The yellow or queen’s ware, is made of die same substancesas the common flint ware, but in different proportions. Theglazing is also different, it is made by mixing together in waterto a consistence of cream, 112 parts of carbonate of lead, 24parts of ground flint, and 6 of flint glass. The ware before itis glazed is baked in the fire, by which it acquires the propertyof strongly imbibing moisture; it is then dipped in this composi-tion and quickly taken out. It is afterwards exposed a secondtime to the fire, by which means the glaze it has imbibed ismelted, a thin glossy coat is formed upon its surface which ismore or less yellow, according as a greater or less proportion oflead has been used. Porcelain, or china, is a semi-vitrifiedearthen ware of an intermediate nature, between common wavesand glass. Chinese porcelain is said to be composed of two in-gredients, one of which is a hard stone called Petuntse, whichthey carefully grind to a very fine powder; and the other, calledby them Kaolin, is a white earthy substance, which they mix in-timately with the ground stone. The former is of the siliceous,and the latter of the aluminous nature.

The manufacture of bricks is a coarser species of the same art.