(1) The material used for the glaze is a natural mixture of felspar and quartz, and is known as " pegmatite." Its average composition is - silica, 74.3; alumina, 18.3; potassic oxide, 6.5; calcic oxide, 0 '4; magnetic oxide, 0.2; water, 0.3; and it may be approximately represented by the formula 2(A12O2 3SiO2). + K2O, 3SiO2. It is therefore an ordinary glass, to which a second equivalent of aluminic silicate has been added, and the transparency of which is destroyed by the excess of infusible material. Each fresh supply of pegmatite is tested in order to ensure a constant result. For use, the pegmatite is first crushed under vertical grinding - wheels turning upon a revolving base. It is then ground with water in a mill with stone runners, and when reduced to a sufficient degree of fineness, is drawn off, sifted, agitated in the presence of magnets, in order to remove particles of iron, passed into a receptacle, and maintained in suspension by constant agitation. During the long process of grinding with water, great care must be taken to prevent a sudden precipitation of the material, either through the slackening or sudden stoppage of the stones. The tendency to precipitation may be retarded by mixing a small quantity of acetic acid with the water.

Into the suspended pegmatite the biscuit ware is dipped, care being taken that no part of one piece remains in the glaze longer than another, and that the thick wares shall be dipped in a thin glaze, and the thin in a thick. The parts of ware which have been held in the dipper's hand are retouched with a brush dipped in the glaze. The wares are replaced in saggers, and the saggers are arranged in the lower division of the oven, the heat of which is more intense than in the biscuit - kiln. The entire absence of lead renders the glaze when fused exceedingly hard and durable; it is bluish in tint, and cold to handle. The grey tint of the body and glaze is due to the reducing action of the atmosphere of the kiln. The glaze is transparent, and rather more fusible than the body, but becomes thoroughly incorporated with it, and, from its similarity of composition, expands and contracts uniformly with the paste. The bases of ware when removed from the saggers are rubbed smooth with sandstone. Owing to the difficulty of manipulating the paste, it is customary to build up elaborate vases from distinct pieces, which are joined together by metallic fittings; this especially applies to feet and handles. (Powell.)

(2) 40 parts Cornish stone, 45 red - lead, 38 borax, 32 1/2 flint, 22 1/2 flint glass, 18 crystal soda, 5 tin oxide, 1 enamel blue; make small, calcine, grind, and mix with water for dipping. (3) 40 Cornish stone, 36 flint glass, 20 red - lead, 20 flint, 15 potash, 10 white - lead, 3 tin oxide. (4) Crystal: 105 Cornish stone, 90 borax, 60 flint, 50 red - lead, 12 crystal soda, 10 tin oxide, 1/4 blue calx; this must be considerably diluted for dipping. (R. W. Hall.)