=3. Grinding the Fused Mass.=—The smalts is next powdered under stamps. These only differ from the ordinary construction in that both stamp and trough are made of granite. The coarse powder from the stamps then goes to mills of ordinary construction, in which it is ground as finely as possible in a current of water. A blue liquid runs from the mills into tubs. The coarser particles which settle in these vessels constitute the article known commercially as strewing smalts, which is of small value. The quantity of this quality is fairly considerable; it cannot all be sold; part is fused in a later operation with a fresh quantity of the fritted mixture. The liquid remaining in the tubs then gives the different qualities of smalts. After having deposited the coarsest particles in the first vessel it is brought into another, in which it stays only a few minutes, when it is run off into another vessel, in which also it remains but a short time. The liquid goes in this manner through from three to five vessels, and in the process deposits all the coarser particles. The oftener the liquid is brought into fresh vessels the finer are the particles still suspended in it, and the longer it should remain before being drawn off into another. When the liquid has run through three or four vessels, as the case may be, it still retains the finest particles in suspension. It is now run into a tank, in which it remains until it is perfectly clear and has deposited all the blue. The deposit in this tank has a dirty bluish-grey colour; it is utilised by being added to a later fusion. It would be expected that this last deposit would have the best shade, since it consists of smalts in the finest state of division, which would no doubt be the case if the smalts remained unchanged. Smalts is, however, a glass which is rather easily decomposed. In grinding, the smalts comes in contact with large quantities of water, and in the succeeding levigation the water decomposes it; the final residue is thus produced. In view of the easy decomposition of smalts by water, it is necessary to carry out all processes in which it is in contact with water as rapidly as possible, in order to obtain the largest yield of smalts. The smalts deposited in the successive vessels have a different degree of fineness, and are sold under particular marks. The Saxony works, which produce the greater part of the smalts used in Germany, distinguish the qualities by letters. The better qualities are distinguished by the same letter, the fineness of the quality being indicated by the repetition of this letter. Thus FFFE, FFE, and FE indicate qualities which are of lower value the less often the letter F occurs in the mark. The qualities following those marked F are distinguished by M; the lowest quality is marked OE. F indicates fine; M, medium; and O, ordinary.