The best crucibles are composed of the following compositions, which are of two kinds-namely, with and without plumbago. 3 parts by measure of the Stourbridge best crucible clay, 2 parts cement, consisting of old used-up fire-bricks, and 1 part hard coke. These ingredients must be ground and sifted through a 1/8 in. mesh sieve; the sieve must not be finer, otherwise the pot will crack. This composition must be mixed with sufficient clean cold water, trodden with the bare foot to the consistency of stiff dough and allowed to stand for 3 or 4 days, well covered with damp cloths, to admit of its sweating and the particles of clay becoming thoroughly matured. It is then ready for use, and must be blocked by hand on a machine. Owing to the coarseness of this composition, the pot can not well be thrown on the potter's wheel; and in no instance can it be made by pressing. The crucible must not be burnt in a kiln, but merely highly and thoroughly dried before being placed in the furnace for use. For brass and copper melting, it will stand one good hard day's work; but care must be taken to replace the pot again in the furnace after the metal has been poured. If the pot be not allowed to go cold, it will last for several days. It will, with the greatest safety, stand one melting of wrought-iron. The cost, when made on the steel manufacturer's own premises, is about forty cents per pot, each pot holding from 100 to 120 pounds of metal. Good Hessian crucibles are composed of 2 parts of the best German crucible clay and 5 parts pure fine quartz sand. This composition must be sifted through a 1/8 in. mesh sieve; it is then tempered and trodden with the bare foot, as before described. When ready for use, it is pressed into different sizes of crucibles, which, when thoroughly dry, are placed in the kiln or furnace and burnt hard.

Another composition: 2 parts best Stourbridge crucible clay, 3 parts cement; sift through a 1/8 in. sieve; temper as before described and block by hand on the machine. When thoroughly dry, it is placed in the kiln and burnt hard. These crucibles are principally used for melting gold and silver, and also for dry analysis. The best and most perfect fire-clay for crucible making is nearly always found in the pavement of coal. Some of the Pittsburg fire-clays, and those found to exist in the pavements of some of the Pennsylvania coal-mines, are excellent fire-clays. But the various compositions can not be described, as they are as numerous as the different kinds of clay. The Birmingham soft tough pot consists of 2 parts of the best Stourbridge crucible clay, 3 parts plumbago, and 1 part cement, consisting of old used-up crucibles ground and sifted through a 1/8 in. mesh sieve.

Another composition: 4 parts of the best Stourbridge crucible clay, 3 parts plumbago, 2 parts hard coke, and 1 part cement, consisting of old pots ground and sifted as before. Where old pots can not be had, the above composition must be burnt hard, ground, and sifted. The scales or chippings of the insides of gas retorts are far superior to the best common hard coke. Hut where scales and chippings can not be had, bard coke is the best substitute. All the ingredients of this composition must be sifted through a 1/8 in. sieve(but not finer), tempered, and made as before described. When thoroughly dry, it is placed in the kiln and annealed, but not burnt hard. This composition makes a pot (for melting the hardest metal) which can not be melted at any pitch of heat, nor can it be cracked with the most sudden heat ing and cooling. It is regularly known to stand 14 and Hi meltings of iron-even wrought iron. Any steel manufacturer can make the pot on bis own premises at a cost of $1.20 or thereabouts, the pot holding from 100 to 120 Lbs. of metal.