Grinding Machines.
1. Grinding Machines.—For the purpose of triturating or properly mixing the several ingredients together, various contrivances have been resorted to. A common iron mortar, such as is used by druggists and apothecaries, is found to answer very well for grinding or pounding the brimstone, charcoal, salt-petre, &c. separately; and apothecary’s close sieves, fitted with wire-cloth, are the best possible implements for obtaining the fire powder; but when corn gunpowder is to be mealed, or the various ingredients are to be mixed together, such mortars cannot be used, as the heat generated by the continued action of the pestle might inflame the mixture, and thereby place the life of the operator in imminent danger. To obviate these dangerous probabilities a very simple contrivance has been effected; this is called the mealing table, and for that purpose has proved very speedy and effectual. It consists of a rectangular elm board, with a rim round its edge, four or five inches high, at one end of which a part of the rim is made to slide in a groove, so that after mealing the powder it may be swept clean out from the table. A representation of it may be seen at plate 1, [fig. 3. Fig. 4] is a small copper shovel, generally made use of for filling and emptying the table. When about to meal a quantity of powder, observe not to put too much on the table at once; but when you have put on a moderate portion, take the muller ([fig. 5],) and rub it till all the grains are well broken; then sift it in a lawn sieve, that has a receiver and top to it, such as is generally used by the apothecaries, and that which does not pass through the sieve must be returned to the table, and with an additional quantity ground over again. Sulphur and charcoal may be ground in the same manner, only these being much harder than powder the muller must be of ebony, or any other hard wood, else the ingredients would stick in the grain of the elm, and be very difficult to grind. As sulphur is apt to stick and clod to the table, it will be found best to have one for that purpose, as they are easily procured; this will be but little trouble, and more than compensated by your sulphur being always kept clean and well ground.