Gunpowder.
It will not be very advisable for the firework boy to make his own powder, but still it will not be amiss that he should know how it is prepared. Pulverize separately 5 drams of nitrate of potass, 1 dram of sulphur, and 1 dram of newly-burnt charcoal; mix them together in a mortar, with a little water, so as to make the compound into a dough, which roll out into round pieces of the thickness of a pin upon a slab. This must be done by moving a board backwards and forwards until the dough is of a proper size. When three or four of these pieces are ready put them together, and cut them off into small grains. Place these grains on a sheet of paper, in a warm place, where they will soon dry, but away from a fire. During granulation the dough must be prevented from sticking by using a little of the dry compound powder. This mode of granulation, though tedious, is the only one to be used for so small a quantity for the sake of experiment. In making powder in a large way it is granulated by passing the composition through sieves.