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. How to Make Touch-Paper. Dissolve in a little spirits of wine or vinegar a little saltpeter, then take some purple or blue paper, and wet it with the above liquor, and it will be fit for use. When pasting paper on any of the following works take care that the paste does not touch that part which is to burn. The method of using this paper is to cut it into slips long enough to go once round the mouth of a serpent, cracker, etc. Cases for Squibs, Flower-Pots, Rockets, Roman Candles, Etc. Procure a hard wooden cylinder, or, if possible, one made of metal, whose diameter corresponds with that of the interior of the proposed case. Roll round it several folds of cartridge paper, and paste the edges well, so that it may be held securely. Tie it round until dry. To Choke the Cases. When the cases are thus made they will require to be tied at the lower end. This is called choking them, and as much force is required it is necessary. Fix a wire into a small solid cylinder. Take another short piece, an inch or two long, with a hole up it to admit the other end of the wire, fit it on, and pass it up the case. Then having fastened a piece of whip-cord to a post, wind it round the part left hollow by the wire, which should be about half an inch from the end; pull it tight with the right hand, and work the case round with the left. Cut out a piece of touch paper two inches long, and an inch and a half broad, wind it round the choke, and tie it on with a piece of fine string--twist it to a point. The cases are best choked while damp. Composition for Squibs, Etc. Gunpowder, half a pound; charcoal, 1 ounce; brimstone, 1 ounce, or in like proportion; grind them in a muller or pound them in a mortar. Or you may take 1 part steel filings, 1 charcoal, 1 sulphur, and 4 powder, which is a very good mixture, and can be rubbed together in a mortar. How to Fill the Cases.