Cast-iron being of so hard a nature, as not to be cut by a file, we are obliged to make use of the following method to reduce it into grains, though somewhat difficult to perform; but if we consider what beautiful sparks this sort of iron yields, no pains should be spared to granulate such an essential material, to do which you must proceed thus: get at an iron foundry some thin pieces of iron, such as generally runs over the moulds, at the time of casting: then have a square block made of cast iron, and a square hammer of the same metal, about four pound weight; then, having covered the floor with cloth, or something to catch the beatings, lay the thin pieces of iron on the block, and beat them thereon with the hammer, till you have reduced them into small grains, which afterwards searce with a very fine sieve, in order to separate from them the fine dust, which is sometimes used in small cases of brilliant fire, instead of steel dust; and when you have got out all the dust, sift what remains with a sieve a little larger, and so on with sieves of different sizes, till the iron will pass through about the bigness of small bird shot: your iron being thus beat and sifted, put each sort into wooden boxes or oiled paper, to keep it from getting rust. When you use any of this iron, observe that you make a difference in its size, in proportion to the cases for which the charge is intended; for the coarse sort of it is only designed for very large gerbes, of six or eight pound weight. Charges for Sky-Rockets, &c. For Rockets of Four Ounces. Mealed powder one pound four ounces, saltpetre four ounces, and charcoal two ounces. For Rockets of Eight Ounces. I. Meal powder one pound, saltpetre four ounces, brimstone three ounces, and charcoal one ounce and a half. II. Meal powder one pound and a half, and charcoal four ounces and a quarter. For Rockets of One Pound. Meal powder two pound, saltpetre eight ounces, brimstone four ounces, charcoal two ounces, and steel filings one ounce and a half. For Sky Rockets in general. I. Saltpetre four pound, brimstone one pound, and charcoal one pound and a half. II. Saltpetre four pound, brimstone one pound and a half, charcoal one pound twelve ounces, and meal powder two ounces. For large Sky Rockets. Saltpetre four pound, meal powder one pound, and brimstone one pound. The following Compositions may be used for Rockets of a middling size. I. Saltpetre eight pound, sulphur three pound, meal powder three pound. II. Saltpetre three pound, sulphur two pound, meal powder one pound, charcoal one pound. Compositions for Rocket Stars. For White Stars. Meal powder four ounces, saltpetre twelve ounces, sulphur vivum six ounces, oil of spike two ounces, and camphor five ounces. For Blue Stars. Meal powder eight ounces, saltpetre four, sulphur two, spirits of wine two, and oil of spike two. Coloured, or variegated Stars.