Gerbes, so called from the French word for wheat-sheaf, which they resemble, are fixed choked cases: they do not show well on wheels. As they contain grains of iron, they must not be under ⁶/₈; for private exhibitions a good size is ⁹/₈, ⁹/₈ internal diameter; ¹²/₈ external; ³/₈ the diameter of the choke; 11¹/₄ inches, length of case. Charge the case on a nipple, exactly like a wheel case. It is advisable to put in, first, a little clay, to protect the choke, as the fire, being fierce, would, otherwise, enlarge it, and diminish the ascent of the sparks. Upon the clay drive in a scoop of starting fire, and fill up with gerbe composition. This, when containing iron borings, is termed Chinese fire; the pieces, Chinese trees.

The most magnificent of all, however, is the coloured gerbe. For this, some green, blue, and crimson grains, or small stars must be prepared. They may be quarter-inch cubes, cut as directed for the chopped nitre stars. A far better way, however, of preparing them, is to remove the pin a, of fig. 2, up to c, so that the stars, driven in the tube, will be ⁵/₈ inch diameter, and ³/₈ thick. When these are dry, chop them into 4 pieces, by holding a knife, or chisel, across them, and giving it a smart blow with the mallet. They are harder made this way.

To charge the cases: having driven in the clay, and the starting fire, put in 7 or 8 stars, then a scoopful of fuse No. 1 or 2, then 7 or 8 more stars, and another scoop of fuse; mallet the whole 4 layers down firm, with blows not too heavy at a time, but many times repeated. Then put in 7 or 8 more stars, another scoopful, 7 or 8 more stars, and another scoop, and mallet the 4 layers as before; and so repeat. The two layers and the two scoopfuls may fill up, when malleted in, ³/₄ of an inch, in a ⁹/₈ case.

Instead of choking the cases, plaster of paris is far preferable. Let it be ³/₈ of an inch thick, and well dried, before charging. After the cases are charged, bore a hole through the plaster, ¹/₃ of a diameter, that is, with a ⁹/₈ case, ³/₈ of an inch diameter. For this purpose it is not necessary to have another shell-bit; bore it with the ³/₁₆, and enlarge it with a penknife. It is better arched under, till conical, as shown in fig. 48. Prime with 4 or 5 pieces of match, and wash with the sash-tool.

The gerbe being finished, make a cylindrical box, or paper bag, of 2 or 3 thicknesses of paper: fill it with a number of crackers, and a scoopful of meal powder, and fasten it to the gerbe.

No single piece is more effective than a coloured gerbe; the stars will be projected 30 feet, or more: they may be put in, mixed; or, one layer may be blue, another green, another crimson. Twist a piece of wire, deprived of its elasticity, round the neck, and another piece round the bottom, and leave long ends; it can then be fastened by them to the top of a post. To remove the elasticity from iron wire, lay it in the fire till red hot; withdraw it with the tongs, and put it aside, to cool slowly. If copper wire is used, it will bend without preparation. String must not be employed, as it might burn, and let the case fall. Common pins, patent short whites, deprived of their elasticity, are useful for connecting the parts of lustres together.