Of Scrolls.
This is a pleasing ornament, either for sky rocket heads, or for the purpose of discharging from pots or mortal's on the ground. Indeed, they are chiefly cal culated for this latter purpose, as their difference from a serpent, in point of effect, is not very sensible at a great distance, although sufficiently visible when near at hand. In effect, it is a sort of tourbillon on a small scale, but provided only with a rotatory motion.
The cases may be from four to six inches long, and the interior diameter half an inch. They must be filled with a lively composition, either of charcoal or iron, and driven hard in a mould. The open end of the case must be then beat down hard, and secured with glue in the manner often mentioned before. When they are thus far made, a hole must be bored at each end of the case, on opposite sides, a semidiameter in breadth. They require no priming, if care be taken that the holes arc free. But if they are to be thrown out of cases that do not contain much exploding powder, it will he safest to insert a bit of quick-match into the upper hole, or that most distant from the charge.
A bounce may also be combined with this simple scroll, but it is then necessary to give it at least a diame ter more in length ; and the middle of the case, for the length of a diameter or more, must be filled with gun powder alone.
Rains.
This is a kind of ornament mentioned in all the books of pyrotechny, but the effect is so very little different from that of a serpent, that it scarcely re quires notice. The cases for these are not choked ; Nv cnce the difference in the burning is, that they do not serpentize as the choked cases do. In sky rockets, they thus descend in straight lines to the ground, when discharged. Hence it is that they are less useful for fixed fireworks, as they are apt to fall to the ground before they are expended.
They must be driven hard in moulds, and need not be above four diameters in length. But, as when used for ornamenting sky rockets, it is desirable that they should carry their fire all the way to the ground, they may be timed so as to burn all the while they arc fall ing. This is easily done; because the time of descent
of the rocket stick, or of these ornaments, is, as nearly as possible, the same as that of the ascent, or, for a pound rocket, about twelve seconds.
In making these, the fire may be varied ; so that one part of the case is filled with a brilliant composition, and the others with a white or blue light. The artist, also, has it in his power to vary the effects, by causing either the one or the other of these to burn first. They may also be provided with a bounce at the end, in which case they come under the following division.
Of Sczucissons.
These, improperly enough named, are compounded of a brilliant fire and a bounce, and are of use only for discharges out of mortars, or pots fixed on the ground. They may be made two ways, either in choked or open cases. The cases may be about four inches, or from four to six inches, or even more in length, and the di ameters from three-eighths to one-half of an inch. The cases must also he strong, and they require to be driven in moulds. If they are to be choked, the brilliant composition must he driven in first, and so as to fill half the case. The case is then to be choked above it upon a small wire, so as to leave the least possible open ing of communication to the powder with which the remainder of the case is to be filled. This must be pressed down, but not rammed hard ; and the end of the case must then be turned in with glue, or else choked quite close upon a cylinder of paper. If they are to be open in the mouth, which must be done if they are to burn a blue or white, instead of a brilliant light, the powder may be introduced first, and then choked to a small priming hole, as before. The case is then to be returned into the mould, and the composi tion rammed in hard. In this way, there is no danger of bruising the powder, as the choke protects it from the force of the rammer. If the composition is to be a white or slow one of any kind, it need not occupy so large a part of the case, and the powder may be allowed proportionally more room.