The measure used in introducing the composition Must be so large, that when that is in the case it will raise the hammer one-half of the interior diameter, so that a separate measure is required for each size of rockets. It must be provided with a handle, and be so constructed as to enter entirely into the ease, that no composition may be lost, as every thing in the ac curacy of the performance depends on these minute attentions. In driving, it is necessary first to give a few gentle blows, that the composition may be con densed before much force is used; as otherwise the condensation of the air would blow it out; and the workman must also take care to turn the rammer, and to ease it in the case before every blow, to prevent it from being jammed by the materials mounting up be tween it and the sides of the tube. The same num ber of blows, and with the same mallet and force, must be given to each ladle-full of the composition; as these are essential to a correct performance. In the smaller, or in those which reach from two to four ounces, sixteen strokes are sufficient; a rocket of one pound will require thirty; of two pounds forty; of four fifty; and of six sixty. But beyond two pounds, we must remark, the force of a man's arm is scarcely available, and it becomes necessary, as in the military iron rock ets, hereafter mentioned, to adopt the pile engine. We have already remarked, that the rammers require to be changed as the composition advances.
When the rocket is filled to the top of the spindle, the quantity of a whole diameter in depth must then be added, in the same manner, by means of the short solid rammer, when the composition is completed.— Above this must be rammed one-third of a diameter of clay, which being afterwards perforated by a small gim blet, a communication is made between the rocket and its head.
The sky-rocket, thus far completed, must measure, from the choke, five diameters and a quarter, and the cases must then be cut to that length. The head is then to be fixed on. Where it is judged essential to have the highest flight, its diameter should not exceed that of the rocket, further than the requisite thickness of its case demands. See Plate CCCCLXXII. Fig. 5. But as in this way it can contain but a small quantity of stars, or ornament of any kind, it is usually made larger, and so as to exceed the exterior diameter of the case by a quarter of an inch all round, for diameters of an inch. The height is in this case near two inches, and in all other sizes the same proportions are preserved. This case or head is made slender, of two or three turns of paper at most, as it is sufficiently strong if it will bear the ordinary rough usage of packing and carrying; and it is surmounted by a paper cone of the same strength, which, for the same dimensions, is an inch and three quarters in length. If the head is simply larger than the case, it may be glued on at once; but if much larger, a ring of turned beech wood is interposed, and the is firmly glued together.
But preparatory to this, it is necessary that the head should receive its charge, whatever that may be. The directions for making stars will be found elsewhere; but we may here say, that if these are made in the or dinary form of balls, or short cylinders, they do not pack close. A better mode is to make the stars in a cylinder of the same diameter as the rocket head, and in the form of sectors, by which means they pack close ly in their place. This is easily done by means of an appropriate copper mould, or else the cylinder may he made, and then divided into compartments by a knife before drying. The directions for making serpents, or rains, or by whatever name these ornaments may be called, are also given in their proper places; and we need scarcely add that the lengths of these must, in all cases, be determined by that of the head in which they are to be enclosed. Before the rocket head is fixed on, care must be taken that the priming hole into the com position is free: as many ornaments, of whatever na ture, as it will contain, are then enclosed in the head, together with the requisite quantity of mealed powder, when the operation of fixing it in may be completed. A quantity of this, equal to one diameter, or less, of the rocket, is amply sufficient for bursting the head and in flaming the ornaments.
These ornaments are not very numerous, and we may describe them in a few words. The stars admit of be ing made of two or three colours, as will be seen when their compositions are mentioned ; but the differences to the eye arc so small at the distance where they are seen, that it is scarcely necessary to use any but the blue antimonial one. For the serpents, in the same way, all kinds of sparks have pretty much the same effect at that great distance; so that the most ordinary charcoal com position answers as well as any other. Where stars or serpents are to be used for ground fireworks, these dif ferences are worth attending to, because they are visi ble. There is a species of serpent, however, called scrolls, which may also be used, and which are made. on the same principle as the tourbillon ; they are de scribed hereafter. Lastly, crackers or maroons may be introduced into rocket heads, either alone, or in com pany with other ornaments, and the effect of these is amusing. They may be combined with the serpent or not. If the former plan be adopted, half the serpent case is fitted with the proper composition, and it is then nearly choked and secured, after which the remainder is filled with powder and choked close. If crackers alone are used, they must consist of similar cases, filled en tirely with powder; but they require a priming of cotton slow-match to give them time, that they may not ex plode within the head. The discretion of the artist will easily teach him how to vary all these subsidiary matters.