A pointed cap, adapted to the summit, will make a rocket ascend to a greater height, as it serves to facilitate its passage through the air. To these rockets may be added several other things; as a petard, which is a box of tin plate, filled with fine gunpowder, placed on the summit. The petard is put on the composition, at the end, when it has been filled, and the remaining paper of the cartridge is folded down over it, to keep it firm. The petard produces its effect, when the rocket is in the air, and the composition is consumed. We have already remarked, that the upper parts of rockets, that is to say, their heads, are generally furnished with some composition, which takes fire, when it has reached its greatest height, emits a considerable blaze, or produces a loud report and whizzing noise. Of this kind are saucissons, marrons, stars, showers of fire, &c. The heads of sky-rockets, are, therefore, furnished with a variety of compositions.
When a rocket is five diameters, and one-sixth in length, the case being cut to this length, after it is filled, the head should be two diameters high, and one diameter 1/6th, and 1/2 in breadth. The perpendicular height of the cone, or cap of the head, must be in diameter, one, and one-third. There is a circular collar, to which the head is fixed, turned out of any light wood; its exterior diameter must be equal to the interior diameter of the head. One-sixth is sufficient for its thickness, and round the outside must be a groove. The interior diameter of the collar should not be quite so wide as the exterior diameter of the rocket. When it is to be glued on the rocket, two or three rounds of paper are to be cut off, which will make a shoulder for it to rest upon. Two or three rounds of paper well pasted, will be sufficient for the head. Put the collar on the mandril, or former, which must fit the inside of the cone when formed; then, with a pinching cord, pinch the bottom of the head into the groove, and tie it with small twine. To make the caps, cut the paper in round pieces, equal in diameter to twice the length of the cone, which is to be made. These pieces, being cut into halves, will make two caps each. Paste over the caps a thin white paper, which must be a little longer than the cone, so as to project about half an inch below the bottom: this projection of paper being matched and pasted, serves to fasten the cap to the head, A conical former is used to shape the head.
Sec. IV. Of the Decorations for Rockets, and the Manner of filling their Heads.
Having, in the preceding section, shown the mode of forming heads, or conical caps, for rockets, we may now remark, that the furniture or decorations for rockets consist of stars of different kinds, such as tailed, brilliant, white, blue, yellow, &c. or gold and silver rain; or serpents, crackers, fire-scrolls, or shining marrons, or small rockets; the kind of the decoration depending entirely upon taste and fancy.
In loading the heads of rockets, a ladleful of powder must be put into each head, along with the decorations. This is absolutely necessary in order to burst the head and disperse the stars, &c.
Various experiments have been instituted, to make rockets, by employing sundry compositions for charging the cases, along with the rocket composition, to produce, like the heads of rockets, when they burst, different appearances. M. Morel informs us, that he made several experiments with that view, but did not succeed. He ascribes the failure to several causes; and, in substance, concludes, that such figures have a greater weight than rockets are able to carry; that their irregular forms and movements produce, in the ascension, a contrariety of effects, which impedes their flight; and that, if they were to succeed, the rapidity, with which the fuse passes through the air, would prevent any thing being distinguished. As such exhibitions are shown with effect, by the bursting of the head of the rocket, after it has ceased to burn; we are of opinion, that the only mode, which can be adopted, with success, is the one already described. For after the rocket has ceased, or finished, the last portion of fire is communicated to the head, containing the decorations, which is blown off, and its contents are inflamed and dispersed. It is true, however, that, in some compositions, stars, previously made, and therefore not mixed with the composition, are put in the cases along with the charge: We have an instance of this in the fire-pump, Roman candle, &c. The cases for these are filled in the following order: first with gunpowder to a certain extent, then a star, then composition; then powder again, then another star, and so on alternately, until the charge is completed; but, in this instance, the star, as well as the gunpowder, is distinct from the composition, which forms the fire-pump. For, while the composition performs one part, the gunpowder acts another, by throwing the stars out, which, by their combustion, give the appearance they are intended to produce. Stars may be formed, or rather exhibited, in this way, which, in fact is much after the manner, in which they are used for the heads of rockets. But the experiments of Morel appear to have been made, with a view to produce that effect from the rocket itself, and altogether by the composition, by varying or otherwise modifying it. Star-composition, it must be observed, is of a greater specific gravity than any ordinary composition, in consequence of the weight, and quantity of metallic and other substances, which enter into it. By arranging stars in cases, in the mode described for the fire-pump, the effect, we have spoken of, always takes place. In rockets, however, which require to be driven with considerable force, and over a piercer, they could not be used.
Sec. V. Of the Dimensions and Poise of Rocket-sticks.
Although we have made some observations on the size, as well as the use of rocket-sticks, in a general way; yet the subject being very important, as rockets, however well made, cannot take a vertical direction without them, we subjoin the following table, which exhibits, at one view, the length, &c. of the stick, compared with the weight of the rocket, and the poise it must necessarily have from the point of the cone. The centre of gravity is a necessary consideration.
| Weight of the rocket. | Length of the stick. | Thickness at top. | Breadth at top. | Square at bottom. | Poise from the point of the cone. | |||
| lbs. | oz. | Ft. | In. | Inches. | Inches. | Inches. | Ft. | In. |
| 6 | 0 | 14 | 0 | 1.5 | 1.85 | 0.75 | 4 | 1.5 |
| 4 | 0 | 12 | 10 | 1.25 | 1.40 | 0.625 | 3 | 9. |
| 2 | 0 | 9 | 4 | 1.125 | 1. | 0.525 | 2 | 9. |
| 1 | 0 | 8 | 2 | 0.725 | 0.80 | 0.375 | 2 | 1. |
| 0 | 8 | 6 | 6 | 0.5 | 0.70 | 0.25 | 1 | 10.5 |
| 0 | 4 | 5 | 3 | 0.3750 | 0.55 | 0.35 | 1 | 8.5 |
| 0 | 2 | 4 | 1 | 0.3 | 0.45 | 0.15 | 1 | 3. |
| 3 | 1 | 2 | 6 | 0.25 | 0.35 | 0.10 | 11 | 0. |
| 0 | 0½ | 2 | 4 | 0.125 | 0.20 | 0.16 | 8 | 0. |
| 0 | 0¼ | 1 | 10½ | 0.1 | 0.15 | 0.5 | 5 | 0.5 |
** Transcriber Note: the last three rows of this table have many typos. The rows were probably intended to be as follows: | ||||||||
| 0 | 1 | 2 | 6 | 0.25 | 0.35 | 0.10 | 1 | 1. |
| 0 | 0½ | 2 | 4 | 0.125 | 0.20 | 0.16 | 0 | 8. |
| 0 | 0¼ | 1 | 10½ | 0.1 | 0.15 | 0.5 | 0 | 5.5 |