From what has been said in the preceding section, it is obvious, that revolving or turning suns may be formed, or any piece put in motion, in the manner already described. The most common mode of forming a sun, is to attach to three naves, which proceed from a hub, that revolves on a spindle, from three to six cases, placing them in such a way, that they may be fired successively. The jets, or spouts, proceeding from the cases, constitute the rays, the sun being in the centre, which revolves with the cases on an axis. The arrangement of these cases should be such, as that the six (as that number is usually employed,) might form the perimeter.
The cases may be charged with one, or with different compositions, given in the following table. They are attached in such a way, that the head of the first is nearly in contact with the ray of the second, and that to the third, &c. When the first case is finishing, it must, therefore, communicate fire to the second, that to the third, and so on in succession. These cases must be attached firmly by wire; and leaders are used to communicate the fire, as in other works. The end must be enclosed in the neck of the first case, and the other end in that of the second, &c. They are secured in their respective positions, by tying them securely to the cases.
With respect to the composition employed, it may be varied according to pleasure. In most instances, however, the ordinary sun-composition is used; but, in other instances, this is varied according to circumstances. Morel has adopted the following composition for a sun of six cases, the cases being eight-twelfths of an inch in diameter. These cases are mounted on the arms of the sun in the same manner as before described.
Composition for a sun with variations, the cases of which are eight-twelfths of an inch in caliber.
It appears evident, that the changes thus produced are owing to the diminution of the quantity of saltpetre and sulphur, or, in other words, to the increase of the quantity of powder; and that the fourth change must contain but a small quantity of each, whilst the sixth or last change contains none, except that which is in the composition of the powder. The effect, therefore, must be proportionate; for, it must be apparent, that this diminution of nitre and sulphur, and the increase of powder, must render each charge more explosive, or, in other words, the combustion more instantaneous, and that this effect characterizes each of the changes in succession, is a result which necessarily follows.
The instructions given by Morel for employing these changes, in the charging of cases, are thus: We take the above composition for the third case of the sun. The first case is of common fire; the second of silver rain; the third of two charges of common fire, and afterwards a charge of No. 1, the second two charges of No. 2, the third three charges of No. 3, the fourth four charges of No. 4, the fifth four charges of No. 5, and two charges of No. 6. The fourth case is composed of brilliant fire; the fifth the same as the third, and the sixth of large or grand jessamine.
We may merely remark, that the sun must be supported very firmly, and that it ceases to revolve at the fourth, fifth, and sixth numbers.
Sec. IV. Of Fixed Suns.
Fixed suns are so called, because they remain stationary, and exhibit the appearance of a sun with innumerable rays. A fixed sun is formed by putting eight or more strips of board across each other, so that each arm may proceed from a common centre, in which a sun is painted on silk. To the extremities of these arms are attached, to each one in succession, a case of brilliant fire, which, by means of bodies fixed in the usual manner, go off together. The two arms below, forming right angles with each other, are longer than the rest; so is also the upper and vertical arm. This, however, depends upon fancy. The cases are tied to these arms; and, after the leaders are fixed from the mouth of one case to that of the other, they terminate at the bottom and hang below the vertical arm. Fire is first communicated to the hanging match.