Erect cylinders may also be rendered entertaining, by causing two, placed near each other, to revolve in opposite directions; and cones may also be treated in the same manner.
Lights placed on a spiral, within a circle, also produce a pleasing effect, (Fig. 33,) as the spiral appears to be unwinding as the circle revolves. Such a figure may be inclosed within a wheel of fire, or else the wheel may form the centre of the spiral. Two spirals placed one before the other, with their tendencies in opposite direc tions, and turned in contrary ways, also produce a very striking kind of firework ; but they required to be ac companied by something else, as their appearance is otherwise naked. They may form appropriate centres for a piece of archite, tore, or they may be accompanied by cones or spiral columns.
The last method which we shall describe, is that of placing lights round a globe, (Fig. 34.) and this may be used at rest or in motion, while the motion may also be either horizontal or vertical. This is a very handsome arrangement, and forms a very appropriate ornatnent for the heads of cones, or pyramids, or columns, or for particular parts on the outline of a piece of architec ture. The lights may be disposed on the globe in me ridians, or in lines parallel to the equaior, or else in spirals. This latter method is chiefly applicable where they are to turn in a vertical manner. Or. lastly, if the globe is of large size, the lights may be disposed all over it at equal distances, so as, if near, to represent a very solid globe of spotted fire. In this case they should not revolve.
The frame work for globes must be disposed accord ing to the different ways in which it is intended to place the lights; and, when they are to revolve, a pro per axis must also be provided. They may also be caused to revolve by means of wheels, in which case they produce complicated appearances, and it is also an impriivement on them for particular purposes, that they should terminate by a gerbe. very large, they may contain one large light in the centre.
Of the Dodecahedron.
\Ve feel it a duty to mention this firework, because it is found in all the books, hut chiefly for the purpose of cautioning the artist against it. It is what ita name expresses, a &Act:al:carom cart ying a wheel upon each face. The effect of this is as confused and had as the connivance is in itself expensive. Many other similar ly confused arrangements are to be found in all these books, which, like the compositions which we have elsewhere condemned, seem to have been put down by mere guess, without even the trouble of considering what the effect would be on burning. \Ve shall not,
however, crowd our pages with any more of this use less matter. Our only object is to caution the artist against making up any firework from these printed di rections, till he has well considered what its effect will be when lighted ; and, fur this purpose, lie will be much assisted by making a detailed drawing of its fires on paper, in the manner we formerly suggested. He must, in all his contrivances, whether borrowed or ori ginal, carefully consider not only the general pictu resque forms, and other circumstances, formerly de scribed, but how the fires are likely to interfere with each other; as, for want of such attentions, he may gain nothing for his trouble but a scene of confusion. And, as all cases throw their fires to a considerable distance, with the exception of lights, he must especially take that into consideration, and not imagine that he has ob tained any particular figure merely because the cases are disposed in a pleasing manner, or in some determi nate form.
There is another great object to be considered in all these contrivances, and that is economy. This dode cahedron is a very good ex..mplc of the neglect of this essential quality; as, in destroying eleven one time, scarcely one half of them would be visible. The best effects are often produced by the least fires, provided they he tastefully. disposed, and the artist cannot do better than keep in his mind the singular economy of the Chinese in all their fireworks, as they often produce better effects than ourselves, with a tenth part of the fire. To keep the fires at a sufficient distance from each other, that their figures may not interfere, is the first requisite for this object; as far greater extent, with greater beauty at the same time, is thus produced. Even in many of the fireworks which we have here introduced, in conformity to the usual practices, there arc many of which the expense is very great, in consequence of the quantity of fire which they consume at once, without at the same time being so entertaining as many others which would not cost half the money. Picturesque arrangement, which costs noting, is also as highly conducive to beauty as it is to economy ; and this object is attained also by a proper contrast of fires, and by a less free use of those violent kinds, which are not only expensive, hut rendered more so by their transitory nature; since they occupy but a small portion of the time which the artist is bound to fill up in some way or other.