All these admit of various additions, from the intro duction of wheels or of white lights, or of smaller cases of sparkling fire; some examples of which will be seen in our figures. We shall content ourselves with here describing one or two varieties, as specimens from which the artist may easily learn to contrive many more.
A hexagon may have a blue light fixed on each an gle where the cases meet, and another in the centre. Or instead of the light in the centre, it may have a small wheel. Wheels for this purpose are convenient ly made of simpler cases when the figure is single, as they may easily be measured for the same duration as the figure in which they arc placed. Thus as the whole hexagon can only burn as long as one of its cases, a wheel that is formed of two cases crossing each other as in the table rocket, each of which burns at both ends, and the two in succession, will last exactly as long as the geometrical figure in which it lies.
Instead of this arrangement, six smaller cases may be placed within the centre of the hexagon, with their fires directed outwards in form of a star. For this pur pose the mouths must be placed together, that all the fires may appear to proceed from the same point, or a light may be placed on this point besides. Or else the cases may be fixed to the circumference of the frame that carries the hexagon, so that their fires may be di rected inwards. The same principles may be applied to all the other figures: and with the effect of producing different varieties of form; as may easily be imagined without the necessity of any further description.
The Ostrich Feather.
This is a very pleasing form of sparkling fires, and Is generally used for terminating complicated fireworks that have a pyramidal form. It is also used to imitate the Prince of Wales's crest. When this latter effect is to be produced, it must be attached behind a transpa rency properly painted to imitate the coronet and the inscription, and this must be strongly illuminated with blue lights placed behind it. (Plate CCCCLXXIII. 6.) Care must be taken that the mouths of the cases may be so placed, as that the feathers may spring from the proper point, and at a right distance from each other. They must also be inclined forward from the perpendi cular, that the fires may turn over at the top of their ascent towards the spectators. Three cases produce the
three feathers, and these must be of brilliant fire, and of considerable size. But the feather may be made richer and fuller, by placing in it three or four of a smaller size. if also it is desired that it should be very durable, it may be made to last for double the time, or even much more, by placing a succession of similar cases behind each other, and so managing the leaders as to light one set wheii the other expires. The same rule may also be applied to all other fixed figures of whatever nature ; which is often of great use, as they may be required to keep time with other fireworks of longer duration.
The ostrich feather may also be used without the co ronet; in which case it may be provided with a small wheel, or a bright light at the point where the feathers spring.
The Tree.
This is the name generally applied to all those corn uinations of fireworks which throw out fires from each side of a perpendicular ; and there are different ways of disposing the cases for this purpose. The simplest method is to dispose the cases upon a perpendicular post, (Fig. 7.) in a parallel manner on both sides, so that when placed they may resemble the feathers upon an arrow. The angle with the perpendicular may be about 30 degrees, so that the fires will diverge at 60, but the artist may vary that angle according to his pleasure. The perpendicular should also be terminated by as many cases as will render the whole figure uniform at the top when burning.
This disposition may be agreeably varied in two ways or more. Thus, instead of fastening the cases on a straight post in a parallel manner, and having all the mouths at the same distances crosswise from the top to the bottom, they may be placed upon two posts inclined at a small angle, so as to make an acute triangle. Or else this position may be reversed, (Fig. 9.) and the broadest side of the triangle may be upwards, so that the tree will appear to spread at the top. In this latter way also, the cases below may be more widely apart than those above ; and as the interval at the top must also be filled with cases, the tree will appear fuller or more bushy above than below.