Wheels, in general, are furnished with cases, and various decorations. Some have two, three, four, and more fires; but, if they are finished too much, the weight they thus acquire would retard the velocity of the wheel. Their centres may be finished in several ways; as, for instance, by attaching, to the inner fells or circles, cases filled with white lance-composition, placed at the distance of two inches from each other, or alternately, white, blue, and yellow, or Chinese gerbes, or cases of blue fire. We may also attach small turning suns, the axes of which being placed upon the spokes. They may also be made to resemble a mirror, by furnishing all the spokes with white lances; and for the last fire, we may attach four cases to the centre, or in its vicinity, placed in such a manner, that their fire may issue from the interior of the wheel. To this, we may add, two other cases, which may cross the former. Leaders are fixed, and they are lighted at the same time.
Automatons with all their joints, or articulations, have been added to exhibitions of this kind, and with particular effect. They are clothed with cases after the usual manner.
Sec. XXIII. Of Globes, with their Various Decorations.
The first we purpose to treat of are the illuminated globes with horizontal wheels.
The hoops for these globes may be made of wood, tin, or iron wire, about two feet in diameter. For a single globe, take two hoops and tie them together, one within the other, at right angles; then have a horizontal wheel made, whose diameter must be a little wider than the globe, and its nave six inches long; on the top of which, the globe is fixed so as to stand three or four inches from the wheel. On this wheel may be put any number of cases, filled with any of the ordinary charges, as the white fire composition. Two of these cases must burn at a time. They may be placed horizontally, or inclining downwards. When the wheel is clothed, fix on the hoops as many illuminations as will stand, within two and a half inches of each other, which are fastened on the hoops with small iron wire. Attach the pipes of communication, and arrange them so as to carry the fire to all at the same time, with the exception of one or two, which are to receive their fire for the last. The spindle, on which the globe is to turn, must go through the block of the wheel up to the inside of the top of the globe; at this place must be fixed a bit of brass or iron, with a hole in it, to receive the point of the spindle, on which the whole weight of the wheel is to bear. When the globe is to be stationary and the wheel to run by itself, the block of the wheel must not be so long, or the spindle any longer than to raise the globe a little above the wheel.
We may remark, that, while the cases of white fire composition give to the piece a rotary motion, those of the lance or illuminating port-fire produce the effect, which characterizes in particular this fire-work.
With respect to fire globes, there are two kinds; namely, one with projected cases, and the other with concealed cases. If we have a globe made of wood, of any diameter, and divide its surface into twenty-four equal parts, and bore a perpendicular hole in each of these divisions to the centre, we may then represent this piece in the following manner: In every hole, except one, put a case filled with brilliant or any other charge, and let the mouths of the cases be even with the surface of the globe. Then cut in the globe a groove from the mouth of one case to that of another for leaders, which must be carried from case to case, so that they may all be fired together. The globe is then covered with a single paper and painted.
Fire globes with projected cases are made in the following way: Prepare a globe with fourteen holes, and fix in every hole except one, a case, and let each case project from the globe two-thirds of its length. Then clothe all the cases with leaders. It must be supported by a spindle made to fit the hole in which there is no case.
The bursting-globe is nothing more than a globe prepared in a particular way. It turns on a pivot, and is made by uniting four segments. These segments or parts are fixed to hinges, which open on the inside, and, when brought together, are kept in their place by a match which goes round the globe. The globe, it is to be observed, is furnished in the inside with several steel springs, which, unless the globe itself were tied, would force it open. When the match is burnt, this effect follows and the globe separates into four parts. It is furnished with lances and cases in the same manner as those already described. The last effect is that we have noticed.
Globes, which leap or roll on the ground, may be formed by procuring a wooden globe, furnished with a cylinder; and, having loaded it with the composition hereafter mentioned, introduce into it four or more petards loaded with grain powder to their orifices, which must be well stopped with paper or tow. If a globe prepared in this manner be fired by means of a match at the mouth of the cylinder, it will leap about as it burns on a smooth horizontal plane, according as the petards are set on fire. The petards may be affixed to the exterior surface of the globes, which they will cause to roll and leap as they catch fire.