Of Ornamental Irlicas.
There are many ways of managing the ornaments in these, but we shall content ourselves with pointing out two or three of the most remarkable, as the artist has it in his power to multiply them iu various ways. The most universally applicable method is that of at taching white or blue lights to the spokes, Fig. 28 ; and these, if made sufficiently numerous, may he caused to perform concentric circles of fire. A light of the same kind may also be placed on the spindle, so as to form a luminous centre, which has always a good effect. Similar lights may be placed outside of the wheel, by prolonging the spokes and fastening one on each ; by using enough of which, a circle of blue fire may be made outside of the principal circle. Or else a gate may be placed in the centre, to take fire with the last case. Thus also serpents or stars may be fired from wheels, by attaching proper cases to the spokes, and lighting them by means of leaders set off from any part of the wheel where it is wished that they should take fire. Crackers and maroons may easily be disposed in the same manner; taking care that they are so loosely attached as to be able to disengage themselves on ex ploding, without injuring the wheel or interfering with its motion.
Of United Circles or Wheels.
The effects of these are also very entertaining, as they may be disposed in various ornamental forms. But the wheels must be so small that the circles of fire may be complete. On a very small scale, these objects are easily accomplished by means of pin-wheels, or of simple case-wheels ; (Fig. 29, 30 ;) but, if intended to be larger, wheels of the ordinary construction with conse cutive cases must be adopted. We may suppose these to be united in the form of a triangle, or four in that of a square, or any number in a straight line. It is only necessary to compute the diameter of the circle of fire, and to choose the places for the spindles accordingly, as it is wished that the circles should intersect each other, or merely come into contact. Thus, for exam ple, four circles may slightly intersect each other, so as to produce a true lover's knot, or they may be dis posed of round a central one, so as to form a row ; or they may be approximated but independent. In the same way a chain may be produced, by disposing a number of wheels in a straight line, so that all the circles of fire may just touch. With a little more trouble, a number of wheels may be so disposed that the circumferences of all of them may meet in a point which is the centre of another ; producing that effect which is so easily represented on paper, by describing circles from various points in the circumference of another.
But not to prolong too much a description of the endless ways in which these may be combined, we shall only mention one more method of producing a brilliant effect in this way. A large circle being form ed by a single wheel, a number may be placed round its circumference, so that each may touch each other, and the larger circle also. Thus a figure somewhat like that of a sunflower may he produced ; and to increase its brilliancy and effect, a white light may be placed in the centre of the larger circle.
. _ Of Comluund Wheels.
These have a very pleasing effect, and may be varied in many different ways. The general principle on which all the effect depends, is that each additional wheel should be carried along by the motion of the principal one, independently of its own proper motion. Thus it describes a complicated path, like a running flourish ; or similar to that which the moon makes round the sun, as we formerly mentioned. For all contrivances of this nature, the smaller wheels should be very much less than the principal one. Hence pin-wheels answer very well, except for very large works, when triangular ones may be adopted.
According to the methods in which these arc ar ranged with respect to the principal one, will the ef fects vary ; and, compared to the little contrivance that is required to produce them, they are very strik ing. Thus let a common hexagonal wheel (Fig. 31, 32, 33,) have as many smaller ones fixed on its spokes in wardly as will be sufficient to last the same length of time, then the principal circle will be attended by one of these flourishing movements in an inner circle. If they are fixed on the spokes prolonged beyond the cir cumference, the same flourishing line will be outside of the principal circle. Otherwise, which is still more beautiful in the performance, the small wheels may be placed between two concentric plain wheels, when there will be two circles of fire with an intermediate flourish, which may also be much improved by adding a light in the centre. In addition to this, a second flourish may be also added outside, which is nearly as great a degree of complication as this kind of wheel will bear.