P Y R O T E C H N Y. 



dull, and requires to be varied by other additions. 

 Mut tint flii-rt may be improved by causing two op- 

 posed cases, one above and one below, to act at the 

 ie tune, or t Ne by making two act above, alternate- 

 ly with two below. The means of effecting this by a 

 proper disposition of the leaders is too obvious to re- 

 quire description. 



PLATE l lu> h r ' /ollta l wheel may also be constructed in 



t-cccLxxn. another manner, and that, such as to discharge its fire 

 Fig. 19-24. at an angle either upwards or downwards. For either 

 of these purposes the rockets are all to be laid oblique- 

 ly as to the wheel, as in the former case ; but in a pa- 

 rallel consecutive manner. Thus all the vents will 

 look either upwards or downwards, as the artist may 

 choose, and each head and tail are then to be alternate- 

 ly connected by means of an attached leader of the 

 requisite length. It is evidertl that the effect of these 

 will be a succession of streams of fire in a direction ob- 

 lique to the revolution of the wheel, but always either 

 upwards or downwards. These wheels may also be 

 made both very forcible and far more durable than a 

 common wheel in one plane. To give them force it is 

 only necessary to make the angle which they form 

 with the plane of the wheel very small, such as 10 or 

 15 degrees instead of 45, by which means the recoil of 

 the rocket is caused to coincide more nearly with the 

 plane of revolution. 



Thus also they may be made of almost any degree of 

 durability, because the cases may, in this way, lie close 

 to each other, so as to form a solid ring round the 

 wheel. As the weight in this case, however, becomes 

 considerable, it will not be amiss to give these wheels 

 an impulse at the commencement. Or, as there is 

 abundance of materials, they may be lighted on both 

 sides at once. 



The same plan is applicable to vertical wheels, and 

 with the same effect of producing a far longer duration 

 than in the common constructions already described. 

 At the same time the effect is somewhat varied from the 

 peculiar direction of the issuing stream of fire. 



All these horizontal wheels, when fixed, are com- 

 monly provided with a central white light, or with a 

 ; _cerbe, or with a succession of these. This is a peculiar 

 Convenience in the horizontal wheel ; as the pressure 

 being downwards on the shoulder of the axis, which 

 must be properly adapted for this purpose, there is no 

 danger of disturbing the equilibrium. It may also 

 carry a Roman candle in the centre, or a number of 

 these or of other fires upon the spokes, and that either 

 upwards or downwards. Thus also these may be fixed, 

 in any order of succession as to the fire of the wheel 

 which the artist pleases ; merely by selecting some par- 

 ticular case for the leaders to each of them. Thus this 

 wheel becomes a complicated firework. But as it is 

 not necessary to treat of it again under that head, par- 

 ticularly considering the endless variety of which it 

 admits, we shall barely suggest here, that it may be 

 varied with good effect even in ten different ways or 

 more, because there is no limit to the number of cases 

 of different kinds, which the spokes will carry, if the 

 centres are made very fine and free, nor to the number 

 of leaders that may be used to fire them in different 

 ways. To put one instance of many, after it has re- 

 volved simply for a time, it may light a circle of white 

 lights looking downwards. These may be followed by 

 a few sparkling fires upwards, to be succeeded by Ro- 

 man candles, then again by cases of serpents, and, lastly, 

 by a central gerbe, ending by a bounce, or by a general 

 explosion of serpents or stars. To say more on this 



VOL. XVII. FART I. 



would be merely to describe what the ingenui- * J 

 ty of the operator will easily suggest. 



Of Compound Spiral Wheel*. 



These are formed on the same principle as the pre- i/r con- 

 ceding, namely, that of oblique forces. The frame- pound .pi- 

 work for this wheel consists of a long nave, capable of r *> ***! 

 carrying two sets of spokes at six inches or a foot dis- 

 tance, as the artist may desire. Thus there is a double 

 wheel of fire revolving on one axis. The cases are to 

 be fixed on these in the oblique manner already de- 

 scribed, but this wheel admits of two principal variations. 

 All the cases may be consecutive and parallel on both 

 wheels, with the fire directed upwards or downwards, 

 if the artist prefers it ; or else they may be reversed, 

 so that one set of fires shall act obliquely upwards, and 

 the other obliquely downwards. Care must be taken, 

 however, that all the recoils may have the same ten* 

 dency ; and it is plain that the force of such a double 

 wheel will, with an inclination of 45 degrees for the 

 rockets, be equal to that of a single horizontal one in 

 one plane. 



Besides this, however, the effect may be varied by 

 causing the fires of the upper circle to tend downwards, 

 and those of the lower one upwards. Thus they may 

 be caused to cross each other, so as to produce a much 

 better effect than in either of the preceding modes. A 

 variation may be produced even upon this plan, by 

 either actually crossing the rockets themselves, so as to 

 separate their streams of fire, or by bringing the two 

 mouths together from the lower and the higher wheel, 

 so that two oblique and diverging streams shall appear 

 to issue from one point. A horizontal wheel may be 

 added to these to increase the revolving force and vary 

 the effect ; and, as in the former kinds, they may carry 

 additional fixed fires upon the spokes. 



This spiral or compound wheel may further be 

 doubled ; or the same axis may carry two pairs, each of 

 which pairs being approximated in the manner already 

 described, a very complicated and brilliant intersection 

 of streams of fire is the consequence. There is no 

 danger in these contrivances of wanting force, pro- 

 vided the machinery be well made, as the friction does 

 not increase in so great a ratio as the powers of re- 

 coil. 



Of Diverging Vertical Wheels. 



The construction and nature of this contrivance may ofdi* 

 be easily apprehended from the description of the for- j D 'g verticil 

 mer. The wheel requires, however, to be differently wheels, 

 made, as far as the felly is concerned. Provision is to 

 be made for attaching the cases to it, not in the outer 

 margin, but in the flat side of the felly, and on both 

 the opposite sides. For this purpose grooves must be 

 cut in it at all the points where the cases are to be at- 

 tached, which may be numerous in proportion to the 

 relative diameter of the wheel and the length? of the 

 cases. These must be made as accurately as possible 

 at angles with the tangent at those points, which may 

 vary from 5 to 20 degrees, according to the degrees of 

 divergence which it is desired that the fire should have. 

 But the angles on one side of the felly must lie above 

 the tangent, and on the other below it. Two cases are 

 then to be attached together, one on each side of the 

 felly, with their mouths parallel, and as near to each 

 other as possible, and in the same way the wheel is to 

 be completed all round. It must then be primed, and 

 regulated by the leaders in such a manner that both 

 rockets, on opposite sides of the wheel, may burn to- 



tx 



