260 



PYROTECHNY. 



Of Compound Wheels. 



Of com- 

 pound 

 wheels. 



Fig. SI,! 

 33. 



Balloon 

 Wheels. 



These have a very pleasing effect, and may be va- 

 ried in many different ways. The general principle 

 on which all the effect depends, is that each addition- 

 al wheel should be carried along by the motion of the 

 principal one, independently of its own proper mo- 

 tion. 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 are 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 have as 

 many smaller ones fixed on its spokes inwardly as will 

 be sufficient to last the same length of time, then the 

 principal circle will be attended by one of these 

 nourishing movements in an inner circle. If they are 

 fixed on the spokes prolonged beyond the circum- 

 ference, the same flourishing line will be outside of the 

 principal circle. Otherwise, which is still more beau- 

 tiful 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. 



The same method is to be followed for all these, 



with the requisite variations for the leaders and other 



connections. We shall suppose the simplest case of 



one flourish within the principal circle, as the method 



of arranging this, will serve for the explanation of the 



whole. If there are six cases in the outer wheel, 



and-^the diameter of it is two feet, then the diameters 



of the smaller wheels will be from four to six inches. 



Three of these will be required ; and of whatever 



shape they are made, each of them must be equal in 



the time of burning to two cases of the outer wheel. 



They must then be fastened in opposite spokes, so as 



to preserve the proper balance of the wheel, by means 



of spindles in the usual way. For firing, a leader 



must join the commencement of the principal wheel 



with one* of the small ones ; a second leader must join 



the beginning of the third case with the next ; and a 



third leader is required to join the fifth case with the 



last. Thus one of the small wheels will burn with 



each two cases of the large one, and the effect will be 



continued during the whole time of the revolution, so 



that the \vhole will expire together. 



Balloon Wheels. 



This is one of the fireworks mentioned in the books 

 on pyrotechny ; but it is scarcely worth describing, after 

 the remarks formerly made on the methods of varying 

 the effects of horizontal wheels. The name is not very 

 appropriate. It is a common horizontal wheel, "with 

 horizontal cases revolving in the usual manner. On 

 each spoke near the end of each case is placed a pot of 

 serpents or of stars, or of both alternately. These 

 communicate by means of a leader with the end of each 



case, so that whenever a new one is lighted, a dis- i'yrotech- 

 charge of serpents or stars takes place. The same v_" y ' i _ J 

 expedient may be applied to a vertical wheel, but in 

 this, stars are not admissible, on account of their dan- 

 ger, as they would be thrown forwards among the 

 spectators. Small serpents may safely be used, as 

 they do not fly forwards, and are therefore not likely 

 to occasion accidents in this way, more than in the 

 horizontal wheel. 



Star Wheels. 



These may be used either horizontally or vertically; Star 

 but in the two kinds the stars require to be differently Wheels, 

 disposed. We shall give a direction for each. If the 

 wheel is to be horizontal, the best method of dispersing 

 the stars is to fix as many Roman candles in the centre 

 of the wheel as there are cases in its circumference. 

 This we formerly alluded to in speaking of horizontal 

 wheels. These must be in a vertical position, so as to 

 throw their stars upwards, and they must be calcu- 

 lated as nearly as possible, so that one may last as 

 long as one of the wheel cases. To prepare this fire- 

 work for firing, a leader must be conducted from the 

 commencement of each case, to the top of each Roman 

 candle in succession ; so that a constant discharge of 

 stars, together with a central fountain of fire, will 

 continue as long as the wheel lasts. The Roman can- 

 dles may also be disposed in such a manner as to 

 throw the stars downwards, instead of upwards, or al- 

 ternately upwards and downwards, or both ways at 

 the same time, all of which produce fireworks of dif- 

 ferent appearances. 



In using stars with vertical wheels, a different dis- pig. 34, 3-3. 

 position of the Roman candles is required. They 

 must be fastened on the spokes of the wheel, with 

 their mouths looking outwards ; and the leaders must 

 be placed in the same manner, so that one Roman 

 candle may fire with each fresh case. The stars will 

 thus be projected sidewise, without any chance of in- 

 jury to the spectators, who are always in the front on 

 those occasions; and as they receive two motions, 

 one from the wheel and the other from their own pro- 

 jectile force, they form very pleasing curves in the air, 

 adding much to the beauty of the effect, while they 

 also seem as if they were projected from the mouths of 

 the wheel itself. 



If it is wished that a vertical wheel should throw 

 up stars in a vertical direction, a separate firework is 

 required for this purpose. This must consist of as 

 many Roman candles as will last out the time of the 

 wheel, and they must be fixed behind the wheel on 

 the same part which carries the axle. But if it is 

 wished that stars alone should be seen, without any 

 vertical fire, so that the wheel itself may appear to 

 throw up thfe stars, they must only have a very slow 

 composition, which gives little fire, such as that used for 

 portfires, which will be found in its proper place. The 

 orifices may be also concealed behind a board, so that 

 nothing but the stars will be seen. As many of them 

 must be connected alternately by the head and tail as 

 will last out the time of the wheel, and the same leader 

 will serve to fire both. It is proper that all wheels and 

 fireworks of this kind should end with a report, or with 

 a general explosion of stars. 



Of the Alternating Wheels. 



The effect of this is entertaining, nor is the construe- Of the ai- 



tion difficult. In burning, a large and a small wheel ternating 



wheels. 



