256 



P Y K O T E C H>N Y. 



Of spiral 

 or fire 



wheels. 



Thus the outer wheel may be caused to btirn first, 

 when, after a few revolutions, the second will take fire, 

 and so on in succession till all the circles are inflamed. 

 It is plain that all these things are very easy to exe- 

 cute, but that they require attention to be well done. 



The single case wheel may also be compounded, by 

 placing and fixing two on a common wooden centre, at 

 right angles to each other, as in the table rocket ; and 

 they admit of the same variations already mentioned. 



Of Spiral or Fire Wheels. 



Of all the fireworks that have been invented, this is 

 the most beautiful in proportion to its expence, while 

 it is scarcely possible that it should fail, if made even 

 with the most common attention. Being on a very 

 small scale, it may be fired in the hand and in a room. 

 It does not indeed admit of being made large, as, if 

 the stream of fire is too great, it is apt to burn the cases 

 irregularly where the turns come into contact, and thus 

 destroy the effect. 



The lengths of the paper for forming the tubes of 

 these wheels should not exceed a foot or fifteen inches, 

 as they become difficult to fire, and it is better, there- 

 fore, to join two or more together, when it is desired 

 that the wheel should burn a long time. The paper 

 must be thin, and must not exceed two or three folds, 

 as it is necessary that the case should burn through 

 every now and then to give vent to the fire. These 

 tubes are pasted up round a wire, and, before filling, 

 are pinched close at one end. They must be filled by 

 means of a funnel, and loosely, else they will crack in 

 the bending; but the first trial will soon show the ope- 

 rator how much composition they will bear. The com- 

 position for them will be found in the table, and it need 

 not be varied, as, owing to the occasional burning of 

 the case, and the more or less difficulty which the fire 

 finds in issuing, they naturally produce sufficient va- 

 riety. It must be made very dry before using, as it 

 would not otherwise fall freely down the tube. 



When the tube is filled and secured by pinching at 

 the end, it is to be passed round a wooden turned 

 button, provided with a groove to receive it, and with 

 a hole in the middle to receive the pin on which it is 

 to revolve. By means of a little glue, the first turn is 

 fastened to the cylinder or button, and the remaining 

 turns may be secured to each other with a little paste. 

 A bit of twine must be used, to prevent them from 

 unfolding in the making, which can be taken off when 

 they are dry. As one tube is expended, another may 

 be inserted into it, and fastened by a slip of paper and 

 paste ; and thus the spiral may be prolonged to an in- 

 definite length. These wheels may therefore be made 

 very durable, so as to last as long as any particular fire- 

 work with which they may be used. When the requi- 

 site size is obtained, the .whole should be pressed flat, 

 and secured by some transverse slips of paper. 



These wheels may also be made without pasting the 

 .turns together; securing them only at particular points 

 with a bit of glue, or sealing-wax. Thus, in burning, 

 the spiral unfolds after each fastening of this nature, 

 so as to increase the diameter of the circle of fire. 



we shall reserve any description of these till we come 

 to treat of combinations of wheels. 



Of Compound Wheels. 



These may be made of any number of cases in the 

 manner already described, disposed round the circum- 

 ference of a circle. Thus they may reach from two 

 up to twelve, as there is no rule but the particular 

 view of the artist. ! 



If two only are required, they may be fastened on 

 the opposite sides of a single arm provided with a pro- 

 per centre and axis, and the leader must then be cross- 

 ed from the end of one to the commencement of the 

 other. Four may be used in the same manner ; and in 

 this case the circle of fire may be improved, with the 

 same duration, by causing the two on opposite sides to 

 burn together. If six, or twelve, or any equal number 

 of cases, enter into the wheel, the artist has it equally 

 in his power to improve the circle, by managing the 

 leaders so as always to burn two on opposite sides at 

 the same time. Nothing more need be added respect- 

 ing the mode of making these, as that was already ex- 

 plained in the general directions for making wheels at 

 the head of this division of the subject. 



In firing these wheels, it is usual to place them ver- 

 tically, as the effect is then best. But they may also be 

 placed in a horizontal position ; a practice which is 

 chiefly adopted when they are attached to some other 

 firework to which they are intended to communicate 

 motion. We shall presently show how they may be 

 varied by compounding them. 



Of Horizontal Wheels. 



This is a wheel, which, although placed in a hori- 

 zontal position, produces a very different effect from the 

 preceding, on account of the peculiarity of its construc- 

 tion. But in making it, it must be remembered,, that 

 as the force of the cases is very much diminished on 

 account of the obliquity of their position, all the com- 

 position must be strong. 



The wheel to carry these cases must be circular, and 

 of considerable size, to give a freer motion ; and the 

 cases for it should also not be less than an inch in dia- 

 meter. As many may be disposed on it as it will 

 hold, as it is indifferent whether they are an odd or 

 an even number. 



To construct this wheel, a case is first to be attached 

 to the wheel by its middle, at an angle of 45, and to 

 insure regularity, it is better that such a number of 

 grooves as is necessary should be cut in the felly, at the 

 proper angle. This case being thus applied, a second 

 must be fastened on the next groove, with its mouth 

 in the contrary direction, so as to be opposite, and 

 close to the extremity of the first. Thus all the cases 

 are to be applied in succession ; so that when the 

 wheel is completed it presents a zig-zag line of rockets 

 surrounding the felly; each rocket being at right angles 

 to the next, and all the mouths and extremities follow- 

 ing each other alternately. The joints must then be 

 primed and attached in the usual manner. 



It is evident that the action of this wheel, when 



ny. 



Of com- 



pound 



wheels< 



ofhorizon- 

 tal wheels. 



In firing such wheels, two may be applied on one burnt, will be to produce alternately an oblique stream 



axis, so as to revolve in opposite directions, which of fire ascending at an angle of forty-five degrees, and. 



produces a very pleasing effect ; but in this case the one descending in the same manner; while it will, at 



pin must be somewhat thicker, and must also be pro- the same time, revolve round its axis. But on account 



vided with an intermediate button, so as to keep them of the resolution offerees, its circular velocity is only 



separate. They may also be variously combined ; but the half of what it is in any wheel of which the cases 



as these combinations are applicable to all wheels alike, are parallel to the plane. Hence the effect is rather 

 6 



