PYHOTECHNY. 



259 



I'yrotech' 

 ny. 



Fig. S7. 



wheels may act at once, and for the whole time, or 

 one may commence when the other is partly exploch <!. 

 ' The arti-t will, <>f course, easily contrive to regulate 

 tin- time ; the great object being that they may both 

 end together, however they may begin. The outer 

 v lu-rl fur this purpose ought to be of considerable size, 

 that tin- fires may not be too close. The inner may 

 also differ in composition from the outer. Thus, if it 

 carries a blue light, while the other is a brilliant com- 

 position, there will be two circles of different fires ; 

 and as the blue fire is far slower than the sparkling 

 one, they may both be managed to burn together from 

 the beginning to the end. Otherwise it may be so 

 managed by laying a leader from any part of the outer 

 circle to the inner one, that this latter shall not com- 

 mence till some time afler the first. It is equally plain 

 that where there is room enough, more circles than two 

 may be adopted, while the fires of all the three or four, 

 and the times of their commencement may also be 

 made to vary. Thus, to put an example, suppose an 

 outer circle of twelve cases, and three inner ones in 

 succession, of nine, six, and three cases, of the same 

 length and of the same composition. A leader is to be 

 conducted from the third case of the outer circle to the 

 beginning of the second ; another from the third case 

 of that to the beginning of the third circle ; and the 

 last from the third case of this one to the beginning of 

 the last circle. Thus, the wheel which commences 

 with one circle of fire, will become double, and at 

 length triple, and quadruple, all in concentric order, 

 and all terminating at the same time. A light may 

 also be attached outside the spindle of such a wheel, 

 which may be properly fitted to receive one without 

 difficulty ; thus forming a bright spot on the centre of 

 all these fires. 



But concentric wheels may also be made to produce 

 a different effect by giving a different velocity to the 

 two or more circles. This is done by having two dis- 

 tinct wheels of different sizes, on one spindle, working 

 independently of each other. By means of a stronger 

 composition, or by boring, the inner wheel may be 

 made to revolve more rapidly than the outer one, to 

 which, from its size, it has also a natural tendency. 

 The same may be done for more wheels, it being only 

 necessary that each should be separated from the other 

 by proper buttons, placed in the spindles between 

 them. If small wheels only are used, this effect is 

 easily produced in a very simple manner, by attaching 

 a common pin-wheel on the top of the spindle of the 

 larger one. 



It is by this last method that concentric reversed 

 wheels are produced ; and the effect of these is even 

 more remarkable than that of the former. It is unne- 

 cessary to give directions for making such wheels, as 

 it must be sufficiently obvious ; it bein/ only requir- 

 ed that the mouths of the cases 'may look in oppo- 

 site directions. But a large kind, of which the effect 

 is very peculiar, may be made by placing four cases 

 on as many long arms, without any wheel ; connecting 

 them by proper leaders. Two of these, of the same 

 size, being placed in reverse order, one before the other 

 in the same spindle, when they are fired they do not 

 produce circles, from their great length and slowness 

 of motion. Instead of this, two curved lines of fire 

 appear to meet and separate alternately, something 

 like a pair of forceps, causing a very singular appear- 

 ance, which the spectators, unaware of the contrivance, 

 are puzzled to account for. The effects of all other 

 opposing motions, whether in large or small circles 



more or less numerous and concentric, are easily un- 

 derstood. 



Of Ornamented Wheel*. 



There are many ways of managing the ornaments o. 

 in these, but we shall content ourselves with pointing minted 

 out two or three of the most remarkable, as the artist * he ** f - 

 has it in his power to multiply them in various ways. 

 The most universally applicable method is that of at- 

 taching white or blue lights to the t- pokes ; and these, g * '' 

 if made sufficiently numerous, may be caused to per* 

 form 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 gerbe 

 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 dig- 

 posed in the same manner ; taking care that they are 

 so loosely attached as to be able to disengage them- 

 selves on exploding, without injuring the wheel or in- 

 terfering with its motion. 



Of United Circles or Wheels. 



The effects of these are also very entertaining, as they Of united 

 may be disposed in various ornamental forms. But circl or 

 the wheels must be so small that the circles of fire w 

 may be complete. On a very small scale, these objects 

 are easily accomplished by means of pin- wheels, or of * : - 

 simple case-wheels; but, if intended to be larger, 

 wheels of the ordinary construction with consecutive 

 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 sun-flower may be produced ; and to increase 

 its brilliancy and effect, a white light uiay be placed m 

 the centre of the larger circle. 



