238 



PYROTECHN Y. 



Fyroteth- cone ; or else the light on the head may be fired before 



n y- the rocket, which answers the purpose equally well. 



T-' it is also easy to make the light of sufficient duration 



to last through all the time of the ascent and descent 



both. 



Rockets may be ornamented in some other ways 

 during their ascent, and be thus made productive of 

 additional variety. Thus they may be made to dis- 

 charge serpents during their fl'ght, either at one or 

 more intervals, without interfering with the final dis- 

 charge from the heads. To effect this, a ring or more 

 of small serpents, as the artist may desire, may be 

 fastened round the rocket case by means of cotton 

 slow-match. The loose end of that must be fired at 

 the same time as the rocket, and its length so calculat- 

 ed as to burn three, four, or more seconds, according 

 to the part of its ascent where it is desired that the 

 serpents should be discharged. This cotton match 

 must also communicate with a quick-match priming 

 to each serpent. Thus when the fire arrives at the 

 serpents, it not only lights the whole ring, but, by 

 burning the match which attaches them, sets them at 

 liberty. If two or more discharges are wanted, as 

 many" rings of serpents may be placed round the roc- 

 ket, and the match duly proportioned so as to light 

 each set in succession. 



As a powerful rocket will carry considerably more 

 weight than its own stick, advantage may also be taken 

 of that, so as to add to its ornamental appearance. Thus 

 a small case with a sparkling composition may be at- 

 tached to the end of the stick, with the mouth down- 

 wards, whichmustbelighted independently oftherocket; 

 'but the operator must of course take care, in adopting 

 any of these contrivances, to ascertain previously what 

 weight his rocket is really able to carry. Another 

 pleasing ornament may be produced, by placing a few 

 illumination lights or speckies along the stick, or by at- 

 taching a larger one to its end ; but whichever of these 

 several plans is adopted, care must be taken that the 

 rocket has great freedom in quitting the support on 

 which it is fired. 



The last project for varying the effects ofsky-roc- 

 k e t s which we shall mention, is that of causing them to 

 suspend a white light in the air after they are burnt 

 out. It requires some little care to make the requisite 

 machinery, but it is neither expensive nor difficult. 

 For this purpose a parachute is attached to the rocket, 

 which is so combined as to open when it is expended, 

 and thus to check the descent of the case and stick. The 

 parachute for this purpose may be applied in different 

 ways ; but is perhaps most conveniently done in the fol- 

 lowing manner : Being made of four or more pieces of 

 slender whalebone, with a thin piece of linen stretched 

 over them, it is attached to the lower end of the rocket 

 just at the choke, so that its open end may lie upwards. 

 Thus when the head of the rocket is turned downwards 

 the parachute will act ; and care should be taken that it 

 does act freely, and without turning inside out, before 

 any attempt is made to complete the arrangement. The 

 rocket head is then filled with a white or blue light, in 

 the manner described before, with a priming hole com- 

 municating with the top of the composition. A hole 

 is also made in a lateral direction, for the purpose of 

 carrying a leader to disengage the parachute at the mo- 

 ment the rocket is burnt out. The parachute must 

 then be collected neatly round the rocket with the 

 points upwards, which are to pass beyond the head, 

 and to be enclosed in a light paper cone that may easily 

 be disengaged. To insure that, the cone is made in 



5 



with para 

 chute. 



two parts, and secured by a bit of cotton quick-match, Pyrotech- 



which is to be also conducted in a spiral manner round ^ 



the rocket and parachute together, so as to render the 

 whole as compact as possible, after which the whole is . 

 to be covered v.'ith a single fold of weak paper. This 

 quick-match is connected with the leader from the 

 rocket head, and with that which serves to set the light 

 on. fire; but it is necessary so to arrange these two 

 leaders, that the parachute may disengage itself before 

 the light takes fire. As soon as this match is burnt, the 

 parachute is disengaged ; an effect which may be aid- 

 ed by forcing the whalebone ribs together, as is easily 

 comprehended ; and as the weight of the rocket cases 

 causes it to overset as soon as the composition is burnt 

 Out, the parachute is then brought into action, so as to 

 suspend the light, which thus continues to burn as it 

 descends slowly. We need scarcely add, that many 

 minute attentions are required to make this act weli, 

 but that a dextrous mechanic can find no difficulty in it. 

 The parachute may also be attached to the middle 

 or end of the stick; but in this case great care must 

 be taken that the leader which is to disengage it may 

 not take fire by the burning of the rocket, until it re- 

 ceives its fire from the end of the composition. For 

 this purpose it must be made strong where it passes 

 below the rocket, and is exposed to the stream of fire. 



On the height lo which Rockets ascend, 



In Mr. Robins's trials, the pound rockets were On the 

 found to ascend perpendicularly, from 4-50 to 500 height to 

 yards; and from some measurements made in the which 

 flights of those that were used at the great firework in roc * ets ds ' 

 the Green Park, they were found to range from 44-0 C * 

 to 526, in general; although there were some that 

 rose to 615 yards. Mr. Robins also seemed to think, 

 in his first experiments, that all sizes of rockets had 

 pretty nearly the same flight. This, however, is not 

 the fact. The ratio of increase indeed is not regular, 

 nor does the ascent correspond in any way to the 

 magnitude of the rocket ; but the greatest ascents, or 

 the longest ranges, if fired at an angle of 45, are ob- 

 tained with the larger sizes. The time for these 

 ascents varies from ten to fourteen seconds. That time 

 does not bear a regular ratio to the altitude of the 

 ascent ; because a considerable part of the force of 

 the recoil is lost in overcoming the inertia of the rock- 

 et. That time, of course, is the same for all; so that 

 those which have the power of flying highest, increase 

 their ranges, as these regard the time of flight in a 

 certain progressive ratio. 



Taking Mr. Robins's computation of 600 yards for the Robins's 

 limit of ascent in signal rockets, that givers an elevation ^pe"- 

 of one-third of a mile nearly. Hence if the light of the ment - 

 exploded stars, which are the proper ornaments of a sig- 

 nal rocket, is sufficiently strong, and the atmosphere is 

 clear, such a signal may be seen at a horizontal dis- 

 tance of fifty miles at sea, or in a level country where 

 there are no advantages. Its rise above the horizon is 

 sufficient to render it quite visible. Mr. Robins need 

 not have doubted if the light was visible at such dis- 

 tances ; as it has been ascertained that the common 

 blue antimonial light, which burns from a case only 

 an inch in diameter, may be seen at the distance of 

 seventy miles without difficulty, and probably much 

 more. In this the mass of light is considerably less 

 than that produced by the stars of a signal rocket, 

 and the composition is, as nearly as possible, the same 

 in both. 



