V R T E C H N V. 



241 



deviate *o far from the vertical line as to destroy its 

 Spectators always judge of the perfection of a 

 rocket by the perpendicularity of its flight, unaware 

 that this C.IM ii'vcr be attempted without the greatest 

 risk of injury to themselves. 



This danger is far from imaginary ; even in the half- 

 pound rwkct, the fall of the stick, from a height of 

 400 yards, is sufficient to give a very hard blow. The 

 weight of the one pounder stick, descending from its 

 iiMinl height of 500 yards, is very considerable, and in- 

 dri <! sufficient to kill a man. They have been known 

 to break an arm, and after that to penetrate deeply 

 into the ground. We have seen them pass through 

 both the wooden sides of a drum, which is made of a 

 very tough ash hoop, and then enter the earth to a foot 

 in depth. 



For this reason, when flights of rockets are fired, as 

 there are generally crowds present, and as it is impossible 

 to regulate their directions, these should never exceed 

 half a pound; but even the quarter pound size is pre- 

 ferable. These are sufficiently showy ; they ascend 

 300 yards, and the fall of the sticks can do little harm, 

 unless a chance spectator should receive one in his face. 

 Fortunately, they generally retain fire enough to fore- 

 warn idle people of this kind of danger. 

 . The last circumstances which we shall notice re- 

 specting the firing of rockets, are the methods which 

 have been proposed for increasing their range or ascent. 

 It is evident, on the slightest inspection of a rocket 

 when about to rise, that a very large portion of the 

 composition is burnt before it is able to quit its place, 

 or, in mathematical language, there is a considerable 

 portion of the force expended in overcoming the iner- 

 tia, just as there is when a team of horses first attempts 

 to set a waggon in motion. When once the motion 

 has commenced, a very small addition of force is suffi- 

 cient, not only to sustain the velocity against the re- 

 sistance of the air and the force of gravity, but to add 

 to it progressively till it has attained the maximum, or 

 till all these forces are balanced. Now, if the initial 

 velocity, or any velocity could be communicated at the 

 beginning, all that would be saved in the burning of 

 the composition, and, consequently, the extent of range 

 or of ascent, would be proportionally augmented. This 

 is but an imaginary advantage, as we shall immediate- 

 ly show. Let the mean times of flight and elevation 

 of the one pound signal rockets be taken, respectively, 

 at twelve seconds and 500 yards, which is near enough 

 to the truth. Now, in firing, about two seconds are 

 expended on the post, in the attempts to first overcome 

 the inertia of the rocket, and two more in communica- 

 ting to it a velocity considerably short of the greatest 

 which it will acquire. We may therefore consider three 

 seconds expended in overcoming the inertia, or in 

 placing the rocket in a state to derive all the advantages 

 which it might from its own power of flight. This 

 amounts to just one-fourth of the whole time of burn- 

 ing. It must not, however, be considered as accurate- 

 ly representing the time which is lost to the flight, 

 as the rocket does not acquire its full force till the bore 

 has become so much enlarged by the fire as to give 

 issue to a considerable torrent of fire, or, correctly 

 speaking, stream of air. Were we to consider it as a 

 true measure of the loss of range, we should find that 

 the pound rocket, burning twelve seconds, and rising 

 500 yards, would lose a fourth part of its range, or 122 

 yards nearly ; but we shall probably not be very wide 

 of the truth if we take it at 80. 



But if this is not of much moment in ornamental rock- 



TOL. XVII. PABT I. 



ets, or even in those used for signal*, it is of considerable P/roted. 

 consequence in military or projectile ones, in which the y- 

 length of range is of great importance. And if we at- ' 

 tend to the nature of the curve formed by the flight of 

 the rocket at 45, we shall find that the variations in 

 the amplitude of projection, or in the actual random, 

 are of even more moment than those in the perpendi- 

 cular ascent. The same reasoning applies to those ca- 

 ges in which rockets have been used to throw out lines 

 to ships in distress on a lee shore. Now, it has been 

 attempted to overcome this inertia, or communicate an 

 initial velocity by firing the rocket* from a piece of 

 ordnance. But the blast of the powder ruins the com- 

 position, and frequently breaks it, so as to cause the 

 rocket to blow up in the piece, or in the frame where 

 it is fired. This, in the case of the iron rockets in par- 

 ticular, is a very dangerous accident, which renders 

 them almost as formidable to the artificers as to the 

 enemy ; and it has in more than one instance been at- 

 tended with fatal results. 



Lately it has been attempted to gain the same end 

 by introducing the stick only into the piece to be fired ; 

 by discharging the rocket in this manner, in fact, from 

 a musket. But this is almost equally dangerous, as the 

 composition will not bear the blast which issues from 

 the mouth of the piece, even at that distance. The mo- 

 ment it cracks, the fire enters from the bore into the 

 fissures, so as to set fire to more composition than there 

 is vent for ; in consequence of which, an explosion is 

 unavoidable. 



The only safe method of gaining this end is by means 

 of a balista, or cross bow. It was by this machine that 

 the Saracens and others threw their fireworks, as we 

 mentioned in the historical part of this article ; nor can 

 there be any difficulty in applying it to the rocket. 

 The balista should be formed on the same principle as 

 the cross bow, with a steel spring, and a sufficient force 

 of machinery to bring it to the bearing. The trigger 

 is to be provided with a string, for the purpose of dis- 

 charging it at a proper distance. Where the bow-string 

 comes near to the fire of the rocket, it should be guard- 

 ed by a copper wire; but it would be still preferable 

 to use strings made of the best German wire, twisted 

 manifold. In place of one string also, two may be used, 

 connected in the middle by a solid plate of metal, where 

 the fire might reach so as to injure it. This balista has 

 for its support a bar of sufficient size and strength to 

 receive the rocket, and furnished with loops, also, for 

 the purpose of retaining it in its proper position, as 

 it flies off. In firing, however, care must be taken that 

 no blow, or impulse, be given to the rocket, for fear of 

 shaking the composition, and producing the effects 

 above mentioned ; but that the contact of the string 

 should be perfect, that it may pass off the support 

 without a shock. It is scarcely necessary to observe, 

 that the priming must be lighted before the trigger 

 is pulled ; and the composition ought, indeed, to burn 

 for at least half a second before the rocket is dis- 

 charged. 



Of other Uses to which Rockets have been applied. 



In our remarks hereafter on die iron rockets, under Of other 

 the military branch of Pyrotechny, we have mentioned uses to 

 their uses in the whale fishery. 



We have only here, therefore, to notice a project for 



rendering them of use, as just mentioned, in relieving 



ships in cases of going on shore. The original project 



of this nature was formed, and not only formed, but 



SB 





