The effect of this is easily understood. When the rocket is expended, and the stick has turned to de scend, the transverse case takes fire at both ends, and spins round the line of descent, so as to form, if suc be lightened by the plane ; if too light, that part of the stick which is fastened to the rocket may be slipped down a little lower.
The same proportions are applicable to all other diame ters, except as to the length of stick ; for which the following table may be consulted.
cessful, a spiritual line of fire. This case may be tied on the stick instead of being fastened on the rocket itself, the stick for that purpose being made so as to pass be yond the rocket head ; but this method is less likely to succeed, as interfering more with the flight. It has been attempted to produce the same effect in a more perfect manner by perforating the transverse case in the middle, and fastening it upon a spindle fixed in the top of the rocket. But this is too complicated ; and, upon all these contrivances we may remark, that al though theoretically practicable, and sometimes suc cessful on trial, they are apt to fail in the fundamental object, by interfering with the ascent of the rocket itself. The operator must recollect that a rocket in its simplest state, and when least encumbered, is a very delicate and ticklish machine, and that it will not easily bear to be tampered with. In all these contrivances, it is necessary to have a longer stick and a more distant point of equili brium than in simple rockets.
A tourbillon may also be combined with a rocket in the act of ascending, but, on account of the weight to be carried, the rocket must have great power. Thus, a two pound rocket will not easily be induced to carry more than an eight ounce tourbillon. In making this attempt the tourbillon must be made complete. as when it is to be fired alone ; that its own force of ascent may assist that of the rocket. But it need not be so com pletely bored; we must, however, be more particular. The transverse case being driven and closed at both ends as before, with the same composition as the rocket, the two horizontal and opposed holes at the extremi ties are to be bored and prolonged obliquely into the case for about a diameter and a half in length, that the force of the issuing fire may be sufficient to produce a circular recoil. Thus, the tourbillon becomes a wheel
revolving round the line of flight of the rocket. When it is fixed on the rocket head, two holes must also be bored simply into the case, one on each side of it, and directed downwards, so that each will produce a stream of fire to assist in the rocket's ascent. Care must be taken to secure the leaders from each of those four holes in such a manner that they must all take fire as soon as the rocket is ready to quit the support, which is easily managed by bringing that which unites the whole, down to the mouth of the rocket, and by put ting about a quarter of an inch of a slow composition into its mouth, so as just to retard for a couple of se conds the communication between the mouth of the rocket and the quick match of the leader. No hole is required at the top of the rocket in this case, but it must be covered as usual, with a cone, to diminish the resistance of the air. Now, as it is essential in this contrivance, that the rocket should be so balanced as to turn round its own axis in ascending, it is requisite that the stick should be round instead of square, and that instead of being attached to the side, as usual, it should be prolonged from the axis. This is managed by fastening it to two metallic stays of light tinned iron,. embracing the opposite sides of the case, so that the stick may not commence till the place where the point of equilibrium is situated, which ought also to be a full rocket length from the vent. This stick ought also to be of unusual length itself. We may add, that the effect of this compound rocket is extremely striking, but that it. requires the greatest nicety in the execution and in. the firing.
The fire of a rocket may be varied in a pleasing man ner by dispersing it during the ascent, so as to produce. a wide or divided shower instead of a simple train of sparks. To produce this effect, a plate of iron, of about the size and figure of a half crown, must be fastened on the stick about two inches below the vent, so as to meet the stream of fire as it issues. The method of doing this is too simple to require any detail, and the effect of it is easily understood.