PYROTECHNY. 



also we can understand why the velocity of a rocket 

 tends to increase during every successive part of its 

 flight; because as the diameter of the bore becomes 

 larged by burning, a much greater extent of sur 



From the action of the stick we can alto account 

 for the effects of wind in disturbing the flight of a 

 rocket, and in altering the line of its direction ; but 

 need not dwell on matters so obvious. But it is 



?lilar|tvll uyuuiiiin^j ***-* ft 1 , 



lace is occupied in the production of gas. Hence also plain, that from the aame great power which it thus 

 the cause of bursting becomes evident; as, in cases of possesses, it is most important, that in quitting the 

 fracture of the composition, so large nn extent of it aupport, it should run clear: as the slightest impedi- 

 raav take fire, that the air cannot find a sufficiently ment or irregularity that may affect its extremi: 

 tree issue at the vent. The necessity of choking, or of particular, may produce very considerable deviations. 

 contracting the vent hole, must now also be so evi- It has been proposed to steady the flight of rockets by 

 lent that we need take no notice of it. means of wings, so disposed, on opposite sides ol 



It remains yet to inquire respecting the use of the case, as to form the whole into the shape of an equi- 

 atick, and the deviations to which the flight of a roc- lateral triangle. But this method is not effica< 



neither is it attended with any particular advantages 

 in other respects. In the books it is also said that 

 rockets may be steadied by a bullet attached to the 

 end of a string at their extremity, which is palpable 



ket is subject. If we assume the simplest case, or 

 that of si vertical rocket, it is plain that it is subject, 

 in a still atmosphere, to two counteracting forces only ; 

 namely, that of gravity, and that of the anterior re- 

 sistance of the atmosphere. If therefore it could be 

 retained in the vertical line without a stick, or any 

 other appendage, it would ascend in a perpendicular 

 direction. But it is subject to several disturbing forces 

 which render it impossible for it to preserve that line. 

 One of these is the wind ; another arises from its own 



nonsense. 



Of Line Rockets. 



These are . o exactly like sky rockets in their con- or line 

 struction, that the same rules for filling the cases, and rockcu. 

 for the composition, are applicable to both. But as 



irregularity of form, which prevents it from meeting they are seen at a less distance, they admit of a variety 

 with an equable resistance on all sides from the cur- of fire, which, in the sky rocket, is almost superfluous. 

 rent of air which it makes by its own flight, and the This is the brilliant iron fire; and the artist may 

 other and principal one is the perpetual variation of adopt, for this purpose, any of the strong compos- 

 its centre of gravity which arises from the burning out tions under the head of brilliant fires, or else that *ky 



rocket composition described in the table, for those 

 j n t which iron enters. For the reader's convenience 

 we may here give it again. 



Saltpetre 8. 

 Sulphur 4. 

 Mealed powder 2. 

 1'ounded iron or steel filings 



part. 



If lines can be stretched far enough, there need be 



of the composition 



If now a stick be attached to the lower extremity, 

 and of sufficient length, parallel also to the axis, it is 

 plain that at whatever instant it tends to deviate from 

 the line of its flight, the rapid stream of air which 

 is passing along parallel to the stick, will meet it on 

 the opposite side and restore the original position. 

 The case is precisely that of a rudder in a ship, si- 



milarly acted on by the current of water that runs no limit, as in sky rockets, to the length of the com- 

 along the keel, in such a manner as to produce the position ; but in no case is it necessary that the corn- 

 effect of restoring the true position wherever it may position should burn longer than the line will admit, 

 deviate ; and further, in this particular case, of pro- as it would at the end of its range remain stationary. 

 ducing a new one when required, merely by causing Thus, as we have just shown that the average flight 

 the rudder to meet the current. The length of the stick o f a sky-rocket of one pound is 480 yards, 500 will be 

 is also necessary, partly to enable it to act with the a sufficient length for the line. If it can be carried 

 greater effect oa the passing current by its distance farther, an additional number of diameters of compo- 

 from the centre of gravity of the rocket, and partly sition may be left above the bore in filling it ; and it 



-------- . ------ *,> j g eag y j^ tr j a | to com p ute tne exa ct relative lengths 



of the line, and the nature of the composition, that 

 this may be finished at the end of the range. We 

 may also here remark, that the flight of a line rock- 

 et may be too rapid for the eye to follow it con. 

 veniently, particularly if it is a simple one, as it 

 has very little resistance to encounter. In such a case 

 it will be proper to reduce the length of the bore, 

 which may easily be done by using a shorter spindle. 



to enable it the more easily to counteract or compensate 

 that change in this centre which arises from the burn- 

 ing out of the composition. 



In flights at low elevations, and at angles less than 

 the perpendicular, the same reasoning, with some va- 

 riations, is applicable. These are, however, so obvious 

 that we need not enter on them. We must, however, 

 remark, that the weight of the stick, in these cases, 

 produces an effect which does not occur in the verti- 

 cal flights. Its tendency is to make the rocket assume 

 an angle of elevation greater than that at which it is 

 placed on the frame. Tims, to produce a curve calcu- 

 lated for an initial direction of 45, the rocket will re- 

 quire an elevation which may be only 42, or even less. 



But if the line rocket is to be compounded, or to carry 

 any considerable weight, the artist may adhere to the 

 usual proportions for sky-rockets. In all cases, it is 

 easy to understand that the flight may be retarded by 

 diminishing the length of the bore, or by increasing 



The explanation of this is easy. At the moment the relatively the unbored part of the composition, in which 

 rocket quits the support, its velocity is yet small ; or case the effect is more pleasing than when the velocity 

 the steerage way, to use a sea phrase, is insufficient is very great, but it is useless to give any positive rule 

 to allow the rudder its full action. The weight of on this subject, as the artist must be regulated by the 

 the after end of the stick thus causes it to drop, and length to which he can stretch his line, 

 consequently to elevate the rocket so as to increase 1'he proper line for this purpose is that which is call- 

 the angle with the horizon. Hence the singular ed jack-line, and it must be stretched as tight as possi- 

 curves which are assumed by such rockets at the com. ble, lest it should come too near the ground in the 

 mencement of their flights. middle. Where simple, or alternating plain rockets. 



