248 



PYROTECHNY. 



Pyrotech. 



Of gerbes. 

 PLATE 



CCCCI.XXIl 



Fig. 10. 



of the water by means of proper floats ; but the me- 

 thod of doing this is so simple as to require no parti- 

 cular description, though we may remark, that large 

 white lights calculated to burn for a considerable time 

 produce a very pleasing effect in this way. 



The simple water rockets may also be combined like 

 the line rockets, so as to produce a more durable and 

 various effect. Thus two or three, or many more, may 

 be united in alternate order, so as that one may fire when 

 the other is expended. But as the water permits of 

 motion in any direction, we are not even limited to 

 this regular order. Thus the cases may be put toge- 

 ther in any disorderly manner that the operator chooses, 

 and the effect of this will be a great variety of intricate 

 serpentine movements, so as to increase very much the 

 effect ; the greatest objection to the water rocket being 

 its want of variety and brilliancy. If they are attach- 

 ed in the form of a wheel, so as to float on the surface, 

 they will also produce a pleasing appearance ; .but the 

 artist must not expect that they will revolve regularly 

 like a wheel in this manner, because of the very une- 

 qual resistance which they meet with from the water 

 in the attempt to revolve. To make a wheel revolve 

 upon water requires a proper contrivance, which must 

 be sufficient to float whatever wheels may be used. We 

 shall describe under the head of Wheels all the kinds, 

 so that the artist may select from them any which he 

 may think proper. 



Of Gerbes. 



This is the most brilliant of all the fixed simple fire- 

 works, being formed entirely of the iron fire. Various 

 receipts for it will be found in the table of composi- 

 tions, so that we need not here repeat them. We must, 

 however, remark, that in proportion to the dimensions 

 of the gerbe may be the size of the particles of iron. 

 Thus the largest fragments of cast iron may be put in- 

 to cases of three or four inches in diameter, while steel 

 filings may be used for the smallest. The proportion 

 of three pounds of mealed powder to one of iron will 

 be found to answer generally as a rule. 



There is a peculiarity in the construction of the cases 

 for the larger gerbes which requires to be described. 

 They should be extremely strong, as the composition, 

 which is very powerful, and requires to be much 

 checked at the issue, might otherwise burst them. But 

 besides the ordinary choke, they must be provided 

 with a second at some distance, and as this is some- 

 what difficult to manage in paper, it is better to have 

 a vacant space in the case above the choke, which is to 

 be filled with a wooden tube, well glued, and secured 

 in it ; the diameter of its bore being the same as that 

 of the choke itself. This may be about two inches in 

 length for the cube of three or four inches in diameter, 

 and so in proportion ; the smallest sizes requiring no- 

 thing more than the ordinary choke. The purposes of 

 this long aperture is to enable the iron to be complete- 

 ly heated in its passage out, without which precaution 

 the larger kinds might be thrown out unburnt ; and 

 also to compel the sparks to spread after their issue, so 

 as to produce that resemblance of a wheat sheaf whence 

 the name is derived. 



The filling of such a case requires some precautions; 

 and, on account of the great force required to drive it 

 firm, a mould is necessary. The length may vary from 

 four diameters to ten or more, according to the views of 

 the artist respecting its duration. When placed in the 

 mould for driving, with the mouth downwards, a plug 



of wood roust be put into the vent so as to fill it up. Pyrotech- 

 Half a diamejer, or a whole one, of a moderate char- n y- 

 coal fire must first be introduced, that the firework s " p "~v " 

 may not break out in all its brilliancy at once, after 

 which it may be filled to the end with the iron compo- 

 sition. If a bounce is required it should be in a sepa- 

 rate maroon case, as it is more manageable and loudsr; 

 and, from economy, as the gerbe case may serve a 

 second time with the addition of a new vent. The 

 driving requires to be performed with as much force 

 as it is possible to give ; fully as great, or even greater 

 than for rockets of the same size ; as the strength of 

 composition necessary for burning the iron effectually 

 is so great, that, if not well driven, it would burst the 

 case. The larger gerbes, indeed, can scarcely be effec- 

 tually driven without the pile engine. When finished, 

 it is advisable to fill up the neck with a blue light or 

 other composition of little show, as the surprise will 

 be the greater when the gerbe comes to take fire. 



The smaller gerbes are sometimes called fountains 

 and Chinese fires, but they differ in no respect from 

 the former, except in size and in the nature of the 

 composition, as already noticed. We mentioned that a 

 common choke would answer, if on a very small scale* 

 When they amount to six or eight ounces, however, 

 a better way of making the choke is to drive a diame- 

 ter of clay first upon it, whieh may, after the composi- 

 tion is driven, be perforated by a gimlet of the proper 

 size, 



In the books of pyrotechny, receipts will be- found 

 for making what is called the Chinese spur fire, which 

 are purely imaginary. This is said to be a cold fire, 

 (not a very intelligible term,) and to be made with 

 saltpetre, sulphur, and lamp black. One of the re- 

 ceipts gives four quarts of lamp black to a pound of 

 saltpetre and half a pound of sulphur ; a composition 

 which may well be called cold, as it would not burn at 

 all. The truth is, that the Chinese spur-fire, sometimes 

 also called flower pots, is merely a gerbe ; and the 

 bright sparks are produced in the usual way by iron. 

 But as the Chinese are great economists in their mate- 

 rials, these are made on a very small scale. The com- 

 position is simply that of gunpowder, or of saltpetre 

 75 parts, sulphur 10, and fine charcoal or lamp black 

 fifteen, by weight, well mixed and rammed. A very 

 few grains of iron are introduced at different distances 

 into the composition during the driving, so that in- 

 stead of yielding a torrent of sparks it gives a red 

 strong flame, with an occasional bright spark. No 

 other directions can be required for making this flower- 

 pot, which is generally made on a very small scale, so 

 as to admit of being fired, like the fire wheels, and all 

 the other Chinese fireworks, in a room. 



We shall not add any thing here respecting the va- 

 rious additions that may be made to gerbes, as it would 

 be in a great measure to repeat that which has been 

 said on this subject in other places. 



Pots de Brins. Pots d'aigrettes. Pots de Saucissons. 



There are three kinds of fireworks described in all p ts de 

 the books of pyrotechny, but as the general principle brins. 

 is the same in all, and as there is indeed no great dif- Pots d'ai- 

 ference among them but the name, we have here class- ? rettes - 



ed them all together. 



_,. i & , ,, it i 4. i i saucissoiifr. 



The pots de brins, as they are called, are intended 



to throw serpents, stars, and crackers ; the pots 

 d'aigrettes throw serpents only, and the last kind is 

 intended to throw up cases which are half serpent and 



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