A Manual of Pyrotechny; or, A Familiar System of Recreative Fire-works

by G. W. Mortimer

Table II.—This table may be perfectly understood by the explanation given of its use, and from considering that a lead bullet of a pound weight, is just 19½ lines in diameter, as may be proved by experiment; the inferior numbers are likewise the diameters of the inferior weight.

Table III.—This table is only an extension of the latter, although its arrangement is somewhat different; for if 19½, the diameter of a ball weighing one pound, be assumed as unity with any number of cyphers, answering to the number of parts which the same diameter is divided into, (which may be done by means of the diagonal scale,) let this number be 100, which answers to one in the column of pounds:—that is to say, if you assume 100 for the first number, and it be rose to the third power,[11] your first cube will be 1,000,000, the cube root of which (being 100) must be placed in your table as the first root, and answering to unity in the column of pounds: then for the second number, which is two pounds, we must extract the cube root of double that number, viz. 2,000,000, which will be 126 nearly, (or continued to more places 1,259,921) and this will be the second number in your Table; and in the same manner will the third number be found, that is, by trebling the first cube and extracting the root as before, which will be 144, and so of the fifth, sixth, &c. to the end of the table. These tables are indispensable in the making of Rockets, in order to preserve an uniformity in Rockets of the same kind, and to render more certain their effects, as has been corroborated by repeated experiments.

Preparing the Cartridges.

Preparing the Cartridges.—For this purpose large stiff paper of a particular kind is to be used; namely, that which from being principally used for this purpose, is known by the name of Cartridge paper. For cases from the smallest size, up to five or six pounds, this is the best material we can employ; it must be wrapped round the former, (whose proportion to the mould we have already given) till it fits tight into the cylinder, and the last fold secured by means of common paste. If some thin paste is used throughout the rolling, the cases will be much improved.

For Rockets of a larger size, the cases must be made of some stronger material, such as pasteboard, of the thin and inferior kind, the folds of which must be well secured with some strong paste or glue. In making the cases a pattern of the outer fold, with one end sloped off, should be preserved for each size, and on it marked the number of sheets or folds requisite to make that size cartridge. This method will help to ensure a regularity in the make and formation of the cases.

The paper being prepared of the proper size, one part of the first sheet must be folded down so far, that the double thickness will go two or three times round the former; the former is then to be laid on this double edge, and the handle projecting over the table, the paper is to be wrapt round within two or three turns; when a second sheet is to be laid on the loose part of the first, and then roll the whole of it tight and evenly on the former; these two sheets should be of lengths sufficient for the size of the case, but if they are not, a third must be added in the same manner as the second.

For the purpose of rolling the cases tight and even, they are passed two or three times under the rolling-board, (which is a smooth piece of deal about eighteen inches long, and in breadth equal to the length of the Rocket, with a handle at the top, when complete something similar to a plaisterer’s float;) taking care to roll them the same way as in rolling them on the former.

The cartridge being formed to the proper size, and the last fold being secured by paste, &c. it is now to receive the contraction, or, as it is generally termed, the choak; which is effected by the simple apparatus represented by [Fig. 7]. Let the former and small end-piece be now joined by means of their connecting wire, and let the short piece be thrust into the case as far as the line B, marked round it for the purpose; then pass the cord once round the case, exactly over the juncture of the formers, and at first press gently with the foot on the treadle, and keep rolling the case on the line, which will cause the choak to be free from wrinkles and other inequalities.

Cases of small dimensions may be easily contracted after the above manner, but when of larger size, they will present more resistance to the choaking cord than it will be able to overcome; but this difficulty may be obviated, by moistening with water the end of the case, and choaking it previous to the envelope of the last sheet; which may then be put on, and again choaked, and the contraction well secured by twine, or strong waxed thread, which must be passed several times round the cartridge, and afterwards secured by two or three running knots made one above another.

The case (still remaining on the former,) is now to be inserted into the cylindrical mould without its foot, and set upon some solid block, and the former driven hard upon its end-piece, so as to make the contraction smooth and close; after which the case is to be cut to its proper length, so as to rise a little above the mould, and allowing half a diameter from the choak to the edge of the mouth: the cutting the case to its proper length will be best effected while on the former, which when done, the former is to be pulled out, and the case being put again into the mould, having the foot and piercer properly fixed to it, must be driven down upon the piercer with the long perforated rammer, so as to make the contraction of the proper size.