In table the first, we find that the compositions for all rockets under one pound are made chiefly of gun-powder and charcoal, which method has been long proved erroneous in many respects: first, that rockets made with such charges will not keep long without spoiling; secondly, that they are very uncertain in performing their proper effect; thirdly, they will carry but a short tail, with a black and smoaky fire.
We also find those charges for rockets above one pound, that are composed of saltpetre, brimstone, and charcoal, to be too strong; by which we should imagine that, at the time when they were used, the piercers did not bear the same proportion to the rockets, as those made use of by our present artists; for it is on the size of the cavity in the composition, that the effect of the rocket and proportion of the charge depends: which we shall endeavour to shew hereafter.
Table the second is given, by the author, as an improvement on the first; wherein he takes notice of the charges being too many in number; he has therefore reduced them to seven only, which, according to his opinion, are sufficient for rockets of any size: he also observes, that the ingredients are expressed in unequal quantities; which he has likewise laid down in a more regular order. By the same author’s account, rockets were made in France, not many years since, with the compositions mentioned in his table. I shall not here pretend to say, that rockets were not made with the charges given in the above-mentioned table; yet can affirm, by practice and experience, that several of them will not agree with our present moulds.
As to the method prescribed in the third and fourth tables, it is difficult to determine whether we shall praise or condemn it, as they were wrote when the art of making fireworks was in it’s infancy; as may be seen by their strange method of determining the proportion of ingredients, and weight of rockets, by the quantity of composition contained in each case; which must have required a very nice calculation, for at that time, they had not fixed upon an exact length for rockets, but made them from six to nine diameters long: all which differ so much from our modern practice, that I never thought it worth the trouble of making a trial: but am of opinion, that very few of the charges will answer.
In table the fifth, the compositions are in proportion to the weight of the rocket, with it’s head and stick, all compleat; which head and stick together are equal to the weight of the rocket, according to the improvement made by M. F***, as may be seen by the second column from the top; he also has added the diameters to the moulds, in proportion to their height, allowing each six diameters, which supposing to be right, the rockets will be nearly reduced to half their weight given in the first column. On the charges in this table I have made no experiment, therefore cannot recommend them as proof.
Having already given a variety of charges for sky-rockets, in the preceding tables, which are collected from the principal authors on this subject, together with remarks on the same; I shall, in the next place, according to my promise of not omitting any thing that may be of service to the reader, add some compositions for rocket-stars of several colours, as inserted by former authors.
Compositions for Stars of different Colours.
I. Meal powder four ounces, saltpetre two ounces, brimstone two ounces, steel dust one ounce and a half, and camphor, white amber, antimony, and mercury-sublimate, of each half an ounce.
II. Rochepetre ten ounces, brimstone, charcoal, antimony, meal powder, and camphor, of each three quarters of an ounce, moistened with oil of turpentine. These compositions are made into stars, by being worked to a paste with aqua vitæ, in which has been dissolved some gum-tragacanth; and after you have roll’d them in powder, make a hole through the middle of each, and string them on quick-match, leaving about two inches from one to the other.
III. Saltpetre eight ounces, brimstone two ounces, yellow amber one ounce, antimony one ounce, and powder three ounces.