As to moulds to prevent the rockets from splitting in the act of charging them, Morel observes, that he has never used them. He remarks, that a case which will not resist the force of the charge, cannot resist the violence of the fire.
On the subject of compositions, he observes, that he has only employed one formula, and, of course, but one standard proportion for all sized calibers; and is of opinion, that it is useless to employ an inferior composition, or one with which we are unacquainted, when we have a formula, on which we may rely. This opinion, however, does not agree with that of others.
Certain rockets, it is to be remarked, show tails of fire in their flight, and others again do not. This depends entirely upon the charcoal; for, if we use charcoal, made from tender and light wood, it burns rapidly, without producing a tail of fire; but if we use the charcoal of oak or of beech, or of other hard wood, the rocket will form a brilliant tail of fire, during the whole period of its ascension. It is said, however, that the charcoal of light wood, is lighter and more inflammable, and for that reason, better calculated for rockets; but, so far from producing the effect, we have mentioned, a quick combustion ensues, leaving no ignited coal to be acted upon by atmospheric air.
It is found by experiment, that even a little more or a little less powder, gives to or takes from, the composition its effective power; and, therefore, that the rockets, in their flight, ascend to a greater or less height.
Some writers have asserted, that powder ought not to enter into the composition of rockets; but in lieu thereof, only its component parts. Where, we may inquire, is the difference? The reason, however, assigned, is, that rockets made with gunpowder and the other substances, will not keep any time, owing to the powder becoming damp, and the composition spoiled. But rockets which have been made in France and carried to the East Indies, and brought back, were found, on trial, not to have lost any of their effect.
Different opinions have also been entertained, respecting the composition for the charging of rockets. Some, it appears, would employ a composition for each rocket, according to its caliber, pre-supposing, that the inflamed matter acquired force by the increase of its volume; without considering, that a large rocket has more weight than a small one, and requires more power to raise it. Experience has demonstrated, that a composition which will completely raise a rocket of three-quarters of an inch, will raise, under the same circumstances, a rocket of three inches; and, on the contrary, that the last will ascend more slowly, in consequence of having to encounter a greater resistance in the air, owing to its size.
Sec. II. Of the Composition of Sky-rockets, and Observations on its Preparation, and on other Subjects respecting Rockets.
The formulæ we here give, which we notice separately from the others, are on the authority of Morel, who, by experience, has found them to excel all others. Nevertheless, we purpose to enumerate other formulæ for the information of the reader.
Composition of Sky-Rockets, according to Morel.