FRANKINCENSE, Alynan.—After the remarks which we made on benzoin, it is almost fruitless to say any thing about these gums, since they are equally useless. It ought, however, to be known to all makers of fire works, that none of these substances yield a smell un less they smoke, and that at a low heat. Whenever they burn, or when the heat is raised, all smell is de stroyed ; and there is no species of firework, unless pastilles are included under this form, in which the heat will not burn all these inflammable substances. It is much more amusingly absurd, to find oil of roses and oil of bergamot recon.mended as ingredients in fireworks.
But we will not pursue this part of our subject fur ther, as our readers may, after these remarks, be ena bled to judge without much difficulty respecting the value and uses of such fantastic ingredients. Yet, that our criticisms may not appear unreasonable or unfound ed, we subjoin one of Captain Jones's receipts for the composition of what he calls an odoriferous water balloon." "Take of saltpetre four ounces, sulphur one ounce, saw dust of juniper half an ounce, saw dust of cypress an ounce, myrrh two drachms, dried rosemary a quar ter of an ounce, cortex elaterii had an ounce ; all to be m...stened with oil of roses." On this we need only icmark that it will not burn, to say nothing of the saw dust, of elaterium bark, which has no existence ; and of oil of roses, which, for a composition of this weight, would probably cost a few hundred pounds.
Method of Grinding the Ingredients The ingredients which require grinding for fireworks, are saltpetre, sulphur, charcoal, and gunpowder, and each of these requires some notice.
SALTPETRE.—It is sometimes recommended in the books of pyrotechny, to pulverize the salt by boiling it down, and stirring it with a stick as it begins to be deposited, in consequence of the evaporation of the water. But it cannot be reduced to powder of suffi cient fineness in this manner, so that mechanical means become indispensable. For artificers who work on a large scale, the common cylinder mill, similar to that used by tanners and druggists, is the most expeditious engine ; and the cylinder may be made of limestone or of metals, than which none is preferable to cast iron. On a smaller scale, a pestle and mortar may be
adopted, and as far as either nitre, sulphur, or charcoal is concerned, both of these may be made of iron. Saltpetre, when produced, can scarcely be passed through a fine sieve, from its adhering together, and therefore the artificer must ascertain its fineness by the feel, or by examining it on a smooth board, on which it is diffused, thinly by means of a muller of another board, furnished with a handle. It is very essential to the correct performance of all fireworks, and particu larly of sky-rockets and illumination lights, that the saltpetre should be rendered perfectly fine. It is per haps cheaper to purchase it in that state, when it can be done, from the powder makers, or the grinders of drugs.
SULPHUR.—This may be powdered in the same man ner, but it admits of being easily sifted through the lawn sieve, which is also required for the charcoal and the mealed powder. The flowers of sulphur are some what more expensive, but they require no grinding. The operator must, however, recollect what we men tioned before, that they generally contain acid, or a portion of oil of vitriol. Hence they should be well washed, till the water is tasteless, with water ; or, what is better, with a weak alkaline lye first, and with water afterwards.
CHARCOAL.—The same machinery serves for pow dering charcoal, but it requires a different process in sifting. One sieve should be formed of fine lawn, and this finest dust is reserved for compositions that are re quired to be very accurate, and to give flame rather than sparks. The remainder may be divided by coar ser sieves into two qualities or more, according to the fancy of the operator, the largest fragments being re served for wide cases and big fires, and the smaller for sparks in cascades or wheels, or other works, according to their respective sizes.