Besides the use of nitre in pyrotechnical compositions, as it forms an essential part in all of them, there is another salt we had occasion to notice, of which an account will be given hereafter, that affords a variety of amusing experiments. This salt is the hyperoxymuriate or chlorate of potassa. Although it has neither been used for fire-works on an extensive scale, nor does it enter into any of the compositions usually made for exhibition, yet its effect is not the less amusing. Some general idea may be had of its effect, by stating a few experiments. If a mixture of this salt and white sugar be made in a mortar, and the mixture laid on a slab or tile, and a string wetted with sulphuric acid, (oil of vitriol), be brought in contact with it, or a drop or two of the acid be let fall upon it, a vivid combustion will take place. In this experiment, the acid decomposes the salt, and the oxygen unites with the carbon and hydrogen of the sugar, and forms carbonic acid and water. The same salt, rubbed in a mortar with sulphur, will produce a crackling noise resembling that of a whip; and if a mixture of the two be struck with a hammer, the percussion will cause a loud detonation. The same thing happens when phosphorus is used, but the detonation is more violent. Various other experiments may be made with it. It forms the principal part of the match, called the pocket lights. These are made, in the first place, by dipping the wood previously cut in splints in melted sulphur, and afterwards in a mixture of this salt with sugar, which is moistened with water. The match is then dried. When used, it is dipped in sulphuric acid. The red colour, usually given to the match, is formed by mixing with the composition some vermillion. Another application of the same principle, is the firing of cannon. For this purpose, after the tube is filled with powder, a covering of the same mixture is applied when mixed with water. It is then dried. When the tube is put in the vent, a drop of sulphuric acid will inflame it, and consequently discharge the gun. This salt also, when mixed with sulphur, may be used to fire fowling pieces, provided the lock be so constructed, as in a late invention, that it acts by percussion. (See [Thenard's Priming powder.])
The Rev. Alexander Forsyth of Alexander Forsyth of Belhelvie, in Aberdeenshire, Scotland, took out a patent for a new kind of gun-lock, to be used without a flint, and has contrived to inflame powder merely by percussion. The powder employed for priming, consists of chlorate of potassa and sulphur. The gun-lock is calculated for firing cannon as well as musquetry; it is contrived to hold forty primings of such powder; and the act of raising the cock primes the piece. Each charge of priming is supposed to contain one-eighth of a grain of the salt. There are other substances which also produce fire by percussion. The fulminating silver, mixed with any substance, or used by itself, will detonate by percussion. It should be used with great caution. A grain or two will explode with great violence. (See [Detonating Works], [Waterloo crackers], &c.)
There are several other metallic preparations which detonate violently, such as the fulminating gold, fulminating mercury, &c. all of which must be used with extreme caution. (See [the respective articles.])
Sec. IV. Of Illuminations.
Although nothing of much importance can be said on the subject of illumination, yet at the same time, as it is connected with some remarks we will hereafter offer, it may be proper to observe, that the practice of illuminating, as well as the exhibition of fire-works in public rejoicings, has been in use for many years. The former indeed has been customary for many centuries. We have, however, appropriated an article to the manner of forming illuminations and transparencies, and also on imitative fire-works.
Illuminations, whether with lamps, candles, flambeaux, &c. may be rendered more impressive from the manner of their arrangement. In some instances different coloured flames have been used; and the effect in this case is more grand and beautiful.
The public lighting of cities on festivals, and particularly on joyful occasions, called illuminations, is of great antiquity. Indeed, illuminations are a general expression of the public feeling, and should, on important occasions, be encouraged. Victories gained over an enemy by the army or navy are subjects of rejoicing. While, in such cases, illuminations may be viewed as an expression of the feelings of the people, they serve moreover to stimulate, in the spirit of the amor patriæ, the future actions of the patriot and the soldier; and while such rejoicings are demonstrative of victory, they are equally expressive of that virtuous feeling, of which every one must partake, on the return of an honourable peace.
What could have been more impressive than the brilliant spectacle exhibited in Paris in 1739, on the return of peace? Besides illuminations, the fire-works on that occasion were truly magnificent. The same may be said of those at Pont Neuf, and those at Versailles in the same year. We shall have occasion to speak of them, when we come to the arrangement or the order of fire-works for exhibition.
The Egyptians at an early period, made use of illuminations, and particularly at a festival, which is mentioned by the Greek authors. During the festival, as Herodotus says, lamps were placed before all the houses throughout the country, and kept burning the whole night.
During the festival of the Jews, called festum encæniorum, the feast of the Dedication of the Temple, the lamps were lighted before each of the houses, and the festival continued eight days. Illuminations were also used in Greece, according to a passage in Æschylus. When games were exhibited in the night-time at Rome, the forum was lighted. Caligula, on a similar occasion, caused the city to be illuminated. In honour of the great orator Cicero, as he was returning home at night, after the defeat of Cataline's conspiracy, lamps and torches were lighted in all the streets. Byzantium, afterwards Constantinople, was ordered to be illuminated with lamps and wax candles on an Easter eve, in the time of Constantine.