Ve have often been puzzled to account for the delight with which popping, and frizzing, and blazing, on the Fourth of July, seems to fill the minds of boys and even men. Whatever may be the cause, the recent display gives no indication of diminished taste for such sports. i However, as the art of pyroteclmy is an industry involving the employment of considerable capital, ingenuity, and artistic taste, it may not be amiss to give our readers an outline of the means employed to produce the efiects so much admired by most people. The word pyroteclmy signifies the art ol employing fire for useful or other purposes. It consists, first, in the combination and admixture of different materials so that they shall produce, when burned, certain colors, explosions, etc., and also so arranging them that they shall represent a preconceived design, or impart, by their explosive force, motion to wheels, rockets, etc. The little that is known in regard to this art seems to indicate that the Chinese had a very early knowledge of it, if they were not the first to originate it. And they are still, perhaps, as skilled in it as any other nation. One of the chief mat rials employed is gunpowder, the nature and composition of wliicli are varied somewhat according to the purposes to whicli it is applied. It is unnecessary to dwell upon its compotitioii, as our readers are already well informed in regard to it, as well as the method of manufacturing it; and doubtless some of them have received, during the late celebration, practical demonstration of the impossibility of restraining its force. In such attempts, hands and arms rarely are found equal to the emergency. Niter is also a material of the greatest importance in this j art. It is obtained in the common form in which it is sold in large establishments, and purified by solution, filtration, and recrystallization. The composition of this salt is one equivalent of potash and one of nitric acid. At a red heat it is decomposed, giving off its nitrogen and oxygen, the latter oi which constitutes nearly one half the weight of the salt. Being so rich in oxygen its presence in connection with a suf ficiently heated combustible affords, by its decomposition, a supply of oxygen to support vigorous combustion, and hence its general use in the art of pyroteclmy. Sulphur, charcoal, steel dust, and iron filings, are also largely used. A material called " iron sand," made by pulverizing cast iron, is also employed. This iron sand is often prepared so as to keep without rusting, by partially combining it with sulphur, in order to coat the grains with a sulphide of iron. It is slowly sifted into melted sulphur, and thoroughly stirred till the mass is cold, when it is finely pulverized, and the extraneous sulphur sifted out. The granules of iron sand give most beautiful sparks when burned. Oil of camphor, benzoin, salts of strontium, antimony, copper, and other metals which impart brilliant colors to flames when burning, glass dust, brass dust, ivory raspings, amber raspings, chlorate of potash, Ethiop's mineral, chalk, orpiment, nitrate of barium, and many other ingredients, are employed. A few recipes will give a clue to the method in which theee materials are used to obtain colors. STARS FOR ROCKETS. 1. Purple.—Chlorate of potash, 42 parts; saltpeter, 22 parts ; sulphur, 23-5 parts; black oxide of copper, 10 parts; Ethiop's minera, 2*5 parts. 2. Potash, 50 parts; sulphur, 25 parts; chalk, 22 parts ; black oxide of copper, 3 parts. 3. Grcm.—Nitrate of barium, 62*5 parts; sulphur, 10*5 parts; potash, 23-5 parts; orpiment, 1*5 parts; charcoal, 1*5 parts. 4. YcUoic.—Nitrate of soda,* 74*5 parts; sulphur, 19*5 parts ; charcoal 6 parts. 5. Crimson.—Chlorate of potash, 17 parts ; nitrate of strontium, 55 parts ; charcoal, 4 parts ; sulphur, 18 parts. The coloring principles of the above mixtures are, in No. 1, the oxide of copper and Ethiop's mineral; in No. 2, the chalk and the copper ; in No. 3 the nitrate of barium ; in No. 4, the nitrate of soda; in No. 5, the nitrate of strontium. In all of them the sulphur modifies the color more or less, and when burned alone it gives a blue flame. Black pitch gives a dusky flame, like thick smoke ; sal ammoniac and copper salt, a greenish flame ; raspings of amber, a lemon yellow ; powder of metallic antiniony a russet ; raspings of ivory, a beautiful silvery flame; steel dust, very brilliant silver-colored spangles. Rockets and wheels are propelled by the reaction of suddenly generated gases, discharging from cases of strong pasteboard. The motion of serpenis is produced by a small piece of paper, or its equivalent, attached to the middle of the case, which, by its rosistjice iipni the air produces the erratic motions of these amusing fireworks. Gerbes, or fountains, a species of firework, which throws up a sparkling jet of fire, resembling somewhat the shape of a water spout, are made ol thick paper or pasteboard, partly filled at the bottom with clay through which a priming hole is bored. Roman candles are very nearly like the gerbes. Between their layers of composition, balls or stars are placed, whicli vary tlu; effect produced. Rockets are strong paper cylinders filled with a composition rammed hard. They may have attached to them " heads "of gunpowder, sparks, stars, serpents, etc., as fancy may dictate. The stick attached to them acts as a rudder to keep their flight in the proper direction. The composition v/ith which rockets are filled varies with the weiglits. For one and two ounce rockets the ingredients may be one pound of gunpowder, two ounces of soft charcoal, and one and a hall ounces of saltpeter. For four-pound rockets, gunpowder one part, saltpeter thirty parts, sulphur four parts, charcoal twelve parts. All the materials are xmlverized exce])t the gunpowder, and the mixture thoroughly incorporated by sifting. The composition is then rammed hard into a case made by cartridge paper upon a brass former, with paste between the laminee. The sticks being attached properly the rocket is completed. To give a more minute description of the details of this art would extend this article too much. Suffice it to say, that the recipes and compositions above given are by no means the only ones by which similar effects may be obtained. To give them all, with all others usedin the art, would require a volume.