In a variety of chemical combinations, it happens, that one or more of the principles assume the elastic state with such rapidity, that the stroke against the displaced air produces a loud noise. This is called fulmination, or much more commonly detonation. Fulminating gold, and fulminating powder, are the most common substances of this kind, except gunpowder. The fulminating powder is made by triturating in a warm mortar, three parts by weight of nitre, two ol carbonate ot potash, and one of flowers of sulphur. These substances should be triturated separately, then mixed. Its effects, when fused in a ladle, and then set on fire, are very great. The whole of the melted fluid explodes with an intolerable noise, and the ladle is commonly disfigured, as if it had received a strong blow downwards. If a solution of gold be precipitated by ammonia, the product will be fulminating gold. Less than a grain of this, held over the flame of a candle, explodes with a very sharp and loud noise. This precipitate, separated by filtration, and washed, must be dried without heat, as it is liable to explode with no great increase of temperature ; and it must not be put into a bottle closed with a glass stopple, as the friction of this would expose the operator to the same danger. Fulminating silver may be made by precipitating a solution of nitrate of silver by lime water, drying the precipitate by exposure to the air for two or three days, and pouring on it liquid ammonia. When it is thus converted into a black powder, the liquid must be poured off, and the powder left to dry in the air. It detonates with the gentlest heat, or even with the slightest friction, so that it must not be removed from the vessel in which it is made. If a drop of water fall upon it, the percussion will cause it to explode. It was discovered by Bertholtet. Brugnatelli made a fulminating silver by powdering a hundred grains of nitrate of silver, putting the powder into a glass, and pouring on it, first, an ounce of alcohol, then as much concentrated nitrous acid. The mixture grows hot, boils, and an ether is visibly formed, that changes into gas. By degrees the liquor becomes milky and opaque, and is filled with small white clouds. When all the grey powder has taken this form, and the liquor has acquired a consistency, distilled water must be added immediately to suspend ebulition, and prevent the matter from being redissolved, and becoming a mere solution of silver. The white precipitate is then to be collected on a filter, and dried. The force of this powder greatly exceeds that of fulminating mercury. It detonates in a tremendous manner, on being scarcely touched with a glass tube, the extremity of which has been dipped in concentrated sulphuric acid. A single grain placed on a lighted coal, makes a deafening report. The same thing happens if it be placed on a bit of paper, or an electric pile, and a spark drawn from it. Fulminating mercury was discovered by Mr. Howard. A hundred grains are to be dissolved with heat in an ounce and a half by measure of nitric acid. The solution, when cold, is to be poured on two ounce measures of alcohol, and heat applied till an effervese cence is excited. As soon as the precipitate is thrown down, it must be collected on a filter, that the acid may re-act on it; washed and dried by a very gentle heat. It detonates with a very little heat or friction. Three parts of chlorate of potash, and one of sulphur, triturated in a metal mortar, cause several successive detonations, like the crack, of a whip, reports of a pistol, or the fire of musketry, according to the rapidity and force of the pressure employed. A few grains, struck with a hammer on an anvil, explode with a noise like that of a musket, and torrents of purple light appear round it. Thrown into concentrated sulphuric acid, it takes fire, and burns with a white flame, but without noise. Six parts of the chlorate, one of sulphur and one of charcoal, detonate by the same means, but more strongly, and with a redder flame. Sugar, gum, or charcoal mixed with the chlorate, and fixed or volatile oils, alcohol, or ether, made into a paste with it, detonate very strongly by the stroke, but not by trituration. Some of them take fire, but slowly and by degrees, in the sulphuric acid. The chloride of azote is the most wonder- j ful fulminating known substance, and was discovered by Sir H. Davy. It is an oily looking liquid, and a small globule of it no larger than a grain of mustard seed, to which heat was applied in a glass, shivered it to fragments. A small globule thrown among olive oil in a tumbler, produced a most violent explosion, and broke the glass in pieces. A small grain of it when touched with a piece of phosphorous or: the end of a penknife, shattered the blade to pieces in an instant. The iodide of azote is also a powerful fulminating substance, and detonates with the smallest shock. A detonating powder can be made with 1 part by weight of the chlorate of potash, 1 of yellow prussiate of potash, and 1 of dry white sugar, carefully mixed together in a mortar, with a wooden spatula. Each substance should be reduced to powder by itself, otherwise it would be dangerous to pound them together. If to this powder one part of sulphur is added, a good percussive powder foi guns—such as for the Prussian needle gun —can be made. The fulminating composition for percussion caps, consists of fulminating mercury 3 parts, chlorate of potash 5, sulphur 1, powdered glass 1. Another kind consists of chlorate of potash 6 parts, sulphur 3, powdered glass 1, and pounded charcoal 1 : theseparfs are by weight, such as one ounce for the unit. The chlorate of potash is exceedingly dangerous when rubbed with sulphur. These fulminating powders are affected by the force applied, and the rapidity of its action. If the force is applied to the powder, like the needle gun, the motion of the needle must be rapid, and the powder should be well packed in the ' cartridge.