a composition of nitre, sulphur, and charcoal, mixed together, and usually granulated; which easily takes fire, and, when fired, rarefies or expands with great vehemence, by means of its elastic force.

It is to this powder we owe all the action and effect of guns, ordnance, &c. so that the modern military art, fortification, &c. in a great measure depend thereon.

Invention of GUNPOWDER. See Gun.

Method of making GUNPOWDER. Dr Shaw's receipt for this purpose is as follows: Take four ounces of refined nitre, an ounce of sulphur, and fix drams of small-coal: reduce these to a fine powder, and continue beating them for some time in a stone mortar with a wooden pestle, wetting the mixture between whiles with water, so as to form the whole into an uniform paste, which is reduced to grains, by passing it through a wire-sieve fit for the purpose; and in this form being carefully dried, it becomes the common gunpowder.

For greater quantities mills are usually provided, by means of which more work may be performed in one day than a man can do in a hundred.

The nitre or saltpetre is refined thus: Dissolve four pounds of rough nitre as it comes to us from the Indies, by boiling it in as much water as will commodiously suffice for that purpose; then let it shoot for two or three days in a covered vessel of earth, with sticks laid across for the crystals to adhere to. These crystals being taken out, are drained and dried in the open air.

In order to reduce this salt to powder, they dissolve a large quantity of it in as small a portion of water as possible; then keep it constantly stirring over the fire till the water exhales, and a white dry powder is left behind.

In order to purify the sulphur employed, they dissolve it with a very gentle heat; then scum and pass it through a double strainer. If the sulphur should happen to take fire in the melting, they have an iron cover that fits on close to the melting vessel, and damps the flame. The sulphur is judged to be sufficiently refined if it melts, without yielding any fetid odour, between two hot iron plates, into a kind of red substance.

The coal for making gunpowder is either that of willow or hazel, well charred in the usual manner, and reduced to powder. And thus the ingredients are prepared for making this commodity: but as these ingredients require to be intimately mixed, and as there would be danger of their firing if beat in a dry form, the method is to keep them continually moist, either with water, urine, or a solution of sal ammoniac: they continue thus stamping them together for 24 hours; after which the mass is fit for corning and drying. Gunpowder drying in the sun, or otherwise, so as sedulously to prevent its firing.

Different kinds of GUNPOWDER. The three ingredients of gunpowder are mixed in various proportions according as the powder is intended for muskets, great guns, or mortars, though these proportions seem not to be perfectly adjusted or settled by competent experience.

Semienowitz, for mortars, directs a hundred pounds of saltpetre, twenty-five of sulphur, and as many of charcoal; for great guns, a hundred pounds of saltpetre, fifteen pounds of sulphur, and eighteen pounds of charcoal; for muskets and pistols, a hundred pounds of saltpetre, eight pounds of sulphur, and ten pounds of charcoal. Miethius extols the proportion of one pound of saltpetre to three ounces of charcoal, and two or two and a quarter of sulphur; than which, he affirms, no gunpowder can possibly be stronger. He adds, that the usual practice of making the gunpowder weaker for mortars than guns, is without any foundation, and renders the expense needlessly much greater: for whereas to load a large mortar twenty-four pounds of common powder is required, and consequently, to load it ten times, two hundred and forty pounds, he shows, by calculation, that the same effect would be produced by one hundred and fifty pounds of the strong powder.

On this subject Count Rumford* observes, that almost all those who have written upon gunpowder, particularly those of the last century, have given different receipts for its composition; and he proposes it as a query, Whether these differences have not arisen from observing that some kinds of powder were better adapted to particular purposes than others, or from experiments made on purpose to ascertain the fact? "There is one circumstance (he says) that would lead us to suppose that this was the case. That kind of powder designed for mortars and great guns was weaker than that intended for small arms: for if there is any foundation for these conjectures, it is certain, that the weakest powder, or the heaviest in proportion to its elastic force, ought to be used to impel the heaviest bullets; and particularly in guns that are imperfectly formed, where the vent is large, and the windage very great. I am perfectly aware (adds he), that an objection may here be made, viz. that the elastic fluid generated from gunpowder must be supposed to have the same properties very nearly, whatever may be the proportion of its several ingredients; and that therefore the only difference there can be in powder is, that one kind may generate more of this fluid, and another less; and that when it is generated it acts in the same manner, and will alike escape, and with the same velocity, by any passage it can find. But to this I answer, that though the fluid may be the same, as it undoubtedly is, and though its density and elasticity may be the same in all cases at the instant of its generation; yet in the explosion, the elastic and unelastic parts are so mixed together, that I imagine the fluid cannot expand without taking the gross matter along with it; and the velocity with which the flame infuses at the vent is to be computed from the elasticity of the fluid, and the density or weight of the fluid and gross matter taken together, and not simply from the density and elasticity of the fluid."

To increase the strength of powder, Dr Shaw thinks it proper to make the grains considerably large, and to have it well sifted from the small dust. We see that gunpowder, reduced to dust, has little explosive force; but when the grains are large, the flame of one grain has a ready passage to another, so that the whole parcel may thus take fire nearly at the same time, otherwise much force may be lost, or many of the grains go away as hot unfired.

In the 71st volume of the Phil. Trans. Count Rumford gives an account of several attempts to augment the force of gunpowder by the addition of different ingredients. The power of steam has by many been overrated to such a degree, as to be supposed capable of answering the purposes of gunpowder; but no attempts to accomplish this have ever succeeded in any degree. Count Rumford attempted to combine the forces of steam and gunpowder together in the following manner. Having procured a number of air bladders of very small fishes, he put different quantities of water into them, from the size of a small pea to that of a pistol bullet, and tying them up with some very fine thread, hung them up to dry on the outside. He then provided a number of cartridges made of fine paper, and filled them with a quantity of gunpowder equal to the usual charge for a common horseman's pistol. He then loaded the pistol with a bullet, fired it against an oaken plank about six feet from the muzzle, and observed the recoil and penetration of the bullet. He next tried the effect of one of these small bladders of water when put among the gunpowder, but always found the force of the powder very much diminished, and the larger the quantity of water the greater was the diminution; the report of the explosion was also diminished in a still greater proportion than the force of the bullet or recoil. It being supposed that the bladder had burnt, and thus by wetting the gunpowder prevented it from taking fire, the experiment was repeated with highly rectified spirit of wine, but the diminution of the force was very little inferior to what it had been with water. Etherial oil of turpentine and small quantities of quicksilver were also tried, but with no better success than before. Thinking, however, that the failure of the quicksilver might be owing to its having been too much in a body, the experiment was repeated with the metal dispersed in small particles through the powder. To accomplish this dispersion the more completely, 20 grains of ethiops mineral were mixed very intimately with 145 grains of powder; but still the force of the bullet was much less than if the powder had been used without any addition. As the explosion of pulvis fulminans appears vastly superior to that of gunpowder, some salt of tartar, in its purest state, was mixed in the proportion of 20 grains to 145 of powder; but on firing the piece, it was still found that the force of the explosion was lessened. Sal ammoniac was next tried, which, under certain circumstances, is found to produce a great quantity of air or elastic vapour; but on mixing 20 grains of it with 145 of gunpowder, the force of the explosion was still found to be diminished. As most of the metals, when dissolved in acids, particularly brats in spirit of nitre, are found to produce much elastic vapour, it was thought worth while to try whether the force of powder could be augmented by this means. Twenty grains grains of brass dust were therefore mixed with 145 grains of powder; but still the force of the explosion was not augmented. In our author's opinion, however, neither brass dust nor ethiop's mineral diminish the force of the explosion otherwise than by filling up the interstices between the grains, obtruding the passage of the flame, and thus impeding the progress of the inflammation. Thus it appears, that little hope remains of augmenting the force of gunpowder by any addition either of liquid or inflammable solids: the reason is obvious; viz. because all of them, the liquids especially, absorb great quantities of heat before they can be converted into vapour; and this vapour, after it is formed, requires more heat to make it expand more forcibly than air; hence, as the effects of gunpowder depend entirely upon the emission of a quantity of air, and its rarefaction by vehement heat, the power must be greatly diminished by the absorption of this heat, which ought to be spent in rarefying the air. Even solid bodies cannot be set on fire without a previous absorption of heat to convert them into vapour; but liquids have this property still more than solids, and must therefore diminish the explosive force still more. Lime added to gunpowder, however, is said to augment the power of the explosion by one third.

In his experiments on gunpowder, Count Rumford had the curiosity to compare the strength of aurum fulminans, when inclosed in a gun-barrel, with that of common gunpowder; but his experiment only verified what has been found by others, viz. that this powder which in the open air makes such a very violent report, has in close vessels scarce any power, comparatively speaking, either of explosion or projecting a bullet. Count Rumford, however, taking it for granted that the power of aurum fulminans would be found much greater than that of gunpowder, took care to have a barrel of uncommon strength prepared for the experiment. The weight of it was 7 lb. 5 oz.; the length 13.25 inches, and the width of the bore 0.55 inches. This barrel, being charged with 27.44 grains of aurum fulminans and two leaden bullets, which, together with the leather put about them to make them fit the bore without windage, weighed 427 grains; it was laid upon a chafing-dish of live coals at the distance of about ten feet from the pendulum, and the piece was directed against the centre of the pendulum. Some minutes elapsed before the powder exploded; but when it did so, the explosion did not much exceed the report of a well-charged air-gun; and it was not until he saw the pendulum in motion, that Count Rumford could be persuaded that the bullets had been discharged. On examination, however, it was found that nothing had been left in the barrel, and that the powder had probably been all exploded, as a great many particles of the revived metal were thrown about. From a calculation of the motion communicated to the pendulum, it was found that the velocity of the bullets had been about 428 feet in a second; whence it appears that the power of aurum fulminans, compared with that of gunpowder, is only as 4 to 13 very nearly.

Method of Trying and Examining GUNPOWDER.—There are two general methods of examining gunpowder; one with regard to its purity, the other with regard to its strength. Its purity is known by laying two or three little heaps near each other upon white paper, and firing one of them. For if this takes fire readily, and the smoke rises upright, without leaving any dross or feculent matter behind, and without burning the paper, or firing the other heaps, it is esteemed a sign that the sulphur and nitre were well purified, that the coal was good, and that the three ingredients were thoroughly incorporated together: but if the other heaps also take fire at the same time, it is presumed, that either common salt was mixed with the nitre, or that the coal was not well ground, or the whole mass not well beat and mixed together; and if either the nitre or sulphur be not well purified, the paper will be black or spotted.

Several instruments have been invented to try the strength of gunpowder; but they have generally been complained of as inaccurate. Mr Thomson, (now Count Rumford), in the 71st volume of the Philosophical Transactions, gives an account of an exact method of proving the strength of it. "As the force of powder (says he) arises from the action of an elastic fluid that is generated from it in its inflammation, the quicker the charge takes fire, the more of this fluid will be generated in any given short space of time, and the greater of course will its effect be upon the bullet. But in the common method of proving gunpowder, the weight by which the powder is confined is so great in proportion to the quantity of the charge, that there is time quite sufficient for the charge to be all inflamed, even when the powder is of the slowest composition, before the body to be put in motion can be sensibly removed from its place. The experiment therefore may show which of the two kinds of powder is the strongest, when equal quantities of both are confined in equal spaces, and both completely inflamed; but the degree of the inflammability, which is a property essential to the goodness of the powder, cannot by these means be ascertained. Hence it appears how powder may answer to the proof, such as is commonly required, and may nevertheless turn out very indifferent when it comes to be used in service. But though the common powder-triers may show powder to be better than it really is, they can never make it appear to be worse than it is; it will therefore always be the interest of those who manufacture the commodity to adhere to the old method of proof, but the purchaser will find his account in having it examined in a method by which its goodness may be ascertained with greater precision.

From several experiments it appears, that the effect of the charge is considerably augmented or diminished, according to the greater or less force employed in ramming it down. To prevent this inconvenience, Count Rumford advises the use of a cylindric ramrod of wood, fitted with a metal ring about an inch or an inch and a half in diameter; which being placed at a proper distance from the end which goes up into the bore, will prevent the powder from being too much compressed. In making experiments of this kind, however, it is necessary to pay attention to the heat of the barrel as well as to the temperature of the atmosphere; for heat and cold, dryness and moisture, have a very sensible effect upon gunpowder to augment or diminish its force. When a very great degree of accuracy therefore Gunpowder therefore happens to be requisite, it will be proper to begin by firing the piece two or three times, merely to warm it; after which three or four experiments may be made with standard powder, to determine the proof mark a second time, for the strength of powder is different at different times, in consequence of the state of the atmosphere. After this the experiments may be made with the powder that is to be proved, taking care to preserve the same interval of time between the discharges, that the heat of the piece may be the same in each trial.

Having determined the comparative degrees of strength of two different kinds of powder, their comparative value may be ascertained by augmenting the quantity of the weaker powder till the velocity of the bullets in both cases becomes the same. The strong powder is therefore precisely as much more valuable than the weak, as it produces the same effect with a smaller quantity. Thus if a quarter of an ounce of one kind of powder discharges a bullet with the same velocity that half an ounce of another kind does, it is plain that the former is twice as valuable as the latter, and ought to be sold at double the price.—By comparisons of this kind, Count Rumford found that the best battle powder (so called from its being made at the village of Battle in Kent) is stronger than government powder, in the proportion of 4 to 3; but from a comparison of the prices, it appears that the former is no less than 41\( \frac{1}{2} \) per cent. dearer than it ought to be; and consequently, that whoever uses it in preference to government powder, does it at a certain loss of 41\( \frac{1}{2} \) per cent. of the money it costs him.

It is supposed by Count Rumford, that very little of the heat acquired in firing a piece of ordnance comes from the powder; for the time that it continues in the piece, perhaps not exceeding the 200th part of a second, is so small, that were the flame four hundred times, instead of four times, as Mr Robins supposes, hotter than red-hot iron, it is by far too short to communicate a sensible degree of heat to one of our large pieces of cannon. Besides, if the heat of the flame was sufficient to communicate such a degree of heat to the gun, it must undoubtedly be capable of burning up all combustible bodies that come in its way, and of melting lead-shot when such were used; but instead of this, we frequently see the finest paper discharged from the mouth of a gun without being inflamed, after it has sustained the action of the fire through the whole length of the bore; and the smallest lead-shot is discharged without being melted. The objection drawn from the heat of bullets taken up immediately after being discharged from fire-arms does not hold; for bullets discharged from air-guns and even cross bows are likewise found hot, especially when they happen to strike any hard body, and are much flattened. If a musket ball be discharged into water, or against any very soft body, it will not be sensibly heated; but if it hits a plate of iron or any other body which it cannot penetrate, it will be broken in pieces by the blow, and the dispersed parts will be found in a state little short of actual fusion. Hence our author concludes, that bullets are not heated by the flame, but by percussion. Another objection is, that the vents of brass guns are frequently enlarged to such a degree by repeatedly firing them, that the piece becomes useless.

But this proves only that brass is easily corroded by the flame of gunpowder; which indeed is the case with iron also. We cannot suppose that in either case any real solution takes place; on the contrary, it is very evident that it does not; for when the vents of fire-arms are lined with gold, they will remain without enlargement for any length of time, though it is well known that gold is much more easily melted than iron. As the heat communicated to bullets, therefore, is not to be ascribed to the flame but to percussion, so the heat acquired by guns is to be attributed, in our author's opinion, to the motion and friction of the internal parts of the metal among themselves by the violent action of the flame upon the inside of the bore. To generate heat, the action of the powder must be not only sufficient to strain the metal, and produce a motion in its parts, but this effect must be extremely rapid; and the effect will be much augmented if the exertion of the force and the duration of its action are momentaneous: for in that case the fibres of the metal that are violently stretched will return with their full force and velocity, and the swift vibratory motion and attrition above mentioned will be produced. Now the effort of any given charge of powder upon the gun is very nearly the same whether it be fired with a bullet or without; but the velocity with which the generated elastic fluid makes its escape, is much greater when the powder is fired alone than when it is made to impel one or more bullets; the heat ought therefore to be much greater in the former than in the latter case, as has been found by experiment. "But to make this matter still plainer, (says our author,) we will suppose any given quantity of powder to be confined in a space that is just capable of containing it, and that in this situation it is set on fire. Let us suppose this space to be the chamber of a piece of ordnance, and that a bullet or any other solid body is so firmly fixed in the bore, immediately upon the charge, that the whole effort of the powder shall not be able to remove it: as the powder goes on to be inflamed, and the elastic fluid to be generated, the pressure upon the inside of the chamber will be increased, till at length all the powder being burnt, the strain upon the metal will be at its greatest height, and in this situation things will remain; the cohesion or elasticity of the particles of metal counterbalancing the pressure of the fluid.—Under these circumstances very little heat would be generated; for the continued effort of the elastic fluid would approach to the nature of the prelure of a weight; and that concussion, vibration, and friction among the particles of the metal, which in the collision of elastic bodies is the cause of the heat produced, would scarcely take effect. But instead of being firmly fixed in its place, let the bullet now be moveable, but let it give way with great difficulty, and by few degrees. In this case the elastic fluid will be generated as before, and will exert its whole force upon the chamber of the piece; but as the bullet gives way to the prelure, and moves on in the bore, the fluid will expand itself and grow weaker, and the particles of the metal will gradually return to their former situations; but the velocity with which the metal restores itself being but small, the vibrations that remains in the metal after the elastic fluid has made its escape will be very languid, as will the heat be which is generated by it. But if, instead of giving way with too much difficulty, the bullet is made lighter, so as to afford but little resistance to the elastic fluid in making its escape, or if it is fired without any bullet at all; then, there being little or nothing to oppose the passage of the flame through the bore, it will expand itself with amazing velocity, and its action upon the gun will cease almost in an instant; the strained metal will restore itself with a very rapid motion, and a sharp vibration will ensue, by which the piece will be much heated."

The Count, however, after more mature reflection, a greater number and diversity of experiments, and the increased knowledge which must always accompany such intellectual exertions as have distinguished him through life, has been enabled to evince, that the amazing force of the elastic fluid generated in the combustion of gunpowder, may be fully accounted for on the hypothesis, that it entirely depends on the elasticity of watery vapour, or steam, which is doubled by every increase of temperature equal to 3° of Fahrenheit's thermometer. If then the mean pressure of the atmosphere at the temperature of 212°, equals the elastic force of steam, this force at the temperature of 242° must be equal to the pressure of two atmospheres, since \( 212 + 30 = 242 \), and so on in the same ratio. The Count also found that the elastic force of gunpowder is equal to the pressure of 131,072 atmospheres at the temperature of 722°. By the flame of gunpowder, brads has been known to be melted, which requires a temperature equal to 3807° of Fahrenheit, or 21° of Wedgwood, to bring it to a state of fusion. He also proved in a satisfactory manner, that gunpowder contains a sufficient quantity of water for supplying the requisite proportion of steam; but for a full account of his very ingenious and detailed experiments on this curious subject, we must refer our readers to Nicholson's Journal, vol. i. 4to. p. 459.

It has been proposed to substitute hyperoxymuriate of potash in place of nitre; but the use of this substance is attended with many inconveniences, some of which preclude its being employed in the composition of gunpowder. See Chemistry, No 959 to No 967.

To recover damaged GUNPOWDER. The method of the powder-merchants is, to put part of the powder on a fail-cloth, to which they add an equal weight of what is really good; and with a shovel mingle it well together, dry it in the sun, and barrel it up, keeping it in a dry and proper place. Others again, if it be very bad, restore it by moistening it with vinegar, water, urine, or brandy; then they beat it fine, searce it, and to every pound of powder add an ounce, an ounce and a half, or two ounces, according as it is decayed, of melted saltpetre. Afterwards, these ingredients are to be moistened and mixed well, so that nothing can be discerned in the composition, which may be known by cutting the mass; and then they granulate it as before. In case the powder be in a manner quite spoiled, the only way is to extract the saltpetre with water according to the usual manner, by boiling, filtrating, evaporating, and crystallizing; and then with fresh sulphur and charcoal to make it up anew again.

In regard to the medical virtues of gunpowder, Boerhaave informs us, that the flame of it affords a very healthy fume in the height of the plague, because the explosive acid vapour of nitre and sulphur corrects the air; and that the same vapour, if received in a small close pent-up place, kills insects.

It is enacted by 5 and 11 of Geo. I. and 5 Geo. II. c. 20, that gunpowder be carried to any place in a covered carriage; the barrels being close-jointed; or in cases and bags of leather, &c. And persons keeping more than 200 pounds weight of gunpowder at one time, within the cities of London and Westminster, or the suburbs, &c. are liable to forfeitures if it be not removed; and justices of the peace may issue warrants to search for, seize, and remove the fame.

GUN-Shot Wounds. See SURGERY.