a composition of saltpetre, sulphur, and charcoal, mixed together, and usually granulated; which easily takes fire, and, when fired, rarifies 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 saltpetre, an ounce of brimstone, and six 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 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 proportion 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 brimstone employed, they dissolve it with a very gentle heat; then scum and pass it through a double strainer. If the brimstone 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 brimstone 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 the making of 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 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 an hundred pounds of saltpetre, twenty-five of sulphur, and as many of charcoal; for great guns, an hundred pounds of saltpetre, fifteen pounds of sulphur, and eighteen pounds of charcoal; for muskets and pistols, an 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 pound of common powder is required, and consequently, to load it ten times, two hundred and forty pound, he shows, by calculation, that the same effect would be had by one hundred and fifty pound of the strong powder.

On this subject Mr Thomson† 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 issues 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 shot unfired.

In the 71st volume of the Phil. Trans. Mr Thomson 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. Mr Thomson 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 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 burst, 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 Ethiop's 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 Gunpowder, 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 brails 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 of brails 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 brails dust nor Ethiop's mineral diminish the force of the explosion otherwise than by filling up the interstices between the grains, obstructing 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 previous absorption of heat to convert them into vapour*; but liquids have this property still more than *See Flame, solids, as is explained under the articles Chemistry, Evaporation, &c., 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, Mr Thomson 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 violent report, has in close vessels scarce any power, comparatively speaking, either of explosion or projecting a bullet. Mr Thomson, 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 chaffing-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 did not much exceed the report of a well charged air-gun; and it was not until he saw the pendulum in motion, that Mr Thomson 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 deemed 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, in the 7th 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."

In order to determine the goodness of powder by Mr Thomson's method, it is necessary to have a barrel suspended by two iron rods in such a manner that it can easily move backward or forward by the vibration of the rods; and the space it moves through ascertained by marking it on a piece of ribbon. The barrel being then charged with powder, and fitted with a proper bullet, is to be fired, and the recoil marked upon the ribbon. The experiment is to be repeated three or four times, or oftener if there is any difference in the recoil; the extremes of which may be marked with black lines on the ribbon, and the word proof written upon the middle line betwixt the two. But if the experiments are made with sufficient accuracy, there will commonly be very little difference in the length to which the ribbon is drawn out. Thus the comparative goodness of powder may easily be ascertained; for the stronger the powder is, the greater will be the recoil, and consequently the greater length to which the ribbon will be drawn out; and if care is taken in proportioning the charge to the weight of the bullet, to come as near as possible to the medium proportion that obtains in practice, the determination of the goodness of gunpowder from the result of this experiment cannot fail to hold good in actual service. The bullets should be made to fit the bore with very little windage; and it would be better if they were all cast in one mould and in the same parcel of lead; as in that case their weights and dimensions would be more accurately the same; and the experiments would of course be more conclusive. The stated charge of powder might be half an ounce, and it should always be put up in a cartridge; and after the piece is loaded, it should be primed with other powder, first taking care to prick the cartridge by thrusting a priming wire down the vent.

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, Mr Thomson 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 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 thus 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 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 comparison of this kind, Mr Thomson 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 4½ 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 4½ per cent. of the money it costs him.

There has been much talk of a white powder, which, if it answered the character given it, might be a dangerous composition; for they pretend that this white powder will throw a ball as far as the black, yet without making a report: but none of the white powder we have seen, says Dr Shaw, answers to this character; being, as we apprehend, commonly made either with touchwood or camphor, instead of coal.

Under the article Gunnery, the physical cause of the explosion of powder, and the force wherewith it expands, have been so fully considered, that it would be superfluous to add any thing here concerning them. Only we may observe, that though it is commonly made use of for military purposes only in small quantities, and confined in certain vessels; yet when large quantities are fired at once, even when unconfined in the open air, it is capable of producing terrible destruction. The accounts of damage done by the blowing up of magazines, powder-mills, &c. are too numerous and well-known to be here taken notice of. The following is a relation of what even a moderate quantity of powder will accomplish, when fired in the open air.

"The king of Navarre took Monsegur. Captain Milon inclosed 500 pounds of powder in a bag, which he found means to introduce, by a drain from the town, into the ditch between two principal gates; the end of the leader was hid in the grats. Every thing being ready to play off this machine, the king gave us leave to go and see its effects; which were surprising. For one of the gates was thrown into the middle of the town, and the other into the field fifty paces from the wall: all the vaults were destroyed, and a passage was made in the wall for three men to enter abreast, by which the town was taken."—For further accounts of the force of large quantities of powder, see the article Mines.

From this and other accounts of the dreadful effects of gunpowder, when fired in large quantity in the open air, it would seem, that great as its power is in close vessels, it is still greater when the air has access to it; for from the quantity of powder requisite to charge great guns, it is by no means probable that double the quantity of powder confined in fire-arms of any size or capacity, and discharged all at once against the walls, would have produced such effects; especially when we consider that the power must have been equally great at an equal distance all round; so that had there been other walls and gates behind this quantity of powder as well as before it, they would in all probability have been thrown down also. This conjecture seems to be somewhat confirmed by the great diminution of the force of pulvis fulminans and aurum fulminans when confined in close vessels. Mr Thomson mentions likewise a very singular fact relative to gunpowder, which seems to be somewhat analogous to that just mentioned; and which indeed seems to explain it; namely, that the heat communicated by gunpowder when slightly confined, is much greater than when otherwise. "I was much surprised (says he), upon taking hold of the barrel immediately after an experiment when it was fired with 330 grains of powder without any bullet, to find it so very hot that I could scarce bear it in my hand, evidently much hotter than I had ever found it before, notwithstanding the same charge of powder had been made use of in the two preceding experiments; and in both these experiments the piece was loaded with a bullet, which one would naturally imagine, by confining the flame, and prolonging the time of its action, would heat the barrel much more than when it was fired with powder alone. I was convinced that I could not be mistaken in the fact; for it had been my constant practice to take hold of the piece to wipe it out as soon as an experiment was finished, and I never before had found any inconvenience from the heat in holding it. But in order to put the matter beyond all doubt, after letting the barrel cool down to the proper temperature, I repeated the experiment twice with the same charge of powder and a bullet; and in both these trials the heat of the piece was evidently much less than what it was in the experiment above mentioned. Being much struck with this accidental discovery of the great degree of heat that pieces acquire when they are fired with powder without any bullet, and being desirous of finding out whether it is a circumstance that obtains universally, I was very attentive to the heat of the barrel after each of the succeeding experiments; and I constantly found the heat sensibly greater when the piece was fired with powder only, than when the same charge was made to impel one or more bullets."

To account for this, our author supposes, 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. 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 pressure 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 slow 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 pressure, 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 vibration 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 so 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 an 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."

This reasoning of Mr Thomson's, however, seems not to be very well founded. In the first place, we are by no means certain that heat is produced by the motion or vibration of the particles of a solid body among each other. On the contrary, even in the hottest bodies we cannot be made sensible of vibration existing among their particles, while certain sounds will cause the most solid substances vibrate perceptibly, and yet without producing any heat.—From this as well as innumerable other experiments, it is probable, that heat consists in the emission of a certain subtle fluid from the heated body, which is every moment replaced from the atmosphere, or from some other source. Hence the more air that has access to any burning body, the hotter it will become, and the more will any other that is in its vicinity be heated. This is evident from the contrivance of Argand's lamp, which is neither more nor less than the admission of a larger quantity of air to the same quantity of flame. The case is the same with the firing of gunpowder, when a bullet is put into the piece, the access of the air is much more effectually prevented than when, only a simple wadding is made use of. In consequence of this, no sooner is the powder fired without a bullet, than the external air rushes down the bore, mingles with the flame, and vehemently augments the heat, as well as the absolute force of the explosion. It is true, that without the external air, the nitre in the gunpowder itself produces as much air as to inflame it very violently; but this does not prove that it could not be inflamed still more by the admission of more air. Besides, when the external air is thus admitted, the flame itself is agitated by its admission, and driven against the sides of the piece with a force superior to what it has by the mere expansive pressure; whence the heat must also be considerably augmented, in the same manner that the heat of any other body will be by the having flame blown against it, instead of being blown away from it, or suffered to burn quietly by its side. Thus, without any recourse to an unknown and conjectural vibration among the particles of a solid metal, we may account for the augmented heat of a piece charged only with powder, and likewise in some measure for the prodigious GUN

GUNpowder.

glious force of gunpowder, aurum fulminans, and pulvis fulminans, when fired in the open air, compared with what they have when exploded in close vessels.—The force of gunpowder is manifestly augmented in close vessels, as has been already said, by being rammed down or compressed together; but this arises from another cause, namely, that a greater quantity of flame is compressed into the same space than when the powder is not rammed; and this compression of the flame is in proportion to the compression of the powder in the chamber of the piece. But in this case the flame is probably less powerful than in the former, though the quantity inclosed in a small space may probably make up for the quality. Mr Thomson's experiments on the increased force of gunpowder by compression are as follow:—Having put a charge of 218 grains of powder, inclosed in a cartridge of very fine paper, gently into the bore of the piece, the velocity of the bullets, at a mean of four experiments, was at the rate of 1225 feet in a second; but in a medium of three experiments, when the same quantity of powder was rammed down by five or six strokes of the ramrod, the velocity was 1329 feet in a second. "Now (says he) the total force or pressure exerted by the charge upon the bullet, is as the square of its velocity; and 1329² is to 1225² as 1776 is to 1; or nearly as 6 is to 5; and in that proportion was the force of the given charge of powder increased by being rammed.—When, instead of ramming the powder, or pressing it gently together in the bore, it is put into a space larger than it is capable of filling, the force of the charge is thereby very sensibly lessened, as Mr Robins and others have found by repeated trials. In my 30th experiment, the charge, consisting of no more than 165 grains of powder, was made to occupy 3.2 inches of the bore, instead of 1.45 inches, which space it just filled. When it was gently pushed into its place without being rammed, the consequence was, that the velocity of the bullet, instead of being 1100 feet or upwards in a second, was only at the rate of 914 feet, and the recoil was lessened in proportion.—Hence we may draw this practical inference, that the powder with which a piece of ordnance or a fire-arm is charged, ought always to be pressed together in the bore; and if it is rammed to a certain degree, the velocity of the bullet will be still farther increased. It is well known that the recoil of a musket is greater when its charge is rammed than when it is not; and there cannot be a stronger proof that ramming increases the force of powder."

To recover damaged GUNPOWDER. The method of the powder-merchants is, to put part of the powder on a sail 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, scarce 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 aforesaid. 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 infects.

It is enacted by 5 and 11 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 peace may issue warrants to search for, seize, and remove the same.

Gun-Shot Wounds. See Surgery.

Gun-Smith, a maker of small fire-arms, as muskets, fowling-pieces, pistols, &c.