CHAPTER II.
ON GUNPOWDER.
Gunpowder being the base on which the superstructure of this treatise is to be raised, the history, the use, and the nature of this explosive compound, are here placed in the foreground; as it is essential to the correct conception of the various matters hereafter to be explained, that the reader be first acquainted with the one grand principle in fire-arms, the propellant power of explosion.
Gunpowder, whether considered relatively to engines of war, or to those arms used with so much success in the sporting field, has, since its first _introduction_, been a source of much and frequent discussion. In regard to its origin, we shall not much enlarge, nor repeat the many suppositions and conjectures promulgated by the searchers after antiquarian evidence.
The inhabitants of India were unquestionably acquainted with its composition at an early date. Alexander is supposed to have avoided attacking the Oxydracea, a people dwelling between the Hyphasis and Ganges, from a report of their being possessed of supernatural means of defence: “For,” it is said, “they come not out to fight those who attack them, but those holy men, beloved by the gods, overthrow their enemies with tempests and thunderbolts shot from their walls;” and, when the Egyptian Hercules and Bacchus overran India, they attacked these people, “but were repulsed with storms of thunderbolts and lightning hurled from above.” This is, no doubt, evidence of the use of gunpowder; but as it is unprofitable to investigate this subject further, we shall merely confine ourselves to the European authorities.
Many ascribe the discovery of gunpowder to Roger Bacon, the monk, who was born at Ilchester, in Somersetshire, in the year 1214, and is said to have died in 1285. No doubt he was by far the most illustrious, the best informed, and the most philosophical of all the alchemists. In the 6th chapter of his Epistles of the Secrets of Arts, the following passage occurs--“For sounds like thunder, and flashes like lightning, may be made in the air, and they may be rendered even more horrible than those of nature herself. A small quantity of matter, properly manufactured, and not larger than the human thumb, may be made to produce a horrible noise; and this may be done many ways, by which a _city_ or an _army_ may be destroyed, as was the case when Gideon and his men broke their _pitchers_ and exhibited their lamps, fire issuing out of them with great force and noise, destroying an infinite number of the army of the _Midianites_.” And in the 11th chapter of the same epistle occurs the following passage:--“Mix together saltpetre with _luru mone cap ubre_, and sulphur, and you will make thunder and lightning, if you know the method of mixing them.” Here all the ingredients of gunpowder are mentioned, except charcoal; which is, doubtless, concealed under the barbarous terms used; indeed, the _anagram_ is easily converted into _carbonum pulvere_, with a little attention.
This discovery has also been attributed to Schwartz, a German monk, and the date of 1320 annexed to it; a date posterior to that which may be justly claimed for Friar Bacon; and as accident is stated to have been the means by which he discovered it, we have taken that incident as the subject of an illustration.
Mr. Hallam, referring to the authority of an Arabic author, infers that there is no question that the knowledge of gunpowder was introduced into Europe through the means of the Saracens, before the middle of the 13th century; and no doubt its use then was more for fireworks, than as an artillerist projectile force. There is good evidence, too, that the use of gunpowder was introduced into Spain by the Moors, at least as early as the year 1343. Now, as Roger Bacon is known to have been an Arabic scholar, it is not at all unlikely that he might have become acquainted with the mode of making the composition, and also with its most remarkable properties, by perusing some Arabian writer with whom we are at present unacquainted.
This invention, by which the personal barbarity of war has certainly been diminished, is, when considered as a means of human destruction, by far the most powerful that skill has ever devised, or accident presented; acquiring, as experience shows us, a more sanguinary dominion in every succeeding age, and subserving all the progressive resources of science and civilization for the extermination of mankind: which, says Mr. Hallam, “appals us at the future prospects of the species, and makes us feel, perhaps, more than in any other instance, a difficulty in reconciling the mysterious dispensation with the benevolent order of Providence.”
The composition of gunpowder, as regards the proportions of the ingredients, has not undergone any material alteration; the chemical proportions of the ancients being nearly those of the present day.
Gunpowder is an explosive propellant compound, consisting of saltpetre or nitre, charcoal, and sulphur. The terms, _explosive_ and _propellant_, are not here used as synonymous--they are not convertible; for a chemical mixture may possess the _explosive_ power in a much higher degree than the _propellant_: fulminating gold, silver, and mercury, are dreadfully explosive; but they have not the same projectile force, nor can they be used as a substitute for it. Several experiments have been made with compounds of this nature, but the result is the reverse of what might be expected. Nothing can resist the exceeding intensity of the action of fulminating powder; a shot, when fired in this way, is not projected as by gunpowder, but is split into fragments by the velocity of its explosion, as we shall hereafter have occasion to show.
Nitre, or saltpetre, is strictly the essence of gunpowder. It is a triple compound of oxygen, nitrogen, and potassium. The chemical action of those elements on each other, and the play of affinities between them at a high temperature, occasion the immense effect produced by gunpowder on the application of fire or heat. By universal consent, sulphur is included in the mixture, but it is not absolutely necessary for the “propellant power;” for nitre and charcoal only will generate effects similar to the compound with sulphur. Gunpowder made without sulphur has, however, several bad qualities; it is not, on the whole, so powerful, nor so regular in its action; it is also porous and friable, possessing neither firmness nor solidity. It cannot bear the friction of carriage, and in transport crumbles into dust. The use of sulphur, therefore, appears to be not only to complete the mechanical combination of the other ingredients, but being a perfectly combustible substance, it increases the general effect, augments the propellant power, and is thought to render the powder less susceptible of injury from atmospheric influence.
“There is one good reason,” says the Edinburgh Encyclopædia, “for the use of sulphur, although it does not contribute to the production of any elastic fluid. The carbonic acid which is generated would doubtless combine with the potash, if it were not for the presence of the sulphur, and thus so much elastic fluid would be lost. That this is the case we know to be true, from the fact that carbonate of potash is always formed when nitre is decomposed by charcoal alone, which I shall almost immediately show.” This certainly would be the case, to a certain extent, with gunpowder without sulphur--some carbonate of potash would be formed.
The sulphur, we have no doubt, from experiments we have made on this subject, is, in part, engaged during the explosion of gunpowder in expelling the sixth proportion of oxygen from the potash, so as to combine with the potassium, to form a true sulphuret of that metal. This fact is easily ascertained, from the circumstance that no sulphuretted hydrogen can be detected, by the most delicate tests, coming from the residuum left after firing gunpowder, until moisture has gained access to it. The bad smell which arises sometime after the burning of gunpowder, is occasioned by the decomposition of the moisture which the sulphuret of potassium attracts from the atmosphere; giving rise, by this decomposition and liberation, to the fœtid foul gas, called sulphuretted hydrogen, and the production of potassa, or the oxide of potassium.
A commission of French chemists and artillerists was appointed by the Government, in the year 1794, to experiment upon the best proportions and constituents of gunpowder for the use of the French service. The following were the proportions of five different kinds prepared at the Essonne works:--
---+------+---------+--------+---------------------- No.|Nitre.|Charcoal.|Sulphur.| ---- ---+------+---------+--------+---------------------- 1 |76·00 | 14·00 | 10·00 |Powder of Bâe. 2 |76·00 | 12·00 | 12·00 | „ Grenelle. 3 |76·00 | 15·00 | 9·00 | „ M. Morveau. 4 |77·32 | 13·44 | 9·24 | „ Ditto. 5 |77·50 | 15·00 | 7·50 | „ M. Keffault. ---+------+---------+--------+----------------------
The first and third, after 200 discharges with the proof mortar, were declared the strongest, and the third proportions were adopted at the recommendation of the commissioners. Some few years elapsed, and the first, owing to its better keeping quality, was substituted, as it contained less charcoal, and a little more sulphur. The French Government having always been extremely impressed with the value of durability in gunpowder, they have since returned to their ancient proportions: 75 nitre, 12-1/2 charcoal, 12-1/2 sulphur. The charcoal, the absorbent of moisture, being further reduced, and the sulphur, the preserving ingredient, being increased in the same ratio.
“Mr. Napier tried a small quantity made of nitre and charcoal only, and was much surprised to find it project a shot as far as the best powder made in the usual manner. It is found that, in small charges, sulphur is advantageous; but, in charges of several ounces, the projecting force is as great without as with it. Therefore, under certain circumstances, sulphur may be dispensed with; but to make a good gunpowder, nitre and charcoal are indispensable.”
Amongst the brilliant discoveries of modern chemistry may be classed the development of the fact, that a chemical combination, to constitute the same compound, always takes place in definite and unalterable ratios. To select one example out of a multitude: one atom of carbon combining with two atoms of oxygen produces the gas; because more would answer no useful end. So, with reference to the sulphur, if it enter into combination only with the potassium--the base of the nitre--the sulphur should be in that proportion to form the sulphuret of that metal; and in this case there would be no superfluity, for that would only add to the weight of the charge of powder, and diminish its absolute and effective energy. The view of the case which we have taken supposes only two combinations, viz. carbon with oxygen, and sulphur with potassium. Should there be a more diversified play of affinities, and the several elements of the powder enter into more complicated action, accurate analysis would conduct us through all difficulties, and point out what the proportions of the ingredients ought to be in order to sustain that action, and to produce a perfect ultimate result.
We thus perceive how analysis bears upon the case. We can see by such reasoning on the subject, that, theoretically, there can be but _one set of proportions calculated to produce the best and strongest gunpowder_, and that those proportions must depend upon the established and unerring laws of nature. The proportions, then, for gunpowder, by these considerations, will be those in which the carbon will just consume the oxygen of the nitre, and combine with the sulphur as much as will exactly saturate the potassium. This will be effected by an atom each of nitre and sulphur, and three atoms of carbon; or nitre 75·5, charcoal 18·8, and of sulphur 11·8.
In the present improved state of chemical science, when the nature of the bodies comprising gunpowder is so well known, as well as the compounds resulting from their action on each other, the proportions we have named may be taken as the best for practice.
The charcoal should, in particular, not be less than the nitre, as the smallest portion less than the whole atom would be the same as to leave out the whole atom, in which case there would be no carbonic oxide formed. If, for example, instead of the proportions of nitre 75·5, charcoal 16·2, sulphur 15, the carbon were 16, then there would be 4·2 of carbon left in the residuum, and no carbonic oxide would be formed, since bodies cannot unite but in definite proportions.
From these considerations we can perceive the reason why a small proportion of carbonic oxide is always formed during the decomposition of nitre by charcoal; for it will be evident, that as the nitric acid contains five atoms of oxygen, four of these must combine with two atoms of carbon to form two atoms of carbonic acid, while the _odd atom of oxygen_ is compelled to take another atom to form carbonic oxide. But this is not the case in the combustion of gunpowder, as carbonic acid and nitrogen are the principal gases generated.
These proportions differ from any other formula yet prescribed; and, though different in a great degree from the proportions laid down by various writers on the subject, the reasons which are here given, as has been seen, are such as carry with them a conviction of their truth: for there cannot possibly be any benefit arising from a greater quantity of any of these materials than is absolutely necessary to form the composition in question; and if the smallest quantity be above what is requisite to consume the whole, that, however small it may be, is highly detrimental to the effective energy of the mass. What we may here call clean gunpowder, such as may be used with confidence for repeated discharges of fire-arms of any description, is of the greatest importance; therefore, it does not appear to us, that any given proportions are so likely to accomplish that object as those before specified.
TABLE OF COMPOSITION OF DIFFERENT GUNPOWDERS.
---------------------------------+------+---------+-------- Mills. |Nitre.|Charcoal.|Sulphur. ---------------------------------+------+---------+-------- Royal Waltham Abbey |75·00 | 15·00 | 10·00 France, National Mills |75·00 | 12·50 | 12·50 French Sporting |78·00 | 12·00 | 10·00 French Mining |65·00 | 15·00 | 20·00 U. S. of America |75·00 | 12·50 | 12·50 Prussia |75·00 | 13·50 | 11·50 Russia |73·78 | 13·59 | 12·63 Austria (Musket) |72·00 | 17·00 | 16·00 Spain |76·47 | 10·78 | 12·75 Sweden |76·00 | 15·00 | 9·00 Switzerland (Round Powder) |76·00 | 14·00 | 10·00 Chinese |75·00 | 14·40 | 9·90 Theoretical proportions as above |75·00 | 13·23 | 11·77 ---------------------------------+------+---------+--------
Gunpowder consists of a very intricate mixture of sulphur, carbon (charcoal), and nitrate of potash (nitre).
The proportions in which they exist are one equivalent of nitre, one of sulphur, and three of carbon. The great explosive power of gunpowder is due to the sudden development from its solid constituents of a large quantity of gases; these gases are nitrogen and carbonic acid.
At the ordinary temperature of the atmosphere these gases would occupy a space three hundred times greater than the bulk of the gunpowder used; but owing to the intense heat developed at the moment of explosion, the gases occupy at least 1,500 times the bulk of the original gunpowder. The mixture, consisting of one equivalent of nitre, one of sulphur, and three of carbon, would yield three equivalents of carbonic acid, one of nitrogen, and one of sulphuret of potassium. The change may be represented thus,--
S + C₃ + KONO₅ = 3 CO₂ + N + KS.
The only solid residue, therefore, is the sulphuret of potassium, and this is the compound which produces the sulphurous odour on washing out a gun barrel; water is decomposed, sulphuretted hydrogen and potash being the result of the decomposition.
Now supposing the elements of gunpowder to exist in these proportions, it is essential, in order to secure their perfect combination, and thus to produce the largest possible volume of gas, that the elements should be in the most minute state of subdivision. Chemical action is a force exerted at insensible distances only, and chemical substances having the greatest affinity for each other will not combine, unless their elements are brought into immediate contact: thus oxygen and hydrogen may be mixed together in the exact proportions to form water; but no chemical combination will occur, simply because the ultimate particles of the two gases are not sufficiently near to each other for their chemical affinities to be brought into play; if, however, these gases are subjected to very strong pressure, so as to bring their particles into immediate contact, combination occurs, and the production of water is the result.
In order to insure the perfect combination of the elements of gunpowder the same conditions are necessary; that is to say, the ultimate particles of the nitre, charcoal, and sulphur, must be brought into the most direct contact, or the explosive power of the gunpowder will be comparatively trifling. If, for instance, the nitre, charcoal, and sulphur be pounded in a mortar, no explosion but a slow combustion will occur when the mixture is ignited; so that unless this intimate mixture of the elements is carefully attended to in the manufacture of gunpowder, it is easy to see that the article produced will be of comparatively little value.
It is evident then that if tons of the elements of gunpowder were stored in a warehouse which accidentally caught fire, no explosion would occur from the formation of gunpowder; though its ingredients would greatly increase the rapidity of combustion.
This remark is elicited by the recollection of a fearful explosion which took place at Gateshead in 1854.
It may be remembered that a warehouse caught fire from an adjoining mill, and the explosion was supposed to have been produced by the ignition of the elements of gunpowder stored in the warehouse in a crude state. The upper story of the building contained a large quantity of crude sulphur, and the basement story about the same quantity of nitre, whilst chemicals of various kinds were stored in other parts of the building; but according to the accounts published there was no large quantity of carbon in the warehouse; nevertheless, a terrific explosion took place, and after a lengthened investigation, the conclusion arrived at was this: the sulphur melting, mixed with the nitre, gunpowder was thus formed, and igniting, exploded, producing the terrible effects.
But gunpowder may be made without sulphur, whereas gunpowder without carbon is an impossibility; and though the elements of gunpowder had all been present, no explosion could have occurred, unless they had become mixed in the intimate manner already described.
It is true some of the chemical substances in the warehouse might have produced a fearful explosion: but a more plausible explanation is to be found in the fact, that gunpowder was at that time much more valuable abroad than at home; and it is quite possible that some kegs of gunpowder might have been stored away in this warehouse, until a convenient opportunity presented itself for their removal.
The foregoing remarks will serve to explain how it is that powder varies so much in strength and quickness of fire. If the elements are imperfectly incorporated, the powder can never be equal to that which is properly made; and the manufacturer, having ascertained the best proportions in which to mix the elements, had better improve his machinery for incorporating them, rather than his knowledge of the chemistry of gunpowder. These observations will also serve to explain the apparent anomaly, that the French, and some of our other continental brethren, are held to produce a much inferior sporting gunpowder to that which is manufactured in old England.
Gunpowder is now made by all the sporting gunpowder manufacturers from No. 1 to No. 5 grain; and it appears certain that a further increase in the size of the grain would be advantageous; for many years of patient and laborious experiment clearly show, that the old notion of gunpowder being blown out of an ordinary sized gun in an unburnt state, is one of the “purest of vulgar errors:” such a thing indeed cannot possibly happen unless the powder be bad, or the gun _imperfectly made_, or injudiciously charged.
I am satisfied that I am under rather than over estimate, when I assert that six drams of ordinary sporting gunpowder may be beneficially and completely exploded in a barrel of 14 bore, 2 feet 6 inches long, with a resisting projectile one ounce in weight above it. This, however, being more than a double charge for such a gun, cannot be pleasantly practised; and it is only asserted by way of argument.
Assuming, then, for argument’s sake, that six drams of gunpowder are exactly consumed in passing from the breech to the muzzle of a gun 2 feet 6 inches long, and that the shot, therefore, acquires its greatest velocity as it leaves the muzzle, it follows that the ordinary charge of 2-1/2 drams will be wholly consumed before it has traversed half the length of the barrel, and consequently the charge of shot must here acquire its greatest velocity. It is certain, then, that the shot must travel the latter half of the barrel at a diminished velocity, and its velocity must continue to diminish as it passes up the barrel; for two obvious reasons--1st, The column of air in front of the charge is more condensed, and thus offers a greater resistance to the exit of the charge; 2nd, The velocity is continually diminished by the increased friction of the charge against the barrel.
The perfection of projectile science is to make the projectile acquire its greatest velocity at the instant of leaving the muzzle; and if, by increasing the size of the grain of gunpowder, we can diminish the rapidity of its explosion--thus causing it to burn and generate fresh gas up to the muzzle of the gun--the projectile will then acquire its greatest velocity, and leave the gun to the best advantage: this is the important point which has hitherto been overlooked, not only in fowling-pieces, but in the expansive principle of rifles.
For artillery practice of every kind, whatever the weight of the projectile, gunpowder of a granulation suited to the weight of that projectile is essential, if we would produce the greatest possible effect by the least expenditure of means.
In artillery, at this most important time in war’s history, no attention whatever is paid to this essential principle. A long 10-inch gun, a 68-pounder, and a short 6-pounder are all charged with powder of the same granulation; whilst by a more judicious use of gunpowder of suitable granulation, the range might be extended, just as it is in sporting arms, to nearly 20 per cent.
Artillerists seek to effect great range by doubling the weight of the gun, and projectile monsters meet us at all points, to become in every case “monster failures.”
I fear that the most important points have been entirely lost sight of. Instead of ascertaining whether we have suited the projectile power to the 8-inch or 56-pounder, so as to get work from it which is now done by the 10-inch, we have, in our anxiety to get range, looked only to the form or material of the gun; vital principles being totally excluded. The construction of the gun being perfect, the question is, can the expellant force be brought to an equal state of perfection?
In order to obtain the best results from a gun, the gun itself must be perfect in construction, and the expellant force must be brought to bear in the best possible manner upon the projectile; and this is to be done by attending to the granulation of the powder, which must be suited to the length of the gun, to its bore, and to the weight of the projectile.
Common-sense, engineering skill, will demonstrate, that according to the weight of matter to be projected must be the nature of the expellant; _accumulative_--until it has overcome the inertia of that matter, _accelerative_--until it has communicated to it the highest state of velocity its power is capable of effecting. If, on the other hand, it is inferior to this, science has not extracted from it the full _horse-power_ it contains; and we are uselessly expending force and destroying our engines by undue pressure being exerted on one part, and inferior pressure on another; whilst by a proper distribution of that force, durability of the cannon is insured, and from twenty-five to thirty per cent. more work may be obtained from an equal quantity of powder, provided its granulation be judiciously selected according to the area of the gun.
There is abundant proof that on this engineering question we have hitherto worked by the “rule of thumb;” prejudice having been a stumbling-block, which nothing but stern necessity will remove. The authorities have but just discovered this, although their attention was directed to it several years ago. In the year 1852, I produced before the Small Arms Committee, at Enfield, a portion of gunpowder suited to the expansive rifle; it was tried to a limited extent, and dismissed with the remark, “We don’t think there is much in it.” Experience, however, has demonstrated the truth of my observations, for, in all extreme range shooting with the expansive or “Greenerian”-principled rifles, not only is considerably greater _accuracy_ obtained with it, but an _increase_ of range equivalent to fifteen or twenty per cent.
Another advantage of using gunpowder of a suitable granulation is the absence of sharp recoil; and thus greater accuracy of range is obtained--accuracy of range and steadiness of weapon being inseparable.
Large-grain gunpowder is not only a more effectual expellant than the fine grain, but is much more safe to use, for by using it the risk of bursting the barrel is much lessened; as a very simple illustration will show. If we estimate the force generated by the usual charge of 2-1/2 drachms (I confine the question to the 14-bore gun, for uniformity) to be 5,000 lbs., whether the powder be fine or coarse grain, it follows that the fine powder, igniting so rapidly, will exert all its force on the breech end of the gun; whereas the coarse powder, igniting less rapidly, distributes this force over the whole length of the barrel: hence the greater risk of a gun bursting with fine powder than with coarse. If we suppose the fine powder to be entirely ignited when it reaches half way up the barrel, then the force of 5,000 lbs. is exerted on the lower half of the barrel; but if the coarser grain is not entirely ignited until it reaches the muzzle, then the force of 5,000 lbs. will be distributed over the whole length of the gun.
But this is not all. The fine powder, igniting almost instantaneously, exerts its force in all directions at once, and the barrel may burst at the side before the charge has time to move; whereas the coarse powder, igniting as it does more slowly, first lifts the charge, and then the volume of gas behind it increasing as the powder becomes more thoroughly ignited, sweeps the charge out of the barrel with a velocity increasing towards the muzzle.
If time is not given for the charge to receive the full advantage of the expansive force of the generated air, the force is exerted, not upon the charge, but upon the barrel of the gun itself; and that time is necessary for the full development of this force, is proved by the fact that miners mix their gunpowder with sawdust, in order to diminish the rapidity of its explosion and thus get the advantage of its force in the distance: from the miners, then, let us learn how to obtain the greatest benefit from this force, and waste it not.
There can be no doubt of the importance of this principle; little progress has, however, been effected from want of scientific illustration; let it be defined like that of steam power, and its adoption will follow as a natural consequence.
For several years I have had gunpowder manufactured of various sizes, at the sight of which most sportsmen would express their astonishment.
One objection held by sportsmen to the large grained gunpowder is that it does not come up the nipple of the gun; now although I do not consider this at all important, still if the specific gravity of the gunpowder were increased by compressing 1-1/2, 2, or 3 grains of gunpowder into the space of 1 grain, by means of hydraulic pressure, this objection would at once be obviated; whilst at the same time, the powder would be less liable to absorb moisture, or to become friable with age: either of which conditions is incompatible with good shooting.
The granulating of gunpowder, to be of the greatest benefit, should be on a uniform principle; the manipulation should be alike in all particulars, but especially in that part of the process which determines the specific gravity. The hydraulic pressure on the cake should be alike in all cases: in fact, the various sizes of grain might be produced from the same cake, and the desired object be thus obtained. But so long as the practice is followed of producing large grain from less condensed cake, the article produced will give unsatisfactory results; and the advantages which might be attained, as my experience denotes, and which would be of the greatest service, alike in sporting, rifle, and artillery powder, will be nullified.
Great improvements are yet to be made, especially in the powder used for artillery; whilst range, accuracy, and lessened recoils are points which may be determined with almost mathematical precision.
Great fame is in prospect for any one who can grasp and handle well this granulation principle; especially if he can define the sizes to be used for different varieties of guns. Artillerists who contend that a medium size grain, to suit all sizes of gun, is advantageous, might as well contend that cannon of a medium size would be preferable to so many different sizes, because, though we lose in range, accuracy, and recoil, it would be more convenient to have but one sized gun.
In making large grained gunpowder, the manufacturers defeat one of the main objects to be gained by granulation, from not subjecting it to the same amount of pressure which is necessary for the granulation of the very fine grain. In granulating very fine powder, it is necessary to subject the cake to such an amount of hydraulic pressure as shall give the mass a marble-like structure, or during the process of granulation, the whole of it crumbles into dust; but the coarser gunpowder may be granulated without subjecting it to this high degree of pressure, hence each grain is more porous and of lesser specific gravity: a difference which it is most important to avoid. It is clear, therefore, that according to the present mode of manufacturing gunpowder, the large and the fine grain are of very different kinds; the main difference being in their specific gravities. Gunpowder of less density burns with greater rapidity, because it is more open and porous; and if uniform density was observed, the diversity in the size of the grain need not be so great; whilst, at the same time, this anomaly might be avoided--that the same measure of fine and large-grained gunpowder contains a difference of the expansive element amounting to fifteen or twenty per cent. As gunpowder is now manufactured, it is highly necessary in all comparative trials to _weigh_, and not to _measure_ the charge, or the results will be deceptive and worthless. The granulation question struggles with undeserved difficulty. Gunmakers, either not understanding the question, or constructing the chambers of their guns improperly, and not using suitable nipples, decry the adoption of large-grained gunpowder; but they forget the increased range obtained in the killing from their guns, and the _éclât_ a long shot produces. In trials of guns at thirty or forty yards, the difference in the shooting with fine and large-grained gunpowder is not so apparent, and the maker exclaims, “Oh! the fine powder shoots stronger, and as close as the coarse.” I admit this to be the case, at short distances; but the great advantage of using the large grain is sufficiently evident when shooting at forty-five, fifty, and sixty yards, for then the fine grain entirely fails: simply from the oft-repeated fact, that the fine powder is more of a propulsive, while the large grain is an expellant force; so that according to the law of resistance in aëriform fluids, the one is sooner reduced to medium velocity than the other, which exerts its action more evenly. Powder of larger grain is thus more suitable for the larger sizes of shot, and would give an increased range in usual shooting, for the shot is kept better together, and is projected to greater distances. A common way of testing the quality of gunpowder is, to rub it between the hands, and observe the darkness of the stain; the darker the stain the more inferior the gunpowder is held to be. This test is, however, decidedly fallacious, because the gunpowder may be of low specific gravity, or it may have become friable from age and other causes.
Whales are shot with gunpowder proportioned to the weight of the harpoon required to kill them. Duck guns of the largest calibre are comparatively useless unless the gunpowder used is granulated according to the weight of the projectile; and the same law holds in regard to the most “mammoth” engine yet to be devised by the mind of man.
Gun-cotton has been before the world for some years, but, except as a curiosity, it has attracted little public attention; neither has it gained any reputation as a projectile force. It may be prepared by steeping cotton wool for a few minutes in a mixture of nitric and sulphuric acids, thoroughly washing, and then drying at a very gentle heat. It consists chemically of the essential elements of gunpowder: viz. carbon, nitrogen, and oxygen; but, in addition, it contains another highly elastic gas, hydrogen. The carbon in the fibres of the wool presents to the action of flame a most extended surface in a small space, and the result is an explosion approaching as nearly as possible to the instantaneous: in consequence of its rapid ignition it produces a violent kick; sufficient time is not given to put heavy bodies in motion, hence it cannot be usefully employed as a projectile agent. No one who values his limbs should trifle with it, for fearful accidents have resulted from its exposure to the heat of the sun, and other very simple causes.
There is an instrument used by some sportsmen, and strongly recommended by many gunmakers, for testing the strength of different kinds of gunpowder. It consists of a chamber closed by a spring, and fired like an ordinary pistol. When the powder explodes the spring is forced forward, and moves an index round a graduated circle; the more quickly the powder explodes the farther does it lift the spring; hence this is a measure of quickness of fire, but not of expellant force; and from the observations which have been made on gunpowder, it must be evident to any one who has paid the least attention to the subject, that this instrument is utterly useless.
An instrument to test the comparative strength of different kinds of gunpowder is yet a desideratum in projectile science; and we cannot doubt that such an instrument will be produced, when the importance of the granulation of gunpowder is more generally known and appreciated.
The charcoal formerly used was made in the common way, by pits, which must have been seen by almost every one. The method is now to _distil_ the wood in cast-iron cylinders, extracting the pyroligneous acid, &c., by heating them red hot, and allowing all other volatile matter to evaporate, the charcoal only being retained in the cylinder or retorts; hence arises the name _cylinder gunpowder_. The best charcoal for sporting powders is the black dog wood; Government use willow and alder. Any charcoal does for common powders. Charcoal is ground in the same way as the nitre. Sulphur is purified simply by fusing, and when in that state, skimming off the impurities: it is cooled and pulverised in the same way as the other two ingredients. The three ingredients, after being carefully weighed in their due proportions, are sifted into a large trough, and well mixed together by the hands. They are then conveyed to the powder mill. This is a large circular trough, having a smooth iron bed, in which two millstones, secured to a horizontal axis, revolve, traversing each other, and making nine or ten revolutions in a minute. The powder is mixed with a small quantity of water put on the bed of the mill, and there kept subject to the pressure of the stones; and if we calculate the weight of the two millstones at six tons, it follows that in four or five hours’ incorporation on this bed, it subjects the ingredients to the action of full 10,000 tons. It is this long-continued grinding, compounding, and blending together of the mixture, that alone renders it useful and good. After this intimate mixing, it is conveyed away in the shape of mill-cake, and firmly pressed between plates of copper. Bramah’s press has been introduced of late years--we should say with a good deal of improvement to the powder, as will be shown hereafter--and by its means the mass is more compressed and in thinner cakes. It is then broken into small pieces with wooden mallets, and taken to the corning-house, where it is granulated, “by putting it into sieves, the bottoms of which are made of bullocks’ hides, prepared like parchment, and perforated with holes about two-tenths of an inch in diameter; from twenty to thirty of these sieves are secured to a large frame, moving on an _eccentric_ axis, or crank, of six inches throw; two pieces of lignum vitæ, six inches in diameter, and two inches or more in thickness, are placed on the broken _press-cakes_ in each sieve. The machinery being then put in rapid motion, the discs of lignum vitæ (called balls) pressing upon the powder, and striking against the sides of the sieves, force it through the apertures, in grains of various sizes, on to the floor, from whence it is removed, and again sifted through finer sieves of wire, to separate the dust and classify the grain. One man works two sieves at a time, by turning a handle and eccentric crank; the sieves being fixed to a frame, which is suspended over a bin by four ropes from the ceiling.”
The grains afterwards undergo a process of _glazing_, by friction against each other, in barrels containing nearly 200 lbs., making forty revolutions in a minute, and lasting several hours, according to the fancy of the purchaser. This part of the business we entirely disagree with, as injurious to the quick and _certain ignition_. Gunpowder is finally dried by an artificial temperature of 140° Fahrenheit, which is suffered gradually to decline. The last process is sifting it clear of dust, and then packing it in canisters or otherwise.
The utility of the process of granulation results from the impossibility of firing mealed powder sufficiently simultaneously to effect an explosion; and also from the fact that gunpowder, in a mass, does not explode. Fire a solid piece of mill-cake, and it does not flash off like unto granulated powder, but burns gradually, though with an extreme fury, until the whole is consumed. This arises from its density, the compression in the press; it also teaches us one fact, that to be of the greatest service, the time each grain should occupy in burning should be proportioned to the size of the gun for which it is required; since it is clear that the explosion of a heap of gunpowder is but the rapid combustion of all its parts. This action, as is well known, is so rapid, even in a large quantity of powder, that it appears to be a sudden and simultaneous burst of flame; though philosophically and actually it is not so.
Fine grain, when unconfined, explodes quicker than large, or is sooner burnt out, and consequently generates more force in the same period of time; but when it comes to large quantities, its very quickness is detrimental to its force, by condensing the air around the exterior of the mass of fluid which thus constrains its bound. In small quantities, the proportion of condensation is not so apparent, and hence the reason why greater velocities can be obtained with small arms than with cannon.
There exists a diversity of opinion in regard to the strength or projectile force of gunpowder. Dr. Ure remarks--“If we inquire how the maximum gaseous volume is to be produced from the chemical reaction of the elements of nitre on charcoal and sulphur, we shall find it to be by the generation of carbonic oxide and sulphurous acid, with the disengagement of nitrogen. This will lead us to the following proportions of these constituents:
Hydrogen 1. Per Cent. 1 prime equivalent of nitre 102 75·00 1 „ „ sulphur 16 11·77 3 „ „ charcoal 18 13·23 --- ------ 136 100·00
“The nitre contains five primes of oxygen, of which three combining with the three of charcoal, will furnish three of carbonic oxide gas, while the remaining two will convert the one prime of sulphur into sulphurous acid gas. The single prime of nitrogen is therefore, in this view, disengaged alone.
“The gaseous volume, in this supposition, evolved from 136 grains of gunpowder, equivalent in bulk to 75-1/2 grains of water, or to three-tenths of a cubic inch, will be, at the atmospheric temperature, as follows:--
Grains. Cubic Inches. Carbonic oxide 42 141·6 Sulphurous acid 32 47·2 Nitrogen 14 47·4 ----- 236·2
being an expansion of one volume into 787·3. But as the temperature of the gases, at the instant of their combustive formation, must be incandescent, this volume may be safely estimated at three times the above amount, or considerably upwards of 2,000 times the bulk of the explosive solid.
“It is obvious that the more sulphur, the more sulphurous acid will be generated, and the less forcibly explosive will be the gunpowder. This was confirmed by the experiments at Essonne, where the gunpowder that contained twelve of sulphur, twelve of charcoal, in 100 parts, did not throw the proof shell so far as that which contained only nine of sulphur and fifteen of charcoal. The conservative property is, however, of so much importance for humid climates and our remote colonies, that it justifies a slight sacrifice of strength.
“When in a state of explosion, the volume,” Dr. Hutton calculates, “is at least increased eight times, and hence its immense power. The pressure exerted, if in a state of confinement, will depend on the dimensions of the vessel containing it; so that it would be no difficult undertaking to obtain any pressure above that of the atmosphere, up, we may fearlessly say, to the enormous amount of 4,000 lbs. per square inch.”
The same quantity of gunpowder subjected to a variety of experimental tests, differs materially in its results; at the same time it is only by such a method that we can arrive at the relative strength or power which it possesses. Dr. Hutton, whose authority in all mathematical calculations is very high, and whose opinions and judgment in matters of this nature ought not to be unthinkingly controverted, states 2,000 feet per second (with cannon) as the highest velocity which any projectile had attained, at the time of his writing, which had gunpowder for its propellant power. A much greater velocity is now given in all guns fired at high elevations. “Monks’” gun attained a velocity of 2,400 feet in the first second of its flight, and this is now exceeded by rifled cannon.
This advantage does not arise, in our opinion, so much from the superior quality of the gunpowder, as from the improvements which have taken place in the manner of applying it. For instance, where experiments are conducted, as was the case with Dr. Hutton, with moving _eprouvettes_, a certain loss is sustained, in the same degree as the instrument is made to recoil from its original position; therefore, by restraining the recoil, an increase of momentum is given to the projectile, to the same extent as had been exerted upon the _eprouvette_, or cannon, in driving it several feet backward; and instead of dividing the force thus acquired between the shot and the gun, by having the latter firmly fixed and the recoil destroyed, the whole power is exerted upon the former, and its velocity accelerated in the same proportion.
Gunpowder, though astonishing in its effect, and tremendous in power, may nevertheless be controlled within a limited sphere, and bounds put upon its destructive energy. The following curious experiment, first tried at Woolwich on a small scale, has since been carried out to a great extent. Screw into each end of the breech part of a gun-barrel a well-fitted plug; drill a communication, and put in a nipple; having filled the barrel with powder, screw in the breech, and fire a cap on it, and the explosive fluid will escape by the small orifice like steam from a pipe. If the barrel be good, it may safely be held in the hand, merely using a towel to protect the hand from the heat the barrel absorbs. We have done it repeatedly with no inconvenience, and even carried this experiment much further; firing two ounces of the best powder in a barrel of good quality (though not in the hand) yet the barrel did not receive any violent motion by which it could be inferred that it might not be done with safety.
We have before observed, that, with very short guns, fine gunpowder produces the greatest result, inasmuch as there is no greater column of air in the barrel than the explosive fluid is equal to _displace_; or, in other words, the charge leaving the muzzle of the gun at the very moment when the explosive force is strongest, all the power is thus obtained of which it is capable; but if used in a longer barrel, and the fluid has obtained its greatest power when the charge has twelve inches of the barrel still to travel, the column of compressed air yet remaining in the muzzle of the barrel, exerts a resisting influence, in proportion to its density, upon the charge, and creates a dangerous and unpleasant recoil.
If a cartridge be placed in the centre of an open barrel eight feet in length, having a bullet abutting at each end large enough to fill the barrel, and a touch-hole is drilled as near the centre of the cartridge as possible, when it is fired, the balls will certainly be discharged from the barrel, but with a very small degree of force: in fact, merely driven out. With the same instrument, vary the experiment: place in it a cartridge charged with one ball, three feet from the muzzle, leaving a column of air five feet in length to act against the explosive force of the gunpowder, and the ball will be driven one hundred yards with considerable force. Again, let a third cartridge be introduced similar to the last, two feet from the muzzle, increasing the column of air to six feet; and the result, in distance and velocity, will nearly double what has been obtained by the last experiment; tending to prove that air thus forced back upon itself obtains a density, and consequent resisting influence, nearly equal to a well-screwed breech. In order to test this principle further, I put into the same tube a double charge of gunpowder, merely backed by a wadding, two feet from the muzzle, and then rammed down four balls as tight as possible into the short portion; in discharging it, the tube was burst immediately in rear of the charge.
In another experiment, I took a common musket barrel, having a plug of iron firmly fixed into the muzzle; the breech being unscrewed, and a ball introduced one-tenth of an inch less in diameter than the bore of the barrel, together with one drachm of gunpowder, I then fired the gunpowder, and the explosive matter escaped by the touch-hole. On examination, it was found that the ball was flattened to the extent of one-third of its sphere. The charge for the next experiment was increased to two drachms; when the ball in the discharge struck the muzzle very slightly, altering its shape in the least conceivable degree. The charge was next increased to three drachms, and the ball was extracted without any perceptible defect. In the fourth trial, another drachm was added, with which the effect was greater than the tube was able to resist; it was in consequence burst, about three inches from the muzzle.
From this I infer that, in the first trial, the velocity of the ball was not so great, but that the air escaped past it, by what is technically called the windage, allowing it to strike the plug at the end of the barrel with sufficient force to alter the shape of the lead in the manner described. The second trial gave an increased velocity; the opposing forces being so nearly balanced that the ball scarcely reached the end of the barrel, and was very little injured. In the third trial the velocity became so great, and the air was condensed to such an extent, that the ball struck upon a cushion-like surface so highly elastic that it was extracted without the least injury to its shape. The last charge was too powerful, inasmuch as the lateral pressure of compressed air rent the tube asunder.
The one great cause of this and other barrels bursting, arises from the velocity becoming too great, and thus driving back the air upon itself, until the mutual repulsion of the particles forms an almost impenetrable barrier, exerting a lateral pressure on the barrel, and resisting the passage of the elastic fluid. To make the explanation plain; supposing that the charge had condensed the air for the distance of three or four inches immediately preceding it, and then come to rest, the waves of vibration, travelling at the rate of 1,300 feet per second, would communicate to the remainder of the column the same pressure, and an equilibrium would take place. But this not being the case, and the air becoming still more highly compressed by the velocity not decreasing but increasing, the lateral pressure becomes greater than the fibres of the iron are able to withstand, and consequently the barrel is burst. Many accidents arise from this cause solely, and without any blame being attached to either the maker or user of the gun. While on this subject, we may remark that this is the more likely, inasmuch as the powder with which barrels are proved is not the strongest, and is also of a large grain; so that it is quite within the range of probability that a barrel may, and it does often, stand proof, and yet burst when it comes to be used with extremely fine-grained strong powder; as it is quite clear that a high velocity must create danger.
To pursue the subject still further: in order to procure conclusive evidence in support of this argument, I had a tube of iron manufactured, sufficiently good in quality to bear an enormous pressure; it was three feet in length, with a bore large enough to admit an ounce ball, and the sides of the arch were full a quarter of an inch in thickness. A piece of steel, one inch in length, was then turned of a size to fit the bore well, but not so tight as to prevent its free action: this I called a piston. From the centre of the tube to the muzzle, were drilled, on all sides, a number of small holes, a quarter of an inch distant from each other, in all amounting to sixty-eight; these were fitted with small pieces of steel needles, hardened, projecting into the interior of the tube a quarter of an inch, so that the piston, in its upward movement, should strike these pins, and thus enable me to judge how far it was driven by each experiment. Each end of the tube was then fitted with a breech, firmly screwed in; the upper one having a flat internal surface, the lower one, where ignition was to be communicated, being a conical or patent breech. This machine I termed an explosion metre; and it answered its purpose. With two drachms of the best canister gunpowder, the piston was propelled nineteen inches along the tube; breaking eight pins. The same quantity of the fine diamond grain reached only eighteen inches, or four pins. No. 3 grain, of both Laurence’s and Pigou and Wilks’ manufacture, reached twenty-four inches, or twenty-eight pins. A very superior powder, containing in one grain five of diamond, four of canister, and two of the above makers’ No. 2, reached twenty-seven inches, and broke forty pins. In each of these experiments the greatest accuracy was observed, in preparing the metre as well as in weighing the charge.
These facts go far to prove that, in all uses of gunpowder, the grain should be of a size proportioned to the length and bore of the gun; for if we have not an accelerating force to overcome the increasing resistance of the compressed column of air in the barrel, there is great danger that the gun may be burst, and probably be productive of great mischief; whilst a judicious application of the extraordinary power thus placed at our disposal, may be alike conducive to our safety and our pleasure. A musket ball can be driven through an half-inch boiler plate; but this can only be accomplished by using as much powder as will generate a gradually, though rapidly, increasing power, until the ball has passed the limits of the tube.
Nitre is not the only salt which has been employed in the manufacture of gunpowder. Its quantity or proportion in the mixture has been lessened, and the deficiency supplied by another elementary combination; namely, by the chlorate of potassa.
The French succeeded in making powder of which potassa forms one of the component parts, and they say it ranges the projectile double the distance; but this is doubtful. The proportions of the mixture are nitrate of potash twenty-five parts, chlorate of potassa forty-five, sulphur fifteen, charcoal seven and a half, and lycopodium seven and a half parts. In the year 1809, a similar kind of powder was proposed to the English Government, by a person of the name of Parr; but its introduction was very properly opposed by Sir William Congreve, on account of the danger attending its use, and also from the fact that there was no piece of ordnance in the service able to withstand its effects. The proportions were, chlorate of potassa six parts, fine charcoal one part, sulphur one part. These ingredients to be _carefully_ mixed together and granulated. The above mixture was laid aside, not only from the want of power to restrain its effects, but because it was useless, from the very extreme rapidity of its explosion: it forms the atmospheric air into a wall of adamant, by the condensation confining it to a comparatively small space; it becomes lightning--an electric fluid, which, from its very intensity, cannot displace any great mass of air.
Neither can any advantage arise from any greater velocity in projectile force, except we can obtain that by a graduated scale; for masses cannot, from a state of rest, be put in extreme motion instantaneously: philosophy teaches us, and experience makes it evident, that a portion of time must be occupied, however short that may be. All motion is gradual, and cannot be obtained otherwise; and hence the fact, that lightning conveyed into a tube filled with projectiles would not drive them out: it would not project them, but the blow would break them in pieces. So is it with this mixture; it is useless from its very rapidity of ignition. We have shown that even fine grain gunpowder is too quick, and that its quickness destroys its power; how much more so is the other: and what would it avail us, with these disadvantages.
A writer mentions what he conceives to be a curious fact: he says, “If a train of gunpowder be crossed at right angles by a train of fulminating mercury, laid on a sheet of paper on a table, and the gunpowder lighted by a red hot wire, the flame will run on until it meets the cross train of fulminating mercury, when the inflammation of the latter will be so instantaneous as to cut off the connection with the continuous train of gunpowder, leaving one half of the train unignited:” and again, “If the fulminating powder be lighted first, it will go straight on, and pass through the train of gunpowder so rapidly as not to inflame it at all.” True; and the cause is quite apparent: the rapidity of combustion condenses the air so quickly, as to remove the grains of gunpowder liable to come in contact with the flame, and to form the condensed air into a line of demarcation: for heat cannot be taken up by the air quicker than the atmosphere will convey sound; and before the heat can evaporate the explosion is over, and is consequently noiseless.
In all mining operations: in the quarrying of stone, the destruction of sunken rocks, or in any other operations where it is desirable to detach large masses, the use of gunpowder is indispensable; not only because it decreases manual exertion but also because it can be used under circumstances and in situations unapproachable by other means. It becomes, therefore, a consideration for the miner what kind is best suited for the purpose; the finest grained powder is useless as is well known: it is also more expensive; but its principal defect arises from its quickness of combustion. Masses cannot be detached without first putting the whole in motion; and as this cannot be done in a very short time, it is necessary to prolong the explosion, so that the wave of vibration may have time to travel throughout the whole of the mass acted upon; and a repetition of these waves is necessary before any mass can move. Now, to obtain this, it is necessary that matter be so incorporated with the powder as to prolong that explosion; bituminous substances might be applied with effect, for their slow burning would keep the heat necessary to hold the permanent gases at their utmost stretch of expansion.
It is obvious, from the extremely high character English sporting gunpowder has obtained all over the world, that considerable improvement must have been effected by the private manufacturers, either in the purification or manipulation of ingredients; indeed the unwearied care bestowed on this point by several of our best makers is beyond all praise. To explain the various methods, or otherwise enlarge upon this point, would be injurious to individual skill and enterprise, and be the means of imparting knowledge to those who have not ability to invent, but who gather from the brains of others. The French set great value on the “Poudre de Chasse” of England. It is rather singular that we should excel those who pride themselves so much on their chemical knowledge; but, as before remarked, it is certain that the intimate incorporation of the ingredients is of more importance than the chemical proportions.
All military and naval gunpowder is not manufactured of the greatest strength that can be acquired “_at the Government mills_;” a sample is furnished to each contractor with each contract, and to this strength he is limited.
The fame of our English gunpowder makers is patent to all the world, and, where skill is equal, to name one rather than another would be invidious; though we must not lose sight of the facts herein established. “Granulation,” properly understood, is an equivalent point to either chemical or mechanical knowledge and manipulation in gunpowder manufacture. Great anxiety to meet the wishes of the sporting world on this point, and to advance with the age, has been aroused; and specimens have been kindly furnished to me, not by one, but by all the following celebrated makers: Messrs. Pigou and Wilks, Curtis and Harvey, Lawrence and Son, John Hall and Son; and I have received also a very excellent specimen from the Scotch mills.
Gunpowder of five sizes of granulation, on the basis before alluded to: namely, No. 2, containing two quantities of No. 1, and No. 3, three, and so on in progression; but it is imperative that all the various sizes be produced from the same mill cake, or be otherwise of the same condensation or specific gravity, and in all experiments of comparison, equal weights are a “sine quâ non,” otherwise the comparison will be futile; as measure is, for these very obvious reasons, inapplicable in comparative tests. When these points are carefully attained, increased power of killing, “decreased recoil,” and much greater safety, will be the important benefits which the gunpowder manufacturers will confer on every one using a gun.