An experiment, made at the same works, by the then proprietor, the father of the late commodore Decatur, by putting the nitre, charcoal, and sulphur, into a barrel, with iron balls covered with lead, which was turned upon its axis, terminated in the same way. It exploded, but no other injury or accident was sustained. On examining the balls, we found, that the lead was entirely worn off, and the explosion must have been owing to the iron. This experiment was performed, in order to find if the mixture could be made in this manner, a plan which was afterwards adopted in France, with success, but brass balls were used. In a series of essays, which I wrote for, and published in, the Aurora, in 1808, on the "Application of Chemistry to the Arts and Manufactures," as manufactures are vitally important to the practical independence of this country, I mentioned the subject of gunpowder, and the different modes of preparing it, and among which, the various experiments on this subject.

The machinery, required in gunpowder mills, is exceedingly simple. The power of the water, which may be given by an overshot, or undershot wheel, is communicated to the parts of the mill, which perform the work. Thus it is, that pounders, like the snuff, or plaster-paris mill, are put in motion, by a horizontal shaft, furnished, at different distances, with pieces of wood, which, by the revolution of the shaft, and meeting with the projecting pieces from the pounders, raises them in succession. They fall, then, in the same order of succession, in the respective mortars.

The mortars of the powder-mill, are hollow pieces of wood, capable of holding twenty pounds of paste, composed of the substances before mentioned, which are incorporated by means of the pestle. There are usually twenty-four mortars in each mill, where are made, each day, four hundred and eighty pounds of gunpowder; care being taken, to sprinkle the ingredients with water, from time to time, lest they should take fire. This precaution is absolutely necessary, and if attended to, would prevent many of the explosions, which, unhappily, take place, in the manufacture of powder. The friction must be great, and, therefore, the increase of temperature, occasioned in this manner, ought to be guarded against. This can only be done, by diminishing the time, or number of the blows, or by proportioning the weight of the pestle, and the frequent addition of water. The last is the most certain, and indeed, the water is in some respects, necessary to promote a more intimate mixture of the materials. The observations of M. David, on the use of water in the manufacture of powder, are certainly correct. The pestle is a piece of wood, ten feet high, and four and a half inches broad, armed at the bottom with a round piece of metal. It weighs about sixty pounds.

Having mentioned one cause of the explosion of powder-mills, that of friction produced by the pestle, we find that it has been accounted for on another principle. The Annales de Chimie, tome xxxv, mentions some instances of spontaneous combustion in powder mills. It is well known, that charcoal has the property of absorbing several gases, and the observations of Rouppe and Berthollet, on this subject, are conclusive. It is also known, that charcoal, which contains hydrogen, when exposed to atmospheric air, will absorb oxygen, and form water; and during this combination, heat must be generated, by the emission of caloric from the oxygen gas. It is said, then, that in cases of spontaneous combustion, when nitre, sulphur, and charcoal, are mixed together, (unless water be added to prevent it), this effect will ensue, and fire be produced. We know, however, that percussion is one source of heat; and in truth, if that opinion be well founded, percussion itself may facilitate the union of hydrogen, with the oxygen of the air, and necessarily operate as a secondary cause of such explosions.

Another opinion has been advanced by Bartholdi, to account for the spontaneous combustion in powder mills: namely, that charcoal sometimes contains phosphorus, combined with hydrogen, which, by the action of the pestle, is disengaged in the form of gas, and inflames, the moment it comes in contact with the air. Others again suppose, that it sometimes contains pyrophorus.

Pulverizing the charcoal, in the first instance, by itself, and adding water, during its mixture, from time to time, a measure proposed in 1808, by M. David, and now generally adopted, will prevent such accidents; for it appears, they have not occurred in France, since the adoption of this plan. Some remarks on spontaneous combustion, may be seen in the article on artificial volcanoes.

M. Sage, (Journal de Physique, vol. lxv, p. 423, or Nicholson's Journal, vol. xxiii, p. 277), has written on the spontaneous ignition of charcoal, and adduced some facts on the subject; by which it appears, that M. de Caussigni was the first, who observed, that charcoal was capable of being set on fire, by the pressure of mill stones.

Mr. Robin, commissary of the powder mills of Essonne, has given an account, in the Annales de Chimie, of the spontaneous inflammation of charcoal, from the black berry bearing alder, that took place the 23d of May, 1801, in the box of the bolter, into which it had been sifted. This charcoal, made two days before, had been ground in the mill, without showing any signs of ignition. The coarse powder, that remained in the bolter, experienced no alteration. The light undulating flame, unextinguishable by water, that appeared on the surface of the sifted charcoal, was of the nature of inflammable gas, which is equally unextinguishable.[17]

The moisture of the atmosphere, of which fresh made charcoal is very greedy, appears to have concurred in the development of the inflammable gas, and the combustion of the charcoal.

It has been observed, that charcoal powdered and laid in large heaps, heats strongly.

Alder charcoal has been seen to take fire in the warehouses, in which it has been stored.

About thirty years ago, M. Sage saw the roof of one of the low wings of the mint set on fire by the spontaneous combustion of a large quantity of charcoal, that had been laid in the garrets.

Mr. Malet, commissary of gunpowder at Pontailler, near Dijon, has seen charcoal take fire under the pestle. He also found, that when pieces of saltpetre and brimstone were put into the charcoal mortar, the explosion took place between the fifth and sixth strokes of the pestle. The weight of the pestles is eighty pounds each, half of this belonging to the box of rounded bell metal, in which they terminate. The pestles are raised only one foot, and make forty-five strokes in a minute.

"In consequence of the precaution now taken," M. Sage observes, "to pound the charcoal, brimstone, and saltpetre separately, no explosions take place; and time is gained in the fabrication, since the paste is made in eight hours, that formerly required four and-twenty.

"Every wooden mortar contains twenty pounds of the mixture, to which two pounds of water are added gradually. The paste is first corned: it is then glazed, that is, the corns are rounded, by subjecting them to the rotary motion of a barrel, through which an axis passes: and lastly, it is dried in the sun, or in a kind of stove.

"Experience has shown, that brimstone is not essential to the preparation of gunpowder; but that which is made without it falls to powder in the air, and will not bear carriage. There is reason to believe, that the brimstone forms a coat on the surface of the powder, and prevents the charcoal from attracting the moisture of the air.

"The goodness of the powder depends on the excellence of the charcoal; and there is but one mode of obtaining this in perfection, which is distillation in close vessels, as practised by the English.

"The charcoal of our powder manufactories is at present prepared in pots, where the wood receives the immediate action of the air, which occasions the charcoal to undergo a particular alteration."

In 1724, (Coll. Academ. t. v, p. 413,) M. de Moraler proposed a new mode of mixing the materials for gunpowder. In 1759, M. Musy proposed another method to prevent explosions; and in 1783, the baron de Gumprecht constructed a very ingenious powder mill, a model of which he presented to the king of Poland, whose approbation it received.

There is an account in detail, of the results of the experiments made by MM. Regnier and Pajot Laforet, with different fulminating powders, in the Archives des Découvertes, iii, p. 337. These experiments, although interesting in a philosophical view, cannot be of service in the present case. They were made with gunpowder, fulminating silver, fulminating silver and mercury combined, fulminating mercury alone, &c. See also the Bulletin de la Société d'Encouragement, cahir 65.

The observations of M. Proust (Journal de Physique for May, 1815) on the mixing of powder, and the consequences that result by following the old process, may be consulted.

The process of manufacturing gunpowder, which we have described, is followed in all, or the greater part of the factories of France. It is, however, tedious, and not exempt from danger. The same process, with some modifications or improvements, is adopted in this country; but of all our gunpowder manufactories, that of the messrs. Dupont of Brandywine, Delaware, has heretofore produced the best powder. Powder, however, equally powerful, has been made in other factories.

The improved process of M. Champy, which, in many respects, is superior to the foregoing, is the following:

1. The nitre, sulphur, and charcoal are first reduced, separately, to very fine powder. This operation is performed in barrels, which are made to turn upon their axis, similar to the barrel-churn, and the substances are introduced gradually. Balls, made of an alloy of copper and tin, are then put in, which by their action reduce the substances to powder.

2. The second operation has for its object, the intimate mixture of the ingredients. The quantities to be mixed are weighed, and put into a drum with a quantity of shot, which is made to revolve during an hour and a quarter. In this manner, three hundred pounds of the mixture are at once operated upon.

3. The mixture is then moistened with water. About fourteen per cent. is added. It is then passed through a sieve made with round holes, and then put into a drum, and submitted for a half hour, to a rotary motion. A number of small round grains are thereby formed, which are separated from the mass by means of a sieve, the holes of which are very small.

4. When a sufficient quantity of these grains are procured, they are put into another drum, of a suitable size, with one and a half times their weight of the original mixture. The drum being put in motion, some water is added, which serves to make them increase in size, by constant rubbing: at the end of a certain time, the whole becomes granulated, or perfectly round. The density of the grains depends on the mixture, and the time they were kept in motion.

5. The powder being thus grained, is passed through sieves, whose holes are of different diameters; and hence it is divided into three kinds: viz. cannon powder, musket powder, and fine grained powder.

6. Finally, the powder is dried, and preserved in the usual manner. Its strength is equal to that made by the old process, and is perfectly round.

It may be proper to observe, that this process presents many important and decided advantages. Although, in our description, we have not gone into details, yet the whole operation will be seen at one view. It was practised in France, by its inventor, M. Champy, and, besides being introduced into the United States, it has also been adopted in Prussia.

M. Proust endeavoured to show, that charcoal made of shoots or branches, makes the best powder, and will mix with more facility with the nitre and sulphur; and in employing the ordinary charcoal, two hours beating is necessary to obtain a perfect mixture. The pestles, as Chaptal observes, usually make fifty-five strokes in a minute. Their weight is various; he gives them at eighty pounds.

M. Carney discovered a new process for the fabrication of powder, and although Chaptal himself made some advantageous changes in the process, yet the merit of the discovery he gives entirely to Carney. The process of M. Champy, is in some particulars the same. It will be sufficient, however, to observe, that it is reduced to three heads: viz.

1. The pulverization, and sifting of the materials;

2. Mixing the materials intimately in vessels similar to casks; and,

3. Giving the mixture the necessary consistence, and the final granulation.

For some details of the process, the reader may consult Chaptal's Chimie Appliqué aux Arts, tome iv, p. 145.

Chaptal is of opinion, that Carney's mode of fabricating powder, presents many advantages, among which he considers the facility of its formation, economy in the expense, and the superiority of the powder. In a memoir on the subject, and the formation of powder at Grenelle, Chaptal has described the process very minutely.

Bottée and Riffault reduce the manufacture of gunpowder in France to the following heads:

1. The mixture of the ingredients. This relates to the manner of uniting the nitre, charcoal, and sulphur, the quantity of the composition put into each mortar, and observations respecting the manipulation.

The time required for reducing gunpowder to its proper consistency, and for effecting the mixture is termed by the French, Battage. They are usually twenty-four hours, (or eight according to the new mode,) in pounding the materials to make good gunpowder. Supposing the mortar to contain sixteen pounds of composition, it would require the application of the pestle 3500 times each hour.

The order in which they are beaten, and mixed, is as before given, and also the rechanging, or transferring the materials from one mortar to another.

2. Granulation, (Grenage Fr.) This operation consists, as before observed, in passing the mixture through different sized sieves, employing also parchment sieves, and afterwards separating the dust by a fine sieve. The size of the grain depends altogether on the sieve. Hence we have cannon-powder, gunning or musket-powder, pistol-powder, and mining-powder. Superfine powder is the very small grained.

3. Glazing. (Lissage Fr.) This operation takes off the asperities of the grain, renders it hard and less liable to soil the hands, and gives it a kind of lustre. It is only used for fine powder, such as the pistol, and hunting-powder. Cannon powder is never glazed. It is performed in a barrel-shaped vessel, which is made to revolve on its axis, like the ordinary barrel-churn. The quantity of powder glazed in one of these barrels at a time, in France, is 150 kilogrammes.

By the rotary motion, the grains of powder rub against each other, by which each grain becomes smooth, and receives a polish. According to the motion of the barrel, so is the glazing more perfect. This, however, is regular. After the operation, which continues several hours, the dust is separated from the grain by a sieve. The state of the atmosphere influences the process. If dry, the grain receives a better polish; if wet or damp, the operation is retarded, and the gloss imperfect. It has been customary to introduce a very small portion of finely pulverized plumbago, (carburet of iron), in order to give the grain a better polish. But such additions, however small, are obviously injurious to the powder. It is said that it prevents the absorption of moisture. Powder, which has been glazed with black lead, (plumbago), may be known by its peculiar shining lustre, and also by experiment. M. Cagniard Latour made some experiments with glazed powder, which may be seen in the work of Bottée and Riffault, p. 233.

4. Drying. (Séchage. Fr.) The drying of powder is performed in two ways, viz. by exposure to the sun, and by exposure to heat in close rooms. The English mode, that of drying by steam pipes, MM. Bottée and Riffault are of opinion, presents many advantages, and particularly that the powder may be dried in all weathers, and with perfect safety.

The mode of drying gunpowder by the vapour of water, (confining it, however, in iron pipes or vessels,) was suggested in 1781, and 1787. See Mémoires de l'Académie des Sciences de Suede, 1781, the Journal des Savants, 1787, and the Transactions of the Society of Arts, vol. xxiv. Mr. Snodgrass, in the last work, gave an account of a method of communicating heat by steam, by using pipes of cast iron, for which the society of arts voted him forty guineas.[18] Chaptal (Elements de Chimie) has some judicious remarks on the exsiccation of powder.

The experiment made at Essonne near Paris, by M. Champy, in 1808, on a contrivance for the drying of powder, was satisfactory. This experiment may be seen in page 242 of Bottée and Riffault.

5. Dusting, (Epoussetage.) This operation is confined merely to the sifting. It is nothing more than the separation of the dust from the grain, which we have before noticed. The dust is put in the mortars, and worked over.

6. Barrelling &c. After the powder has gone through the several operations described, it is then put into barrels, and taken to the magazine.

After speaking of gunpowder under these heads, they describe the manner of treating the green, (verd) and dry meal powder; the police of powder establishments, for order and economy; the workmen necessary in a powder manufactory;[19] the process of making powder in the revolution; and for the manufacture of imperial powder (which contains 0.78 saltpetre 0.10 sulphur, and 0.12 charcoal); the process of Berne, where the powder is made of 0.76 saltpetre, 0.14 charcoal, and 0.10 sulphur; the process of Mr. Champy, noticed in this article; observations respecting different processes; on powder magazines; gunpowder made of other saline substances besides nitre; different modes of proving powder, examination of powder; description of workshops, mechanics, and utensils, &c. &c. with a variety of engravings. We have merely to remark, that this work of Bottée and Riffault (a large quarto volume, of 340 pages, besides the plates, which make a distinct volume) ought to be in the possession of every gunpowder manufacturer, as it contains all the information known on that subject. Of this fact there can be no difference of opinion, that in consequence of the great attention paid to the subject of gunpowder in France, not only by the government, but by scientific associations and individuals, their knowledge generally must be more minute and accurate, and their works, as authentic records of facts, more to be depended on.

Besides many interesting works, and memoirs in French,[20] there have appeared some valuable dissertations in the English language. Mr. Coleman, in his paper in the Phil. Mag. ix, p. 355, may be considered the first, who, as superintendant of one of the Royal powder mills, was enabled to present a body of facts on this subject.

As the mode of manufacturing gunpowder at the Royal Powder Mills of Waltham Abbey, in England, may be interesting and useful, in connection with the different processes already given; we will introduce in this place the account of Mr. Coleman, having extracted it from the Artist's Manual, &c. of the author, and having taken it from the original memoir of that gentleman.

The ingredients of gunpowder are taken in the following proportion, namely, 75 of saltpetre, 15 of charcoal, and 10 of sulphur. The saltpetre used is almost entirely that which is imported from the Indies, which comes over in the rough state mixed with earthy and other salts, and is refined by solution, evaporation, and crystallization. After this it is fused in a moderate heat, so as to expel all the pure water, but none of the acid, and is then fit for use. The great use of refining the nitre is to get rid of the deliquescent salts, which by rendering the powder made of it liable to become damp by keeping, would most materially impair its goodness. The sulphur used is imported from Italy and Sicily, where it is collected in its native state in abundance. It is refined by melting and skimming, and when very impure, by sublimation. It should seem that the English sulphur, extracted in abundance from some of the copper and other mines, is too impure to be economically used for gunpowder, requiring expensive processes of refining.

The charcoal formerly used in this manufacture was prepared in the usual way of charring wood, piles being formed of it and covered with sods or fern, and suffered to burn with a slow smothering flame. This method however cannot with any certainty be depended on to produce charcoal of a uniformly good quality, and therefore a most essential improvement has been adopted in this country, to which the present superior excellence of American powder may be in a good measure attributed, which is, that of enclosing the wood, cut into billets about nine inches long, in iron cylinders placed horizontally, and burning them gradually to a red heat, continuing the fire till every thing volatile is driven off, and the wood is completely charred. But as the pyroligneous acid, the volatile product of the wood heated per se, is of use in manufacture, it is collected by pipes passing out of the iron cylinder, and dipping into casks where the acid liquor condenses. This acid is used in some parts of calico-printing, chiefly as the basis of some of the iron liquors and mordants for dark-coloured patterns. The wood before charring is barked. It is generally either alder or willow, or dog-wood, but there does not appear to be any certain ground for preferring one wood to another provided it be fully charred.

The above three ingredients being prepared, they are first separately ground to fine powder, then mixed in the proper proportions, after which the mixture is fit for the important operation of thoroughly incorporating the component parts in the mill. A powder mill is a slight wooden building, with a boarded roof, so that in the event of any moderate explosion, the roof will fly off without difficulty, and the sudden expansion will thus be made in the least mischievous direction. Stamping mills were formerly used here, which consisted simply of a large wooden mortar, in which a very ponderous wooden pestle was made to work, by the power of men, or horses, or water, as convenience directed. These performed the business with very great accuracy, but the danger from over-heating was found to be so great, and the accidents attributable to this cause were so numerous, that stamping mills have been mostly disused in large manufactures, and the business is now generally performed by two stones placed vertically, and running on a bed-stone or trough.

The mixed ingredients are put on this bed-stone in quantities not exceeding 40 or 50 pounds at a time, and moistened with just so much water, as will bring the mass in the grinding to a consistence considerably stiffer than paste, in which it is found by experience that the incorporation of the ingredients goes on with the most ease and accuracy. These mills are worked either by water or horses.

The composition is usually worked for about seven or eight hours before the mixture is thought to be sufficiently intimate, and even this time is often found, by the inferior quality of the powder, to be too little. The fine powder manufactured at Battle in Sussex, is still however made in large mortars or stamping mills, in the old way, with heavy lignum vitæ pestles. Only a very few pounds of the materials are worked at a time.

The composition is then taken from the mills and sent to the corning-house, to be corned or grained. This process is not essential to the manufacture of perfect gunpowder, but is adopted on account of the much greater convenience of using it in grains than in fine dust. Here the stiff paste is first pressed into hard lumps, which are put into circular sieves with parchment bottoms, perforated with holes of different sizes, and fixed in a frame connected with a horizontal wheel. Each of these sieves is also furnished with a runner or oblate spheroid of lignum vitæ, which being set in motion by the action of the wheel, squeezes the paste through the holes of the parchment bottom, forming grains of different sizes. The grains are then sorted and separated from the dust by sieves of progressive dimensions.

They are then glazed or hardened, and the rough edges taken off, by being put into casks, filling them somewhat more than half-full, which are fixed to the axis of a water-wheel, and in thus rapidly revolving, the grains are shaken against each other and rounded, at the same time receiving a slight gloss or glazing. Much dust is also separated by this process. The glazing is found to lessen the force of the powder from a fifth to a fourth, but the powder keeps much better when glazed, and is less liable to grow damp.

The powder being thus corned, dusted and glazed, is sent to the stove-house and dried, a part of the process which requires the greatest precautions to avoid explosion, which in this state would be much more dangerous than before the intimate mixture of the ingredients.

The stove-house is a square apartment, three sides of which are furnished with shelves or cases, on proper supports, arranged round the room, and the fourth contains a large cast-iron vessel called a gloom, which projects into the room, and is strongly heated from the outside, so that it is impossible that any of the fuel should come in contact with the powder. For greater security against sparks by accidental friction, the glooms are covered with sheet copper, and are always cool when the powder is put in or taken out of the room. Here the grains are thoroughly dried, losing in the process all that remains of the water added to the mixture in the mill, to bring it to a working stiffness. This Mr. Coleman finds to be from three to five parts in 100 of the composition. The powder when dry is then complete.

The government powder for ordnance of all kinds as well as for small arms, is generally made at one time, and always of the same composition; the difference being only in the size of the grains as separated by the respective sieves.

A method of drying powder by means of steam-pipes running round and crossing the apartment has been tried with success: by it all possibility of an accident from over-heating is prevented. The temperature of the room when heated in the common way by a gloom-stove is always regulated by a thermometer hung in the door of the stoves.

The strength of the powder is sometimes injured by being dried too hastily and at too great a heat, for in this case some of the sulphur sublimes out (which it will do copiously at a less heat than will inflame the powder) and the intimate mixture of the ingredients is again destroyed. Besides if dried too hastily, the surface of the grain hardens leaving the inner part still damp.

Mr. Coleman deduces from experiment the following inferences, namely: that the ingredients of gunpowder only pulverized and mixed have but a very small explosive force: that gunpowder granulated after having been only a short time on the mill, has acquired only a very small portion of its strength, so that its perfection absolutely depends on very long-continued and accurate mixture and incorporation of the ingredients: that the strength of gunpowder does not depend on granulation, the dust that separates during this process being as strong as the clean grains: that powder undried, is weaker in every step of the manufacture than when dried: and lastly, that charcoal made in iron cylinders in the way already mentioned, makes much stronger powder than common charcoal. This last circumstance is of so much consequence, and is so fully confirmed by experience, that the charges of powder now used for cannon of all kinds have been reduced one-third in quantity, when this kind of powder is employed.

In barrelling powder, particular care must be taken to avoid moisture, and this business is also generally reserved for dry weather.

When powder is only a little damp, it may be restored to its former goodness merely by stoving; but if it has been thoroughly wetted, the nitre (the only one of the ingredients soluble in water) separates more or less from the sulphur and charcoal, and by again crystallizing, cakes together the powder in whitish masses, which are a loose aggregate of grains covered on the surface with minute efflorescences of nitre. In this case the spoiled powder is put into warm water merely to extract the nitre, and the other two ingredients are separated by straining and thrown away.

The specific gravity of gunpowder is estimated by Count Rumford to be about 1.868.

The strength and goodness of powder is judged of in several ways; namely, by the colour and feel, by the flame when a small pinch is fired, and by measuring the actual projectile force by the eprouvette, and by the distance to which a given weight will project a ball of given dimensions under circumstances in all cases exactly similar.

When powder rubbed between the fingers easily breaks down into an impalpable dust, it is a mark of containing too much charcoal, and the same if it readily soils white paper when gently drawn over it. The colour should not be absolutely black, but is preferred to be more of a dark blue with a little cast of red. The trial by firing is thus managed; lay two or three small heaps of about a dram each on clean writing paper, about three or four inches asunder, and fire one of them by a red-hot iron wire: if the flame ascends quickly with a good report, sending up a ring of white smoke, leaving the paper free from white specks and not burnt into holes, and if no sparks fly off from it, setting fire to the contiguous heaps, the powder is judged to be very good, but if otherwise, either the ingredients are badly mixed, or impure.

Gunpowder mixed with powdered glass, and struck with a hammer is said to explode.

An advertisement appeared in the public papers some time in 1813 or 14, signed T. Ewel, addressed to powder manufacturers, by which it appears, in the words of the advertisement, that "he obtained from the United States a patent right for three very simple and important improvements in the manufacture of gunpowder, which do most truly diminish more than one half the risk, the waste, and the expense of the manufacture. They consist in boiling the ingredients by steam, in incorporating them without the objection of barrels, the danger of pounders, or the tediousness of stones running on the edge: and in the granulation effected by a simple machine turning by hand or water, and graining more in a day than twenty hands, losing not a particle of dust, and making not half the quantity for re-manufacture. The advantages of this mode have been so great that he had to discharge half his workmen from his manufactory, as will be readily accounted for by those accustomed to the tediousness and loss from graining, particularly the press powder by the sifter and rollers, &c."

We have not seen the plan in operation, and, therefore, can say nothing respecting it; but it would appear, from the description, that the process was conducted altogether by steam. It is true, that the use of steam is no new application, nor was it then, as it had been used in Europe for heating of dye kettles, in soap boiling, distilling, for warming apartments, and many other purposes. The application to that particular use, that of the manufacture of gunpowder, may be original as far as we know, notwithstanding steam has been applied by means of pipes, &c. as is used at present in some manufactories, for the drying of gunpowder. Professor, now president Cooper, of Columbia College, S. C. (Emporium of Arts and Sciences vol. ii, p. 317) in making some observations respecting that publication, believes, that the application of steam to the manufacture of gunpowder to be practicable, and in reference to the advertisement, also a real improvement; and speaking of steam for that purpose adds, "whether it be adopted in England or not, or whether among the numerous patents granted for the application of steam to the arts and manufactures of that country, I know not."

On a general principle of heating apartments by steam, we may remark, that one cubic foot of boiler will heat about two thousand feet of space, in a cotton mill, whose average heat is from 70° to 80° Fahr. One square foot of surface of steam pipe, is adequate to the warming of two hundred cubic feet of space. Cast iron pipes are preferable to all others for the diffusion of heat. For drying muslins and calicoes, large cylinders are employed, and the temperature of the apartment is from 100° to 130°. Dr. Black observes that steam is the most effectual carrier of heat that can be conceived, and will deposite it only on such bodies as are colder than boiling water.

Dr. Ure (Researches on Heat) has given a new table of the latent heat of vapours, by which it appears that the vapour of water, at its boiling point, contains 1000 degrees, while that of alcohol of the specific gravity, .825 contains 457°, and ether, whose boiling point is 112°, only 312.9. We see then not only by the recent experiments of Ure, but also those of Dr. Black, Lavoisier and Laplace, Count Rumford, Mr. Watt and some others, that water is the best carrier of heat, using the expression of Dr. Black, and hence is admirably calculated for the warming of apartments and other purposes.

Steam may be applied for the heating of water or other fluids, either for baths or manufactures, and consequently for the saltpetre and sulphur refineries, attached to a gunpowder establishment, either by plunging the steam pipe with an open end into the water cistern, if it be for the heating of water, or by diffusing it around the liquid in the interval between the wooden vessel and an interior metallic case. This last mode is applicable to all purposes.

A gallon of water in the form of steam will heat 6 gallons at 50° up to the boiling point, or 162 degrees; or one gallon will be adequate to heat 18 gallons of the latter up to 100 degrees, making an allowance for waste in the conducting pipe.

Mr. Woolf (Monthly Magazine vol. xxxii, p. 253) has taken out a patent for a steam apparatus for various purposes, among which that for the drying of gunpowder is specified. This patent is considered under three heads; viz. the construction of the boilers, which are cylindrical vessels properly connected together, and so disposed as to constitute a strong and fit receptacle for water, or any other fluid, intended to be converted into steam, and also to present an extensive portion of convex surface to the current of flame, or heated air or vapour from a fire. Secondly, of other cylindrical receptacles placed above these cylinders, and properly connected with them, for the purpose of containing water and steam, and for its reception, transmission, &c. Thirdly, of a furnace so adapted to the cylindrical parts just mentioned, as to communicate heat with facility and economy. By means of this invention, he states, that any desired temperature, necessary for the drying of gunpowder, may be produced where the powder is to be dried, without the necessity of having fire in, or so near the place as to endanger its safety; for by employing steam only, conveyed through pipes, and properly applied and directed, without allowing any of it to escape into the room or apartment where the powder is, any competent workman can produce a heat equal to that found necessary for drying gunpowder, or much higher if required. The heat may be regulated, to effect the purpose, without producing the sublimation of the sulphur, which has sometimes taken place.

Among the numerous patents of the late D. Pettibone are some for ovens, both fixed and portable, for the drying of gunpowder. Speaking of the use of heated air (Description of the Improvements of the Rarefying air-stove, p. 19) he observes, that powder makers would derive a very great advantage by using rarefied air for drying their gunpowder.

Mr. Ingenhouz (Nouvelles experiences et observations sur divers objects de physique) attributed the effect of gunpowder to the simultaneous disengagement of dephlogisticated air from the nitre, and inflammable air from the charcoal at the moment of ignition. He followed the calculation of Bernouilli with respect to the quantity of gas generated, viz: that one cubic inch of gunpowder at the moment of inflammation, calculating at the same time its expansion, occupies not less than 2276 cubic inches.

That the effective force of gunpowder depends on the generation and expansion of sundry gaseous fluids, is evident, from the chemical action which takes place in the combustion. At a red heat gunpowder explodes. This ensues even in a vacuum; a fact at once conclusive, that, while it possesses the inflammable principle, it has also the supporter of combustion. It is to be observed that the particle of powder which is struck by the spark, is instantaneously heated to the temperature of ignition, and is thereby decomposed; and the affinity existing between its oxygen or the oxygen of the nitric acid, and the charcoal and sulphur produces the principal part of the gases. The caloric thus evolved, inflames successively, though with rapidity, the remaining mass. The expansive force of powder, is therefore attributed to the sudden production of carbonic acid gas, sulphurous acid and nitrogen gas, with the water which is instantaneously converted into steam; all of which are greatly augmented by the quantity of caloric liberated.

The combustion, therefore, is owing to the action of the charcoal and sulphur on the nitre; and the decomposition is the effect of the union of the charcoal with a part of the oxygen of the nitric acid, with which it forms carbonic acid, and also with the sulphur producing sulphurous acid gas. It is asserted, that sulphuretted hydrogen gas is also produced; if so, there must be a sulphuret formed, which decomposes a part of the water. After combustion, what remains is carbonate of potassa, sulphate of potassa, and a small proportion of sulphuret of potassa and unconsumed charcoal. Good powder, however, should leave no very sensible residue when inflamed: this is one of the proofs recommended. Thenard observes, (Traité de Chimie, ii, p. 498,) that the products of the combustion of gunpowder are numerous; some gaseous, and some solid. The gaseous products are carbonic acid, deutoxide of azote (nitrous gas) and azotic gas, besides the vapour of water; and the solid products are sub-carbonate of potassa, sulphate of potassa, and sulphuret of potassa.

M. Proust considers, that nitrite of potassa, prussiate of potassa, charcoal, sulphuretted hydrogen gas, carburetted hydrogen gas, nitrous gas, and carbonic oxide gas may be generated or result, as the products of the combustion, when the materials have not been properly mixed. Our object in all cases should be to render the materials pure, and the proportions so accurate, as to produce the greatest possible effect, which, of course, must depend on the formation and the consequent expansion of the gases. The effect of fired gunpowder is owing in a great degree to the generation of carbonic acid gas; for while the charcoal acts primarily in the combustion, by taking a greater part of the oxygen from the nitric acid of the nitre, with which we have said it produces carbonic acid; the sulphur has a secondary influence, by forming sulphurous acid gas, although it renders the combustion more rapid, and in this respect enables the charcoal to act at once on the nitric acid of the saltpetre.

We learn then, that in gunpowder, the quantity of charcoal should be such as to effect the decomposition; and, that while the sulphur has a secondary effect, in the formation of sulphurous acid gas, it promotes, if so we may term it, the rapid combustion, and consequent action of the charcoal.

MM. Bottée and Riffault (Traité de l'art de Fabriqué la poudre à canon, p. 197,) after making some observations on the constitution of powder, and the action which takes place when it is burnt, with the aeriform products that result, give some remarks on the proportion of charcoal necessary to decompose a given quantity of nitric acid; and conclude generally, that in the production of carbonic acid gas, the principal gas which is formed, while the nitric acid is decomposed, and gives up its oxygen to the carbon, the azote is liberated in the state of gas, and at the same time caloric is evolved. They observe then, that the ancient formula for the manufacture of gunpowder, as used in France, consists of the following proportions, viz: 0.750 saltpetre, 0.125 charcoal, and 0.125 sulphur, which agrees with modern experiments, although chemistry at that period was in its infancy. M. Pelletier, a member of the National Institute, and M. Riffault made several experiments at Essonne, on different proportions of nitre, charcoal, and sulphur in the fabrication of powder. It is unnecessary to state the different proportions, made use of, or the experiments on the strength of the powder made with the eprouvette. They observe, however, that powder made in the following proportions, was more satisfactory, viz. 0.76 saltpetre, 0.15 charcoal, 0.09 sulphur, and 0.76 saltpetre, 0.14 charcoal, and 0.10 sulphur.

Before we give the gaseous products, according to these gentlemen, it will be necessary to observe, that the quantity of nitric acid in nitrate of potassa, is 48.62 in the hundred, and according to Gay-Lussac, nitric acid is composed in volume of 250 oxygen and 100 azote, or in weight of 69.488 oxygen, and 30.512 azote.

Using the French gramme in the present instance, it appears that 75 grammes of nitrate of potassa, the proportion of this salt which enters into 100 grammes of gunpowder for war, contains 36.47 grammes of nitric acid; and that this quantity of acid is formed of 25.34 grammes of oxygen, and 11.13 grammes of azote. That quantity of oxygen (25.34) is disengaged from its combination with azote in the nitric acid, at the instant of the inflammation of the powder by the charcoal, forming carbonic acid; the constituents of which, according to the proportions established by Gay-Lussac and others, must be in the ratio of 27.376 of carbon and 72.624 of oxygen. If 25.34 grammes of oxygen exist in 75 grammes of nitrate of potassa, the proportion usually admitted, then it will require 9.55 grammes of carbon to saturate it, so as to produce carbonic acid. It is necessary to consider, that this is independent of any foreign earthy or saline matter or moisture which may exist.

With respect to the presence of hydrogen in charcoal, the observations of Dr. Priestley, Cruikshanks, Kirwan, Berthollet, Gay-Lussac, Thenard, Vauquelin, Lowitz and some others, are conclusive on that head. Lavoisier made the quantity of hydrogen in charcoal upon an average, to be 0.125 of its weight. See Memoirs de la Société d'Arcueil, tome ii, p. 343, and the Statique Chimique, tome ii, pages 44 and 45, and also charcoal in a preceding section.

It is said, that by employing more charcoal than is necessary to decompose the nitric acid of the nitre, the excess passes off, not as carbonic acid, but carbonic oxide, or gaseous oxide of carbon, which is necessarily inflamed, and finally forms carbonic acid, as one of the products with the carbonic acid originally formed. But the carbonic oxide, to be changed into carbonic acid, requires in fact the oxygen of the atmosphere.

If 34.89 grammes of carbonic acid result from the combustion of 9.55 grammes of carbon, it must unite with a quantity of oxygen, as before expressed, and according to the temperature, be more or less expanded. The 11.13 grammes of azote thus disengaged from its combination with oxygen, in the nitric acid, remains, of course, in the gaseous state, and is also expanded by caloric. The quantity of the latter is stated by Lavoisier, to be 430 degrees, using a scale of 80 parts; and according to more recent experiments, it is fixed at 600 degrees of the centigrade thermometer. The experiments of Gay-Lussac are more recent, in which he has given the dilatation of the gases, and the quantity of free caloric evolved, which corresponds with the last data. We have not room to insert his remarks.

The use of sulphur with the charcoal, in the fabrication of powder, Bottée and Riffault state to be, (page 204) that it inflames more rapidly than charcoal, and at a lower temperature, which accelerates the combustion of the charcoal, and consequently the detonation of the powder. The presence of the sulphur augments the volume of gas, by producing sulphurous acid gas. The proportion of sulphur in the powder for war, is, 0.125, for musket powder, 0.10, and for mining powder, 0.20, according to the same gentlemen.

M. Fourcroy (Système des Connaissances Chimiques, tome iii, p. 122.) among other products of the combustion of powder, mentions ammonia. If ammoniacal gas be formed, the hydrogen must proceed from decomposed water, and the azote from the nitric acid. Prussine, cyanogen, or carburet of nitrogen, the radical of prussic acid, may also be generated by the union of carbon and nitrogen or azote, in the same manner. We know that cyanogen may exist in the form of gas; but as it is inflammable, burning with a bluish flame mixed with purple, we may infer, nevertheless, that, if generated, it must undergo decomposition by the process of combustion. Although I know of no experiments on this subject, either by Gay-Lussac, Vauquelin or Davy, all of whom have investigated the properties of this compound of carbon and azote, which Dr. Ure has called prussine; yet it would appear, that during its combustion, the carbon is changed into carbonic acid, and whether the azote be also combined with oxygen, or merely set at liberty, is altogether uncertain. Many difficulties present themselves to a complete and satisfactory set of experiments on the gaseous products of fired gunpowder.

With respect to the granulation of powder, we may observe, that although some writers consider that granulated powder is stronger than the fine powder, yet others are of opinion, that its strength is not increased by granulation. Grained powder is more fit for use; but the graining of it prevents the whole of the powder from taking fire instantaneously. Gunpowder, although prepared in the best manner, is not wholly consumed by inflammation. However remarkable it may appear, yet nevertheless it is true, that a considerable portion of gunpowder fired in a confined space is thrown out without being kindled. That gunpowder passes through a volume of fire without being consumed, may seem incredible, yet the fact may be proved by firing with a musket upon snow, or upon a paper screen.

M. Morveau communicated to the Institute some experiments, which may be seen in the Archives des Découvertes, i, p. 269, relative to the time necessary for the inflammation of a given mass of gunpowder, &c. He infers that large grain powder inflames more readily than the fine grain.

Since during the combustion of powder, gaseous bodies more or less considerable are generated, it follows that the full force of fired gunpowder must depend on the maximum of the quantity of those gases; and the powder is more strong as it is susceptible of forming more gas in a given time. Besides the purity and the proper proportion of the materials, the gunpowder, to produce the greatest possible effect, should not only be intimately mixed, but dried perfectly and with care.

It is a fact which is well known, that a musket, fowling piece, &c. are very apt to burst, if the wadding is not rammed down close to the powder. Hence it is obvious, that in loading a screw barrel pistol, care should be taken that the cavity for the powder be entirely filled with it, so as to leave no space between the powder and the ball.

Experience has shown, that if a shell is only half or two-thirds filled with gunpowder, it breaks into a great number of pieces, and on the contrary, if completely filled, it separates only into two or three pieces, which are thrown to a very great distance.

It is also found that the same principle, of leaving a space for air, is applied with success in blasting rocks, and splitting trunks of trees. If the trunk of a tree is charged with gunpowder, and the wadding is rammed down very hard upon the powder, in that case (unless the quantity of powder is great,) the wadding is only driven out, and the tree remains entire; but if, instead of ramming the wad close to the powder, a certain space is left between them, the effects of the powder are then such as to tear the tree asunder.

Addison (Travels through Italy and Swisserland) speaking of the celebrated Grotto Del Cani, which contains carbonic acid gas, and on that account extinguishes flame, and is fatal to animal life, observes, that he laid a train of gunpowder in the channel of a reed, and placed it at the bottom of the grotto, and on inflaming it, that it burnt entirely away, although the carbonic acid gas in the same spot would immediately extinguish a lighted taper, snuff and all; for, he remarks, fire is as soon extinguished in it as in water. If gunpowder did not contain within itself that which was necessary to produce combustion, how are we to account for its combustion in an atmosphere of carbonic acid gas, or in vacuo?

Whether gunpowder be fired in a vacuum or in air, a permanently elastic fluid is generated, the elasticity or pressure of which is, cæteris paribus, directly as its density.

Gregory, (Treatise on Mechanics, &c. ii, p. 56) has given a summary of the results of the experiments of Mr. Robins, which we insert verbatim. "To determine the elasticity and quantity of this fluid (the elastic) produced from the explosion of a given quantity of gunpowder, Mr. Robins premises, that the elasticity increases by heat, and diminishes by cold, in the same manner as that of the air; and that the density of this fluid, and consequently its weight, is the same with an equal bulk of air, having the same elasticity at the same temperature. From these principles, and from the experiments by which they are established (for a detail of which we must refer to the book itself,) he concludes that the fluid produced by the firing of gunpowder, is nearly ³/₁₀ths of the weight of the generating powder itself; and that the volume or bulk of this air or fluid, when expanded to the rarity of common atmospheric air, is about 244 times the bulk of the said generating powder. Count Salace in his Miscel. Phil. Math. Soc. Priv. Taurin, p. 125, makes the proportion as 222 to 1; which he says agrees with the computation of Messrs. Hawkesbe Amontons, and Belidor. Hence it would follow that any quantity of powder fired in any confined space, which it adequately fills, exerts at the instant of its explosion against the sides of the vessel containing it, and the bodies it impels before it, a force at least 244 times greater than the elasticity of common air, or, which is the same thing, than the pressure of the atmosphere; and this without considering the great addition arising from the violent degree of heat, with which it is endued at that time; the quantity of which augmentation is the next head of Robins's inquiry.

He determines that the elasticity of air is augmented in a proportion somewhat greater than that of 4 to 1, when heated to the extremest heat of red-hot iron; and supposing that the flame of fired gunpowder is not of a less degree of heat, increasing the former number a little more than four times, makes nearly 1000; which shows that the elasticity of flame, at the moment of explosion, is about 1000 times stronger than the elasticity of common air, or than the pressure of the atmosphere. But, from the height of the barometer, it is known that the pressure of the atmosphere upon every square inch is on a medium of 14³/₄ths, and therefore 1000 times this, or 14750 lbs. is the force of pressure of inflamed gunpowder, at the moment of explosion, upon a square inch, which is very nearly equivalent to six tons and a half. This great force, however, diminishes as the fluid dilates itself, and in that proportion; viz. in proportion to the space it occupies, it being only half the strength, when it occupies a double space, one-third the strength, when a triple space, and so on. Mr. Robins further supposed the degree of heat above mentioned to be a kind of medium heat; but that in the case of large quantities of powder the heat will be higher, and in very small quantities lower; and that therefore in the former case the force will be somewhat more, and the latter somewhat less, than 1000 times the force of the atmosphere.

He further found, that the strength of powder is the same in all variations in the density of the atmosphere: but that the moisture of the air has a great effect upon it; for the same quantity which in a dry season would discharge a bullet with the velocity of 1700 feet in one second, will not in damp weather give it a velocity of more than 12 or 1300 feet in a second, or even less, if the powder be bad, or negligently kept. Robins's Tracts vol. i, p. 101, &c. Further, as there is a certain quantity of water, which, when mixed with powder, will prevent its firing at all, it cannot be doubted but every degree of moisture must abate the violence of the explosion; and hence the effects of damp powder are not difficult to account for.

The velocity of expansion of the flame of gunpowder, when fired in a piece of artillery, without either bullet or other body before it, is prodigiously great, viz. 7000 feet per second. But Mr. Bernoulli and Mr. Euler think it is still much greater.

Dr. Hutton, after applying some requisite corrections to Mr. Robins's numbers, and after remarking that the powder does not all inflame at once, as well as that about ⁷/₁₀ths of it consist of gross matter not convertible into an elastic fluid, gives

for the initial velocity of any ball of given weight and magnitude, and

for the value of the initial force n of the powder in atmospheric pressures: when a = length of the bore occupied by this charge, b = whole length of the bore, d = diameter of the ball, w = its weight, 2 p = weight of the powder, q = ^a/_d. In his experiments and results, he found n to vary between 1700 and 2300, and the velocity of the flame to vary between 3000 and 4732; specifying, however, the modification in his computations, which would give more than 7000 feet per second for that velocity. Taking 2200 for an average value of n, and substituting 47 for its square root in the above formula for v, it becomes

for the velocity of the ball, a theorem which agrees remarkably well with the Doctor's numerous and valuable experiments. (Tracts, vol. iii, p. 290, 315.)

In a French work entitled, "Le Mouvement Igné considéré principalement dans la charge d'une pièce d'artillerie," published in 1809, there are advanced, among other notions which we apprehend few philosophers will be inclined to adopt, some which may demand and deserve a careful consideration. The author of this work observes, that if a fluid draws its force partly from a gaseous or aeriform matter, and partly from the action of caloric, which rarefies that aeriform matter; then its density in proportion to its dilatation, will follow the inverse ratios of the squares of the spaces described. He then investigates two classes of formulæ: the first appertains to fluids which possess simply the fluid or aeriform elasticity, which are free from all heat exceeding the temperature of the atmosphere. Whether there be one or many gaseous substances signifies not, provided their temperature agrees with that of the atmosphere; for when these dilate they conform to the inverse of the spaces described. The second relate to those which derive their elasticity as well from the aeriform fluids, as from the matter of heat which pervades them, and which are denominated fluids of mixed elasticity, to distinguish them from those of simple or purely aeriform elasticity. These fluids, in dilating, conform to the inverse ratio of the squares of the spaces described. Thus the celerity of action of mixed elastic fluids, is to that of simple elastic fluids as S² to S; whence it follows that mixed elastic fluids are more prompt and energetic in their action than others; and hence also is inferred why the fluid produced by the combustion of gunpowder, is more impetuous and more terrible in its operation than atmospheric air, however compressed it may be. The force exerted by the caloric to dissolve a quantity of powder, is regarded as equal to that possessed by the fluid which results from that dissolution, and is named the force of dissolution of powder by fire: and the surface of least resistance is that (as of the ball,) which yields to the action of the fluid. The gunpowder subjected to experiment by this author, was of seven different qualities, varying from 1000, the density of water, down to 946, the density of powder used by sportsmen. It was found by theory, and confirmed by experiment, that the real velocity with which the elastic fluid, considered under the volume of the powder, and penetrated by a degree of heat capable of quadrupling the volume, would expand, when it had only the resistance of the atmosphere to surmount, is 2546.49 feet, that is, about 2734.4 feet English.

Comparing the several forces which were calculated for the same quantity of powder, in three different circumstances:

1. When the fluid has only to surmount the atmospheric pressure, it has a force of dissolution which is proper to it, and which in a charge of 8 lbs. of powder (the specific gravity 944.72, for a 24 pounder,) acts upon the surface of the least resistance with an energy equivalent to 9747.8074 lbs.

2. The fluid retarded in its expansion by a surface of least resistance, whose tenacity (occasioned by the compactness and pressure of the wadding, &c.) is t = 31, acquires by its elasticity of force = 52839.1463 lbs. at the instant when that surface yields to its action.

3. If the tenacity t = 298 lbs., the force of the fluid at the moment when the resisting surface yields to it, will be equivalent to 417371.4275 lbs. If each of these forces be divided by the surface of least resistance, the quotient will indicate the equation of each filament, namely, 1st. That of the force of dissolution = 173.63 grains; 2d. when t = 31 lbs. that of elasticity = 923.26 grains; 3d. when t = 298 lbs. force elastic equal to 7433.99 grains.

Dividing again these latter values by the length of the charges, we shall have for the mean force of each elementary fluid particle,

1. Force of dissolution, 0.14205 grains.

2. When t = 31 lbs. the force elastic = 0.75540 grains.

3. When t = 298 lbs. the force elastic = 6.08174 grains.

It appears, however, that equal charges of powder of the same quality employed in the same piece, produce very different velocities; the more considerable being the resistance to the expansion of the fluid, the less the velocity becomes. Thus, it is found, when t = 31 lbs. the velocity of the ball when expelled at the mouth of the piece, is 1563.6 feet: when t = 298 lbs. v = 1350.9 feet.

The following table will exhibit in one view the velocities with which a 24 lb. ball issues from the mouth of a gun, when propelled with the several charges expressed in the first column.

1st. According to the theory developed in the volume, from which we have made these extracts.

2d. According to the experiments of M. Lombard, at Auxerre, on guns for land service.

3d. According to the experiments of M. Teixiere de Norbec, at Toulon, on guns for sea service.

4th and 5thly. According to the determination of Mr. Robins and Dr. Hutton.

It is the prodigious celerity of expansion of the flame of fired gunpowder, which is its peculiar excellence, and the circumstance in which it so eminently surpasses all other inventions, either ancient or modern; for as to the momentum of these projectiles only, many of the warlike machines of the ancients produced this in a degree far surpassing that of our heaviest cannon, shot or shells; but the great celerity given to them cannot be approached with facility by any other means than the explosion of powder."

Dr. Hutton, in conjunction with several able officers of the artillery and other gentlemen, made an extensive course of experiments at Woolwich, at the expense of the British government, by the direction of the then master-general of the ordnance, (the late duke of Richmond,) in the years 1783, 1784, and 1785, which demonstrated the following facts:

1. That the velocity continually increases as the gun is longer, though the increase in velocity is but very small in respect of the increase in length; the velocities being in a ratio somewhat less than that of the square roots of the length of the bores, but somewhat greater than the cube roots of the same, and nearly indeed in the middle ratio between the two.

2. That the charge being the same, very little is gained in the range of a gun, by a great increase of its length; since the range or amplitude is nearly as the fifth root of the length of the bore, and gives only about a seventh part more range with a gun of double length.

3. That with the same gun and elevation, the time of the ball's flight is nearly as the range.

4. That no sensible difference is produced in the range or velocity, by varying the weight of the gun, by the use of wads, by different degrees of ramming, or by firing the charge of powder in different parts of it.

5. That a great difference, however, in the velocity, is occasioned by a small variation in the windage; so much so, indeed, that with the usual windage of one-twentieth of the caliber, no less than between one-third and one-fourth of the whole charge of the powder escapes and is entirely lost; and that as the windage is often greater, one-half the powder is unnecessarily lost.

6. That the resisting force of wood to balls fired into it, is not constant, and that the depths penetrated by different velocities, or charges, are not as the charges themselves, or, which comes to the same thing, as the squares of the velocities.

7. That balls are greatly deflected from the direction they are projected in, sometimes, indeed, so much as 300 or 400 yards in a range of a mile, or almost a fourth part of the whole range, which is nearly a deflection of an angle of 15 degrees.

The observations of Glenie, (History of Gunnery, 1776,) show the theory of projectiles in vacuo by plain geometry, or by means of the square and rhombus; with a method of reducing projections on inclined planes, whether elevated or depressed below the horizontal plane, to those which are made on the horizon.

This author, in his treatise, after stating in page 48, the two following positions of Mr. Robins, namely, "that till the velocity of the projectile surpasses that of 118 feet in a second; the resistance of the air may be estimated to be in the duplicate of the velocity;" that "if the velocity be greater than that of 11 or 1200 feet in a second, the absolute quantity of the resistance will be nearly three times as great as it should be by a comparison with the smaller velocities;" says, that he is certain from some experiments, which he and two other gentlemen tried with a rifle piece properly fitted for experimental purposes, that the resistance of the air to a velocity somewhat less than that mentioned in the first of these proportions, is considerably greater than in the duplicate ratio of the velocity; and that to a celerity somewhat greater than that stated in the second, the resistance is less than that which is treble the resistance of the same ratio. He observes, also, that some of Mr. Robins's own experiments come to this conclusion; since to a velocity no quicker than 200 feet in a second, he found the resistance to be somewhat greater than in that ratio, and remarks, therefore, that "after ascertaining the velocities of the bullets with as much accuracy as possible, I instituted a calculus from principles which had been laying by me for some time before, and found the resistance to approach nearer to that, which exceeds the resistance in the duplicate ratio of the velocity, by that which is the ratio of the velocity, than to that, which is only in the duplicate ratio."

The experiments of Mr. Dalton, confirm the premises of Mr. Robins, that the elasticity of the gases produced from a given quantity of powder, is equally increased by heat and diminished by cold as that of atmospheric air. Hence, as we before remarked, and from direct experiments, he concludes that the elastic fluid produced by the firing of gunpowder, is nearly three-tenths of the weight of the powder itself, which, expanded to the rarity of common air, is about 244 greater than the elasticity of common air, or in other words, than the pressure of the atmosphere. To this, however, must be superadded the increase of expansive power produced by the heat generated, which is very intense. The mere conversion of confined powder into elastic vapour, would exert against the sides of the containing vessel, an expansive force 244 times greater than the elasticity of common air, or, in other words, than the pressure of the atmosphere. If the heat, for the expansion of the gases, should be equal to that of red-hot iron, this would increase the expansion of common air, (and also of all gases) about four times, which in the present instance would be as we stated in the preceding pages, 244 to nearly 1000; so that in a general way it may be assumed, that the expansive force of closely confined powder at the instant of firing, is 1000 times greater than the pressure of common air; and as this latter is known to press with the weight of 14³/₄ pounds on every square inch, the force of explosion of gunpowder is 1000 times this, or 14750 lbs. or about six tons and a half upon every square inch. This enormous force diminishes in proportion as the elastic fluid dilates, being only half the strength when it occupies a double space, one-third of the strength when in a triple space, and so on.