Part 1 — CHAPTER II. (continued 2)

Phosphorus in the state of acidification, and united with lime, is found in abundance. Whole mountains in the province of Estremadura in Spain, are said to be composed of this combination. According to Mr. Bowles, this stone is whitish and tasteless, and affords a blue flame without smell when thrown upon burning coals. Mr. Proust observes, that it is a dense stone, not hard enough to strike fire with steel, and is found in strata, which always lie horizontally upon quartz, and which are intersected with veins of quartz. He adds, that it does not decrepitate on burning coals, but burns with a beautiful green light. This stone is the common phosphorite. It contains, according to Klaproth, 32.25 per cent. of phosphoric acid.

Several substances are known under the name of phosphorus, although they do not contain it, such as Baldwin's phosphorus, or ignited muriate of lime, Canton's phosphorus, or oyster-shells calcined with lime, and Bologna phosphorus, or calcined sulphate of barytes.

Sec. VI. Of Charcoal.

Charcoal performs an important part in all the various kinds of fire-works. The facility with which it decomposes nitric acid, when it is combined with salifiable bases, as with potassa in saltpetre, and its action in all cases wherein nitre is concerned, are sufficient examples of its effect.

Pure carbon is the diamond. It affords by combustion in oxygen gas, the same gas as common charcoal, when charcoal is burnt in oxygen, or in atmospheric air. This gas is carbonic acid, or fixed air. Charcoal has been considered a long time an oxide of carbon, and according to some, as Berthollet, a compound of carbon, hydrogen, and oxygen.

Charcoal is insoluble in water. It is not affected by the most violent heat, if confined in close vessels. It is an excellent conductor of electricity, but a bad conductor of heat. It is very indestructible; and, therefore, when wood is charred, it will remain a long time under ground without rotting. As an antiseptic, it is powerful. It will therefore prevent the putrefaction of bodies, and even recover tainted meat. As a preservative of water, for sea-voyages, it has been long known. The charring of water casks is designed for the same purpose. The quality of wine is said to be improved by having the casks previously charred. It possesses the property of absorbing gases, and to this property is ascribed its use as an antiseptic, and its disinfecting quality. To the distiller it is useful, as it destroys effectually the burnt or empyreumatic smell of liquor. When heated to eight hundred degrees in the open air, it burns. In oxygen gas the combustion is brilliant, forming in both instances carbonic acid gas, called also aerial acid, fixed air, mephitic air, and calcareous acid. This acid is formed in a variety of processes, and is carbon saturated with oxygen.

Carbon exists in various states of combination, and many of the compounds into which it enters are inflammable; hence carbonic acid is generated in the combustion of coal, oils, fat, &c. In the form of an acid, it is abundant in various stones, such as the calcareous carbonates, as chalk, marble, limestone, and calcareous spar, barolite, &c. all which effervesce with acids, the carbonic acid being liberated. When limestone is burnt, to obtain quicklime, the carbonic acid is disengaged, for the presence of this acid distinguishes limestone from pure lime. Carbonic acid is generated in various processes of nature as well as art. Hence it is produced in the respiration of animals, and is found in a gaseous state in wells, cellars, caverns, &c. It neither supports animal life, nor combustion. In mines it is called choke damp; and the Grotto del Cani, in the kingdom of Naples, has been long celebrated, on account of it. This cave is in the side of a mountain, near the lake Agnano, measuring not more than eighteen feet from its entrance to the inner extremity; where if a dog or other animal that holds down its head be thrust, it is killed by the gas. Some experiments were made in this cave with gunpowder, which see. Carbonic acid, during the formation of alcohol, in the vinous fermentation, is generated, and its production appears to be designed by nature to carry off the excess of carbon, which gives rise to that phenomenon called fermentation. When combined with water, it forms aerated water, and with alkalies and water, the aerated alkaline waters. Its union with bases forms salts called carbonates. Plants have the property of decomposing it, and in this respect nature has employed a mean of regenerating the atmosphere, on the purity of which depends, in an eminent degree, the very existence of animal life. The prime equivalent of carbonic acid is 2.75, and carbonic acid is composed of carbon 0.75 + 2.0 oxygen.

Carbonic acid may be decomposed when combined with a base, as lime, by phosphorus and heat, for charcoal and a phosphate of lime will be produced. But carbonic acid in the state of gas may be decomposed by potassium. Five grains of potassium will decompose three cubic inches of gas, and be converted into potassa, producing at the same time three-eighths of a grain of charcoal. If passed over a coil of fine iron wire heated to redness, in a porcelain tube, and the operation repeated, the iron will be oxidized, and the carbonic acid changed into carbonic oxide gas.

Charcoal will not burn in dry chlorine. It unites with a less proportion of oxygen, and forms carbonic oxide gas, which burns with a deep blue flame. This combination is formed by distilling in a red heat, a mixture of equal parts of iron filings and chalk. This gas mixed with chlorine gas, and exposed to the sun's rays, will unite with it, and form chlorocarbonic acid gas. Carbon unites with azote, and forms cyanogen, the base of Prussic acid. It unites likewise with hydrogen in two proportions, forming the hydroguret and the bihydroguret of carbon, both of which are carburetted hydrogen gases. The former is obtained by distilling a mixture of four parts of sulphuric acid, and one of alcohol. The gas is very inflammable, and burns with great splendour; and on that account may be used for exhibition, in an apparatus similar to that of Cartwright. (See Fire-works with Inflammable air.) It was called by the German chemists olefiant gas. The other species, called also the light carburetted hydrogen gas, may be obtained by agitating the mud at the bottom of stagnant pools; and by the distillation of moist charcoal, wood, pitcoal, pitch, or almost any animal or vegetable substance. The gas, used for gas-lights, is the same. It is usually obtained from pit coal. We may merely observe, that the gas used for that purpose, i. e. for illuminating streets, theatres, manufactures, &c. as obtained in the common method, is not altogether the bihydroguret of carbon; but, according to the experiments of Dr. Henry, a mixture of that gas with the hydroguret, and occasionally carbonic oxide.

Carbon enters into other combinations. It exists as a component part of gums, resins, sugar-starch, and other vegetable products, as the vegetable acids, its union with iron forms steel, a substance greatly used in the preparation of some fire-works, especially in some of the rains and stars, and in the composition of brilliant fire. (See Iron.)

As charcoal enters into the composition of gunpowder, and the effective force of powder depends considerably on the quality, as well as the proportion of charcoal, it is obvious for this purpose, it should be as pure as possible.

Carbon is always obtained from some of its combinations, as from pitch, tar, rosin, wood, and oil. Various processes are employed for this purpose. Thus, by the combustion of rosin and oil, as well as pitch, tar, turpentine, &c. a soot is formed that collects, called lampblack, which is nothing more than the carbon or charcoal. When pit-coal is charred in an oven, called a coke oven, all the bitumen and sulphur contained in it are disengaged, and a charcoal remains, called, however, coke. Wood, when charred is decomposed; all the volatile parts are disengaged with carburetted hydrogen gas, and the woody fibre is converted into coal. This coal is more or less dense according to the compactness of the wood. Hard woods furnish the most solid coal, and light woods on the contrary.

When the solid parts of animals, as bone, are charred, the volatile products, principally ammonia or volatile alkali, are dissipated, and there remains a substance called bone-black, improperly called, ivory black.

The carbonization of wood in the common way is well known: after it is cut to the lengths required, it is piled on the ground in a pyramidal form, and covered with sod and clay, leaving a place for the current of air, and the smoke. The wood is then set on fire, and when the whole is burnt to a coal the vents, &c. are closed with sod and clay.

Nicholson (Chemical Dictionary) observes, that in the forest of Benon, near Rochelle, great attention is paid to the manufacture, so that the charcoal made there fetches twenty-five or thirty per cent. more than any other. The wood is that of the black oak. It is taken from ten to fifteen years old, the trunk as well as the branches, cut into billets about four feet long, and not split. The largest pieces, however, seldom exceed six or seven inches in diameter. The end that rests on the ground is cut a little sloping, so as to touch it merely with an edge, and they are piled nearly upright, but never in more than one story. The wood is covered all over about four inches thick with dry grass or fern, before it is enclosed in the usual manner with clay; and when the wood is charred, half a barrel of water is thrown over the pile, and earth to the thickness of five or six inches is thrown on, after which it is left four-and-twenty hours to cool. The wood is always used in the year in which it is cut.

Turf or peat has been charred lately in France, it is said, by a peculiar process, and, according to the account given in Sonnini's Journal, is superior to wood for this purpose. Charcoal of turf kindles slower than that of wood, but emits more flame, and burns longer. It boiled a given quantity of water four times, while an equal weight of wood charcoal boiled the same quantity but once. In a goldsmith's furnace, it fused eleven ounces of gold in eight minutes, while wood charcoal required sixteen. The malleability of the gold, too, was preserved in the former instance, but not in the latter. Iron heated red-hot by it, in a forge, was rendered more malleable.

In charring wood it has been conjectured, that a portion of it is sometimes converted into a pyrophorus, and that the explosions that happen in powder-mills are sometimes owing to this.

Bartholdi supposes, that such explosions are owing to the formation of phosphoretted hydrogen gas, while others attribute them to the absorption of oxygen, by the hydrogen contained in the coal, and the consequent evolution of free caloric. Percussion, which necessarily takes place in mixing the materials of gunpowder by stampers, no doubt accelerates the combustion. The addition of water, and having the charcoal previously pulverized, will prevent such accidents. (See Gunpowder.)

Coal prepared in the manner above stated, is liable to many foreign admixtures, nor can the process be so well regulated as to produce coal of a uniform quality throughout. The present improved process has many advantages, as experience has proved. It consists in charring the wood in confined vessels, made of iron. These are usually cylindrical, furnished with an iron cover, and placed in furnaces. The pyroacetic, formerly called the pyroligneous, acid, which is formed in the destructive distillation of wood, is caught for use. This acid is useful to the calico printer, dyer, &c. in making their iron liquor, and when purified, is employed in Europe in the place of vinegar, as it is more pungent, and highly concentrated.

When pine and various kinds of wood, which yield turpentine, are carbonized, we obtain tar during the process.

Chaptal informs us, that tar is obtained from the wood of the trunk, branches, and roots of the pine, which are heaped together, covered with turf, and set on fire to produce a close combustion, in the same manner as for making charcoal. The oily parts which are disengaged, trickle down, and are received in a gutter, which serves to convey them to a tub. The most fluid part is sold under the name of huile de cade; and the thicker part is the tar used for paying or painting the parts of shipping and other vessels.

According to the wood submitted to the process of charring, the products are, more or less, various; but in all cases it is only the solid part, or ligneous fibre, that furnishes the coal. By the ordinary process we obtain sundry volatile products, among which are pyroacetic acid and carburetted hydrogen gas.

When wood is carbonized in the usual manner, it yields from 16 to 17 parts of charcoal in the hundred; but when the operation is conducted in close vessels, the product is 28 per cent. a saving of eleven or twelve per cent. By this difference in the quantity, it appears that eleven or twelve per cent. is burnt in the common process.

M. Mollerat was the first who tried the experiment with iron cylinders.

M. Vauquelin (Annales de Chimie, tome lxvi, p. 174) has given some observations on the carbonization of wood in close vessels, predicated on a Memoir of M. Mollerat; both of which are interesting. The apparatus used by M. Mollerat is described by Thenard, (Traité de Chimie, iii, p. 373,) to be composed of two parts, viz: a furnace with a moveable dome, and a cylindrical kettle, or vessel of iron sufficiently large to contain a cord of wood. It is furnished with a cover and pipe. The pyroacetic acid is collected. Smaller cylinders are preferred, because the wood is ignited more readily and the charcoal is more of a uniform quality.

From 100 parts of the following named woods, Messrs. Allen and Pepys (Phil. Trans. 1807) obtained the following proportional parts of charcoal:

Beech15.00 Oak17.40

Mahogany15.75 Fir18.17

Lignum Vitæ17.25 Box20.25

See also the experiments of Mr. Mushet, in the third volume of Tilloch's Magazine.

It appears by the Annales de Chimie, vol. 66, and the Retrospect of Discoveries, vol. vi, p. 100, that three brothers have established at Pellerey, near Nuits, Cote d'Or, a manufactory on a large scale, for making charcoal in close vessels.

The quantity of charcoal they obtained is double that by the usual mode, while it requires only one-eighth part of wood to be consumed in the distillation; it is also better than the common, as a given quantity evaporates one-tenth more water than the other; hence iron masters may obtain twice as much iron from the use of a given quantity of wood; and in addition to this, there is also prepared a number of other articles, of each of which in order.

350 kilogrammes (700 lbs.) of wood, yield 25 or 30 of tar, which retains so much acid that it is soluble in water; but when it is washed, and rendered thick by boiling, for some time, it offers more resistance to water. If mixed with one-fifth of rosin it is rendered equally fit for the use of ships, &c. as the common tar.

Four sorts of vinegar are prepared, all of which are perfectly limpid, which do not, like the common, contain any tartar, malic acid, resinous or extractive matter, nor indeed any mineral acid, lime, copper, or other substances. The simple vinegar marks—2° hydrometer for salts, at 12° centigrade thermo. it is stronger tasted than common vinegar, and produces a disagreeable irritation. The aromatic vinegar is prepared with tarragon, the smell is agreeable, but it has the same fault as the former. The vinous vinegar is formed by adding some alcohol to simple vinegar; it has a very sensible odour of acetic ether; the alcohol softens the flavour in some degree, but the vinegar is still very sharp. The acid, called strong vinegar, is in fact a very good acetic acid at 10¹/₂° hydr., it is very white, clear, and sharp, without the usual burnt flavour, and seems to form the basis of the preceding kinds. It can be sold for 8 or 9 francs (7s.) per lb. which is only half the price of that distilled from verdigris. Although not so agreeable to the taste as common vinegar, these new kinds are more elegant to the eye, and do not mother.

The editor of the Retrospect makes the following observations:

The proprietors of this manufactory seem to be perfectly aware of all the several productions which could be prepared from the refuse of their principal object; and we have no doubt but that the substances they procure in this manner will amply compensate them for the use of the capital that must be invested in building the furnaces.

The nature of the vessels in which they distil the wood is not mentioned, but they are probably cast iron retorts, or vessels of a similar nature, in which a distillation per latus takes place. The application, therefore, of lord Dundonald's furnaces for procuring coke to this purpose would be still more advantageous.

A cubic yard of wood yields 100 quarts of acid liquor, besides 50 or 60 lbs. of thick oil.

The method of making charcoal of a uniform quality, for which a Mr. Kurtz has taken out a patent, is the following:

A sheet-iron chest, which has a cover that fits it tight, and a pipe, or tube, that descends nearly to the bottom, and coming out from its side above, is fixed in brick work. In this the billets of wood are put. Fire is then made underneath. It is obvious, that the wood is kept at one temperature from its being immersed in vapour, as the vapour cannot escape at the top, but must descend to the bottom, and then proceed up the pipe, by which it is conveyed away. The effect is, that the charring process goes on regularly, and the wood is charred equally. The carbonization is finished when the vapour ceases to appear, and nothing but carburetted hydrogen gas escapes. The charring of bones is performed in iron cylinders, furnished with tubes to receive, and convey away, the impure ammonia.

In the manufacture of powder, particular kinds of wood are selected for carbonization. These are generally, willow, hazle, maple, poplar, linden, buckthorn, or alder, or those which are tender and light, because, as they are less dense, and consequently more friable, they enflame and consume more rapidly: they are known in the arts by the name of white wood. When a less sudden effect is to be produced with the gunpowder, and the combustion prolonged, as in some sky-rockets, the charcoal of hard wood is to be preferred, such as the oak, beech, &c. When the wood is gathered, the bark is removed, and the wood exposed to the sun to dry: it is then cut into billets, and charred. The ashes, if any be formed, are to be carefully separated.

In considering the use of charcoal, therefore, for the preparation of gunpowder, we are to direct our inquiries to the choice of wood for carbonization, and the best process for carbonizing it. All light woods, we remarked, as the linden, willow, poplar, &c. furnish the lightest coal, and on that account are preferred. It is remarked, that tender wood, besides making a light, friable, and porous coal, is more combustible than ordinary hard, and more compact wood, and the coal that it furnishes leaves less residue after combustion.

Many experiments have been made with coal prepared from different kinds of wood, with a view of ascertaining the kind best adapted for the manufacture of gunpowder. M. Letort, at the powder mills of Essonne, in France, instituted a number of experiments of this kind. He made gunpowder with the coal of several kinds of wood, and compared its effects by a mortar eprouvette. The result was, that the powder made with the coal of poplar, was the strongest; and the other powder, made with the coal of the linden, willow, &c. was of the same quality throughout. As to the second inquiry, it is hardly necessary to repeat, that for the complete and thorough carbonization of the wood, to produce at the same time coal of a uniform quality, the process of charring in iron cylinders or close vessels, is to be preferred. The point to be attended to is, to bring the wood to a complete state of ignition, and consequently to disengage all the volatile or fluid parts. When the gas (carburetted hydrogen) ceases to appear, it is a criterion that the operation is finished. This gas, it is to be recollected, will come over even after the whole of the wood is completely ignited. The first volatile product is the pyroacetic acid. Some saturate the acid liquor with chalk, and decompose the acetate of lime with sulphate of soda, and separate the acetic acid from the acetate of soda by distillation with sulphuric acid. The acetic acid is then tolerably pure, and may be diluted for use.

It is observed, however, that when charcoal, prepared in iron cylinders, is designed for gunpowder, the last portion of vinegar and tar must be allowed to escape, and the reabsorption of the crude vapours prevented, by cutting off the communication between the interior of the cylinders and the apparatus for condensing the pyroacetic acid, whenever the fire is withdrawn from the furnace. If this precaution be not taken, the gunpowder made with the charcoal would be of inferior quality.

On a large scale, when the object is also to prepare the vinegar of wood, a series of cast-iron cylinders, about four feet diameter, and six feet long, are built horizontally, in brick-work, so that the flame of one furnace may play round about two cylinders. Both ends project a little from the brick-work. One of them has a disc of cast iron well fitted and firmly bolted to it, from the centre of which disc an iron tube about six inches diameter proceeds, and enters at a right angle, the main tube of the refrigeration. The diameter of this tube may be from 9 to 14 inches, according to the number of cylinders. The other end of the cylinder is called the mouth of the retort. This is closed by a disc of iron, smeared round the edge, with clay lute, and secured in its place by wedges. The charge of wood for such a cylinder is about 8 cwt. The hard woods, oak, ash, birch, and beech, are alone used. Fir does not answer. The heat is kept up during the day-time, and the furnace is allowed to cool during the night. Next morning the door is opened, the coal removed, and a new charge of wood is introduced. The average product of crude vinegar is 35 gallons. Its total weight is about 300 lbs. But the residuary charcoal, according to Ure, (Chemical Dictionary), from whom we have taken this account, is found to weigh no more than one-fifth of the wood employed. The crude pyroacetic acid is rectified by a second distillation, in a copper still, in the body of which about 20 gallons of viscid tarry matter are left for every 100. Its acid powers are now superior to the best household vinegar in the proportion of 3 to 2. Ure observes, that by distillation, saturation with quicklime, evaporation of the liquid acetate to dryness, and gentle torrefaction, the empyreumatic matter is so completely dissipated, that on decomposing the calcareous salt by sulphuric acid, a pure, perfectly colourless, and grateful vinegar rises in distillation. Pyroacetic acid is said to be a powerful antiseptic. M. Monge, Dr. Jorg, and more lately, Mr. Ramsay, of Glasgow, have made experiments with it. Fish dipped in it have been preserved for many days, and meat treated in the same manner, has also been preserved from putrefaction.

With respect to the pulverization of charcoal, the operation is so exceedingly simple, that we deem it unnecessary to notice it. It is obvious, that mortars, mills, &c. may be used, with fine or coarse sieves. For fire-works, charcoal is frequently pulverized in a leather sack, in the same manner as grained powder is reduced to meal-powder. It may be made either coarse or fine, to answer different purposes, by employing sieves of different kinds. Charcoal may be separated from nitre and sulphur, in gunpowder, by a simple process, which may be seen by referring to the section on gunpowder.

The quantity of carbon in coal, is directly proportionate to the quantity required for the decomposition of nitrate of potassa, a fact necessary to be considered in the theory of the action of charcoal in gunpowder. Thus, Mr. Kirwan found that, 12.709 of carbon are necessary to decompose 100 of nitrate of potassa. It will be easy to deduce the quantity of carbon, in a given weight of coal, from the quantity of nitrate of potassa it is capable of decomposing. The experiment is made very readily by fusing in a crucible, five hundred or more grains of nitre, and when red-hot projecting by degrees the powdered coal on the nitre. When the detonation produced by one projection of coal has ceased, add a new portion till it produces no farther effect.

Charcoal may be made intensely black, resembling ivory black, according to M. Denys-de-Montfort, (Bibliothèque Physico-Economique, for March 1815,) by pulverizing it very fine, mixing it with wine lees, and drying the mixture, and then subjecting it to a strong heat in a covered crucible, or other vessel.

Sec. VII. Of Gunpowder.

Having remarked, that the quality of gunpowder depends upon the purity of the materials, of which it is formed, and that they should be prepared in a state of purity; the subject that will now particularly claim our attention, is the proportions of the ingredients, their mixture, and the final preparation of gunpowder for use. To this, we purpose to add, the theory of its explosive effects, the different modes of proving it, and the experiments necessary to determine the quality of its respective ingredients, on all which we will be as brief as the importance of the subjects will admit. Previously, however, it may be interesting to notice the history of gunpowder, the invention of which has so completely changed the art of war.

The history of gunpowder has been fully treated by many writers of eminence; but by none more largely, and, at the same time, more satisfactorily than by the French. Beckman, in his History of Inventions, is full on this subject. Our purpose is not to go into details, as it would enlarge our volume, to the exclusion, perhaps, of other and more important matter. We shall, therefore, confine ourselves to a few facts and observations.

Notwithstanding much has been written on the subject, the original invention of gunpowder seems to be in obscurity. By whom, and at what time it was invented, is a question not fully settled. It is said to have been known in the east from time immemorial, and whatever claim Roger Bacon, who died in 1292, may have had to the discovery, or that he knew the properties of gunpowder, it is certain, that the use of fire-arms was then unknown in Europe.

Professor Beckman, who examined all the authors extant on the origin of gunpowder, is of opinion, that it was invented in India, and brought by the Saracens from Africa to the Europeans, who improved the preparation of it, and employed it in war, as well as for small arms and cannon.

M. Langles, who read a memoir on this subject to the National Institute, in 1798, observes, that the Arabians obtained a knowledge of gunpowder from the Indians, who had been acquainted with it from the earliest periods. The use of it was forbidden in their sacred books, the veidam or vede. It was employed in 690 at the battle near Mecca. As nitre was employed in all probability in the Greek fire, invented about the year 678, it is supposed, that that composition gave rise to the invention of gunpowder.

Various prescriptions, or formulæ, have been given for the preparation of this fire. The oldest is by princess Anna Commena, in which, however, there is only resin, sulphur, and oil. Beckman observes, that the first certain mention of saltpetre will be found in the oldest account of the preparation of gunpowder, which, in his opinion, became known in the thirteenth century, about the same time that the use of the Greek fire, of which there were many kinds, began to be lost. The oldest information on this subject is to be found in the works of Albertus Magnus, and the writings of Roger Bacon. The true recipe for making the Greek fire, and the oldest for gunpowder, were found in a manuscript, preserved in the electoral library at Munich. Various copies of this manuscript were made. Bacon employed this writing, which was mentioned by Jebb, in the preface to his edition, from a copy preserved in the library of Dr. Mead. Whether the writer was Marcus Græcus, is of no moment; for Cardan observes, that the fire that can be kindled by water, or rather not extinguished by water, was prepared by Marcus Gracchus.

The former Marcus, mentions two kinds of fire-works; and the composition, which he prescribes for both, is two pounds of charcoal, one pound of sulphur, and six pounds of saltpetre, well powdered and mixed together in a stone mortar.

Friar Bacon, who lived three centuries after Græcus, was in possession of the recipe. It was concealed, however, from the people, veiled in mystery. In his treatise De Secretis Operibus Artis et Naturæ, &c. the secret of the composition is thus expressed: "sed tamen salispetræ, LURU MOPE CAN URBE et sulphuris; et sic facies tonitrum et corruscationem, si scias artificium." Luru mope can urbe, is the anagram for carbonum pulvere. Bacon supposes, that it was with a similar composition that Gideon defeated the Midianites, with only three hundred men. Besides the use of gunpowder in the 9th century, in the war between the Tunisians and the Moors, in which the former are said to have employed "certain tubes or barrels, wherewith they threw thunderbolts of fire," the Venetians employed it against the Genoese, and it was reprobated as a manifest contravention of fair warfare.

Peter Mexia, in his "Various Readings," relates, that the Moors, being besieged, in 1349, by Alphonso the eleventh, king of Castille, discharged a kind of iron mortars upon them, which made a noise like thunder. This, with the sea-combat between the Tunisians and the Moors, stated on the authority of don Pedro, bishop of Leon, places the invention much earlier than by some writers.

Polydore Virgil ascribes the invention of gunpowder to a chemist, who, having put some of his composition in a mortar, and covered it with a stone, was blown up, in consequence of its accidentally taking fire. The person here alluded to, according to Thevet, was a monk of Friburg, named Constantine Anelzen. Others, as Belleforet, with more probability, hold it to be Bartholodus Schwartz, or the black, who discovered it, as some say, about the year 1320. Du Cange, however, remarks, that there is no mention made of gunpowder in the registers of the chamber of accounts in France, as early as the year 1338. Roger Bacon knew of gunpowder, near one hundred years before Schwartz was born. (See the invention of cannon, in military fire-works, fourth part.)

It is certain, that Albert de Bollstædt indicated the constituent parts of gunpowder, when he says, in his Mirabilis Mundi, "Ignis volans, accipe libram unam, sulphuris, libras duas, carbonas salicis, libras sex, salis petrosi, quæ tria subtilissime terantur in lapide marmorea; postea aliquid posterius ad libitum in tunica de papyro volante, vel tonitrum faciente ponatur.

"Tunica ad volandum debet esse longa, gracilis, pulvere illo optime plena, ad faciendum vero tonitrum brevis, grossa et semiplena."

Gunpowder was of a much weaker composition than that now in use, or that described by Marcus Græcus. Tartalgia, (Ques. and Inv. lib. 3, ques. 5), observes, that, of twenty-three different compositions, used at different times, the first, which was the oldest, contained equal parts of the three ingredients. When guns of modern construction came into use, gunpowder of the present strength was introduced.

The strength of powder depends upon the proportions of the ingredients, they being pure; and Mr. Napier observes, (Trans. Royal Irish Academy, ii.) that the greatest strength is produced, when the proportions are, nitre, three pounds, charcoal, nine ounces, and sulphur, three ounces. The cannon powder was in meal, and the musket powder in grain.

In the time of Tartalgia, the cannon powder was made of four parts of nitre, one of sulphur, and one of charcoal; and the musket powder of forty-eight parts of nitre, seven parts of sulphur, and eight parts of charcoal; or of eighteen parts of nitre, two parts of sulphur, and three parts of charcoal.

The intimate mixture, therefore, and the determinate proportions of saltpetre, charcoal, and sulphur, form gunpowder; the different qualities of which, depend, as well upon the proportions which are used, as on the purity of the materials, and the accuracy with which they are mixed.

Gunpowder is reckoned to explode at about 600° Fahr; but, if heated to a degree just below that of faint redness, the sulphur will mostly burn off, leaving the nitre and charcoal unaltered.

The saltpetre should be perfectly refined, and entirely free from deliquescent salts; the sulphur as pure as possible, and, for that reason, a preference should be given, to that which is sublimed, or distilled; and the charcoal should be prepared in iron cylinders, as described under that head, from woods, which are light and tender, as the linden, willow, hazle, dogwood, etc.

There is a considerable difference in the proportions used by different nations; but, from the many accurate and conclusive experiments of the French chemists, their formula is certainly the most perfect. In English powder, three-quarters of the composition are nitre, and the other quarter is made up of equal parts of charcoal and sulphur; but sometimes, to seventy-five parts of nitre, fifteen of charcoal is used, adding ten of sulphur. Their government powder is the same for cannon, as for small-arms.

According to a number of experiments, made at Grenille, it was found, that the proportion of saltpetre in gunpowder, must be in a given ratio with the charcoal, so that the latter might effectually decompose it in the act of combustion; and hence the ratio is as 12 of the latter to 75 of the former, and these, with 12 of sulphur, are the proportions generally employed. Ruggeri (Pyrotechnie Militaire, p. 91,) gives, as the proportions, 12 parts of saltpetre of the third boiling, 2 parts of charcoal, and 1 part of sulphur. The proportions, used in Sweden, are 75 saltpetre, 9 sulphur, and 16 charcoal; in Poland, 80 saltpetre, 8 sulphur, and 12 charcoal; in Italy, 76 saltpetre, 12 sulphur, and 12 charcoal; in Russia, 70 saltpetre, 11 sulphur, and 18¹/₂ charcoal; in Denmark, 80 saltpetre, 10 sulphur, and 10 charcoal; in Holland, 76 saltpetre, 12 sulphur, and 12 charcoal; in Prussia and Austria, 78 saltpetre, 11 sulphur, and 11 charcoal; and in Spain, 77 saltpetre, 11¹/₂ sulphur, and 11¹/₂ charcoal.

According to Klaproth and Wolff, (Dictionnaire de Chimie, translated into French by MM. Lagrange and Vogel), Berlin powder is composed of three-quarters nitre; one-eighth sulphur, and one-eighth charcoal; Chinese powder, of 16 parts nitre, 6 charcoal, and 4 sulphur; Swedish powder, of 75 parts nitre, 16 sulphur, and 9 charcoal; the powder of Lissa, of 80 nitre, 12 sulphur, and 8 charcoal; and English powder, on the authority of Beckman, as follows: Powder for war, 100 parts of nitre, 25 charcoal, and 25 sulphur; musket powder, 100 nitre, 18 sulphur, and 20 charcoal; pistol powder, 100 nitre, 23 sulphur, and 15 charcoal; strong cannon powder, 100 nitre, 20 sulphur, and 24 charcoal; strong musket powder, 100 nitre, 15 sulphur, and 18 charcoal; and strong pistol powder, 100 nitre, 10 sulphur, and 18 charcoal. German powder, for war, is composed, generally, of 0.70 saltpetre, 0.16 charcoal, and 0.14 sulphur. A small portion of gum is sometimes added, to make the grain firmer; but such additions retard the combustion, and the effect.

The addition of gum arabic, however small, must injure the quality of gunpowder, although it has the effect of making the grain firmer, and less liable to fall into meal powder. The grain is also made heavier, and less liable to absorb moisture. M. Proust, in his second memoir on gunpowder, mentions the use of icthyocolla, a fish glue, for the same purpose; and, nevertheless, speaks of some advantages that the gunpowder, prepared with it, possesses.

It is observed by Mr. Coleman, of the Royal Powder Mills of Waltham abbey, that it is not exactly ascertained, whether there is any one proportion, which ought always to be adhered to, and for every purpose. We have no hesitation in believing, for our own part, that the French formula is the most correct, from the numerous experiments made at the royal manufactory at Essone, near Paris.

A very considerable variation is found in the proportions of the ingredients of the powder of different nations and different manufactories. The powder made in England, is the same for cannon as for small arms, the difference being only in the size of the grains; but in France, it appears, that there were formerly six different sorts manufactured; namely, the strong and the weak cannon powder, the strong and the weak musquet powder, and the strong and the weak pistol powder. The following are the proportions in each, though the reason of this nicety of distinction is not very obvious. For the strong cannon powder, the nitre, sulphur, and charcoal were in the proportions of 100 of the first, 25 of the second, and 25 of the third: for the weak cannon powder, 100, 20, and 24: for the strong musket powder, 100, 18, and 20; for the weak, 100, 15, and 18: for the strong pistol powder, 100, 12, and 15; for the weak, 100, 10, and 18.

The Chinese powder appears, by the analysis of Mr. Napier, to be nearly in the proportions of 100 of nitre, 18 of charcoal, and 11 of sulphur. This powder, which was procured from Canton, was large-grained, not very strong, but hard, well coloured, and in very good preservation.

The following proportions are now used in France, for the manufacture of gunpowder for war, for hunting, and for mining.

For war.For the chase.For mining.

Saltpetre,75.07865.

Charcoal,12.51215.

Sulphur,12.51020.

After having made choice of the materials, the nitre being pulverized, is passed through a brass sieve; the sulphur is pulverized by means of a muller, or other contrivance, and also sifted in a bolter; the quantities are then weighed, as well as the charcoal.

The mixing of these substances is performed in a series of mortars, hollowed out of a strong piece of oak wood; and by the aid of pestles or stampers, which are set in motion by machinery and water power, the mixture is thoroughly made. The end of the stampers is usually covered with, and sometimes made of, brass, and the mortars are also, in some powder mills, lined with brass. The mill has generally two rows of mortars and stampers, of ten each. The nitre, sulphur, and charcoal, in proper proportions, are put into each mortar. The charcoal is first introduced into the mortar, being sometimes previously pulverized; then wetted with water, and the pounding is continued for thirty minutes. The nitre and the sulphur are then added, and the whole is stirred with the hand. More water is then added; it is again stirred, and the operation of pounding is continued. The object of adding the water is to prevent the so called volatilization of the ingredients, and to give the mixture the consistency of paste, and at the same time to prevent the explosion of the powder; a circumstance, which must be always guarded against.

After the operation is continued for half an hour, the pounders are stopt, and the powder is then re-exchanged by means of copper or brass ladles; that is to say, the powder of the first mortar is removed, and put into a box, and the contents of the second mortar are put into the first, that of the third is put into the second, that of the fourth into the third, &c. in succession, and in the last, the contents of the first mortar.

We make, in this manner, twelve exchanges, allowing one hour between two, and adding water from time to time, to the mixture, and especially during the summer months. After this, the pounders are again set in motion, for the space of two hours, and the operation is finished. Fourteen hours are generally required to complete the mixture, which is then in the form of paste. It is then granulated. After being partially dried, the graining is performed by passing it through sieves, which are more generally formed of parchment. These sieves are made to work horizontally, and the powder is caught in vessels placed beneath. The size of the grain depends on the sieve; hence, fine grain, or coarse grain powder is thus obtained. In the sieve is usually placed a contrivance to break the masses, and to cause the powder to pass through in grains. After this, the powder is again passed through a second sieve, commonly called a grainer, the holes of which are of the same diameter as the powder we wish to obtain. It is then put into another sieve, which permits only the dust to pass, whilst the grain-powder remains. As the powder, however, contains some grains too large, as well as others too small, we may separate the former by a fourth sieve, of a suitable size. The dust and fine grain are carried to the mill, and worked over. The powder for war, and for mining, is dried immediately after the graining.

Formerly, the powder was dried in the open air, by spreading it on tables lined with cloth, or in oblong boxes; but serious inconveniences resulted from it, and, particularly, the powdermakers were obliged to watch the temperature, as well as the state of the atmosphere. When the latter was moist, the drying was suspended.

M. Champy, however, has obviated these inconveniences by a very advantageous process, which consists in raising the temperature of the air to 50 or 60 degrees, and causing it to pass from the chamber in which it is heated, through cloths, on which is spread a bed of powder, of a certain thickness. By this means, large quantities of powder may be dried, in all seasons of the year, in a short time, and at little expense. In whatever manner the drying is performed, there is always more or less dust formed, which, to make the grain of one uniform appearance, must be separated by a hair sieve. This operation is called the dusting.

Whether we adopt the plan recommended by M. Champy, or heat the rooms for the drying of powder to a certain temperature, by means of steam pipes, a plan which presents every advantage, or use the old mode, the effect is the same.

The musket, or hunting powder, undergoes an operation more than the powder for war, namely, that of glazing, which is performed before it is dried. With the exception of this process, it is made in the same manner, using, however, a finer sieve in granulating it. The glazing has for its object the smoothing, or removing the asperities of the grain, and to prevent its falling into dust, and soiling the hands.

The powder intended for glazing is first exposed an hour to the sun on one cloth, in winter, and between two cloths in summer, in order to dry it more perfectly, which is very necessary before the operation of glazing. For this purpose, it is put into a vessel like a barrel, which is turned horizontally upon its axis, by machinery. This barrel is furnished with bars that go across, intended to augment the friction, or rubbing of the grain, and expedite the process. The barrels are made to turn slowly, to avoid breaking the grain, and at the expiration of eight or twelve hours, the glazing is finished, the powder having acquired a sufficient hardness and polish. After removing the powder, the dust is separated in the usual manner.

Gunpowder-mills are mills, in which powder is prepared, by pounding and beating together the ingredients of which it is composed. They are always worked by water-power, and as there are generally many of them belonging to the same manufactory, one dam of water will furnish a sufficient supply. In the construction of powder-mills, the frame of the house is made very stout, and the roof put on lightly, so that in case of explosion, it may be carried off easily, and thus give vent to the powder, without much injury to the works. The lights, to enable the work to be carried on at night, are placed on the outside of the building, beyond the reach of the powder, and by means of glass windows, the light passes into the mill. It is lamentable, indeed, that so many accidents occur in the operation of making powder. This may take place, as it has to our knowledge, by the friction of the pounders. Their weight, the rapid succession of the blows, and the dryness of the powder, are the principal causes of such accidents, and sometimes by the inattention of the workmen, suffering nails, and the like, to get among the materials. I once witnessed the effect of an explosion of the kind, in the neighbourhood of Frankford, in the vicinity of Philadelphia, at the old and well-known powder mills, at that place. It was produced, in consequence of the friction, by the neglect of the men not adding water at a proper time, to keep the materials moist. The mill in which the explosion took place was not much injured; but the roof, together with the men, were sent a considerable distance. Some of the latter fell into the mill-race, and were much injured. The effect, however, did not stop here; for the fire communicated, strange as it may appear, to some of the other mills, although at some distance, and blew them up. Several explosions have happened at the same mills.

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.