There is one more fact worthy of notice, that Mr. Robins found the strength of powder to be the same in all variations of the density of the atmosphere, but not so in every state of moisture, being much impaired by a damp air, or with powder damped by careless keeping, or any other cause; so that the same powder which will discharge a bullet at the rate of 1700 feet in a second in dry air, will only propel it about 1200 feet when the air is fully moist, and a similar difference was observed between dry and moist powder. The sum of these remarks, with the necessary illustrations, may be found in the extract we have given from Gregory's Mechanics.

Before we mention the different modes of proving powder, we will offer some remarks respecting the use of sulphur in gunpowder. The conclusions on this head are drawn from the experiments made at Essonne, near Paris.

The sulphur is not (properly speaking) a necessary ingredient in gunpowder, since nitre and charcoal alone, well mixed, will explode; but the use of the sulphur seems to be to diffuse the fire instantaneously through the whole mass of powder. But, if the following experiments are correct, it should seem that the advantage gained by using sulphur in increasing the force of explosion only applies to small charges; but in quantities of a few ounces, the explosive, or at least the projecting force of powder without sulphur, is full as great as with sulphur.

The following are a few out of many trials made at the Royal Manufactory at Essonne, near Paris, in the year 1756, to determine the best proportions of all the ingredients. Of powder made with nitre and charcoal alone, 16 of nitre and 4 of charcoal was the strongest, and gave a power of 9 in the eprouvette. With all three ingredients, 16 of nitre, 4 of charcoal, and 1 of sulphur, raised the eprouvette to 15, and both a less and a greater quantity of sulphur produced a smaller effect. Then diminishing the charcoal, a powder of 16 of nitre, 3 of charcoal, and 1 of sulphur gave a power of 17 in the eprouvette, which was the highest produced by any mixture. This last was also tried in the mortar-eprouvette against the common proof powder, and was found to maintain a small superiority. The powder made without sulphur in the proportions above indicated was also tried in the mortar-eprouvette, and with the following singular result: when the charge was only two ounces it projected a sixty pound copper ball 213 feet, and the strongest powder with sulphur projected it 249 feet; but in a charge of three ounces, the former projected the ball 475 feet and the latter only 472 feet; and on the other hand the great inferiority of force in the smaller eprouvette of the powder without sulphur has been just noticed.

It is a fact, known from time immemorial, that by the combustion of bodies caloric is generated, or chemically speaking, is given out in a free state; but the cause was not known until the anti-phlogistic theory of chemistry was established, which abolished as untenable the old doctrine of phlogiston; The quantity of caloric, which passes from a latent to a free state in combustion, as combustion is nothing more than the phenomena occasioned by this transition, is variable; and depends therefore on the substances burnt, and the nature of what is denominated the supporter of combustion.

The experiments of MM. Lavoisier and Laplace have shown the quantity of caloric produced by the combustion of different substances by the calorimeter, a table of which may be seen in Thenard. (Traité de Chimie, &c. t. i, p. 81). From this table it appears, that while a mixture of one pound of saltpetre with one pound of sulphur liquefied, by its combustion, thirty-two pounds of ice, one pound of hydrogen gas melted 313 lbs. phosphorus 100 lbs. and the same quantity of charcoal 96.351 lbs.; and by the detonation of a mixture of one pound of saltpetre with 0.3125 lbs. of charcoal (French weight) melted only 12 lbs. of ice.

In the table of the elevation of temperature by the combustion of different substances, the caloric being communicated to water, (Thenard, Traité de Chimie, vol. i, p. 82), it appears, that by the combustion of equal weights of hydrogen gas, phosphorus, charcoal, and oak, the caloric produced was as follows:

The reader may find some interesting calculations on this subject in Biot's Traité de Physique, &c. tome iv, p. 704, and 716.

It appears also, that in the combustion of one pound of hydrogen gas, six pounds of oxygen were consumed, and according to Crawford's experiment the caloric given out melted 480 lbs. of ice. One pound of phosphorus requires for combustion one and a half pounds of oxygen gas; one pound of charcoal, 2.8; and one pound of sulphur, 1.36. See Thomson's System of Chemistry, vol i, p. 133.

While noticing this subject we may remark, that in combustion heat and light, according to the Lavoiserian doctrine, are given out from the oxygen gas, while the oxygen unites with the combustible body: which has since been modified by supposing, that while caloric is evolved from the gas, the light is emitted from the burning body. There are some facts contrary to the received theory of combustion; that of gunpowder furnishes one. We have also another instance in the combustion of oil of turpentine by nitric acid.

Gunpowder will burn with great avidity in close vessels, or under an exhausted receiver, and we know that the oxygen is already combined with azote in the nitric acid of the nitrate of potassa, and consequently not in a gaseous but a solid state; yet we also know that a great quantity of caloric and light are emitted during the combustion, and nearly all the products are gaseous. The other anomaly is, that as combustion is produced by pouring nitric acid on spirit of turpentine, the oxygen being already combined with azote, caloric and light are evolved by the mixture of the two fluids, from which it is inferred, that oxygen is capable of giving out caloric and light, not only when liquid, but even after combustion. In the instance of gunpowder, in order to explain the combustion which takes place independently of atmospheric air, or any aeriform supporter, "the caloric and light," in the opinion of Dr. Thomson, (Chemistry, i, 128) "must be supposed to be emitted from a solid body during its conversion into gas, which ought to require more caloric and light for its existence in the gaseous state than the solid itself contained."—Mr. Lavoisier (Elements of Chemistry, p. 157,) observes, that he and M. De la Place deflagrated a convenient quantity of nitre and charcoal in an ice apparatus, and found that 12 lbs. of ice were melted by the deflagration of one pound of nitre. After giving the proportions of acid and alkali in nitre, and the quantity of oxygen and azote in the acid, he observes, that during the deflagration, 145¹/₃ grains of carbon have suffered combustion along wit 3738.34 grains of oxygen; and as 12 lbs. of ice were melted, one pound of oxygen burnt in the same manner would have melted 29.5832 lbs. of ice. To which, if we add the quantity of caloric retained by a pound of oxygen, after combining with carbon to form carbonic acid gas, which was already ascertained to be capable of melting 29.13844 lbs. of ice, we shall have for the total quantity of caloric remaining in a pound of oxygen when combined with nitrous gas in the nitric acid, 58.72164; which is the number of pounds of ice, the caloric remaining in the oxygen in that state is capable of melting. In the state of oxygen gas it contains at least 66.66667. M. Lavoisier infers then, that the oxygen in combining with azote to form nitric acid, only loses 7.94502, and that "this enormous quantity of caloric, retained by oxygen in its combination into nitric acid, explains the cause of the great disengagement of caloric during the deflagration of nitre; or, more strictly speaking, upon all occasions of the decomposition of nitric acid." This view of the subject may enable us to explain the production of caloric, in those cases of combustion which cannot be explained on the ordinary principles; and, with regard to gunpowder, the accension of oil of turpentine by nitric acid, and similar cases, we may conclude, as the only rationale which seems applicable, that it is nothing more than the transition of caloric from one state to another, from a latent to a free state. Be this as it may, the combustion in such instances furnishes an anomaly to the already established doctrine, of the absorption of oxygen, or the base of the supporter, and the evolution of caloric from the gas, and not from the combustible; or, in other words, the change of caloric in the supporter from a combined to an uncombined state.

The idea of latent heat may be had from Dr. Black's own expression (Black's Lectures by Robinson:) "By this discovery," says the doctor, "we now see heat susceptible of fixation—of being accumulated in bodies, and, as it were, laid by till we have occasion for it; and are as certain of getting the stored-up heat, as we are certain of getting out of our drawers the things we laid up in them." Murray's System of Chemistry, 2d edition, p. 398, and Watson's Chemical Essays, vol. iii, &c. may be consulted on this subject with advantage. See Introduction.

We will consider, in the next place, the subject of gunpowder proof. The first examination of gunpowder is by rubbing it in the hands, to find whether it contains any irregular hard lumps. If it is too black, it is a sign that it is moist, or else, that it has too much charcoal in it; so, also, if rubbed upon white paper, it blackens it more than good powder does; but, if it be of a kind of azure colour, it is a good indication. If on crushing it with the fingers, the grains break easily, and turn into dust, without feeling hard, it is a criterion, that it has too much coal; or, if in pressing it under the fingers upon a smooth hard board, some grains feel harder than the rest, it is inferred that the sulphur is not well mixed with the nitre. By blasting two drachms of each sort on a copper plate, and comparing it with approved powder. In this proof it should not emit any sparks, nor leave any beads or foulness on the copper. The method of burning, which is commonly employed, Mr. Robins observes, is to fire a small heap on a clean board, and to attend nicely to the flame and smoke it produces, and to the marks it leaves behind on the boards.

Another trial of powder is to expose it to the atmosphere. One pound of each sort, accurately weighed, is exposed to the atmosphere for 17 or 18 days; during which time, if the materials are pure, it will not increase any thing material in weight, by attracting moisture from the air. One hundred pounds of good powder should not absorb more than twelve ounces, or somewhat less than one per cent. See Mr. Coleman's account of the manufacture of powder in England, page 110.

To determine the strength of powder in the easiest manner, is by comparing its effect with improved powder; as, for instance, by using a given weight of powder, as two ounces, and discharging a ball of a known weight, say 64 pounds, from an 8 inch mortar. The best cylinder powder generally gives about 180 feet range, and pit 180, with a ball and charge of the above weights; but the weakest powder, or powder that has been reduced, &c. only from 107 to 117 feet.

The practice adopted in England, we are told, is, that the merchant powder, before it is received into the king's service, is tried against powder of the same kind made at the king's mills, and it is received if it gives a range of ¹/₂₀ less than the king's powder, with which it is compared. In this comparison, both sorts are tried on the same day, and at the same time, and under exactly the same circumstances.

James (Mil'y Dictionary, p. 348) remarks, that the proof of powder as practised by the board of ordnance, besides that of comparing it by combustion on paper, is that 2 drachms, when put into the eprouvette, must raise a weight of 24 pounds to the height of 3¹/₂ inches.

According to Bottée and Riffault, before gunpowder is received into the arsenals of France, for service, it undergoes a variety of proofs; and the instructions for that purpose are contained under forty-two heads, embracing, at the same time, the specific duties of the officer employed for that service. The principal points, however, refer to a standard proof, made with the eprouvette, and differ, in no essential part, from the methods practised elsewhere. There is a uniformity in the French service, which cannot but be admired. In every thing which relates to the ordnance especially, even in the most minute details, the French, without doubt, exceed any other nation.

Having examined the different kinds of proof, not only for gunpowder, but for cannon and small arms, as established by an act of parliament, it appears, that musket powder undergoes another description of proof. A charge of four drachms of fine grain or musket powder in a musket barrel, should perforate, with a steel ball, a certain number of half inch wet elm boards, placed ³/₄ inch asunder, and the first 39 feet 10 inches from the barrel. The powder manufactured at the Royal Powder Mills generally passes through fifteen or sixteen, and restored powder, from nine to twelve.

There are other contrivances made use of, such as powder-triers, acting by a spring, commonly sold at the shops, and others again that move a great weight, throwing it upwards, which is an imperfect kind of eprouvette.

Dr. Hutton is of opinion, that the best eprouvette is a small cannon, the bore of which is about one inch in diameter, and which is to be charged with two ounces of powder, and with powder only; as a ball is not necessary; and the strength of the powder is accurately shown, by the arc of the gun's recoil.

The whole machine is so simple, easy, and expeditious, that, as Dr. Hutton remarks, the weighing of the powder is the chief part of the trouble; and so accurate and uniform, that the successive repetition, or firings, with the same quantity of the same sort of powder, hardly ever make a difference in the recoil of the one-hundredth part of itself.

Gregory (Treatise of Mechanics, vol. ii, p. 178) has given a more particular description of the eprouvette of Dr. Hutton; namely, that it is a small brass gun, 2¹/₂ feet long, suspended by a metallic stem, or rod, turning, by an axis, on a firm and strong frame, by means of which, the piece oscillates in a circular arch. A little below the axis, the stem divides into two branches, reaching down to the gun, to which the lower ends of the branches are fixed, the one near the muzzle, the other near the breech of the piece. The upper end of the stem is firmly attached to the axis, which turns very freely by its extremities in the sockets of the supporting frame; by which means, the gun and stem vibrate together in a vertical plane, with a very small degree of friction. The charge is the same we have mentioned, usually about two ounces, without any ball, and then fired; by the force of the explosion, the piece is made to recoil or vibrate, describing an arch or angle, which will be greater or less, according to the quantity or strength of the powder.

To measure the quantity of recoil, and consequently the strength of the powder, a circular brazen or silver arch of a convenient extent, and of a radius equal to its distance below the axis, is fixed against the descending two branches of the stem, and graduated into divisions, according to the purpose required by the machine: viz.

1st. Into equal parts, or degrees, for the purpose of determining the angle actually described in the vibration.

2nd. Into equal parts, according to the chords, being, in fact, 100 times the double sines of the half angles, and running up to 100, as equivalent to 90 degrees.

3d. Into unequal parts, according to the versed sines; they are, in truth, 100 times the versed sines of our common tables, 141¹/₂ corresponding with 90 degrees. These serve to compare the forces.

The divisions in these scales are pointed out by an index, which is carried on the arch during the oscillation, and then, stopping there, shows the actual extent of the vibration. Two ounces of powder, give, on an average, according to the experiments of professor Gregory, about 36 on the chords, or about 21° on the arch. A more detailed account, with diagrams, may be seen, by consulting Hutton's Tracts, vol. iii, p. 153.

The eprouvette constructed by the late Mr. Ramsden, differs from the preceding simply by the gun's recoiling in a direction parallel to itself, instead of its vibrating as a pendulum. The gun is suspended by two hanging frames, which serve to make it rise and fall, during its recoil and return, so as always to retain the horizontal direction. The degrees are measured upon a fixed arch, by means of a moveable index, nearly as in Dr. Hutton's eprouvette.

We remarked, that the common powder-triers are small strong barrels, in which a determinate quantity of powder is fired, and the force of expansion measured by the action excited on a strong spring, or a great weight. The French eprouvette is usually a mortar of seven inches (French) in caliber, which with three ounces of powder should throw a copper globe of sixty pounds weight to the distance of 300 feet. No powder is admitted that does not answer this trial. This eprouvette, however, has been improved, as we shall mention hereafter. These methods have been objected to, the former because the spring is moved by the instantaneous stroke of the flame, and not by its continued pressure, which is somewhat different; and the other, on account of the tediousness attending its use, when a large number of barrels of powder are to be tried.

J. Bodington of London, invented a machine to try the force of gunpowder. M. the chevalier d'Arcys made an eprouvette on the principle of Mr. Robins. M. Le Roy proposed to employ the different elastic forces of inflammable air, but his method has never been used. M. Tresnel also proposed an eprouvette, which was announced in the French journal, entitled Nouvelles de la République des Lettres et des Arts, par M. de la Blancherie, for 1782, p. 190.

It is hardly necessary to observe, that the eprouvette has undergone some improvements: thus, the eprouvette of Darcy consists of a cannon suspended at the extremity of a bar of iron, and the graduated arc measures the recoil; the eprouvette of Regnier is nearly the same, and the arc determines the force of the powder.

A description of mortar-eprouvettes generally, may be seen in the work of MM. Bottée et Riffault, (Traité sur l'art de Fabriquer la poudre à canon,) and in the Memoirs of Proust (Journal de Physique, tome lxx, et suiv.), &c.

I saw a model of an improved eprouvette, which appeared to possess every advantage, at the Ordnance Arsenal near Albany; an index hand moved in an arc.

Quicklime is said to increase the force of powder. Dr. Baine says, that three ounces of pulverized quicklime being added to one pound of gunpowder, its force will be augmented one-third; shake the whole together, till the white colour of the lime disappears.

The preservation of gunpowder in properly constructed magazines, of which we will have occasion to speak hereafter, is a subject that should claim our attention. The greatest difficulty, if any, exists at sea, and on this head we have a variety of opinions.

Mr. James (Military Dictionary, p. 348) says, that it has been recommended to preserve gunpowder at sea by means of boxes lined with sheet-lead. M. D. Gentien, a naval officer, tried the experiment by lodging a quantity of gunpowder and parchment cartridges in a quarter of the ship which was sheathed in this manner. After they had been stowed for a considerable time, the gunpowder and cartridges were found to have suffered little from the moisture; whilst the same quantity, when lodged in wooden cases, became nearly half destroyed.

It has been recommended to line powder magazines with lead, as a mean for preserving the powder from dampness. The lead, it seems, so far attracts moisture, as to condense it. In the last volume of the Transactions of the American Philosophical Society, is a memoir on leaden cartridges, by Wm. Jones, Esq. the late secretary of the navy, which, besides preserving the powder, has advantages over either paper or flannel. See Magazine.

What is termed the analysis of gunpowder, is nothing more than the separation of its component parts, and determining the relative proportions of its respective ingredients. We may indeed examine the quality of the nitrate of potassa, by dissolving a portion of powder in distilled water, and employing the reagents mentioned under the head of nitre; but for the purpose of separating, as well as determining the proportion of saline matter, charcoal and sulphur, it may be readily accomplished in the following manner: Take a given quantity of gunpowder and affuse it in distilled water sufficient to dissolve the salt; after suffering it to remain for some time, applying heat to assist the solution, decant the whole upon a filter of unsized paper. The saltpetre and other saline matter will pass through, and the sulphur and charcoal remain on the filter. By evaporating the solution to dryness, and weighing it, the quantity of saltpetre will be found; or, after drying the mass on the filter, and weighing it, by subtracting its weight from that of the original, it will give the loss sustained, which of course is the saltpetre. By exposing the mass to a heat sufficient to evaporate the sulphur, it will be expelled; the loss sustained will indicate its quantity, and the weight of the residue the proportion of charcoal. The sulphur may be even separated by subjecting gunpowder itself to the action of a well regulated heat; it will sublime, and leave the nitre and charcoal. It takes a much higher temperature to inflame gunpowder than is required to volatilize sulphur. The method of extracting the nitre from damaged powder, we have already noticed. See nitre. This process also depends on the solubility of the nitre, and the insolubility of the charcoal and sulphur. Bishop Watson, in his Chemical Essays, proposed the examination of gunpowder by solution and sublimation; a process sufficiently accurate. If it should be our object to ascertain the presence and quantity of foreign substances, in the saltpetre, this may be accomplished by following the process already given, viz: by collecting the precipitates, &c. determining their weights, and making the necessary allowance, for the new compounds, as the carbonates of lime, sulphate of barytes, muriate of silver, and the like.

Baumé proposed the analysis of powder by sublimation, in order to separate the sulphur, using however a graduated heat. Another mode consists in distilling the powder in a retort with water, and collecting the sulphur and sulphuretted hydrogen gas, and then separating the charcoal, &c. A third process was recommended by Pelletier, after the separation of the nitre, by subliming a mixture of the residue with mercury, which, however, presents no advantages. The use of nitric acid has also been recommended, in order to acidify the sulphur. For this purpose nitric acid is poured on the residue, and the whole is digested for some time, renewing the acid as it is decomposed. By this means the carbon, as well as the sulphur, is acidified, and carbonic acid gas with deutoxide of azote are disengaged, leaving the sulphuric acid formed by the union of oxygen with the sulphur, in the remaining fluid, from which it is separated by nitrate of barytes, and its quantity ascertained by the sulphate of barytes produced. The proportion of sulphur, in the sulphuric acid, is then calculated.

Caustic potassa has been employed for the separation of the sulphur from the charcoal. It unites with the sulphur, forming a sulphuret; and as sulphuretted hydrogen gas is also produced, the sulphuret must likewise contain the hydroguretted sulphuret of potassa. The charcoal is not acted upon.

M. Vito Caravelli, professor of chemistry at Naples, (Elements d'Artillerie, 1773,) has given a more simple process for the separation of these substances, which depends on their specific gravity. When mixed with water, the sulphur will deposite, and the charcoal float on the fluid.

Vauquelin directed his attention to this subject, and has recommended various processes, not only for the separation of the sulphur and charcoal, but also the nitre.

The process of Smithson Tennant is nearly of the same nature.

The separation of sulphur from charcoal may be effected more perfectly, according to Brande, by introducing the mixture into a small retort furnished with a stop cock, exhausted, and filled with chlorine gas; the chlorine will unite with the sulphur, forming a chloride, and leave the charcoal, which may be washed, dried, and weighed.

Baumé found, that when all the sulphur is expelled which will be driven off in the heat, a certain portion will still remain, and not burn away at a lower temperature than will consume the charcoal; so that to the last the burning residue will smell strongly sulphurous. This retained portion of sulphur he finds, by the results of many other experiments, to be very uniformly about one-twenty-fourth part of the whole sulphur employed; whence, for all common purposes, an adequate correction may be made, by estimating that the slow weak combustion of the residue, after the nitre has been extracted, destroys only ²³/₂₄ths of the sulphur instead of the whole. On trying to separate them by an alkaline solution, he found some of the sulphur to remain undisturbed, and still adhering to the charcoal. In consequence of this circumstance, it is recommended, to insure a perfect analysis, to separate the nitre in the first place from gunpowder, by hot water, and to treat the residue with nitric acid. After the sulphur is acidified, the addition of nitrate or muriate of barytes will separate, effectually, the sulphuric acid from the fluid, and form a sulphate of barytes; this being collected, washed, dried, and weighed, will give the quantity of sulphuric acid, and of sulphur in the acid, by the well known proportion of acid in the salt, and of sulphur in the acid. One hundred parts of sulphate of barytes, when perfectly dry, indicate fourteen and a half parts of sulphur; or, which is the same, according to Chenevix, one hundred and fifty-five grains denote twenty-two and a half grains of sulphur.

The observations of M. Champy and professor Proust on humid powder, seem to place the quantity of water absorbed, at 8, 10, and 14 per cent. These proportions, it is evident, depend greatly on the quality of the nitre; and if deliquescent salts exist in any quantity, the absorption, and consequently the increase of weight must be greater. Chemical examination will readily determine this fact.

The different sorts of gunpowder are usually distinguished by marks on the heads of the barrels. Gunpowder marks are various. All gunpowder for service is mixed in proportions according to its strength, so as to bring it as much as possible to a mean and uniform force. This sort of powder, says Adye, (Bombardier and Pocket Gunner,) is marked with a blue L. G. and the figure ¹/₂; or with F. ¹/₂ G. and the figure 3, whose mean force is from 150 to 160 of the eprouvette. This is the powder used for practice, for experiments, and for service. The white L. G. or F. G. is a second sort of powder of this quality. It is sometimes stronger but not so uniform as the L. G. It is, therefore, generally used in filling shells, or such other things as do not require accuracy. The red L. G. F. G. denotes powder in the British service, made at the King's mills, with the coal made in cylinders, and is used at present only in particular cases, and in comparisons, and to mix with other sorts to bring them to a mean force. The figures 1, 2 or 3 denote that the powder is made from saltpetre, obtained from the rough. Other marks are also in use to designate the rifle, musket, cannon powder, and the like.

Powder merchants recover damaged gunpowder, by putting a part of the powder on a sail cloth, and adding an equal quantity of good powder, which is well mixed with it, and the mixture is then dried.

Sec. VIII. Of Lampblack.

Lampblack, which is nothing more than a finer kind of coal, is so named from its being produced and originally made by the combustion of oil in lamps. It is hardly necessary to say, that it is formed in the combustion of turpentine, various species of the pinus, tar, pitch, rosin, &c. as all these substances yield it more or less, and of different qualities. It is the result of imperfect combustion; for, if the combustion were rapid, and the smoke itself consumed, we would then have only carbonic acid. This fact is exemplified in the argand lamp, which, on account of the glass cylinder, consumes its own smoke. The process of forming lampblack is conducted in lampblack houses. After the combustion has ceased, the soot or lampblack is swept down, as it collects above and on the sides of the room. When it is obtained by burning the dregs and coarser parts of tar, furnaces of a particular construction are used. The smoke is conveyed through tubes into boxes, each covered with linen, in the form of a cone. Upon this linen the soot is deposited, from which it is, from time to time, beaten off into boxes, and afterwards packed in barrels for sale. There is also a very fine black, superior in many respects to lampblack, especially in making the ink for copperplate printers, prepared by carbonizing grape stalks, &c. in close iron vessels.

There are two kinds of lampblack in common use. One is the light soot, from burning wood, of the pine and other resinous kinds, usually made in Sweden. In Sweden the impure turpentine is also burnt for this purpose. It is collected from incisions made in pine and fir-trees, and the turpentine is boiled down with a small quantity of water, and strained, while hot, through a bag; and while this part is used for another purpose, the dregs and pieces of bark remaining in the strainer, are burnt in a low oven, whence the smoke is conveyed through a long passage into a square chamber, which contains a sack, as above stated, where the greater part of the lampblack collects, and the remainder is caught in the chamber.

The other kind of lampblack is formed by carbonization, a process similar to that for preparing the black, called blue-black, from grape stalks, or for preparing the German black, a pigment made by charring principally the lees of wine and husks of grapes.

The lampblack made in Philadelphia, for the purpose of printers' ink, is prepared by the combustion of tar. One barrel of Carolina tar will produce forty pounds of soot or lampblack.

A patent was granted 1798 to a Mr. Row, (Repository of Arts, vol. x.) for a newly invented mineral lampblack. It is nothing more than the smoke obtained by the combustion of pit coal. In the county of Sarrbrook on the Rhine, are some establishments for making coke and lampblack at the same time; and from 100 lbs. of coal, 33 lbs. of coke, and 3¹/₂ of lampblack are obtained. Jeanson (Archives des Découvertes, &c. i, p. 21) has described a process for carbonizing oil.

Lampblack has the same chemical properties as charcoal, and being remarkably fine, and containing sometimes a portion of oil, is used on that account in the composition of some fire-works. Its quality may be known by its colour, and, when burnt, leaving no residue. It may be sufficient to remark, that like charcoal, it decomposes nitric acid; and the nitrates, when mixed with it, and projected into a red-hot crucible, will deflagrate or produce a vivid combustion. It may therefore be used in all kinds of fire-works, in which charcoal is employed. Concentrated nitric acid, when poured on lampblack, previously dried, will produce combustion. It is to the carbon, as well as the hydrogen, in oil of turpentine, that turpentine inflames when brought in contact with nitric acid; and although much charcoal is deposited, yet a considerable part passes off in the state of carbonic acid gas. By a proper treatment, lampblack like charcoal may be converted into artificial tannin by nitric acid. It has also antiseptic qualities; but to be used for this purpose it should first be exposed to heat, in order to drive off any oil which it may have contracted, or with which it might be contaminated. The quality of lampblack may, we suspect, be improved by bringing it to a state of ignition in close iron vessels. If required intensely black, as for the making of printers' ink, this process might be advantageously used. Mixed with gum water, it makes a durable writing ink, or, according to Mr. Close, by mixing it with a solution of copal in oil of lavender. This ink is not, like the common kind, acted upon by acids.

Sec. IX. Of Soot.

Soot, or that substance formed by the combustion of wood, &c. which collects in chimnies, is used in some of the pyrotechnical preparations, partly to assist the flame, and partly to modify its appearance. It is found, that soot, produced by the combustion of wood, is formed by the condensation of the carbon evolved in the smoke. It also contains volatile products, the nature of which, depends on the kind of combustible. Wood-soot is considered a good manure, on account of the carbon and some volatile salts, it is said to contain. That it contains ammonia, is evident, since it may be detected by experiment; and that this alkali is combined with carbonic acid, and sometimes with muriatic acid, a number of facts prove. Soot, then, when used in fire-works, may, like sal ammoniac, but in a lesser degree, produce a particular coloured flame. When soot is well washed in water, in order to free it from saline and other soluble matter, and probably from pyroacetic acid, and then pulverized, it forms the pigment called bistre. It is a fact, that the excrement of some animals, the camel for instance, which feed on saline vegetables, when burnt, will yield a soot, which contains an abundance of muriate of ammonia, or sal ammoniac. Hence, by re-subliming this soot, sal ammoniac was originally prepared in Egypt. The quantity of muriate of ammonia, contained in the soot of camels' dung, is considerable. It is found that 26 lbs. of soot yield on an average 6 lbs. of that salt; See Sal Ammoniac. Camels' dung, and in fact the dried excrement of animals, furnish a very good fuel. In Egypt it is used with advantage. The soot of oil, &c. is of a different kind; it is the substance, which forms our lampblack.

Sec. X. Of Turpentine, Rosin, and Pitch.

All these substances enter into the composition of fire-works, either to increase the rapidity of combustion, as in incendiary fire-works, or, in some cases, as with rosin, to produce a coloured flame. That they contain carbon and hydrogen, as their principal ingredients, is well known; to which we may attribute their rapid combustion, and the facility with which they decompose nitrous salts. The Greek fire, for example, owed, it is said, its powerful effect to turpentine, which, with other substances employed, made the composition remarkably inflammable, and the decomposition of the nitre, (which some say it contained) so rapid, as even to defy the action of water.

All of the turpentines are obtained from different species of pinus. Common turpentine is the resinous juice, which exudes chiefly from the Pinus Sylvestris, or Scotch fir, and is obtained by boring holes into the trunks of the trees, early in the spring, and placing vessels beneath for its reception. This turpentine, and in fact all others, are composed of rosin and a volatile oil. The latter is obtained by distilling the turpentine with water. It passes over with the water, from which it is afterwards separated, and is then known by the name of the essential oil, or spirit of turpentine. The substance, remaining in the still, is common rosin, or yellow rosin, known likewise by the names of fidlers' rosin and colophony. Tar is also obtained from the roots and refuse parts of the fir tree, by cutting them in billets, piling these in a proper manner, in pits or ovens, formed for the purpose, covering them partly over, and setting them on fire. During the combustion, a black and thick matter, which is tar, falls to the bottom, and is conducted into barrels.

Pitch is nothing more than tar boiled down to a solid consistence; it is usually made, however, by melting together coarse hard rosin, and an equal quantity of tar. The ancient pitch possessed a flavour and fragrance. White pitch is the same as the white turpentine.

Melted pitch, sulphur, and camphor, mixed, when nearly cold, with pulverized saltpetre, and afterwards thinned with spirit of turpentine, will form a composition, that is very inflammable, and will almost resist the action of water. A similar composition must have formed the Greek fire, of which, according to Beckman, there were several kinds.

The turpentine trees furnish various products: Thus, the Pinus Abies, or spruce fir, yields the Burgundy pitch, and its branches produce the Essence of Spruce; but other species of pinus are used for the same purpose, which are nearly allied to it, and which grow abundantly in Canada. From the Pinus laryx, or larch, Venice Turpentine is obtained; but that sold, is usually made by melting rosin, and adding the spirit of turpentine. From the sap of the larch, the Russians prepare a gummy substance, known in Russia by the name of Orenburg gum. Turpentine is extracted in France, in great quantity, from the pinus maratima. Gallipot, colophony, tar, pitch, &c. are likewise obtained from it.

The turpentine of cedar, according to Dr. Pocoke (Travels through Egypt) was employed by the Egyptians for embalming, the operation being performed in several ways. It was injected, and used with salt, nitre, &c.

Pitch, tar, and turpentine all enter into sundry compositions, used in war. The different incendiary preparations, noticed in the last part of the work, are composed, in general, of either one or all of these substances. Their use is obvious. Being very inflammable, and brought in contact with gunpowder, nitrate of potassa, &c. they burn with great rapidity, and consume every thing before them. Hence the tourteaux of the French, tarred links, and fascines, carcasses, &c. owe their effect to the presence of these substances.

Rosins are considered to be volatile oils, saturated with oxygen.

Thus, or frankincense, of which there are several varieties, has been long used in fire-works; it is frequently employed in the composition of odoriferous fire. It is obtained from the pinus abies, and appears in tears. During winter, the wounds made in fir trees become incrusted with a brittle substance, called barras or gallipot, consisting of rosin united with a small portion of oil. All rosins, according to the experiments of Gay-Lussac, and Thenard, (Recherches physico-chimiques) are composed of a great quantity of carbon and hydrogen, united with a small quantity of oxygen. To this, we attribute their great inflammability, and it enables us to account for the rapid decomposition of nitre, in those preparations, in which nitre and resinous substances are employed. See General Theory of Pyrotechny, sec. ii.

For the accension which takes place by mixing oil of turpentine and nitric acid, see the properties of nitric acid, under the head of nitre.

Morey (Silliman's Journal, vol. ii, p. 121) observes, that a small quantity of spirit of turpentine being added to a mixture of iron-filings, sulphuric acid, and water, the hydrogen gas produced, will burn with a very pleasant white flame, and without smoke. He also observes, that, if the vapour of spirit of turpentine be made to pass through a tube, covered at the upper end with a fine wire gauze, it burns with much smoke; but, if a quantity of atmospheric air be allowed to mix with it, the smoke ceases, and the flame continues white. If more still be added, the flame lessens, and becomes partly blue. By adding still more and more, it will burn with a very small flame, entirely blue, and with a singular musical sound. If still more be added, the flame, and every ray of light cease; but that the combustion still continues, is certain, from the explosive detonating noise, continuing to be distinctly heard.

Mr. Morey further remarks, that, if tar, containing a considerable proportion of water, is dropped on brick or metal, at a temperature, which will readily evaporate them, the vapours will burn with white shooting streaks, much flame, and without smoke, while the water lasts. Inflamed drops of tar, burn, while falling, with a red flame, and much smoke; but, on reaching boiling water, the smoke instantly disappears, and streaks of a white flame shoot up. He also says, that, if water in one cylinder be made to boil, and the steam be led to the bottom of another, containing rosin, or tar, at a high temperature, after passing up through it, the water, together with the vapourized portion of the rosin or tar, will, when the preparations are properly regulated, burn with an intense white flame, and no smoke; much the greater part of which appears, (by alternately shutting the steam out, or letting it in) to be derived from the water; and also, that if steam be led over the surface of tar in a cylinder, and made to force out a small stream of it through a pipe, into which a quantity of steam is also admitted, and made to mix intimately with it, they burn, with a great body of flame and intense heat, and without smoke, provided the proportions are well regulated. These facts are remarkable, and may probably lead to some useful applications. That water is decomposed, appears more than probable. If water is thrown, in considerable quantities, on oil or tar, in a state of inflammation, as Morey observes, the flame is greatly increased; and if ever so small a drop of water fall into oil at a temperature near boiling, an explosion will take place. He draws the following conclusion, from these circumstances; that we have only to pass the steam of water through oil, heated to the temperature, at which it boils, or takes fire, to produce combustion.

Sec. XI. Of Common Coal, or Pitcoal.

All the variety of coals, belonging to the coal family, are composed principally of charcoal and bitumen, with small quantities of earthy, and metallic matter. Whether we consider the formation of coal, the localities or situation in which it occurs, whether in beds or strata, accompanying other minerals, such as clay-slate, bituminous schistus, sandstone, &c. is of no moment, except so far as the situation in which it is found, indicates or determines its character and qualities. The different kinds of coal owe their variety to the presence or absence of bituminous matter, whether great or small, the quantity of the carbonaceous ingredient, and the presence or absence of anthracite, and other foreign substances. Coal, which is, or ought to be preferred in fire-works, should contain the greatest quantity of bituminous matter; and, while it contains the due proportion of carbon, should be entirely free from anthracite. Coal, and all other inflammable fossils, are characterized by their inflammability, insolubility in water, alcohol, and acids, and by their specific gravity, which scarcely exceeds 2, unless loaded with foreign matter. Coal surcharged with bitumen, burns with a bright flame, and, by distillation, affords more carburetted hydrogen gas, which is used for gas light. Common coal, or pitcoal, burns in cakes, more or less, during combustion. Besides charcoal and bitumen, it contains sometimes pyrites, sulphate of iron, and earth. Slate-coal, however, contains more clay.

The collieries, from which pitcoal is obtained, are more or less extensive in England, and elsewhere. Immense beds of coal are found near Pittsburgh, and Richmond. The Lehigh, and other localities in the United States, produce it also in abundance, but of various qualities. Coal districts, or places in which it is found, may be considered a valuable acquisition to a country; and as coal is so essential in many manufactories, it is a satisfaction to know, that our resources in this particular, are almost inexhaustible;—a fact, which shows, that, while our national industry is the main pillar of national independence, in its true acceptation, the arts, which require a supply of coal, will, for centuries to come, be abundantly furnished with it.

When coal is exposed to the action of heat, in iron retorts or cylinders for the preparation of coal gas, or when it is exposed to heat in coke-ovens, the bitumen, &c. are disengaged, and there remains a coal called coke. Coke, therefore, is nothing more than charred pitcoal.

Mr. Mushet made some valuable experiments on the carbonization and incineration of coals. He found that the Scotch cannel-coal afforded 56.57 volatile matter, 39.43 charcoal, and 4 ashes; while the stone-coal, found under basalt, gave 16.66 volatile matter, 69.74 charcoal, and 13.6 ashes, and oak wood, 80.00 volatile matter, 19.5 charcoal, and 0.5 ashes. The quantity of gas, however, depends entirely on the quality of the coal. A temperature of about 600° to 700° is sufficient to disengage it. A pound of good cannel coal, properly treated in a small apparatus, will yield five cubic feet of gas, equivalent in illuminating power to a mould candle, six in the pound. One pound of coal, on a large scale, affords only 3¹/₂ cubic feet of gas. A gas jet, which consumes half a cubic foot per hour, gives a steady light equal to that of a candle of the above-mentioned size.

The cannel coal, known in Scotland by the name of parrot coal, is very inflammable, takes fire immediately, and produces a brilliant flame. It is used by the poor as a substitute for candles. This coal, we have seen, furnishes an abundance of carburetted hydrogen gas. It has the appearance of jet, and admits of being turned in a lathe.

Stone coal, Kilkenny coal, Welch coal, and glance coal consist almost entirely of charcoal; and hence, when laid on burning coals, they become red-hot, emit a blue lambent flame, in the same manner as charcoal, and at length are wholly consumed, leaving behind a portion of red ashes. They burn without smoke or soot.

The pitch coal, which has a brownish-black colour, and is generally found massive in plates, the bovey coal, called brown coal, and bituminous wood, with the anthracite coal, and some others of lesser note, form the remaining varieties of coal.

When coal is employed in fire-works, it is to be pulverized, and sifted in the usual way. For some purposes it is preferred to charcoal, in consequence of the bitumen it contains, which appears to contribute to the rapidity of the combustion. It is to be observed, that, as the base of coal is carbon, its action is the same as charcoal, and therefore, by producing the same effects, or nearly so, as charcoal itself, the phenomena it presents are analogous. As 12.709 parts of carbon, according to Kirwan, are required to decompose 100 parts of nitrate of potassa, we may readily ascertain the quantity of real carbon in any specimen of coal. According to Kirwan, 50 grains of Kilkenny coal will decompose 480 grains of nitrate of potassa, from which it is inferred, that ten grains would have decomposed 96 of nitrate of potassa, precisely the same quantity of charcoal, which would have produced the same effect. Therefore, Kilkenny coal is composed almost entirely of carbon. Cannel coal, when treated in the same manner with nitrate of potassa, left a residuum of 3.12 in the hundred parts of earthy ashes; and 66.5 of it were required to decompose 480 grains of nitrate of potassa, but 50 of charcoal would have been sufficient. From this experiment, it appears, that 66.5 grains of cannel coal contain 50 grains of charcoal, and 2.08 of earth; the remaining 14.42 grains must be bitumen. In a similar manner, by knowing the quantity of coal required to decompose a given quantity of nitrate of potassa, when melted in a crucible, the quantity of carbon in any variety of this substance may be ascertained.

With respect to the earthy and metallic ingredients of coal, we may ascertain them by burning the coal, with free access of air. What remains unburnt must be considered an impurity. Its weight may be ascertained, and its nature by analysis. As the object, however, is generally to determine the relative proportion of combustible matter, or carbon, which different species of coal are capable of yielding, that point may be determined in the manner already stated.

That coal originates from vegetables, whatever opinion may be formed to the contrary, we may fairly infer from a variety of vegetable remains, and impressions of animals that are both found in the strata of coal, and in earthy strata above and below them. Of its submarine origin, there can also be no doubt; or why do we find in it shells, the impression of fish, and other productions of the ocean? That coals grow like vegetables, an opinion with the uninformed, is contrary to fact, and the nature of things.

We may notice, in this place, another substance which sometimes is found partially carbonized; we mean turf.

Turf or peat, obtained from morasses, consists of a multitude or congeries of vegetable fibres, partly in a decomposed state, and is frequently so inflammable as to inflame by a spark. Very extensive morasses are found in some countries from which the inhabitants are supplied with fuel. Some improvements in the manner of preparing turf for use, have been made; that of charring it in kilns is one. By this process it kindles sooner, burns with less air, and forms a moderate and uniform fire, without much smoke, though it is not so lasting as that produced by turf. The method of reducing turf to coal is still practised in some parts of Bohemia, Silesia, and Upper Saxony, which was first proposed in 1669, by John Joachim Becher, who also recommended, at that time, a process for depriving coals of their sulphur, by burning them in an oven, and the use of the oil procured from them. What are our modern patents on this subject? What are lord Dundonald's coke ovens and coal tar? Are they original? Boyle (Usefulness of Natural Philosophy,) speaks of Becher's invention. Anderson, (History of Commerce,) however, observes, that something of the kind was attempted before Becher's time; for in the year 1627, John Hacket and Octavius Strada obtained a patent for their invention of rendering coals as "useful as wood for fuel in houses, without hurting any thing by their smoke."

With respect to turf, it appears that Hans Charles von Carlowitz, to save wood, introduced the use of it in Saxony, in the smelting houses, in 1708.

Turf has been known for a long time. It was used from the earliest periods, in the greater part of Lower Saxony, and throughout the Netherlands; as is fully proved by Pliny's account of the Chauci, who inhabited that part of Germany. Pliny (Hist. Nat. lib. xvi, c. i.) observes, that they pressed together with their hands, a kind of mossy earth which they dried by the wind rather than by the sun, and which they used, not only for cooking their victuals, but also for warming their bodies. We also read that a morass in Thessaly, having become dry, took fire, and the same thing ensued in some part of Russia, where a morass burned several days and did much damage. Very dry turf is nearly as inflammable as spunk, and when prepared with nitre, has been used for the same purpose. See Pyrotechnical sponge.

Ure (Chemical Dictionary) observes, that "turf has been charred lately in France, it is said by a peculiar process, &c." The truth is, that the charring of turf is by no means a recent invention, as we stated above. Sonnini (Journal, &c.) says, that it is superior to wood. It kindles slower than charcoal of wood, but emits more flame and burns longer. In a gold-smith's furnace, it fused eleven ounces of gold in eight minutes, while wood charcoal required sixteen.

Turf frequently contains phosphoric acid; for bogs or morasses, and bog-iron ores abound, more or less with it, in different states of combination. The siderite of Bergmann which he supposed to be a peculiar metal, and found in bog-ore, is a phosphate of iron. The native Prussian blue, which also occurs in such localities, is generally admitted to be a combination of phosphoric acid iron and alumina.

Sec. XII. Of Naphtha, Petroleum, and Asphaltum.

Hanway (Travels through Russia into Persia, i, 263,) mentions the naphtha of Baku, and remarks that the earth is strongly impregnated with it; for, he adds, by taking up two or three inches of the surface, and applying a live coal, the part which is so uncovered, immediately takes fire, almost before the coal touches the earth. Eight horses were consumed by the fire from naphtha, being under a roof where the surface of the ground was turned up, and, by some accident took fire. A cane, or tube, even of paper, set two inches in the ground, and the top of it touched with a live coal, and blown upon, immediately emits a flame, without hurting either the cane or paper, provided the edges be covered with clay. Three or four of these lighted canes will boil water in a pot.

Pinkerton, (Petralogia ii, p. 148,) speaks of the naphtha of Baku, which exists on the western side of the Caspian sea, being carried to Constantinople, "where it formed the chief ingredient of the noted composition called the Grecian Fire; which, burning with increased intensity under water, became a most formidable instrument against an inimical fleet." See Greek fire.

Naphtha is obtained of several qualities by suffering it to remain in pits or reservoirs. The Persians, who use it in their lamps, and to boil their food, find it to burn best with a small mixture of ashes. They keep it at a small distance from their houses, in earthen vessels, under ground, to prevent any accident by fire, of which it is extremely susceptible.

Hanway speaks also of what is called the everlasting fire, about ten miles from Baku, which is an object of devotion to the followers of Zoroaster. Near the altar of their temple, he observes, is a large hollow cane, from the end of which issues a blue flame, which the Indians pretend has continued to burn ever since the flood, and which, they fancy, will last to the end of the world.

We have no hesitation in believing, that the ancients made use of this oil in their exhibitions; and, from its properties, that when mixed with other substances, it would make a brilliant fire-work.

Petroleum, called also mineral tar, is less fluid and less transparent than naphtha. It has an oily consistence, more or less viscid. It occurs of a black or brown colour. It burns rapidly, but not so readily as naphtha, and exhales a black smoke. By distillation, it forms a liquid like naphtha, and leaves a thick tar in the retort.

It exudes from rocks, is found in wells, &c. In Pegu, the wells furnish annually 400,000 hogsheads. It is used there in the place of oil for lamps. When boiled with rosin, it is used for painting houses, and the bottoms of vessels. In the embalming of dead bodies, it was employed by the ancient Egyptians; and, in some countries, clay, soaked in it, is used as fuel.

It is found in the United States, in Kentucky, Ohio, the western parts of Pennsylvania, in New York at the Seneca lake, &c. The Seneca or Genessee oil is the same bitumen.

When petroleum is exposed to the atmosphere, it acquires a greater degree of consistence, and passes into another bituminous substance, called maltha. This has the properties, and frequently the appearance of pitch. When burnt, it yields more smoke and soot than petroleum. According to its original meaning, it signifies a kind of cement; and the maltha mentioned by Pliny, Heineccius, Festus, and others, which was employed in the same manner as our modern sealing wax, was a mixture of pitch and wax, and was also used to make reservoirs, pipes, &c. water-tight. Maltha also sometimes resembles wax. Mr. Kirwan, however, gave it the name of mineral tallow.

Mineral or Barbadoes tar is somewhat thicker than petroleum, and nearly of the consistence of common tar. It is used for the same purposes as the ordinary petroleum. Elastic bitumen, a variety between the softer and harder bitumens, resembles caoutchouc. It burns with a bright flame, and bituminous odour.

Asphaltum, or solid bitumen, is much harder than pitch, brittle, and of a brownish-black colour. It burns freely, and leaves but little residue. In Judea, it is found on the waters of the Dead sea, or the lake of Asphaltes. It is also called Jews' pitch. It was employed by the Egyptians for embalming under the name of mumia mineralis.

Both maltha and asphaltum were used by the ancients as a cement. The walls of Babylon were cemented with these substances, as obtained from the river Is, which falls into the Euphrates. It may be observed, that those countries, which yield bitumen, contain salt springs, and it frequently accompanies pyrites. Limestone, particularly the black, contains it, and the colour is often owing to its presence. The stink stone, or bituminous carbonate of lime, is of this kind. The retinasphaltum, a combination of bitumen and earth, having a yellow colour, burns with a bright flame, and fragrant odour, which at last becomes bituminous. Many stones, and particularly some of the black marbles, owe their colour to bitumen; hence they burn white. The bituminous schistus, or bituminous shale, sometimes contains so much of this substance as to burn in the fire. Jet is a mineral of a black colour, and resembles the cannel coal. It is inflammable, producing a green flame, with a strong bituminous odour.

With respect to bitumens, we may observe, that they all possess one character, that of being inflammable; and that they are more or less so in proportion as they partake of the principle of naphtha; or, at least, the rapidity of their combustion depends upon the presence of this oil. The following additional facts, therefore, with respect to naphtha, may be interesting: Certain liquids have the property of uniting with naphtha, which has also the property of dissolving and combining with solid substances, of which the following examples may be stated:

At the degree of ebullition, it dissolves sulphur, which, on cooling, is in part deposited in needle-form crystals. At the same temperature, it also dissolves phosphorus, part of which is again separated.

It unites also with iodine. With camphor, it also combines, and in large quantity. It takes up a much larger proportion of pitch. In the cold, its action on wax is feeble, but assisted by heat, it unites with it in all proportions. On lac and copal, its action is feeble. In the cold, it does not dissolve caoutchouc; but when assisted by heat, it dissolves this substance, though not completely. These facts may determine its action in certain mixtures.

According to Theodore de Saussure's Analysis, (Bibliot. Universelle, iv, p. 116), it appears, that naphtha is composed of 87.60 carbon, and 12.78 hydrogen.

Sec. XIII. Of Oil of Spike.

This oil is principally used as a vehicle for mixing the ingredients of some kinds of fire-works; and, although it is employed in that way, yet it has also an effect in combustion, having similar properties with liquid bitumen. It enters into the composition of some of the preparations, and perhaps is equally good as liquid bitumen. Indeed, the oil of spike, as sold in the shops, and used principally by farriers as an embrocation for horses, is an artificial preparation, made by mixing together about five ounces of Barbadoes tar, with a pint of the spirit of turpentine.

Sec. XIV. Of Amber.

Amber, succinum, karabe, the electron of the ancients, which are synonimous terms, is very inflammable. A piece of it, put on the point of a knife, and set on fire, will burn entirely away, emitting, at the same time, a white smoke, and a somewhat agreeable odour. It is used in the composition of fire-works, and particularly in some kinds of rockets. All the preparation it undergoes, when thus used, is to reduce it to powder in a mortar, and to pass it through a fine sieve. It also forms a part of the composition of odoriferous fire; but the formulæ for the latter are various.

Amber is of various colours, either yellowish, white, or honey-yellow. It is translucent, and sometimes transparent. It may be turned or polished. It occurs in grains or in irregular masses. Alluvial deposites of sand, gravel, &c. frequently contain it. It is also found with bituminous wood, brittle lignite, or jet, and with other substances. It has been discovered in New-Jersey, near Trenton, in alluvial soil. Naturalists believe, that amber was once a resinous juice. Masses weighing 20 lbs. have been found. Sometimes it contains insects. It is formed into beads and the like. As amber becomes electric by friction, and the ancients called it electron, the term electricity is derived from it. By distillation, it yields both an acid, (the succinic), and an oil. Jet is usually considered black amber.

We may introduce here a few remarks respecting ambergris:

Ambergris is a substance, which has a peculiar fragrance, and for that reason is used as a perfume, and may be employed like similar substances in odoriferous fire. As to its origin, we have no certain account; but it seems, from its general properties, to be formed in the same manner as bituminous substances, although it is mostly found on the sea-shore, where it has been probably washed up from the sea.

Ambergris is found principally on the shores of Ceylon, and is known to be good, by laying some of it on a very hot knife, when, if pure, it will not only melt and run like wax, but entirely evaporate, leaving no residue.

Ambergris, on account of its price, (the retail price in London being a guinea per ounce), is frequently adulterated with various mixtures of benzoin, labdanum, meal, &c. scented with musk. But pure ambergris, when heated, has a greasy feel, and appearance, and is soluble in hot ether and alcohol.

Sec. XV. Of Camphor.

Camphor is a resinous substance, although generally called a gum, which has a peculiar, and powerful smell. It is obtained principally from the Laurus Camphora. It is extracted from this, and other trees in the East Indies. We are informed, that, in Borneo and Sumatra, the larger pieces which contain the most camphor, are picked out with sharp instruments. The Chinese cut off the branches, chop them small, and place them in spring water. They are then boiled, and stirred with a stick. As soon as the camphor is observed to adhere to the stick, the fluid is strained. It is then poured into a basin, and the camphor separates, in Japan, the roots and the extremities of the branches are steamed. It is also obtained by sublimation. The roots, wood, and leaves are all boiled in large iron pots, and the camphor is collected on straw, placed in a tubular head.

With respect to the refining of crude camphor, in order to produce heads, as they are called, and to free it from impurities, the operation is nothing more than sublimation. Sublimers made of glass are used; and into each, the camphor, along with a small portion of lime, is introduced, and they are then placed in a sand bath. Heat is applied, and the pure camphor rises and attaches itself to the upper part of the vessel, forming the refined camphor.

The general properties of camphor are the following: It is not altered by the atmospheric air, but is volatilized during warm weather. It is insoluble in water; is soluble in alcohol, forming the spirit of camphor, and also in volatile and fixed oils. It is not acted upon by the alkalies. It is dissolved in acids without effervescence, and by some it is decomposed. Nitric acid converts it into a peculiar acid, called the camphoric. It melts between 300 and 400 degrees. It takes fire, and burns with a white flame, and, generally, while it presents the character of a resin, it shows, by its combustion, like other inflammable bodies, that it contains, in its composition, a large quantity of carbon and hydrogen.

There are several species of camphor, which have been examined by chemists and which differ in their properties. These are, common camphor, the camphor of volatile oils, and the artificial camphor, formed by treating oil of turpentine with muriatic acid.

The base of camphor forms a constituent part of some volatile oils, which are in a liquid state; and for its separation, it appears to require a combination with oxygen.

Camphor may be apparently set on fire by means of water, an experiment, which is nothing more than producing chemical action by it, in the following manner: Put a portion of nitrate of copper on some tin-foil, along with camphor; then by adding some water, and quickly wrapping the foil up, pressing the edges close, it will inflame, and sparks of fire be produced.

Camphor has been used in the manufacture of candles. For this purpose, it is dissolved in brandy, and the wick, composed of equal parts of cotton and linen, is dipped in. It is then dried, and covered, in the usual manner, with tallow or wax. The tallow, recommended as the best for candles, is a combination of equal parts of mutton and beef suet.

Camphor has been burnt, like ether and alcohol, by platinum wire, previously heated. Dr. Ure observes, that a cylinder of camphor may be used for both wick and spirit, in the aphlogistic lamp; and the ignition is very bright, while an odoriferous vapour is exhaled. By adding various essential oils in small quantities to the alcohol of the lamp, various aromas may be made to perfume the air of an apartment. See Scented Fires for rooms.