a sort of artificial coal, or fuel, consisting of wood half burnt; chiefly used where a clear strong fire, without smoke, is required; the humidity of the wood being here mostly dissipated, and exhaled in the fire wherein it is prepared.

The microscope discovers a surprising number of pores in charcoal: they are disposed in order, and traverse it lengthwise; so that there is no piece of charcoal, how long soever, but may be easily blown through. If a piece be broken pretty short, it may be seen through with a microscope. In a range the 18th part of an inch long, Dr Hook reckoned 150 pores; whence he concludes, that in a charcoal of an inch diameter, there are not less than 5,724,000 pores. It is to this prodigious number of pores, that the blackness of charcoal is owing: for the rays of light striking on the charcoal, are received and absorbed in its pores, instead of being reflected; whence the body must of necessity appear black, blackness in a body being no more than a want of reflection. Charcoal was anciently used to distinguish the bounds of estates and inheritances; as being incorruptible, when let very deep within ground. In effect, it preserves itself so long, that there are many pieces found entire in the ancient tombs of the northern nations. M. Dodart says, there is charcoal made of corn, probably as old as the days of Caesar: he adds, that it has kept so well, that the wheat may be still distinguished from the rye; which he looks on as proof of its incorruptibility.

The operation of charring wood, is performed in the following manner: The wood intended for this purpose is cut into proper lengths, and piled up in heaps near the place where the charcoal is intended to be made: when a sufficient quantity of wood is thus prepared, they begin constructing their flacks, for which there are three methods. The first is this: They level a proper spot of ground, of about twelve or fifteen feet in diameter, near the piles of wood; in the centre of this area a large billet of wood, split across at one end and pointed at the other, is fixed with its pointed extremity in the earth, and two pieces of wood inserted through the clefts of the other end, forming four right-angles; against these cross pieces four other billets of wood are placed, one end on the ground, and the other leaning against the angles. This being finished, a number of large and straight billets Charcoal. Billets are laid on the ground to form a floor, each being as it were the radius of the circular area: on this floor a proper quantity of brush or small wood is strewed, in order to fill up the intertices, when the floor will be complete; and in order to keep the billets in the same order and position in which they were first arranged, pegs or stumps are driven into the ground in the circumference of the circle, about a foot distant from one another: upon this floor a stage is built with billets set upon one end, but something inclining towards the central billet; and on the tops of these another floor is laid in a horizontal direction, but of shorter billets, as the whole is, when finished, to form a cone.

The second method of building the stacks for making charcoal is performed in this manner: A long pole is erected in the centre of the area above described, and several small billets ranged round the pole on their ends: the intertices between these billets and the pole is filled with dry brushwood, then a floor is laid, on that a stage in a reclining position, and on that a second floor, &c., in the same manner as described above; but in the lower floor there is a billet larger and longer than the rest, extending from the central pole to some distance beyond the circumference of the circle.

The third method is this: A chimney, or aperture of a square form, is built with billets in the centre, from the bottom to the top; and round these, floors and inclined stages are erected, in the same manner as in the stacks above described, except that the base of this, instead of being circular like the others, is square; and the whole stack, when completed, forms a pyramid.

The stack of either form being thus finished, is coated over with turf, and the surface plastered with a mixture of earth and charcoal-dust well tempered together.

The next operation is the setting the stack on fire. In order to this, if it be formed according to the first construction, the central billet in the upper stage is drawn out, and some pieces of very dry and combustible wood are placed in the void space, called, by workmen, the chimney, and fire set to these pieces. If the stack be built according to the second construction, the central pole is drawn out, together with the large horizontal billet above described; and the void space occupied by the latter being filled with pieces of very dry combustible wood, the fire is applied to it at the base of the stack. With regard to the third construction, the square aperture or chimney is filled with small pieces of very dry wood, and the fire applied to it at the top or apex of the pyramidal stack. When the stack is set on fire, either at the top or bottom, the greatest attention is necessary in the workman; for in the proper management of the fire the chief difficulty attending the art of making good charcoal consists. In order to this, care is taken, as soon as the flame begins to issue some height above the chimney, that the aperture be covered with a piece of turf, but not so close as to hinder the smoke from passing out: and whenever the smoke appears to issue very thick from any part of the pile, the aperture must be covered with a mixture of earth and charcoal dust. At the same time, as it is necessary that every part of the stack should be equally burnt, it will be requisite for the workman to open vents in one part and shut them in another. In this manner the fire must be kept up till the charcoal be sufficiently burnt, which will happen in about two days and a half, if the wood be dry; but if green, the operation will not be finished in less than three days. When the charcoal is thought to be sufficiently burnt, which is easily known from the appearance of the smoke, and the flames no longer issuing with impetuosity through the vents; all the apertures are to be closed up very carefully with a mixture of earth and charcoal-dust, which, by excluding all access of the external air, prevents the coals from being any further consumed, and the fire goes out of itself. In this condition it is suffered to remain, till the whole is sufficiently cooled; when the cover is removed, and the charcoal is taken away. If the whole process is skilfully managed, the coals will exactly retain the figure of the pieces of wood: some are said to have been so dexterous as to char an arrow without altering even the figure of the feather.

There are considerable differences in the coals of different vegetables, in regard to their habituie to fire: the very light coals of linen, cotton, some fungi, &c., readily catch fire from a spark, and soon burn out; the more dense ones of woods and roots are set on fire more difficulty, and burn more slowly: the coals of the black berry-bearing alder, of the hazel, the willow, and the lime-tree, are said to answer best for the making of gunpowder and other pyrotechnical compositions, perhaps from their being easily inflammable: for the reduction of metallic calces those of the heavier woods, as the oak and the beech, are preferable, these seeming to contain a larger proportion of the phlogistic principle, and that, perhaps, in a more fixed state: considered as common fuel, those of the heavy woods give the greatest heat, and require the most plentiful supply of air to keep them burning; those of the light woods preserve a glowing heat, without much draught of air, till the coals themselves are consumed; the bark commonly crackles and flies about in burning, which the coal of the wood itself very seldom does.

Mathematical instrument makers, engravers, &c., find charcoal of great use to polish their bras and copper-plates after they have been rubbed clean with powdered pumice-stone. Plates of horn are polishable in the same way, and a glofs may be afterwards given with tripoli.

The coals of different substances are also used as pigments; hence the bone-black, ivory-black, &c., of the shops. Most of the paints of this kind, besides their incorruptibility, have the advantage of a full colour, and work freely in all the forms in which powdery pigments are applied; provided they have been carefully prepared, by thoroughly burning the subject in a close vessel, and afterwards grinding the coal into a powder of due fineness. Pieces of charcoal are used also in their entire state for tracing the outlines of drawings, &c.; in which intention they have an excellence, that their mark is easily wiped out. For these purposes, either the finer pieces of common charcoal are picked out and cut to a proper shape; or the pencils are formed of wood, and afterwards burnt into charcoal in a proper vessel well covered. The artists commonly make choice of the smaller branches of the tree freed from the bark and pith; and the willow and vine. Charcoal vine are preferred to all others. This choice is confirmed by the experiments of Dr Lewis, who has found that the wood of the trunks of trees produces charcoal of a harder nature than their small twigs or branches; and the hard woods, such as box and guaiacum, produced coals very sensibly harder than the softer woods. Willow he prefers to all others. The shells and stones of fruits yielded coals so hard that they would scarce mark on paper at all; while the coals of the kernels of fruits were quite soft and mellow. The several coals produced by the doctor's experiments were levigated into fine powder, mixed both with gum-water and oil, and applied as paints both thin and thick, and diluted with different degrees of white. All of them, when laid on thick, appeared of a strong full black, nor could it be judged that one was of a finer colour than another; diluted with white, or when spread thin, they had all somewhat of a bluish cast.

Horns and the bones both of fishes and land animals, gave coals rather gloffer and deeper-coloured than vegetables; and which, in general, were very hard, so as difficultly, or not at all, to stain paper. Here also the hardness of the coal seemed to depend on that of the subject from whence it was prepared; for silk, woollen, leather, blood, and the fleshy parts of animals, yielded soft coals. Some of these differed from others very sensibly in colour: that of ivory is superior to all the rest, and indubitably the finest of all the charcoal blacks. The animal coals had much less of the bluish cast in them than the vegetable, many of them inclining rather to a brown. Charred pit-coal, on the other hand, seemed to have this blueness in a greater degree.

Charcoal is not soluble in any of the acids; but may be dissolved in considerable quantities by a solution of hepatic sulphuris, to which it communicates a green colour. Melted with colourless fats or glases, it gives a pale yellow, dark yellow, reddish, brownish, or blackish colour, according as the inflammable matter is in greater or less proportion; the phlogiston, or inflammable matter of the coal seeming to be the direct tinging substance. When the phlogistic matter is thus diffused through glass, it is no more affected by continued strong fire than charcoal is when excluded from the air.

The vapour of burning charcoal is found to be highly noxious, being no other than fixed air. How this affects the animal system is explained under the article Blood.

From some late experiments it appears, that charcoal possesses many extraordinary properties altogether unsuspected by former chemists. It has particularly a great attraction for what is called the phlogiston, or rather for any kind of oily matter with which other substances may be filled; so that it now promises to be very useful in the arts in various ways never thought of before. M. Lowits has found that it is useful in preparing crystals of tartar of a very white colour; and that the marine and nitrous acids are decomposed by being distilled upon it; the red juices of vegetable fruits are discoloured, without losing any of their acidity; brown rancid oils are rendered sweet and clear by agitating them for some days with charcoal in powder; it changes the smell of putrid vegetables to that of a pure volatile alkali, and it produces the same effect on fresh meat. On boiling coals in powder with honey, the pure saccharine parts of the latter are said to be separated, and the honey to become a well-tasted sugar; the purification of real sugar is also said to be facilitated by the same method. Thus also the mother-water of the Prussian alkali and of the tartaric acid are made to crystallize easily; terra foliata tartari may be made white without calcination, by previously diluting the vinegar from coals. Vinegar concentrated by freezing, and distilled from a large proportion of powdered coal, is extremely strong, pure, and fragrant. Corn spirit merely shaken with coal loses its bad flavour; and if honey is added, it becomes a sweet and pleasant liquor. Even when ardent spirits are impregnated with any vegetable oils, the flavour is destroyed in this way; and if the spirit be distilled, the residuum is said not to be brown; so that if the distillation is carried too far, no inconvenience ensues. With Peruvian bark a clear decoction was formed, and the residuum was a salt, in taste like digestive salt. These effects were produced by every kind of coal, whether fossil or charred vegetable substances.

Charcoal has lately been separated from the pure spirit of wine in the process for making ether*; and *See Chr. by M. Lavosier is supposed to be one of the constituent parts or elements of that very volatile liquid. But the most extraordinary modern discovery concerning this substance is that of Dr Priestley, who has found that several of the metals may be converted into charcoal by passing the steam of spirit of wine over them when red-hot; and this, by way of distinction, he calls the charcoal of metals.

This surprising discovery was made accidentally, while the Doctor was repeating the experiments by which M. Lavosier imagined water might be converted into air. Having transmitted the steam of water through a copper tube, on which it had no effect, he was willing to try the effects of that of other fluids; and for this purpose made choice of spirit of wine, having before procured inflammable air by sending the same steam through a red-hot tobacco-pipe. No sooner had the vapour of this fluid, however, touched the red-hot copper, than he was astonished at the rapid production of air from it, which resembled the blowing of a pair of bellows; and before four ounces of the spirit were expended, the tube was found to be perforated in two or three places. In a moment afterwards it was so far destroyed, that it fell to pieces on attempting to remove it from the fire; the inside being filled with a black matter resembling lamp-black. Having now recourse to earthen tubes, the Doctor found that, by melting copper and other metals in them, and transmitting the vapour of spirit of wine in contact with them while in a state of ignition, different substances were formed according to the metals employed. On sending three ounce-measures of spirit of wine over two ounces of copper, the metal lost 28 grains of its weight, and 446 grains of charcoal were procured, chiefly in the form of powder, though some of it was in large flakes several inches long; having separated at once from the surface of the melted metal. These pieces were almost quite black, and bore handling without any danger of being broken. In another experiment, 508 grains of charcoal were obtained from 19 grains of copper; but here the metal had been previously reduced. Charcoal was indestructible by any other means than burning in an open fire, though of late it is found totally dissipable and convertible into inflammable air, by the heat of a burning lens in vacuo, at least with the assistance of a small quantity of water. By burning in dephlogisticated air, it is found to convert almost the whole of it into fixed air. See Aerology, no 110—113, 129, 131. From the experiments there related, it is now evident, that charcoal as such, and without any decomposition, is an ingredient in both those aerial fluids, and is indeed the phlogiston of Stahl so long fought in vain. This discovery, however, has not by any means put an end to the disputes betwixt the Phlogitians and Antiphlogitians, though it certainly ought to have done so, and must assuredly do so in a short time. The experiments of Dr Priestley are not doubted; and charcoal, the gravitating matter of light inflammable air, and phlogiston, are allowed to be the same by the Antiphlogitians as well as by the opposite party. "The present controversy (says Mr Higgins) amongst philosophers depends upon the following questions: 1. Whether water be or not composed of dephlogisticated and light inflammable air? 2. Whether or no the condensation of dephlogisticated air, or its union to different bodies, does not depend upon one principle, common to all combustible bodies? or, in other words, whether or no all bodies which burn or calcine, such as sulphur, phosphorus, charcoal, oils, metals, phlogisticated air, &c., contain the matter of light inflammable air as one of their constituent principles? One should suppose, if these substances were composed of two principles, namely a peculiar basis, and the matter of light inflammable air or phlogiston, that it would be possible to resolve them into these principles; more especially when we consider the great attraction of the matter of light inflammable air to fire; but the maintainers of phlogiston have not as yet been able to do this," &c.

The limits of this work will not allow us to enter on a full discussion of this controversy, nor can we pretend to be able to settle the disputes on the subject. It nevertheless seems somewhat unnatural to call iron, lead, copper, sulphur, phosphorus, &c., simple and unchangeable bodies, or if we please elements; as thus the number of elementary bodies might be increased without number, and water, which has generally been reckoned a simple one, supposed to be almost the only compound body in nature. It is also certain, that Dr Priestley has made some very striking and apparently decisive experiments on the subject of metals, to which no proper reply has ever been made. In order to see the force of these experiments, however, we must still observe, that, according to the Phlogitians, the calces of metals are reduced, on the addition of charcoal, not only by emitting the dephlogisticated air which adheres to them when in the form of calces, but by the admission of a quantity of the charcoal itself into their substance. This the Antiphlogitians deny; and though they admit the necessity of charcoal in the operation, yet they affirm that it acts only by attracting the dephlogisticated air contained in the calx, with which it forms fixed air; and hence they must say, that in all metallic reductions a quantity of fixed air is produced, equivalent not only to the weight of the charcoal employed, but also to that of the dephlogisticated air. Charcoal contained in the calx. The decisive experiment therefore would be, to expel from a metallic calx all the air it contained, to weigh it exactly in that state, and then observe whether it gained anything in weight by being reduced to a metal. This, however, has not been done; and the Antiphlogitians complain that their adversaries have not been able to produce a pure metallic calx free from all kind of aerial vapour. But though it is not pretended that any such calx has yet been produced, if the Phlogitians can show the possibility of reducing a calx without the production of fixed air, it would seem to be equally destructive of the antiphlogistic doctrine. This appears to have been done by Dr Priestley; in the experiments above alluded to; and it is even doubtful whether he did not obtain the so much desired calx, viz., one perfectly free from air altogether. "I put (says he) upon a piece of broken crucible, which could yield no air, a quantity of minium, out of which all air had been extracted; and placing it upon a convenient stand, introduced it into a large receiver filled with inflammable air confined by water. As soon as the minium was dry, by means of the heat thrown upon it, I observed that it became black, and then ran in the form of perfect lead, at the same time that the air diminished at a great rate the water ascending within the receiver. Before this first experiment was concluded, I perceived, that if the phlogiston in inflammable air had any base, it must be very inconsiderable; for the process went on till there was no more room to operate without endangering the receiver; and examining the air that remained, I found that it could not be distinguished from that in which I began the experiment, which was air extracted from iron by oil of vitriol.

"I afterwards carefully expelled, from a quantity of minium, all the phlogiston, and every thing else that could have affixed the form of air, by giving it a red heat when mixed with spirit of nitre; and immediately using it in the manner mentioned above, I reduced 107 ounce-measures of inflammable air to two. To judge of its degree of inflammability, I presented the flame of a small candle to the mouth of a vial filled with it, and observed, that it made 13 separate explosions, though weak ones (topping the mouth of the phial with my finger after each explosion); when fresh made inflammable air, in the same circumstances, made only 14 explosions, though stronger ones. In this experiment, however, I overlooked one obvious consideration, viz: that water, or any thing soluble in water, might be the basis of inflammable air. All that could be absolutely inferred from the experiment was, that this basis could not be any thing that was capable of subsiding in the form of air. It will be seen, that I afterwards made the experiment with air confined by mercury."

In this experiment it is to be regretted, that the Doctor did not inform us whether the weight of his calces was on the whole increased or diminished by the operation. As it stands, though sufficient to overthrow the doctrine of the Antiphlogitians, it is not altogether sufficient to establish that of their adversaries. Mr Higgins, however, though he does not reply to this experiment, gives an account of another from Dr Higgins, which he considers as absolutely decisive against the Phlogitians. "Dr Higgins (says he) introduced some pieces of well-burned charcoal into a Charcoal deep crucible, and covered them over an inch deep with powdered charcoal. Having luted on a cover, he exposed them for two hours to heat sufficient to melt silver; he then placed the crucible in such a manner that the powder might remain red hot for some time after the pieces next the bottom had cooled. This he had done, as the charcoal must imbibe something on cooling, both to supply it with inflammable air, and to prevent a communication with the external air, which the charcoal would otherwise have imbibed.

"One hundred and twenty grains of this charcoal quickly powdered, were well mixed with 7680 grains of litharge, which had been previously fused to separate any uncalcined lead it might contain. This mixture was charged into a coated retort just large enough to contain it; so that the common air must have been nearly excluded. Being then placed in a reverberating furnace, and heat duly applied, it yielded by elimination, after cooling to the mean temperature of the atmosphere, 384 grains of fixable air, at the rate of 0.57 grains to a cubic inch, 8,704 of phlogisticated air, and 0.911 grains of deplogisticated air, besides 49 grains of water. On breaking the retort, 3888 grains of revived lead were found, besides some vitrified litharge; but not an atom of charcoal was left, nor was there a particle of inflammable air produced. Now, let my reader consider the weight that 3888 grains of lead acquire by its conversion to litharge, and the quantity of inflammable air that 120 grains of charcoal will afford (which, according to Dr Priestley, is about 360 ounce-measures), and he will find, making allowance for the phlogisticated air, that these nearly correspond with the proportion of heavy inflammable air and deplogisticated air necessary to the formation of fixable air by the electric spark. Hence we may conclude, that not a particle of charcoal entered into the constitution of the revived lead, but must have been wholly converted into fixable air."

To this experiment, however, the Phlogitians will reply, that so far from being decisive of the subject, no conclusion whatever can be drawn from it, on account of its enormous inaccuracy. The quantity of matter put into the retort was 7680+120, or 7800 grains, and the whole produce was 3888+384+8,704+0.911+0.49=4330.615 grains; a deficiency therefore of no less than 3469.385 grains is to be accounted for; and of this we hear not one word; so that we are at liberty to suppose that the vitrified litharge had perforated the retort in such a manner as to admit the fixed and phlogisticated air from without, as Dr Priestley found earthen retorts pervious to air from without; and this, though coated, might by a corrosion of the glass (if it was a glass one) be reduced to a similar situation.

We do not mean that this should be reckoned a formal answer to Dr Higgins's experiment; all we intend here, is to state the arguments fairly on both sides, so that the reader who has not an opportunity of making experiments himself, may be able to judge on which side the truth lies. Dr Priestley informs us, that in his experiment, the calx of lead absorbed a quantity of inflammable air without the extrication of fixed air, or any thing else that could be perceived. Whether or not have we reason to conclude from thence, that the gravitating, solid, or coally, part of the inflammable air was received into the calx, and became part of the revived metal? In Dr Higgins's experiment a quantity of elastic fluid was produced, and a quantity of lead revived; but we neither know how much of the calx went to this lead, how much the licharge had originally attracted from the air, nor whether the elastic fluids were certainly produced; or indeed whether any of them, the small quantity of dephlogisticated air alone excepted, came from the materials or not. From such a state of the case then, have we reason to "conclude, that not a particle of charcoal entered into the constitution of the lead?"

We shall next consider an experiment made by Mr Higgins himself, and which he likewise considers as decisive against the Phlogitians. "I introduced (says he) some iron nails, free from rust, into strong volatile vitriolic acid; when it stood for a few minutes, it acquired a milky appearance, and the solution went on without ebullition or extrication of air. On standing for a few hours, the solution acquired a darkish colour, and a black powder was precipitated. This powder, when collected and washed, put on red hot iron, burned partly like sulphur and partly like charcoal dust, and the incombustible residuum was of a purple colour. The filtered solution was perfectly neutralized, and free from the least sulphureous pungency. Its taste was strongly chalybeate, but not so disagreeable as that of the solution of iron in the perfect vitriolic acid, or in any of the mineral acids. Nitrous acid dropped into the solution instantly produced a cloudiness, which immediately disappeared without ebullition, though volatile sulphureous acid was extracted in its utmost degree of pungency. The vitriolic, marine, and acetic acids decomposed this solution, but caused no turbidness, nor was any inflammable air produced.

"In order to know whether the sulphur was disengaged from the volatile sulphureous acid or the iron, I poured marine acid on the same nails, when light inflammable air and hepatic air were copiously produced, and likewise sulphur was deposited in its crude state. When I used vitriolic or the nitrous acid, no sulphur was produced. I tried different nails, and likewise iron-filings, with the same result. These facts convinced me that the sulphur came from the iron; but that all sorts of iron contain sulphur is what I cannot pretend to know, as I have not tried steel, or varieties enough of malleable iron. However, I have strong reason to suspect, that sulphur has more to do in the different properties of iron than we are aware of. That iron should contain sulphur, notwithstanding the different processes it must necessarily undergo before it acquires malleability, considering the volatility of sulphur, points out the force of their attraction to one another; and the separation of this again by volatile sulphureous acid, shows likewise the greater attraction of iron to sulphur and dephlogisticated air jointly. That volatile sulphureous acid should dissolve iron without the extrication of inflammable air or phlogiston, is a very strong instance of the fallacy of the phlogistic doctrine. A small quantity of inflammable air is produced, but it is so trifling comparatively to what should be produced from the quantity of iron dissolved, that it is hardly worth noticing; and in my opinion proceeds from a portion of perfect vitriolic Charcoal acid, which is generally inseparable from the volatile acid. If volatile vitriolic acid were a compound of phlogiston, a certain basis, and dephlogisticated air, a greater quantity of inflammable air should have been disengaged during the solution of iron in this acid than when the perfect vitriolic acid is used. Let us even suppose volatile sulphureous acid to be composed of the basis of sulphur, phlogiston, and dephlogisticated air, which is the opinion of all the Phlogitians, though they differ with respect to the modification of these three principles; and likewise iron to be composed of a certain basis and phlogiston; I would ask the Phlogitians, What becomes of the phlogiston of the iron during its solution?"

But however much Mr Higgins may be convinced, from this experiment, of the fallacy of the phlogistic doctrine, his adversaries, instead of being silenced, will urge his own experiment against himself. He owns, that during the solution something was separated of a black colour, and which burned like charcoal dust. Unless therefore Mr Higgins shall prove the contrary, they will say, that this was the real phlogiston or charcoal which entered into the substance of the metal; and that it appeared in its native form, because the volatile vitriolic acid had not specific or latent heat sufficient to convert it into inflammable air. At any rate, it was incumbent on Mr Higgins to have accounted for the coally part of his residuum as well as the sulphureous one; yet he has been at considerable pains to deduce the latter from the iron, without speaking a word about the former. Indeed, whether he deduced this from the iron or the vitriolic acid, it will make equally against him; for his principles do not allow that the volatile vitriolic acid contains any charcoal. That the latter really does so, however, appears from an experiment of Dr Priestley, in which he reduced a calx of lead by means of vitriolic acid air, the same with the vitriolic or volatile sulphureous acid. It is true, that only a small quantity of metal was thus procured; but however small this was, the Antiphlogitians do not pretend that metals can be reduced to their metallic state in any quantity, except by the mediation of charcoal.

Thus it appears, that with regard to metals the dispute is as yet far enough from being decided in favour of the Antiphlogitians. Their cause is equally doubtful with regard to sulphur and phosphorus, both of which Dr Priestley has produced by heating vitriolic and phosphoric acid in inflammable air. Indeed, by some experiments on sulphur, the matter seems to be decided against them. "Perhaps (says Dr Priestley) as decisive a proof as any, of the real production of fixed air from phlogiston and dephlogisticated air, may be drawn from the experiments in which I always found a quantity of it when I burned sulphur in dephlogisticated air. In one of these experiments to which I gave more particular attention, six ounce-measures and an half of the dephlogisticated air were reduced to about two ounce-measures, and one-fifth of this was fixed air." Now, though the Doctor inferred from this, that fixed air was composed of phlogiston and dephlogisticated air, on the supposition of sulphur containing phlogiston; yet, admitting from other proofs, that fixed air is composed of these two principles, the experiment Charcoal. riment unanswerably proves, that sulphur contains phlogiston or charcoal, though indeed in a very small quantity: but if the sulphur contained none at all, and the dephlogisticated air as little, as the Antiphlogitians would have it, how is it possible that a compound, of which phlogiston makes a part, should result from an union of the two? Another experiment equally decisive, even with regard to metals, is that quoted from Dr Priestley in the place just referred to (a), where he obtained pure fixed air from a mixture of red precipitate and iron-fillings. Now, according to the antiphlogistic doctrine, neither of these materials contained an atom of charcoal or phlogiston; whence then came the phlogiston in the fixed air which issued from the mixture?

Thus the Antiphlogitians seem to be unanswerably refuted with regard to sulphur and metallic substances; for if the two experiments just related be accurate, it is impossible to invalidate them by any argumentation whatever. Their last resource therefore is the decomposition of water: and even here it is evident they have little reason to boast. On this subject, however, we are sorry to observe, that the opinions have been so many, so various, and so fluctuating, that it is not only impossible to say what are the prevailing ones, but even difficult to ascertain what are the sentiments of any individual on the subject. Under the article Aerology, n° 81, we have quoted Dr Priestley as favouring the doctrine of the decomposition of water; and in Mr Higgins's work we find him quoted as opposing it. "Dr Priestley (says he) supposes that the water produced by the condensation of inflammable and dephlogisticated air, is only what was suspended and attached to them in their elastic state, and that their respective gravitating particles form a different compound, namely, the nitrous acid. To ascertain this, he confined his mixture of airs with dry fixed alkali over mercury, in order to abstract from it as much water as possible. Having thus prepared his mixture of airs, he found, after exploding them, that the product of water fell far short of the weight of both airs; and he observed a dense vapour after every explosion, which soon condensed, and adhered in a solid state to the sides of the vessel, which he found afterwards to be the nitrous acid." To this Mr Higgins answers, that the airs ought to have been accurately weighed before abstracting the water from them, when (he supposes) the weight of water produced would have equalled them. This indeed ought to have been done; but Mr Higgins, or some Antiphlogitian, ought to have done so before he decided positively in favour of the opposite doctrine. At any rate, it cannot be pretended, that in any experiment, let the circumstances of it be what they would, the quantity of water produced ever equalled that of the two airs. It is evident therefore, that till this shall somehow or other be cleared up, the matter must remain uncertain. That the purest water we can obtain always contains phlogiston, is what no Phlogitian denies; that it essentially belongs to it is doubtful, though indeed it must be probable, that it does so until experiments show the contrary. Mr Cavendish supposes that dephlogisticated air and dephlogisticated water may be the same; and indeed this would seem to be almost certain, were it not for a circumstance taken notice of by Mr Higgins, viz., that in the firing of iron in dephlogisticated air the latter appears to be totally absorbed; though it is certain, that a quantity of undecomposed water enters into its composition.

How far this circumstance throws any obscurity on the matter the reader must determine. For a more full investigation of the subject, however, we must refer to the article Water; and in the mean time shall dismiss the article with a few observations on the composition of charcoal.

From the days of Stahl till very lately, the component parts of this sublimate have been reckoned a certain kind of earth combined with what was called phlogiston. The late experiments of Dr Priestley have shown, that this doctrine is erroneous, and that charcoal is wholly dissipable into vapour. "On the whole (says the translator of Wiegbleb's Chemistry), charcoal appears, from the experiments of Lavoisier and Berthollet, to be an oil deprived of its inflammable gas. But coal of wood (or common charcoal) likewise contains fixed alkali, which the foot (or the coal of oil) does not, but instead of this exhibits volatile alkali. The fixed alkali of the former proceeds from the plant itself, and this, in the case of foot, is joined with inflammable gas, and forms volatile alkali, the earthy part being left behind, as happens when this latter is prepared from fixed alkali. Genuine charcoal, therefore, consists of this vegetable principle, united with a little fixed alkali and part of the phlogiston that constituted the oil of the plant of which it is made: for some of this principle is carried off, together with the hydrophlogiste (b), in the form of inflammable gas, if distilled in close vessels; but if burned in the open air, the hydrophlogiste unites with the pure part of the air, and forms water. From these considerations, as well as from the experiments and observations of M. Berthollet, in the Mem. de l'Acad. des Sciences pour 1786, p. 33. et seq. it appears, that common charcoal consists of the vegetable principle, some phlogiston, fixed alkali, and no inflammable gas."

On all this, however, we must observe, that it is entirely disproved by the experiments of Dr Priestley, so often quoted, in which it was totally dissipated into inflammable air. On this occasion indeed he acknowledges, that some very minute particles of ashes were observed, which could not have amounted to a single grain from many pounds of wood. Even these, according to what he observes in the same place, may be supposed to have come from the small quantity of air in the receiver; and it is to be wished that the Doctor would repeat the experiment in one of those perfect vacuums through which the electric fluid cannot be made to pass. From undoubted experiments, however, it appears, that charcoal cannot be decomposed by mere heat; as in vacuo it is dissipated into inflammable air:

(a) See Encycl. Vol. I. p. 169. col. i. where, in lines 18, 19 from the top, read precipitate for charcoal. (b) A word used by Mr Wiegbleb, as far as we can comprehend the author's meaning, for one of the component parts of water. See his General System of Chemistry, translated by Hopson, p. 39. charcoal, and this, on presenting a proper substance to attract the solid part, again discovers itself, by its blackness, to be real charcoal. As little does it appear destructible by burning in the open air; for though some ashes are left, it appears probable that these differ from the coal itself in nothing but having a quantity of air attached to them. By far the greatest part of it, even in the common way of burning, is converted into fixed air; and from this it may again be separated by taking the electric spark in that fluid, when it is resolved into very pure dephlogisticated and inflammable air. The same separation may be effected by merely heating iron in fixed air; in which case the dephlogisticated part will unite to the iron, and the coaly part, together with part of the phlogiston of the metal, be converted into inflammable air. From all these, and other considerations, a suspicion is induced, that the matter of charcoal is not different from the element of earth itself; and that, according to the different modifications of this substance, it either appears as coal, ashes, earth of various kinds, or even metals. This receives some confirmation from the following experiments of Mr Watt, related in the 74th volume of the Philosophical Transactions: "I dissolved (says he) magnesia alba, calcareous earth, and minium, in nitrous acid dephlogisticated by boiling, and diluted with proper proportions of water. I made use of glass-retorts coated with clay; and I received the air in glass-vessels, whose mouths were immersed in a glazed earthen basin containing the smallest quantity of water that could be used for the purpose. As soon as the retort was heated a little above the degree of boiling water, the solutions began to distil watery vapours containing nitrous acid. Soon after these vapours ceased, yellow fumes, and, in some of the cases, dark red fumes, began to appear in the neck of the retort; and, at the same time, there was a production of dephlogisticated air, which was greater in quantity from some of these mixtures than from others, but continued in all of them until the substances were reduced to dryness. I found in the receiving water, &c. very nearly the whole of the nitrous acid used for their solution, but highly dephlogisticated, so as to emit nitrous air by the application of heat; and there is reason to believe, that with more precaution the whole might have been obtained. As the quantity of dephlogisticated air produced by these processes did not form a sufficient part of the whole weight to enable me to judge whether any of the real acid entered into the composition of the air I obtained, I ceased to pursue them further, having learned from them the fact, that however much the acid and the earths were dephlogisticated before the solution, the acid always became highly dephlogisticated in the process.

"In order to examine whether this phlogiston was furnished by the earths, some dephlogisticated nitrous acid was distilled from minium till no more air or acid came over. More of the same acid was added to the minium as soon as it was cold, and the distillation repeated, which produced the same appearances of red fumes and dephlogisticated air. This operation was repeated a third time on the same minium, without any sensible variation in the phenomena. The process should have been still farther repeated, but the retort broke about the end of the third distillation; the quantity of minium used was 120 grains, and the quantity of nitrous acid added each time was 240 grains, of such strength that it could dissolve half its weight of mercury by means of heat. It appears from this experiment, that unless minium be supposed principally to consist of phlogiston, the source of the phlogiston thus obtained, was either the nitrous acid itself, or the water with which it was diluted; or else that it came through the retort with the light; for the retort was in this case red hot before any air was produced. Yet this latter conclusion does not appear very satisfactory, when it is considered, that in the process wherein the earth made use of was magnesia, the retort was not red hot, or very obscurely so, in any part of the process, and by no means luminous when the yellow and red fumes first made their appearance."

To these experiments, however, the Antiphlogitists will no doubt reply, that there was no phlogiston in the case, and that the nitrous acid was only decomposed; and indeed the decisive experiment here would be, the entire distillation of a quantity of earth into some kind of air, as may be done with charcoal; but to do this in the way of distillation must be attended with incredible labour, though, as finally deciding this point, it seems to be well worth pursuing.

A pretty strong proof of the identity of metallic calces with charcoal, is their conversion into it in the manner already related. Experiments, however, are yet wanting on the subject; though it seems probable from what Dr Priestley has already done, that they may thus be entirely dissipated into air as well as common charcoal.