Is that science which teaches us the properties of mineral bodies, and by which we learn how to characterize, distinguish, and class them into a proper order.

INTRODUCTION.

Mineralogy seems to have been in a manner coeval with the world. Precious stones of various kinds appear to have been well known among the Jews and Egyptians in the time of Moses; and even the most rude and barbarous nations appear to have had some knowledge of the ores of different metals. As the science is nearly allied to chemistry, it is probable that the improvements both in chemistry and mineralogy have nearly kept pace with each other; and indeed it is but of late, since the principles of chemistry were well understood, that mineralogy has been advanced to any degree of perfection. The best way of studying mineralogy, therefore, is by applying chemistry to it; and not contenting ourselves merely with inspecting the outsides of bodies, but decomposing them according to the rules of chemistry. This method has been brought to the greatest perfection by Mr Pott of Berlin, and after him by Mr Cronstedt of Sweden. To obtain this end, chemical experiments in the large way are without doubt necessary; but as a great deal of the mineral kingdom has already been examined in this manner, we do not need to repeat all those experiments in their whole extent, unless some new and particular phenomena should discover themselves in those things we are examining; else the tediousness of those processes might discourage some from going farther, and take up much of the time of others that might be better employed. An easier way may therefore be adopted, which even for the most part is sufficient, and which, though made in miniature, is as scientific as the common manner of proceeding in the laboratories, since it imitates that, and is founded upon the same principles. This consists in making the experiments upon a piece of charcoal with the concentrated flame of a candle directed through a blow-pipe. The heat occasioned by this is very intense; and the mineral bodies may here be burnt, calcined, melted, and scorified, &c. as well as in any great works.

For a description of the blow-pipe, the method of using it, the proper fluxes to be employed, and the different subjects of examination to which that instrument is adapted, see the article Blow-Pipe, where all those particulars are concisely detailed. It may not be improper here, however, to resume those details at greater length; avoiding, at the same time, all unnecessary repetitions. After which we shall exhibit a scientific arrangement of the mineral kingdom, according to the most approved system.

PART I. EXPERIMENTAL MINERALOGY; with a DESCRIPTION OF THE NECESSARY APPARATUS (A).

SECT. I. Of Experiments upon Earths and Stones.

When any of these substances are to be tried, we must not begin immediately with the blow-pipe; but some preliminary experiments ought to go before, by which those in the fire may afterwards be directed. For instance, a stone is not always homogeneous, or of the same kind throughout, although it may appear to the eye to be so. A magnifying glass is therefore necessary to discover the heterogeneous particles, if there be any; and these ought to be separated, and every part tried by itself, that the effects of two different things, examined together, may not be attributed to one alone. This might happen with some of the finer micae, which are now and then found mixed with small particles of quartz, scarcely to be perceived by the eye. The trapp (in German schwartzstein) is also sometimes mixed with very fine particles of felspar (spatium scintillans) or of calcareous spar, &c. After this experiment, the hardness of the stone in question must be tried with steel. The flint and garnets are commonly known to strike fire with steel; but there are also other stones, which, though very seldom, are found so hard as likewise to strike fire. There is a kind of trappe of that hardness, in which no particles of felspar are to be seen. Coloured glasses resemble true gems; but as they are very soft in proportion to these, they are easily discovered by means of the file. The common quartz-crystals are harder than coloured glasses, but softer than the gems. The loadstone discovers the presence of iron, when it is not mixed in too small a quantity in the stone, and often before the stone is roasted. Some kinds of haematites, and particularly the cerulecens, greatly resemble some other iron ores; but this distinguishes itself from them by a red colour when pounded, the others giving a blackish powder, and so forth.

The management of the Blow-pipe has been described under that article; but a few particulars may be here recapitulated, or added.

The candle ought to be snuffed often, but so that the top of the wick may retain some fat in it, because the flame is not hot enough when the wick is almost burnt to ashes; but only the top must be snuffed off, because a low wick gives too small a flame. The blue flame is the hottest; this ought, therefore, to be forced.

(A) From Engelstrom's Treatise on the Blow-Pipe, and Magellan's Description of Pocket-Laboratories, &c., subjoined to the English Translation of Cronstedt's Mineralogy, 2d edit. in 2 vols. Dilly. forced out when a great heat is required, and only the point of the flame must be directed upon the subject which is to be affayed. M. Magellan recommends, as being most cleanly and convenient, that the candle be made of wax, and the wick should be thicker than ordinary. Its upper end must be bended towards the matter intended to be heated, and the stream of air must be directed along the surface of the bended part, so as not absolutely to touch it.

The piece of charcoal made use of in these experiments must not be of a disposition to crack. If this should happen, it must gradually be heated until it does not crack any more, before any affay is made upon it. If this be not attended to, but the affay made immediately with a strong flame, small pieces of it will split off in the face and eyes of the affayer, and often throw along with them the matter that was to be affayed. Charcoal which is too much burnt consumes too quick during the experiment, leaving small holes in it, wherein the matter to be tried may be lost; and charcoal that is burnt too little, catches flame from the candle, burning by itself like a piece of wood; which likewise hinders the process.

Of those things that are to be affayed, only a small piece must be broken off for that purpose, not bigger than that the flame of the candle may be able to act upon it at once, if required; which is sometimes necessary, as, when the matter requires to be made red hot throughout, the piece ought to be broken as thin as possible, at least the edges; the advantage of which is obvious, the fire having then more influence upon the subject, and the experiment being more quickly made.

Some of the mineral bodies are very difficult to be kept steady upon the charcoal during the experiment, before they are made red hot; because, as soon as the flame begins to act upon them, they split asunder with violence, and are dispersed. Such often are those which are of a soft consistence or a particular figure, and which preserve the same figure in however minute particles they are broken; for instance, the calcareous spar, the sparry gypsum, the sparry fluor, white sparry lead-ore, the potters ore, the teffellated mock-lead or blende, &c. even all the common fluors which have no determinate figure. These not being so compact as common hard stones, when the flame is immediately urged upon them, the heat forces itself through and into their clefts or pores, and causes this violent expansion and dispersion. Many of the clays are likewise apt to crack in the fire, which may be for the most part ascribed to the humidity, of which they always retain a portion.

The only way of preventing this inconvenience is to heat the body as slowly as possible. It is best, first of all, to heat that place of the charcoal where the piece is intended to be put on; and afterwards lay it thereon: a little crackling will then ensue, but commonly of no great consequence. After that, the flame is to be blown very slowly towards it, in the beginning not directly upon, but somewhat above it, and so approaching nearer and nearer with the flame until it become red hot. This will do for the most part; but there are nevertheless some, which, notwithstanding all these precautions, it is almost impossible to keep on the charcoal. Thus the fluors are generally the most difficult; and as one of their principal characters is discovered by their effects in the fire per se, they ought necessarily to be tried that way. To this purpose, it is best to make a little hole in the charcoal to put the flour in, and then to put another piece of charcoal as a covering upon this, leaving only a small opening for the flame to enter. As this stone will nevertheless split and fly about, a larger piece thereof than is before-mentioned must be taken, in order to have at least something of it left.

But if the experiment is to be made upon a stone whose effects one does not want to see in the fire per se, but rather with fluxes, then a piece of it ought to be forced down into melted borax, when always some part of it will remain in the borax, notwithstanding the greatest part may sometimes fly away by cracking.

1. Of substances to be tried in the fire per se. As the stones undergo great alterations when exposed to the fire by themselves, whereby some of their characteristics, and often the most principal, are discovered, they ought first to be tried that way, observing what has been said before concerning the quantity of matter, direction of the fire, &c. The following are generally the results of this experiment.

Calcaceous earth or flone, when it is pure, does not melt by itself, but becomes white and friable, so as to break freely between the fingers; and, if suffered to cool, and then mixed with water, it becomes hot, just like common quick-lime. As in these experiments only very small pieces are used, this last effect is best discovered by putting the proof on the outside of the hand, with a drop of water to it, when instantly a very quick heat is felt on the skin. When the calcareous substance is mixed with the vitriolic acid, as in gypsum, or with a clay, as in marle, it commonly melts by itself, yet more or less difficulty in proportion to the differences of the mixtures. Gypsum produces generally a white, and marle a grey, glas or flag. When there is any iron in it, as a white iron ore, it becomes dark, and sometimes quite black, &c.

The silicee never melt alone, but become generally more brittle after being burnt. Such of them as are coloured become colourless, and the sooner when it does not arise from any contained metal; for instance, the topazes, amethysts, &c. some of the precious stones, however, excepted: And such as are mixed with a quantity of iron grow dark in the fire, as some of the jaspers, &c.

Garnets melt always into a black flag, and sometimes so easily that they may be brought into a round globule upon the charcoal.

The argillacee, when pure, never melt, but become white and hard. The same effects follow when they are mixed with phlogiston. Thus the soap-rock is easily cut with the knife; but being burnt it cuts glass, and would strike fire with the steel, if as large a piece as is necessary for that purpose could be tried in this way. The soap-rocks are sometimes found of a dark brown and nearly black colour, but nevertheless become quite white in the fire like a piece of China ware. However, care must be taken not to urge the flame from the top of the wick, there being for the most part a foamy smoke, which commonly will darken all that it touches; and, if this is not observed, a mistake in the experiment might easily happen. But if it is mixed with iron, as it is sometimes found, it does not so easily part with its dark colour. The argillaceæ when mixed with lime melt by themselves, as above-mentioned. When mixed with iron, as in the boles, they grow dark or black; and if the iron is not in too great a quantity, they melt alone into a dark flag; the same happens when they are mixed with iron and a little of the vitriolic acid, as in the common clay, &c.

Mica and alabaster become somewhat hard and brittle in the fire, and are more or less refractory, though they give some marks of fusibility.

The flours discover one of their chief characteristics by giving a light like phosphorus in the dark, when they are slowly heated; but lose this property, as well as their colour, as soon as they are made red hot.—They commonly melt in the fire into a white opaque flag, though some of them not very easily.

Some sorts of the zeolites melt easily, and foam in the fire, sometimes nearly as much as borax, and become a frothy flag, &c.

A great many of those mineral bodies which are impregnated with iron, as the boles, and some of the white iron ores, &c. as well as some of the other iron ores, viz. the bloodstone, are not attracted by the loadstone before they have been thoroughly roasted, &c.

2. Of substances heated with fluxes. After the mineral bodies have been tried in the fire by themselves, they ought to be heated with fluxes to discover if they can be melted or not, and some other phenomena attending this operation. For this purpose, three different kinds of salts are used as fluxes, viz. sal soda, borax, and sal fusible microcosmic (see the article Blow-Pipe).

The sal soda is, however, not much used in these small experiments, its effects upon the charcoal rendering it for the most part unfit for it; because, as soon as the flame begins to act upon it, it melts instantly, and is almost wholly absorbed by the charcoal. When this salt is employed to make any experiment, a very little quantity is wanted at once, viz. about the cubical contents of an eighth part of an inch, more or less. This is laid upon the charcoal, and the flame blown on it with the blow-pipe; but as this salt commonly is in form of a powder, it is necessary to go on very gently, that the force of the flame may not disperse the minute particles of the salt. As soon as it begins to melt, it runs along on the charcoal, almost like melted tallow; and when cold, it is a glairy matter of an opaque dull colour spread on the coal. The moment it is melted, the matter which is to be tried ought to be put into it, because otherwise the greatest part of the salt will be soaked into the charcoal, and too little of it left for the intended purpose. The flame ought then to be directed on the matter itself; and if the salt spreads too much about, leaving the proof almost alone, it may be brought to it again by blowing the flame on its extremities, and directing it towards the subject of the experiment. In the assays made with this salt, it is true, we may find whether the mineral bodies which are melted with it have been dissolved by it or not; but we cannot tell with any certitude whether this is done hastily and with force, or gently, and slow; nor whether a less or a greater part of the matter has been dissolved: neither can it be well distinguished if the matter has imparted any weak tincture to the flag; because this fact always bubbles upon the charcoal during the experiment, nor is it clear when cool; so that scarcely any colour, except it be a very deep one, can be discovered, although it may sometimes be coloured by the matter that has been tried.

The following earths are entirely soluble in this flux with effervescence: Agate; chalcedony; carnelian; Turkey stone†; (cos Turcica); fluor minerals†; onyx; opal; quartz; common flint; ponderous spar. The following are divisible in it with or without effervescence, but not entirely soluble: Amianthus; asbestos; bafaltes; chrysolite‡; granate‡; hornblende; jasper; marlstone; mica; the mineral of alum from Tofla; petroflex; aluminous slate and roof slate from Helsingia; emeralds; feldspars; common flint; schoerl; talc; trapp; tripoli; tourmalin. And the following are neither fusible nor divisible in it: Diamond; hyacinth; ruby; sapphire; topaz.

The other two salts, viz. borax and the sal microcosmicum, are very well adapted to these experiments, because they may by the flame be brought to a clear uncoloured and transparent glass; and as they have no attraction to the charcoal, they keep themselves always upon it in a round globular form. The sal fusible microcosmic is very scarce, and perhaps not to be met with in the shops; it is made of urine.

The following earths are soluble in borax, with more or less effervescence: Fluor minerals†; marle; micat‡; the mineral of alum from Tofla; aluminous slate, and roof-slate from Helsingia†; ponderous spar; schoerl; talc†; tourmalin. And the following without effervescence: Agate; diamond; amianthus; asbestos; bafaltes; chalcedony; cornelian; chrysolite; cos turcica; granate; hyacinth†; jasper; lapis ponderosus; onyx; opal; petro-flex; quartz*; ruby; sapphire; common flint*; feldspar; trapp; tripel, or tripoli; topaz; zeolite; hydrophanes.

In the microcosmic salt, the following are soluble with more or less effervescence: Bafaltes†; turkey stone†; fluor minerals†; marle; mica; the mineral of alum from Tofla; schilts aluminares, schilts tegularis from Helsingia†; schoerl; spathum ponderosum†; tourmalin†; lapis ponderosus. And the following without visible effervescence: Agate; diamond; amianthus; asbestos; chalcedony; carnelian; chrysolite; granate; hyacinth; jasper; onyx‡; opal; petro-flex; quartz‡; ruby; sapphire; common flint‡; emerald; talc; topaz; trapp; tripel; zeolite; hornblend; hydrophanes; lithomarga; feldspar.

Calcareous earth, ponderous spar, gypsum, and other addiments, often assist the solution, as well in the microcosmic salt as in borax. To which it is necessary to add, that in order to observe the effervescence properly, the matter added to the flux should be in the form of a small particle rather than in fine powder; because in this last there is always air between the particles, which being afterwards driven off by the heat afford the appearance of a kind of effervescence (A).

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(a) In the above lists, the articles marked † effervesce very little; those marked ‡ not at all; those marked * require a larger quantity of the flux and a longer continuance of heat than the rest; those marked † are more difficultly dissolved than the others. The quantity of those two salts required for an experiment is almost the same as the sal soda; but as the former are crystallized, and consequently include a great deal of water, particularly the borax, their bulk is considerably reduced when melted, and therefore a little more of them may be taken than the before-mentioned quantity.

Both those salts, especially the borax, when exposed to the flame of the blow-pipe, bubble very much and foam before they melt to a clear glass, which for the most part depends on the water they contain. And as this would hinder the assayer from making due observations on the phenomena of the experiment, the salt which is to be used must first be brought to a clear glass before it can serve as a flux; it must therefore be kept in the fire until it become transparent that the cracks in the charcoal may be seen through it. This done, whatsoever is to be tried is put to it, and the fire continued.

Here it is to be observed, that for the assays made with any of these two fluxes on mineral bodies, no larger pieces must be taken than that altogether they may keep a globular form upon the charcoal; because it may then be better distinguished in what manner the flux acts upon the matter during the experiment. If this be not observed, the flux, communicating itself with every point of the surface of the mineral body, spreads all over it, and keeps the form of this salt, which commonly is flat, and by that means hinders the operator observing all the phenomena which may happen. Besides, the flux being in too small a quantity in proportion to the body to be tried, will be too weak to act with all its force upon it. The best proportion therefore is about a third part of the mineral body to the flux; and as the quantity of the flux above mentioned makes a globe of a due size in regard to the greatest heat that is possible to procure in these experiments, so the size of the mineral body must be a third part less here than when it is to be tried in the fire by itself.

The sal soda, as has been already observed, is not of much use in these experiments; nor has it any particular qualities in preference to the two last mentioned salts, except that it dissolves the zeolites easier than they do.

The microcosmic salt shows almost the same effects in the fire as the borax, only differing from it in a very few circumstances; of which one of the principal is, that, when melted with manganese, it becomes of a crimson hue instead of a jacinth colour, which borax takes. This salt is, however, for its scarcity still very little in use, borax alone being that which is commonly employed. Whenever a mineral body is melted with any of these two last mentioned salts, in the manner already described, it is easily seen, whether it quickly dissolves; in which case an effervescence arises, that lasts till the whole be dissolved; whether the solution be slowly performed; in which case few and small bubbles only rise from the matter; or, whether it can be dissolved at all; because, if not, it is observed only to turn round in the flux, without the least bubble, and the edges look as sharp as they were before.

In order farther to illustrate what has been said about these experiments, we shall give a few examples of the effects of borax upon the mineral bodies.—The calcareous substances, and all those stones which contain anything of lime in their composition, dissolve readily and with effervescence in the borax. The effervescence is the more violent the greater the portion of lime contained in the stone. This cause, however, is not the only one in the gypsum, because both the constituents of this do readily mix with the borax, and therefore a greater effervescence arises in melting gypsum with the borax than lime alone.—The fluxes do not dissolve; some few excepted which contain a quantity of iron.—The argillaceous, when pure, are not acted upon by the borax; but when they are mixed with some heterogeneous bodies, they are dissolved, though very slowly; such are, for instance, the stone-marrow, the common clay, &c.

The granates, zeolites, and trapps, dissolve but slowly. The fluors, apatite, and micacee, dissolve for the most part very easily; and so forth.—Some of these bodies melt to a colourless transparent glass with the borax; for instance, the calcareous substances when pure, the fluors, some of the zeolites, &c. Others tinge the borax with a green transparent colour, viz. the granates, trapps, some of the argillaceous, and some of the micaceae and apatites. This green has its origin partly from a small portion of iron which the granates particularly contain, and partly from phlogiston.

Borax can only dissolve a certain quantity of the mineral body proportional to its own. Of the calcareous kind it dissolves a vast quantity; but turns at last, when too much has been added, from a clear transparent to a white opaque flag. When the quantity of the calcareous matter exceeds but little in proportion, the glass looks very clear as long as it remains hot; but as soon as it begins to cool, a white half opaque cloud is seen arise from the bottom, which spreads over the third, half, or more of the glass globe, in proportion to the quantity of calcareous matter; but the glass or flag is nevertheless shining, and of a glassy texture when broken. If more of this matter be added, the cloud rises quicker and is more opaque, and so by degrees till the flag becomes quite milk white. It is then no more of a shining, but rather dry appearance, on the surface; is very brittle, and of a grained texture when broken.

Sect. II. Of Experiments upon Metals and Ores.

What has been hitherto said relates only to the stones and earths; we shall now proceed to describe the manner of examining metals and ores. An exact knowledge and nicety of procedure are so much the more necessary here, as the metals are often so disguised in their ores, as to be very difficultly known by their external appearance, and liable sometimes to be mistaken one for the other: Some of the cobalt ores, for instance, resemble much the pyrites arsenicalis; there are also some iron and lead ores, which are nearly like one another, &c.

As the ores generally consist of metals mineralized with sulphur or arsenic, or sometimes both together, they ought first to be exposed to the fire by themselves, in order not only to determine with which of these they are mineralized, but also to set them free from those volatile mineralizing bodies: This serves instead of calcination, by which they are prepared for further assays. Here it must be repeated, that whenever any metal or fusible ore is to be tried, a little concavity must be made in that place of the charcoal where the matter is to be put; because, as soon as it is melted, it forms itself into a globular figure, and might then roll from the charcoal, if its surface was plain; but when borax is put to it, this inconvenience is not so much to be feared.

Whenever an ore is to be tried, a small bit being broke off for the purpose, it is laid upon the charcoal, and the flame blown on it slowly. Then the sulphur or arsenic begins to part from it in form of smoke; these are easily distinguished from one another by their smell; that of sulphur being sufficiently known, and the arsenic smelling like garlic. The flame ought to be blown very gently as long as any smoke is seen to part from the ore; but after that, the heat must be augmented by degrees, in order to make the calcination as perfect as possible. If the heat be applied very strongly from the beginning upon an ore that contains much sulphur or arsenic, the ore will presently melt, and yet lose very little of its mineralising bodies, by that means rendering the calcination very imperfect. It is, however, impossible to calcine the ores in this manner to the utmost perfection, which is easily seen in the following instance, viz., in melting down a calcined potter's ore with borax, it will be found to bubble upon the coal, which depends on the sulphur which is still left, the vitriolic acid of this uniting with the borax, and causing this motion. However, lead in its metallic form, melted in this manner, bubbles upon the charcoal, if any sulphur remains in it. But as the lead, as well as some of the other metals, may raise bubbles upon the charcoal, although they are quite free from the sulphur, only by the flames being forced too violently on it, these phenomena ought not to be confounded with each other.

The ores being thus calcined, the metals contained in them may be discovered, either by being melted alone or with fluxes; when they show themselves either in their pure metallic state, or by tingling the flag with a colour peculiar to each of them. In these experiments it is not to be expected that the quantity of metal contained in the ore should be exactly determined; this must be done in larger laboratories. This cannot, however, be looked upon as any defect, since it is sufficient for a mineralogist only to find out what sort of metal is contained in the ore. There is another circumstance, which is a more real defect in the miniature laboratories, which is, that some ores are not at all capable of being tried by so small an apparatus; for instance, the gold ore called pyrites aurata, which consists of gold, iron, and sulphur. The greatest quantity of gold which this ore contains is about one ounce, or one ounce and a half, out of 100 pounds of the ore, the rest being iron and sulphur: and as only a very small bit is allowed for these experiments, the gold contained therein can hardly be discerned by the eye, even if it could be extracted; but it goes along with the iron in the flag, this last metal being in so large a quantity in proportion to the other, and both of them having an attraction for each other.

The blends and black-jacks, which are mineral zinc ores, containing zinc, sulphur, and iron, cannot be tried this way, because they cannot be perfectly calcined, and besides the zinc flies off when the iron scorifies. Neither can those blends, which contain silver or gold mineralised with them, be tried in this manner, which is particularly owing to the imperfect calcination. Nor are the quicksilver ores fit for these experiments; the volatility of that semifluid making it impossible to bring it out of the poorer sort of ores; and the rich ores, which sweat out the quicksilver when kept close in the hand, not wasting any of these alloys, &c. These ores ought to be assayed in larger quantities, and even with such other methods as cannot be applied upon a piece of charcoal.

Some of the rich silver ores are easily tried: for instance, minera argentis vitrea, commonly called silver-glass, which consists only of silver and sulphur. When this ore is exposed to the flame, it melts instantly, and the sulphur goes away in fume, leaving the silver pure upon the charcoal in a globular form. If this silver should happen to be of a dirty appearance, which often is the case, then it must be melted anew with a very little borax; and after it has been kept in fusion for a minute or two, so as to be perfectly melted and red-hot, the proof is suffered to cool: it may then be taken off the coal; and being laid upon the steel-plate,† the silver is separated from the flag by one or two strokes of the hammer‡. Here the use of the article brass ring‡ is manifest; for this ought first to be placed upon the plate, to hinder the proof from flying off by the violence of the stroke, which otherwise would happen. The silver is then found inclosed in the flag of a globular form, and quite thinning, as if it was polished. When a large quantity of silver is contained in a lead ore, viz., in a potter's ore, it can likewise be discovered through the use of the blow-pipe, of which more will be mentioned hereafter.

Tin may be melted out of the pure tin ores in its metallic state. Some of these ores melt very easily, and yield their metal in quantity, if only exposed to the fire by themselves; but others are more refractory; and as these melt very slowly, the tin, which sweats out in form of very small globules, is instantly burnt to ashes before these globules have time to unite in order to compose a larger globe, which, might be seen by the eye, and not so soon destroyed by the fire; it is therefore necessary to add a little borax to these from the beginning, and then to blow the flame violently at the proof. The borax does here preserve the metal from being too soon calcined, and even contributes to the reader collecting of the small metallic particles, which soon are seen to form themselves into a globule of metallic tin at the bottom of the whole mass, nearest to the charcoal. As soon as much of the metallic tin is produced as is sufficient to convince the operator of its presence, the fire ought to be discontinued, though the whole of the ore be not yet melted; because the whole of this kind of ore can be seldom or never reduced into metal by means of these experiments, a great proportion being always calcined; and if the fire is continued too long, perhaps even the metal already reduced may likewise be burnt to ashes; for the tin is very soon deprived of its metallic state by the fire.

Most part of the lead ores may be reduced to a metallic state upon the charcoal. The minera plumbi calciformes, which are pure, are easily melted into lead; but such of them as are mixed with an acbra ferri, or any kind of earth, as clay, lime, &c. yield very little of lead, and even nothing at all, if the heterogeneous are combined in any large quantity; this happens even with the minera plumbi calciformis arsenico mina. These therefore are not to be tried but in larger laboratories. However, every mineral body suspected to contain any metallic substance may be tried by the blow-pipe, so as to give sufficient proofs whether it contain any or not, by its effects being different from those of the stones or earths, &c.

The minera plumbi mineralisate leave the lead in a metallic form, if not too large a quantity of iron is mixed with it. For example, when a tessellated or flint-grained lead ore is exposed to the flame, its sulphur, and even the arsenic if there be any, begins to fume, and the ore itself immediately to melt into a globular form; the rest of the sulphur continues then to fly off, if the flame be blown slowly upon the mass; but, on the contrary, very little of the sulphur will go off, if the flame be forced violently on it; in this case, it rather happens that the lead itself crackles and dissipates, throwing about very minute metallic particles. The sulphur being driven out as much as possible, which is known by finding no fulphureous vapour in smelling at the proof, the whole is suffered to cool, and then a globule of metallic lead will be left upon the coal. If any iron is contained in the lead-ore, the lead, which is melted out of it, is not of a metallic shining, but rather of a black and uneven surface; a little borax must in this case be melted with it, and as soon as no bubble is seen to rise any longer from the metal into the borax, the fire must be discontinued; when the mass is grown cold, the iron will be found scorified with the borax, and the lead left pure and of a shining colour.

Borax does not scorify the lead in these small experiments when it is pure; if the flame is forced with a violence on it, a bubbling will ensue, resembling that which is observed when borax dissolves a body melted with it; but when the fire ceases, the flag will be perfectly clear and transparent, and a quantity of very minute particles of lead will be seen spread about the borax, which have been torn off from the mass during the bubbling.

If such a lead ore is rich in silver, this last metal may likewise be discovered by this experiment; because as the lead is volatile, it may be forced off, and the silver remain. To effect this, the lead, which is melted out of the ore, must be kept in constant fusion with a slow heat, that it may be consumed. This will be sooner obtained, and the lead part quicker, if during the fusion the wind through the blow-pipe be directed immediately, though not forcibly, upon the melted mass itself, until it begin to cool; at which time the fire must be directed on it again. The lead, which is already in a volatilising state, will by this sacrifice be driven out in form of a subtil smoke; and by thus continuing by turns to melt the mass, and then to blow off the lead, as has been said, until no smoke is any longer perceived, the silver will at last be obtained pure. The same observation holds good here also, which was made about the gold, that, as none but very little bits of ores can be employed in these experiments, it will be difficult to extract the silver out of a poor ore; for some part of it will fly off with the lead, and what might be left is too small to be discerned by the eye. The silver, which by this means is obtained, is easily distinguished from lead by the following external marks, viz. that it must be red-hot before it can be melted; it cools sooner than lead; it has a silver colour; that is to say, brighter and whiter than lead; and is harder under the hammer.

The minera cupri calciformes (at least some of them), when not mixed with too much stone or earth, are easily reduced to copper with any flux; if the copper is found not to have its natural bright colour, it must be melted with a little borax, which purifies it. Some of these ores do not all discover their metal if not immediately melted with borax; the heterogeneous contained in them hindering the fusion before these are scorified by the flux.

The grey copper ores, which only consist of copper and sulphur, are tried almost in the same manner as above mentioned. Being exposed to the flame by themselves, they will be found instantly to melt, and part of their sulphur to go off. The copper may afterwards be obtained in two ways: the one, by keeping the proof in fusion for about a minute, and afterwards suffering it to cool; when it will be found to have a dark and uneven appearance externally, but which after being broken discovers the metallic copper of a globular form in its centre, surrounded with a regulus, which still contains some sulphur and a portion of the metal: the other, by being melted with borax, which last way sometimes makes the metal appear sooner.

The minera cupri pyritaceae, containing copper, sulphur, and iron, may be tried with the blow-pipe if they are not too poor. In these experiments the ore ought to be calcined, and after that the iron scorified. For this purpose a bit of the ore must be exposed to a slow flame, that as much of the sulphur as possible may part from it before it is melted, because the ore commonly melts very soon, and then the sulphur is more difficulty driven off. After being melted, it must be kept in fusion with a strong fire for about a minute, that a great part of the iron may be calcined; and after that, some borax must be added, which scorifies the iron, and turns with it to a black flag. If the ore is very rich, metallic copper will be had in the flag after the scorification. If the ore be of moderate richness, the copper will still retain a little sulphur, and sometimes iron: the product will therefore be brittle, and must with great caution be separated from the flag, that it may not break into pieces; and if this product is afterwards treated in the same manner as before said, in speaking of the grey copper-ores, the metal will soon be produced. But if the ore is poor, the product after the first scorification must be brought into fusion, and afterwards melted with some fresh borax, in order to calcine and scorify the remaining portion of iron; after which it may be treated as mentioned in the preceding paragraph. The copper will in this last case be found in a very small globule.

The copper is not very easily scorified with this apparatus, when it is melted together with borax, unless it has first been exposed to the fire by itself for a while in order to be calcined. When only a little of this metal is dissolved, it instantly tinges the flag of a red... dish brown colour, and mostly opaque; but as soon as this flag is kept in fusion for a little while, it becomes quite green and transparent: and thus the presence of the copper may be discovered by the colour, when it is concealed in heterogeneous bodies, so as not to be discovered by any other experiment.

If metallic copper is melted with borax by a slow fire, and only for a very little time, the glass or flag becomes of a fine transparent blue or violet colour, inclining more or less to the green: but this colour is not properly owing to the copper, but it may rather be to its phlogiston; because the same colour is to be had in the same manner from iron; and these glasses, which are coloured with either of those two metals, soon lose their colour if exposed to a strong fire, in which they become quite clear and colourless. Besides, if this glass, tinged blue with the copper, is again melted with more of this metal, it becomes of a good green colour, which for a long time keeps unchanged in the fire.

The iron ores, when pure, can never be melted per se, by the means of the blow-pipe alone; nor do they yield their metal when melted with fluxes; because they require too strong a heat to be brought into fusion; and as both the ore and the metal itself very soon lose their phlogiston in the fire, and cannot be supplied with a sufficient quantity from the charcoal, so likewise they are very soon calcined in the fire. This easy calcination is also the reason why the fluxes, for instance borax, readily scorch this ore, and even the metal itself. The iron loses its phlogiston in the fire sooner than the copper, and is therefore more easily scorched.

The iron is, however, discovered without much difficulty, although it were mixed but in a very small quantity with heterogeneous bodies. The ore, or those bodies which contain any large quantity of the metal, are all attracted by the loadstone, some without any previous calcination, and others without having being roasted. When a clay is mixed with a little iron, it commonly melts by itself in the fire; but if this metal is contained in a limestone, it does not promote the fusion, but gives the stone a dark and sometimes a deep black colour, which always is the character of iron. A minera ferri californis pura crystallifata, is commonly of a red colour: This being exposed to the flame, becomes quite black; and is then readily attracted by the loadstone, which it was not before. Besides these signs, the iron discovers itself, by tingling the flag of a green transparent colour, inclining to brown, when only a little of the metal is scorched; but as soon as any larger quantity thereof is dissolved in the flag, this becomes first a blackish brown, and afterwards quite black and opaque.

Bismuth is known by its communicating a yellowish brown colour to borax; and arsenic by its volatility and garlick smell. Antimony, both in form of regulus and ore, is wholly volatile in the fire when it is not mixed with any other metal except arsenic; and is known by its particular smell, easier to be distinguished when once known than described. When the ore of antimony is melted upon the charcoal, it bubbles constantly during its volatilising.

Zinc ores are not easily tried upon the coal; but

the regulus of zinc exposed to the fire upon the charcoal burns with a beautiful blue flame, and forms itself almost instantly into white flowers, which are the common flowers of zinc.

Cobalt is particularly remarkable for giving to the glass a blue colour, which is the saffire or smalt. To produce this, a piece of cobalt ore must be calcined in the fire, and afterwards melted with borax. As soon as the glass, during the fusion, from being clear, seems to grow opaque, it is a sign that it is already tinged a little; the fire is then to be discontinued, and the operator must take hold, with the pincers, of a little of the glass, whilst yet hot, and draw it out slowly in the beginning, but afterwards very quick, before it cools, whereby a thread of the coloured glass is procured, more or less thick, wherein the colour may earlier be seen than in a globular form. This thread melts easily, if only put in the flame of the candle without the help of the blow-pipe.—If this glass be melted again with more of the cobalt, and kept in fusion for a while, the colour becomes very deep; and thus the colour may be altered at pleasure.

When the cobalt ore is pure, or at least contains but little iron, a cobalt regulus is almost instantly produced in the borax during the fusion; but when it is mixed with a quantity of iron, this last metal ought first to be separated, which is easily performed since it scorches sooner than the cobalt; therefore, as long as the flag retains any brown or black colour, it must be separated, and melted again with fresh borax, until it shows the blue colour.

Nickel is very seldom to be had; and as its ores are seldom free from mixtures of other metals, it is very difficultly tried with the blow-pipe. However, when this semimetal is mixed with iron and cobalt, it is easily freed from these heterogeneous metals, and reduced to a pure nickel regulus by means of scorchification with borax, because both the iron and cobalt sooner scorch than the nickel. The regulus of nickel itself is of a green colour when calcined: it requires a pretty strong fire before it melts, and tingles the borax with a hyacinth colour. Manganese gives the same colour to borax; but its other qualities are quite different, so as not to be confounded with the nickel.

By means of the foregoing explanations, and those given under the article Blow-Pipe, any gentleman, who is a lover of this science, will be able, in an easy manner, to amuse himself in discovering the properties of those works of nature, with which the mineral kingdom furnishes us; or more usefully to employ himself by finding out what sorts of stones, earths, ores, &c. there are on his estate, and to what economical purposes they may be employed. The scientific minerologist may, by examining into the properties and effects of the mineral bodies, discover the natural relation these bodies stand in to each other, and thereby furnish himself with materials for establishing a mineral system, founded on such principles as Nature herself has laid down in them; and this in his own study, without being forced to have recourse to great laboratories, crucibles, furnaces, &c. which is attended with much trouble, and is the reason why so few can have an opportunity of gratifying their desire of knowledge in this part of natural history. Farther improvements of this apparatus may still be made by those who choose to bestow their attention upon it.

A great number of fluxes might, perhaps, be found out, whose effects might be different from those already in use, whereby more distinct characters of those mineral bodies might be discovered, which now either show ambiguous ones, or which it is almost impossible to try exactly with the blowpipe. Instead of the sal soda, some other salt might be discovered better adapted to these experiments. But it is very necessary not to make use of any other fluxes on the charcoal than such as have no attraction to it; if they, at the same time, be clear and transparent, when melted, as the borax and the sal fusibile microcosmicum, it is still better; however, the transparency and opacity are of no great consequence, if a substance be employed only in order to discover its fusibility, without any attention to its colour; in which case, some metallic slag, perhaps, might be useful.

When such ores are to be reduced whose metals are very easily calcined, as tin, zinc, &c., it might perhaps be of service to add some phlogistic body, such as hard resin, since the charcoal cannot afford enough of it in the open fire of these essays. The manner of melting the volatile metals out of their ores per defensionem might also, perhaps, be imitated; for instance, a hole might be made in the charcoal, wide above and very narrow at the bottom; a little piece of the ore being then laid at the upper end of the hole, and covered with some very small pieces of the charcoal, the flame must be directed on the top; the metal might, perhaps, by this method, run into the hole below, concealed from the violence of the fire, particularly if the ore is very fusible, &c.

The use of the apparatus above referred to, and which may be called a pocket laboratory (as the whole admits of being easily packed into a small case), is chiefly calculated for a travelling mineralist. But a person who always resides at one and the same place, may by some alteration make it more commodious to himself, and avoid the trouble of blowing with the mouth. For this purpose he may have the blowpipe go through a hole in a table, and fixed underneath to a small pair of bellows with double bottoms, such as some of the glass-blowers use, and then nothing more is required than to move the bellows with the feet during the experiment; but in this case a lamp may be used instead of a candle. This method would be attended with a still greater advantage, if there were many such parts as c, fig. 13, the openings of which were of different dimensions; those parts might by means of a screw be fastened to the main body of the blowpipe, and taken away at pleasure. The advantage of having these nozzles of different capacities at their ends, would be that of exciting a stronger or weaker heat as occasion might require. It would only be necessary to observe, that in proportion as the opening or nozzle of the pipe is enlarged, the quantity of the flame must be augmented by a thicker wick in the lamp, and the force of blowing increased by means of weights laid on the bellows; a much intenser heat would thus be produced by a pipe of a considerable opening at the end, by which the experiments must undoubtedly be carried farther than the common blowpipe.

A traveller, who has seldom an opportunity of carrying many things along with him, may very well be contented with this laboratory and its apparatus, which are sufficient for most part of such experiments as can be made on a journey. There are, however, other things very useful to have at hand on a journey, which ought to make a separate part of a portable laboratory; if the manner of travelling does not oppose it; this consists of a little box including the different acids, and one or two matrasses, in order to try the mineral bodies in liquid menstrua if required.

These acids are, the acid of nitre, of vitriol, and of common salt. Most of the stones and earths are attacked, at least in some degree, by the acids; but the calcareous are the easiest of all to be dissolved by them, which is accounted for by their calcareous properties. The acid of nitre is that which is most used in these experiments; it dissolves the limestone, when pure, perfectly, with a violent effervescence, and the solution becomes clear; when the limestone enters into some other body, it is nevertheless discovered by this acid, through a greater or less effervescence in proportion to the quantity of the calcareous particles, unless there are so few as to be almost concealed from the acid by the heterogeneous ones. In this manner a calcareous body, which sometimes nearly resembles a siliceous or argillaceous one, may be known from these latter, without the help of the blowpipe, only by pouring one or two drops of this acid upon the subject; which is very convenient when there is no opportunity nor time of using this instrument.

The gypsa, which consist of lime and the vitriolic acid, are not in the least attacked by the acid of nitre, if they contain a sufficient quantity of their own acid; because the vitriolic acid has a stronger attraction to the lime than the acid of nitre; but if the calcareous substance is not perfectly saturated with the acid of vitriol, then an effervescence arises with the acid of nitre, more or less in proportion to the want of the vitriolic acid. These circumstances are often very essential in distinguishing the calcarea and gypsa from one another.

The acid of nitre is likewise necessary in trying the zeolites, of which some species have the singular effect to dissolve with effervescence in the above mentioned acid; and within a quarter of an hour, or even sometimes not until several hours after, to change the whole solution into a clear jelly, of so firm a consistence, that the glass wherein it is contained may be reverved without its falling out.

If any mineral body is tried in this menstruum, and only a small quantity is suspected to be dissolved, though it was impossible to distinguish it with the eye during the solution, it can be easily discovered by adding to it ad saturitatem a clear solution of the alkali, when the dissolved part will be precipitated, and fall to the bottom. For this purpose the sal soda may be very useful.

The acid of nitre will suffice for making experiments upon stones and earths; but if the experiments are to be extended to the metals, the other two acids are also necessary.

Another instrument is likewise necessary to a complete complete Pocket-Laboratory, viz. a washing-trough (fig. 21.), in which the mineral bodies, and particularly the ores, may be separated from each other, and from the adherent rock, by means of water. This trough is very common in laboratories, and is used of different sizes; but here only one is required of a moderate size, such as 12 inches and a half long, three inches broad at the one end and one inch and a half at the other end, sloping down from the sides and the broad end to the bottom, where it is three quarters of an inch deep. It may, however, be made of much smaller dimensions. It is commonly made of wood, which ought to be chosen smooth, hard, and compact, wherein are no pores in which the minute grains of the pounded matter may conceal themselves.

It is to be observed, that if any such matter is to be washed as is suspected to contain some native metal, such as silver or gold, a trough should be procured for this purpose of a very shallow slope; because the minute particles of the native metal have then more power to assemble together at the broad end, and separate from the other matter.

The management of this trough, or the manner of washing, consists in this: That when the matter is mixed with about three or four times its quantity of water in the trough, this is kept very loose between two fingers of the left hand, and some light strokes given on its broad end with the right, that it may move backwards and forwards; by which means the heaviest particles assemble at the broad and lower end, from which the lighter ones are to be separated by inclining the trough and pouring a little water on them. By repeating this process, all such particles as are of the same gravity may be collected together, and separated from those of different gravity, provided they were before equally pounded; though such as are of a clayey nature, are often very difficult to separate from the rest, which, however, is of no great consequence to a skilful and experienced washer. The washing process is very necessary, as there are often rich ores, and even native metals, found concealed in earths and sand in such minute particles as not to be discovered by any other means.

Sect. III. Description of an Improved Portable Laboratory for assaying Minerals.

The chief pieces and implements of the portable laboratories are represented in Plate XCIX. at Blow-Pipe, and in Plate CCCXIII. annexed to the present article.

1. The first contains those belonging to the Dry Laboratory, so called on account of its containing whatever is required to try all kinds of fossils in the dry way by fire, without any of the humid menstruums. They are made to pack in a box of the size of an octavo book, lined with green velvet, and covered with black silk-skin; the inside divided into different compartments, suited to the size, form, and number of the implements it is to contain. Of these the principal are described under Blow-Pipe. We must here, however, add the following remarks and alterations of that instrument by Mr Magellan.

D and Q (fig. 13.) are the two pieces that form the blow-pipe, which is here represented entire. This very useful instrument has been considerably improved of late in England. The mouth-piece aa is made of ivory, to avoid the disagreeable sensation of having a piece of metal a long time between the teeth and lips, which, if not of silver or gold, may be very noxious to the operator; a circumstance that has been hardly noticed before.

1. If the mouth-piece aa be made of a round form, it cannot be held for any length of time between the teeth and lips, to blow through it, without straining the muscles of the mouth, which produces a painful sensation. It must, therefore, have such an external figure, as to adapt itself accurately to the lateral angles of the lips, having a flattened oval form externally, with two opposite corners to fit those internal angles of the mouth, when it is held between the lips, as may be seen in that represented in the figure.

2. The small globe bb is hollow, for receiving the moisture of the breath; and must be composed of two hemispheres, exactly screwing into one another in bb; the male-screw is to be in the lower part, and foldered on the crooked part Q of the tube Q D, at such a distance, that the inside end of the crooked tube be even with the edge of the hemisphere, as represented by the pointed lines in the figure. But the upper hemisphere is to be foldered at the end of the straight tube D. By these means, the moisture arising from the breath falls into the hollow of the lower hemisphere, where it is collected round the upper inside end of the crooked part Q of the blow-pipe, without being apt to fall into it.

3. The small nozzles, or hollow conical tubes, advised by Messrs Engelstrom, Bergman, and others, are wrong in the principle; because the wind that passes from the mouth through such long cones loses its velocity by the lateral friction, as happens in hydraulic spouts; which, when formed in this manner, do never throw the fluid so far as when the fluid passes through a hole of the same diameter, made in a thin plate of a little metallic cap that screws at the end of the large pipe. It is on this account that the little cap e is employed, having a small hole in the thin plate, which serves as a cover to it; and there are several of these little caps, with holes of smaller and larger sizes, to be changed and applied whenever a flame is required to be more or less strong.

4. Another convenience of these little caps is, that even in case any moisture should escape falling into the hemisphere bb, and pass along with the wind through the crooked pipe Q, it never can arrive at nor obstruct the little hole of the cap e, there being room enough under the hole in the inside, where this moisture must be stopped till it is cleaned and wiped out.

The stream of air that is impelled by the blow-pipe (as seen in fig. 3.) upon the flame, must be constant and even, and must last as long as the experiment continues to require it. This labour will fatigue the lungs, unless an equable and uninterrupted inspiration can at the same time be continued. To succeed in this operation without inconvenience, some labour and practice are necessary, as already explained under the detached article.

Every assay ought always to begin by the exterior flame, which must be first directed upon the mass under examination; and, when its efficacy is well known, then the interior blue flame is to be employed. After the ore is roasted, it is to be rounded up on the steel plate by the hammer; the particles being prevented from being dissipated by the ring H (fig. 9, Plate XCIX.), within which the pieces to be broken are to be put.

Among the apparatus, beside the particulars already mentioned, three phials are necessary, containing the required fluxes, viz. the borax, the sal soda, and sal fusibile microcosmicum. Other useful particulars are, A small link of hard steel, to try the hardness or softness of mineral substances, and also to strike fire for lighting the candle when required: A piece of black flint, to serve as a touchstone; (for being rubbed with any metal, if it be gold the marks will not be corroded by aqua fortis); and also to strike fire, when necessary, with the link of steel: An artificial loadstone, properly armed with iron, for the better preservation of its attractive power; (it serves to discover the ferruginous particles of any ore after it has been roasted and powdered:) A triple magnifier, which, differently combined, produces seven magnifying powers, the better to distinguish the structure and metallic parts of ores, and the minute particles of native gold, whenever they contain that metal: A file, to try the hardness of stones and crystals, &c.: Some pieces of dry agaric or tinder, and small bits or splinters of wood tipped with brimstone, to serve as matches for lighting the candle; and various other little articles of use in these experiments.

II. For performing experiments in the Humid Way, the chief additional articles (and which must be kept in a separate case) consist of a collection of phials, containing the principal acids, tests, precipitants, and re-agents, both for examining mineral bodies by the humid way, and for analyzing the various kinds of mineral waters. Those with acids and corrosive solutions have not only ground stoples, but also an external cap to each, ground over the stople, and secured downward by a bit of wax between both, in order to confine the corrosive and volatile fluids within. But those which contain mild fluid liquors have not such external caps; and those with dry inoffensive substances are only stopped with cork. Besides these phials, there are two smaller cylindrical ones, which serve to exhibit the changes of colour produced by some of the re-agents in those analytical assays. There are also two or three small matrasses, to hold the substances with their solvents over the fire; a small glass funnel for pouring the fluids; a small porcelain mortar, with its pestle; one or two crucibles of the same substance; a small wooden trough to wash the ground ores; some glass sticks to stir up the fluid mixtures; and, finally, pieces of paper tinged red, yellow, and blue, by the tinctures of Fernambuc wood (commonly called Brazil wood), turmeric, and litmus, thickened with a little starch.

The following list contains the names of the various fluid tests and re-agents that are necessary for these assays. But the whole number being too large to be all contained in a portable case, every one may give the preference to those he likes best.

1. Concentrated vitriolic acid, whose specific gravity may be expressed in the outside. 2. Nitrous acid, purified by the nitrous solution of silver. 3. Concentrated marine acid, with its specific gravity. 4. Marine acid dephtlogificated. 5. Aqua regia for gold, viz. 2 nit. and 1 marine. 6. Aqua regia for platinum, viz. half marine and half nitrous acid. 7. Nitrous solution of silver. 8. Nitrous solution of mercury, made in the cold. 9. Muriatic solution of barytes. 10. Nitrous solution of lime. 11. Muriatic solution of lime. 12. Mercury in its metallic state. 13. Corrosive sublimate of mercury. 14. White arsenic. 15. Nitrous solution of silver. 16. Nitrous solution of copper. 17. Acid of sugar. 18. Liquor probatorius vini. 19. Hepar sulphuris. 20. Oil of tartar per deliquium. 21. Salt of tartar. 22. Caustic vegetable alkali. 23. Pearl-ashes. 24. Soap-makers ley. 25. Common salt. 26. Vitriolated argilla (alum.) 27. Vitriol of iron (cupperas.) 28. Nitrous solution of silver. 29. Acetous solution of lead. 30. Acetous solution of barytes. 31. Phlogisticated alkali by the Prussian blue. 32. Lime-water phlogisticated by the Prussian blue. 33. Mild volatile alkali (dry) 34. Caustic volatile alkali. 35. Rectified spirit (alcohol) 36. Spirituous tincture of galls. 37. Ether. 38. Spirituous tincture of violets. 39. Spirituous solutions of soap. 40. Syrup of wood. 41. Tincture of litmus. 42. Tincture of Brazil wood. 43. Tincture of turmeric. 44. Oil of olives. 45. Oil of linseed. 46. Oil of turpentine. 47. Essential oil of wild sorrel. 48. Hepar sulphuris. 49. Sugar of lead. 50. Solution of alum.

The method of applying the above tests of acids and re-agents may be seen in Bergman's treatises of the Analysis of Waters, and of Allying by the Humid Way; in Kirwan's Elements of Mineralogy; in the Elements of Chemistry of Dijon; in the Memoirs of the same Academy; in Fourcroy's Lectures of Chemistry, &c.

III. The Lamp-furnace Laboratory, for experiments both by the humid and the dry way, is a very curious and useful, though small apparatus. It is an improvement of that which was contrived by M. de Morveau, in consequence of the information he received from his friend the president de Virly, who saw at Upsal how advantageously the late eminent professor Bergman availed himself of this convenience for many analytical processes in miniature, by the use of very small glass vessels about one inch diameter, and other implements of proportional size, for performing various chemical operations. (See the Dijon Memoirs for 1783, Part I. p. 171.) There can be no doubt but that whenever these processes are properly conducted, though in miniature, the lamp-furnace will prove amply sufficient to perform in a few minutes, and with very little expense, the various solutions, digestions, and distillations, which otherwise would require large vessels, stills, retorts, reverberatory furnaces, &c., to ascertain the component parts of natural bodies; though it is not always sufficient to ascertain their respective quantities. In this last case, operations must be performed in great laboratories, and on a large scale, at a considerable expense. But the substances are sometimes too valuable; as, for instance, when precious stones are examined; and of course the last way never can be attempted in such cases.

These small processes have likewise another advantage before noticed, which cannot be obtained in works at large. It consists in one's being able to observe the gradual progress of each operation; of easily retarding or urging it, as it may require; and of ascertaining at pleasure each step of every experiment, together with the phenomena attending the same.

The lamp-furnace is mounted in a small parallelogram of mahogany, about six inches long and four wide, marked fig. 5. This is kept steady over the edge of a common table, by means of the metallic clamp w, which is fastened by the screw x. The pillar r is screwed in a vertical position on the plate t, being about ten inches high; the other is screwed to the opposite corner, marked p, and is only 7½ inches long; both are composed of two halves, that screw at t, to be easily packed up with all the implements in a case covered with black fish-skin, and lined with green velvet, like the other laboratory already described.

The lamp k, fig. 3, is supported on the plate f, which has a ring l that runs in the column p, and may be fixed by its screw l at the required height.—This lamp has three small pipes of different sizes, to receive as many wicks of different thicknesses, and to be filled with spirit of wine. By a similar method, a piece of charcoal is mounted and supported by the pliers or little forceps screwed to the arm ac, fig. 1, which has all the motions requisite for being fixed by means of proper screws, at a proper distance from the flame of the wick b. The blow-pipe, fig. 4, is, by a similar mechanism, mounted on the smaller column p, at such a distance as to blow the flame h to the piece of ore m, which is upon the charcoal g.

Everything being disposed in this manner, the operator blows through the mouth-piece of the blow-pipe, fig. 4, and remains with his hands free to make the changes and alterations he may think proper.—[N.B. The large round cavity e in the middle of the parallelogram, fig. 5, is to receive the lamp k, fig. 3, when all the implements are packed up in their case of black fish-skin; and the cover of the lamp is represented by fig. 12.]

But if the operator has the double bellows, fig. 14, and 15, he fixes them, at a due distance, to the same table by the brass clamp y. He then unscrews the blow-pipe at z, joins the mouth m of the flexible tube to the hemisphere z, passing each orifice, thro' the leather tube fig. 11, and tying both ends with a waxed thin pack-thread. If he works with his foot on the pedal, the string of which is seen hanging from the end of the bellows, fig. 15 (and is always up, on account of the weight e), then the air is absorbed by the bellows fig. 15, from whence it is propelled by the motion of the foot on the pedal to the bellows, fig. 14, whose constant weight r drives it out through the flexible pipe, fig. 10, it of course enters the curved part zz of the blow-pipe, and drives the flame on the piece m of the ore, that is to be examined upon the charcoal.

[N.B. 1. This double bellows is packed up by itself in a mahogany case, about 9 inches long, 6½ wide, and about 3½ deep, outside measure. 2. The last blowing bellows, fig. 14, has an inside valve, which opens when the upper surface of it is at its greatest height; in order to let the superfluous air escape out, as it would otherwise issue with great velocity out of the tube, fig. 11, and spoil the operation.]

If the operator chooses to apply the vital or dephlogisticated air in his process, let him fill the glass jar b, fig. 17, with this air; and put it within the tub marked by abze, filled with water, fattening the neck of the jar within by a crofs board cd, which has a hole in it for that purpose; then introducing the two ends of the flexible hollow tube, fig. 16, both to the mouth of the jar and to the hole of the bellows fig. 15, he opens the hole m of the jar, that was stopped with the stopple n; the column of the water passes in through m, and forces up the vital air, which enters the bellows, and of course, by the alternate motion of the pedal, passes through the end of the blow-pipe, to urge the flame upon the piece of ore m, fig. 2, on the charcoal g. But the dephlogisticated air may be also received at the same time that it is produced, by tying the pipe, fig. 16, to the mouth of an earthen retort, or even of a glass retort well-coated, according to the method of Mr Willis, described in the Transactions of the Society of Arts, Vol. V. p. 96. This last consists in dissolving two ounces of borax in a pint of boiling water, and adding to the solution as much flaked lime as is necessary to form a thin paste; this glass retort is to be covered all over with it, by means of a painter's brush, and then suffered to dry. It must then be covered with a thin paste made of linseed oil and flaked lime, except the neck that enters into the receiver. In two or three days it will dry of itself; and the retort will then bear the greatest fire without cracking. Two ounces of good nitre, being urged in the retort, by a good fire on a chafing-dish, will afford about 700 or 800 ounce-measures of dephlogisticated air.

To make any other kind of chemical assays, the forceps of fig. 2, which supports the charcoal, is taken off, by unscrewing the screw b; the blow-pipe is also taken off, by loosening the screw n; the hoop fig. 7, is put in its place, where the metallic basin of fig. 19, is put filled with sand; the piece of fig. 8, is set on the other pillar rs, fig. 1, to hold the matsras, fig. 18, upright, or the receiver fig. 20, &c.

In the same manner, the retort, fig. 9, may be put in the sand-bath instead of the matsras, with its receiver fig. 20, which may be supported on a bit of cork or wood, hollowed to its figure, and held by the pliers, instead of the charcoal fig. 2.

But if the operation is to be made in the naked fire, fire, the neck of the retort, fig. 9, being fitted to the receiver, or balloon, fig. 20, may be hanged by a little chain with its ring over the flame, being suspended from the piece of fig. 7, or 8, screwed to either of the pillars as may be most convenient. Otherwise the receiver, fig. 20, may be supported by the round hoop of bras, fig. 8, or 7, screwed at a proper height to the pillar, fig. 1, tying round it some packthread to defend the glass from the contact with the metallic support.

The pieces of fig. 6, may be screwed by its collar and screw ef to any of the pillars; carrying with it the retort and its receiver, at proper distances, higher or nearer to the lamp according as the flame is more or less violent.

It easily may be conceived, that these implements afford all sorts of conveniences for making any kind of small operations and assays in miniature, provided the operator pays a proper attention to the disposition requisite for each process or operation.

Every glass retort, receiver, matsrals, bacon, small funnels, &c. are made by the lamp-workers, that blow beads, thermometers, and other small glass instruments.

It is directed that the lamp k, fig. 3, be filled with spirit of wine, because it gives no disagreeable smell, and does not produce any fuliginous and disagreeable crust on the vessels as oil does; moreover, the spirit gives a dry flame, without smoke, and stronger than oil; besides the spots and disagreeable consequences this last causes, if split, &c. M. de Morveau adds, that the expense of spirit is quite inconsiderable; and that he performed in eight or ten minutes, with this apparatus, various dissolutions, evaporations, and other processes, which otherwise would have taken more than three hours, with the expense only of two or three halfpence for the spirit of wine, whilst the fuel of charcoal would have cost near ten or eleven pence.

But a very important circumstance is, as Morveau observes likewise, that many philosophers do not apply themselves to chemical operations, for want of opportunity of having a laboratory to perform them: it requiring a proper room, and suitable expenses of many large furnaces, retorts, crucibles, and numerous other implements, &c. whilst these miniature laboratories may in great measure afford the same advantages; at least to that degree of satisfaction sufficient to ascertain the contents and products of any substance that is subjected to trial: for with this simple apparatus a man of some abilities may, without any embarrassment, in a very short time, and with little expense, perform such distillations as require a reverberatory furnace; all sorts of processes, digestions, and evaporations, which require a regular sand heat; he may vary his experiments or trials, and multiply them to a great number of various performances, draw up his conclusions, and reason upon them, without loss of time, without the hinderance of long preparations to work at large. And even when such large works are to be performed, he may observe beforehand various phenomena of some substances, which being known in time, would otherwise impede the processes at large, or make them fail absolutely; and all this without the risk of a considerable loss, and without exposing himself to a great fire, &c.

**Part II. ARRANGEMENT (A) of MINERAL BODIES (B).**

THE bodies belonging to the mineral kingdom are divided into four different classes, viz.

1. **Earths (c),** or those substances which are not ductile, are mostly indissoluble in water or oil, and preserve their constitution in a strong heat.

2. **Salts:** these dissolve in water, and give it a taste; and when the quantity of water required to keep them in dissolution is evaporated, they concreted again into solid and angular bodies.

3. **Inflammables,** which can be dissolved in oils, but not in water, and are inflammable.

4. **Metals,** the heaviest of all bodies; some of which are malleable, and some can be decomposed.

Here, however, it must be observed, that these classes are unavoidably blended one with another; and therefore some exceptions must be allowed in every one of them: for instance, in the first class, the calcareous earth is in some measure dissoluble in water, and pipe-clay with some others diminish somewhat in their bulk when kept for a long time in a calcining heat.

In the third class, the calx of arsenic has nearly the same properties as salts; and there is no possible definition of salt that can exclude the arsenic, though at the same time it is impossible to arrange it elsewhere than among the semimetals. In the fourth class it is to be observed, that the metals and semimetals, perfect or imperfect, have not the same qualities common to them all; because some of them may be calcined, or deprived of their phlogiston, in the same degree of fire in which others are not in the least changed, unless particular artifices or processes are made use of: some of them also may be made malleable, while others are by no means to be rendered so. That the convex surface metals take after being melted, is a quality not particularly belonging to them, because every thing that is perfectly fluid in the fire, and has no attraction to the vessel in which it is kept, or to any added matter, takes the same figure; as we find borax, sal fusible microcopticum, and others do, when melted upon a piece of charcoal: therefore, with regard to all that has

---

(a) According to the system of Cronstedt†; altered, augmented, and improved from the Observations of other Mineralogists.

(b) Of the different bodies enumerated in the following classification, full explanations are given under their respective names as they occur in the course of this Work. See also Metallurgy, and Chemistry, Index.

(c) By earths, the author (Mr Cronstedt) does not mean (strictly speaking) only earths, but includes under that title all the kinds of stones or fossils not inflammable, saline, or metallic. Earth has been said, it is hardly worth while to invent such definitions as shall include several species at once; we ought rather to be content with perfectly knowing them separately.

**Class I. Earths.**

Earths, are those mineral bodies, not ductile, for the most part not dissoluble in water or oils, and which preserve their constitution in a strong heat.

These bodies are here arranged according to their constituent parts, so far as hitherto discovered; and are divided into five orders. See the article Earth.

**Order I. Calcareous Earths (d).**

The properties of these are as follow:

1. Friability and falling into a fine white powder after calcination. 2. Partial solution in water, with which they contract.

(d) Calcareous earth is most commonly found in the form of lime-stone; hard, compact, and of various colours; under which general name may be comprehended all the different kinds of marbles. Near Bath in England is found a kind of grey stone, rather soft than hard. This contains calcareous earth in a mild state, and likewise some in a state of causticity; hence, when newly dug out of the earth, it will dissolve sulphur, or make lime-water without any calcination. By attraction of fixed air from the atmosphere, it soon hardens after it has been dug up.

Mr Williams * divides the lime-stones of Scotland into the following species:

1. Grey, whitish, and pure white; regularly stratified; of a granulated texture; and much used in the Highlands for building bridges. Some of it is composed of fine glittering spangles like the scales of fishes; and some is as pure white as the best refined sugar, which kind he thinks may be called Parian marble.

2. Coarse-looking grey mountain-limestone, hard and strong, of a granulated texture, difficult to work in some places rough and unequal, in others smooth and even. Sometimes regularly stratified, at other times appearing like one vast irregular bed or rock, of various thicknesses.

3. Ash-coloured mountain-limestones, consisting of small grains of a fine smooth texture; when broken resembling flint. In the Highlands there are hills of this kind of stone, which our author informs us he has seen; some of which have regular strata, while others appear in one vast mass like a rock of granite.

4. Regularly-stratified lime-stone, found in the low countries, exhibiting a vast variety of colours; as black, blue, grey, brown, purple, red, and ash coloured, with various mixtures, of all degrees of hardness and purity.

5. Limestone accompanying coal, and frequently the immediate roof of the vein. This likewise shows a great variety of colour, texture, and quality; some being so much adulterated with clay and other heterogeneous mixtures as to be good for nothing, while others are very pure and fine. These limestones are always found in regular strata. "They are found (says our author) as regular as the coals they accompany; and the coal strata are more regular in continuation upon the bearing, as far as the clasps of strata belonging to the coal reaches, than any other that I have investigated; and I look upon it, that this observation may be of use in practice."

For discovering limestone at some distance, Mr Williams gives the following directions:—"Let them keep the line of stretch, or bearing of the strata; and, in the coal-country, they will be sure to discover it at nearly the same parallel distance from a seam of coal or other given stratum, as the place where it was last seen. But many of the mountain-limestones are not much to be depended on. Though you may have a good and plentiful quarry in one place, yet, perhaps, half a mile, or half a quarter of a mile farther forward, you cannot discover it; it is dwindled away to nothing, and yet will appear again farther forward; which makes the mountain-limestones uncertain to be discovered where you do not see them; as these rocks very frequently grow thicker or thinner, and sometimes squeeze out to nothing: and I comprehend under this denomination all the limestones not accompanying the coals and coal-metals.—The limestones of the coal-fields are often distinguishable by containing a great variety of shells, coral, and other marine bodies, which are found blended in the heart and composition of the stone."

6. The Scotch marbles are of great variety and beauty; and the parts of the kingdom most unfit for cultivation are found to abound most in them. Affint in Sutherland has a kind of white statuary marble, which Mr Williams says is the purest and best he ever saw. "I am persuaded (says he) there is none better, if any so good, in all Europe, and there is enough of it to serve all Britain; perfectly solid and pure, free of any blemishes, flaws, or stains, and blocks or slabs of any size may be cut out; but there is bad access to it; nor would it be easily quarried, there being a little cover above it, of a soft, loose, whitish limestone. This marble accompanies a prodigious rock of grey limestone, of a granulated texture, appearing in regular strata at Affint; but it is one of those which varies in thickness as you advance along the bearing of the strata. The good white marble of Affint is only to be seen in the bed of the river, near a considerable house a mile or two-fouth of the church; but I cannot remember the name of the particular place."

Near Blairgourie in Perthshire, not far from the side of the high road, is an excellent, granulated, broad-bedded limestone, of a sugar-loaf texture, and as white as the finest statuary marble, which Mr Williams supposes to be a good species of the true Parian marble, and that it requires only to be known and brought into use to become of great value. In the duke of Gordon's lands, in the forest of Glenavon, there is also a kind of marble composed of broad glittering grains like spangles, as large as the scales of fishes; but the situation is remote, and difficult of access. tract great heat, and by sprinkling with water they fall more readily into powder.

3. Insolubility without addition.

4. They attract the fixed air from the vegetable and mineral alkalies, and thus rendering them much more caustic, becoming at the same time mild themselves.

5. Solubility in all acids except the vitriolic, tartrous, and some anomalous vegetable acids.

6. Fusibility with borax and microcosmic salts.—The fusion is attended with effervescence, and the result is a transparent and colourless glass.

7. With metallic calces they melt into a corrosive fluid.

8. They imperfectly reduce the calces of lead and bismuth, and have even some effect upon those of copper and iron.

The calcareous earth is found,

I. Pure.

1. In form of powder. Agaricus mineralis, or lac lune. a. White, in moors, and at the bottom of lakes. b. Red. c. Yellow.

2. Friable and compact. Chalk, creta. a. White, creta alba. Chalk is a name often applied to other earths; whence we hear of chalks of various colours: but there are none which are known to be of a calcareous nature, except this kind here described, and of which there are no other varieties, otherwise than in regard to the looseness of the texture, or the fineness of the particles.

3. Indurated, or hard; Limestone; Lapis calcareous.

A. Solid, or not granulated. a. White. b. Whitish yellow. c. Flesh-coloured, found in loose masses. d. Reddish brown. e. Grey. f. Variegated with many colours, and particularly called marble. g. Black.

B. Grained or granulated limestone. 1. Coarse-grained, and of a loose texture, called salt-flag in Swedish, from its resemblance to lumps of salt. a. Reddish yellow. b. White.

2. Fine-grained. a. White. b. Semi-transparent, from Solfatara in Italy, in which native brimstone is found.

3. Very fine grained. a. White and green. b. White and black.

C. Scaly limestone. 1. With coarse or large scales. a. White. b. Reddish yellow. 2. With small scales. a. White. 3. Fine glittering or sparkling. a. White. b. Of many colours.

D. Lime or calcareous spars.

(1.) Of a rhomboidal figure. A. Transparent or diaphanous. 1. Refracting spar; Spatium islandicum; Iceland spar, or Iceland crystal.—This represents the objects seen through it double, 2. Common spar, which shows the object single. a. White, or colourless. b. Yellowish and phosphorescent.

B. Opaque. 1. White. 2. Black. 3. Brownish yellow.

(2.) Foliated or plated spar. a. Opaque white.

E. Crystallized calcareous spars. Spar. Drujen (e.)

(1.) Transparent. a. Hexagonal truncated. b. Pyramidal. 1. Dog's teeth; Pyramidales distincta. 2. Balls of crystallized spar, Pyramidales concretæ.

F. Stalactitical spar; Stalactites calcareus. Stalactites, Stone-icicle, or Drop-stone.

(1.) Scaled stalactites of very fine particles. a. Of a globular form. 1. White, the pea-stone. 2. Grey, pisolithus, ooliticus. Also the hammites, from its resemblance to the roes or spawn of fish. It has been exhibited by authors as petrified roes. The Ketton free-stone, of Rutlandshire, is a remarkable stone of this sort.

b. Hollow, in the form of a cone. 1. White. c. Of an indeterminate figure. d. Of coherent hollow cones.

(2.) Solid stalactites of a sparry texture. a. Hollow, and in form of a cone. 1. White, and semitransparent.

II. Sa-

In Lochaber, near the farm-houses on the north side of the ferry of Ballachylsh, is a limestone or marble rock, of a beautiful ashen-grey colour, and a fine regular uniform grain or texture; capable of being raised in blocks or slabs of any size, and of receiving a fine polish. It is beautifully sprinkled with fine bright grains of mundick or pyrites, and likewise with grains or specks of beautiful lead ore of a fine texture.

About three miles south of Fort-William, in the bed of a river, is a curious kind of marble with a black ground, flowered with white, like fine needle-work, or rather resembling the frost flowering upon glass windows in winter; and this flowering is not only on the outside, but quite through all parts of the body of the stone.

Scotland has also chalk in abundance; some of which is regularly stratified, and much appears in thick irregular masses like sediment.

(e) The translator of Mr Cronstedt's Treatise has adopted this German term druken into the English language, for a cluster of regular figured bodies, as a group conveys the idea of a cluster only, whether regular or of indeterminate figures. Calcaceous II. Saturated or combined with the acid of vitriol.

Gypsum, Plaster-stone, or Parget.

1. Looser and more friable than a pure calcareous earth. 2. Either crude or burnt, it does not excite any effervescence with acids; or, at most, it effervesces but in a very slight degree, and then only in proportion as it wants some of the vitriolic acid to complete the saturation. 3. It readily falls into a powder in the fire. 4. If burnt, without being red-hot, its powder readily concretes with water into a mass, which soon hardens; and then, 5. No heat is perceived in the operation. 6. It is nearly as difficult to be melted by itself as the limestone, and shows mostly the same effects with other bodies as the lime-stone: the acid of vitriol seems, however, to promote its vitrification. 7. When melted in the fire with borax, it puffs and bubbles very much, and for a long while, during the fusion, owing to the nature of both the salts. 8. When a small quantity of any gypsum is melted together with borax, the glass becomes colourless and transparent; but some sorts of alabaster and sparry gypsum, when melted in some quantity with borax, yield a fine transparent yellow coloured glass, resembling that of the best topazes. This phenomenon might probably happen with every one of the gypseous kind. But it is to be observed, that if too much of such gypsum is used in proportion to the borax, the glass becomes opaque, just as it happens with the pure limestone. 9. Burnt with any inflammable matter, it emits a sulphureous smell; and may as well by that means, as by both the alkaline salts, be decomposed; but for this purpose there ought to be five or six times as much weight of salt as of gypsum. 10. Being thus decomposed, the calx or earth which is left shows commonly some marks of iron.

The gypseous earth is found,

(1.) Loose and friable. Gypseous earth, properly so called; Gubr. A. White. (2.) Indurated. A. Solid, or of no visible particles, Alabaster. a. White, alabaster. 1. Clear and transparent. 2. Opaque. b. Yellow. 1. Transparent, from the Eastern countries. 2. Opaque.

B Gypsum of a sealed or granulated structure. This is the common plaster-stone. 1. With coarse scales. a. White. 2. With small scales. a. Yellowish. b. Greyish.

C Fibrous gypsum, or plaster-stone, improperly (though commonly) called English tale by our druggists. 1. With the fibres coarse. a. White, from Livonia.

N° 222.

2. With fine fibres. a. White.

D Spar-like gypsum. Selenites, by some also called glacies mariae; and confounded with the clear and transparent mica. 1. Pure selenites. A. Transparent. a. Colourless. b. Yellowish. 2. Liverstone, so called by the Swedes and Germans.

E Crystallised gypsum. Gypseous druse. (1.) Druse of crystals of pure sparry gypsum. A. Wedge-formed, composed of a pure spar-like gypsum. a. Clear and colourless. b. Whitish yellow. B. Capillary. a. Opaque, whitish yellow. b. Hexagonal, prismatic. c. Globular, consisting of cuneated rays proceeding from the centre.

F Stalactitical gypsum. Gypsum finiter. 1. Of no visible particles; in French, grignard. A. Of an irregular figure. a. Yellow. b. White. 2. Of a spar-like texture. A. In form of a cone. a. White and yellow. B. Of an irregular figure. a. White.

III. Calcaceous earth saturated with the acid of common salt. Sal ammoniacum fuscum naturale. This is found, 1. In sea-water. 2. In salt-pits.

IV. Calcaceous earth combined or saturated with sparry acid, known by the name of sparry fluor and blue john.

These are commonly called fluxing, vitreous, or glassy spars; because most part of them have a sparry form and appearance; they are, however, often met in an indeterminate figure.

They are only known in an indurated state, and distinguish themselves from the other earths by the following characters.

1. They are scarce harder than common calcareous spars, and consequently do not strike fire with steel. 2. They do not ferment with acids neither before nor after calcination. 3. They do not melt by themselves; but crack and split into pieces when exposed to a strong fire. But, 4. In mixtures with all other earths they are (generally) very fusible, and especially with calcareous earth, with which they melt into a corroding glass that dissolves the strongest crucibles, unless some quartz or argillaceous clay be added thereto. 5. When heated slowly, and by degrees, they give a phosphorescent light: but as soon as they are made red-hot, they lose this quality. The coloured ones, especially the green, give the strongest light, but none of them any longer than whilst they are well warm. 6. They melt and dissolve very easily by the addition of borax; and, next to that, by the microcosmic salt, without ebullition.

A. Indurated fluor. (1.) Solid, of an indeterminate figure; of a dull texture, semitransparent, and full of cracks in the rock.

a. White.

(2.) Sparry fluor. This has nearly the figure of spar; though on close observation it is found not to be so regular, nothing but the glossy surfaces of this stone giving it the resemblance of spar.

a. White. b. Blue. c. Violet. d. Deep green. e. Pale green. f. Yellow.

(3.) Crystallised fluor.

1. Of an irregular figure. a. White. b. Blue. c. Red.

2. Of a cubical figure. a. Yellow. b. Violet.

3. Of a polygonal spherical figure. a. White. b. Blue.

4. Of an octoedral figure. a. Clear, colourless.

V. Calcareous earth saturated with a particular acid, perhaps of the metallic kind, viz. the tungstic acid. The tungstein of the Swedes.

This resembles the garnet-stone and the tin-grains; is nearly as heavy as pure tin; very refractory in the arc, and excessively difficult to reduce to metal. Iron has, however, been melted out of it to more than 30 per cent. It is very difficultly dissolved by borax and alkaline salts, but melts very easily with the microcosmic salt, giving a black slag; and for this reason the last mentioned salt must be employed in the assays of this stone. It is found,

1. Solid and fine-grained.

a. Reddish or flesh-coloured. b. Yellow.

2. Spathofe, and with an unctuous surface.

a. White. b. Pearl-coloured.

VI. Calcareous earth united with the inflammable substance.

These have a very offensive smell, at least when rubbed. They receive their colour from the phlogiston, being dark or black in proportion as it predominates.

(1.) Calcareous earth mixed with phlogiston alone;

Lapis suillut, fetid stone and spar, or swine-stone and spar.

A. Solid, or of no visible or distinct particles.

a. Black.

B. Grained.

a. Blackish brown.

C. Scaly, particulis micaceis.

1. With coarse scales, a. Black.

2. With fine sparkling scales. a. Brown.

D. Sparry.

a. Black. b. Light brown. c. Whitish yellow.

E. Crystallised.

1. In a globular form.

VII. Calcareous earths blended with an argillaceous earth. Marle, Marga.

1. When crude, it makes an effervescence with acids; but,

2. Not after having been burnt; by which operation it is observed to harden, in proportion as the clay exceeds the calcareous substance.

3. It easily melts by itself into a glass, and even when it is mixed with the most refractory clay.

4. It is of great use in promoting the growth of vegetables, since the clay tempers the drying quality of the calcareous earth.

5. When burnt in a calcining heat, it readily attracts calcareous water; and, exposed to the air, in time it falls into a powder.

The varieties of this kind worthy to be taken notice of, depend on the different quantities of each of their component parts, and on the quality of the clay. The following are specified as examples.

A. Loofe and compact, Marga friabilis.

a. Reddish brown.

b. Pale red. This, when burnt, is of a yellowish colour, and used for making earthen ware in some places.

B. Semi-indurated; which is nearly as hard as stone when first dug up, but moulders in the open air.

a. Grey. b. Red.

C. Indurated, or stone marle.

a. In loose pieces, Marga indurata amorpha; by the Germans called flachlein or tophlein.

a. White. b. Grey, formed from a sediment which the water carries along with it.

e. In continued strata. Hard flaky marle.

VIII. Calcareous earth united with a metallic calx.

Here, as well as in the others, such a mixture or combination is to be understood, as cannot be discovered by the eye alone without the help of some other means.

The subjects belonging to this division lose the property of raising an effervescence with acids, when they are rich in metal, or contain any vitriolic acid. However, there have been found some that contained 20 or 30 per cent. of metal, and yet have shown their calcareous nature by the nitrous acid.

There are no more than three metals hitherto known to be united in this manner with the calcareous earth, viz.

(1) With iron. White spar like iron ore, Minera ferri alba. The flachlein or weifte eisenzor of the Germans.

1. This ore, however, is not always white, but commonly gives a white powder when rubbed.

2. It becomes black in the open air, as likewise in a calcining heat.

3. In this last circumstance it loses 30 or 40 per cent. of its weight, which by distillation has been found owing to the water that evaporates; and it is possible that some small quantity of vitriolic acid may, at the same time, evaporate with the water.

4. It is of all the iron ores the most easy to melt, and is very corrosive when melted.

This kind is found,

A. Loofe; the mouldered part of the indurated sort.

a. Black, like foot.

b. Dark brown, somewhat resembling umbre.

B. Indurated.

1. Solid, of no distinct particles.

a. Red. Looks like red ochre, or the red hematites, but dissolves in the acid of nitre with a great effervescence.

2. Scaly, particulis micaceis.

a. White.

b. Blackish grey.

3. Spar-like.

a. Light brown.

K

4. Drusen. 4. Drusen. a. Blackish brown. b. White.

1. Porous. This is often called eisenblute, or flor ferri. 2. Cellular.

(2.) With copper. A. Loose and friable. Mountain blue; Germanic, Bergblau. This dissolves in aquafortis with effervescence. B. Indurated. 1. Pure calcareous earth mixed with calx of copper. Armenian stone, lapis Armenus. 2. Gypseous earth united with calx of copper. Is of a green colour; and might perhaps be called turquois ore, or malachites; though we do not know if all sorts of turquoise ore are of this nature. a. Semi-transparent, is found at Ardal in Norway.

(3.) With the calx of lead. This is a lead ochre, or a spar-like lead-ore, which, in its formation, has been mixed with a calcareous earth, and for that reason effervesces with acids. A. Loose and friable. 1. White. B. Indurated. 1. Scaly. a. Yellowish.

Both these varieties contain a considerable quantity of lead, viz. 40 per cent. more or less; and the calcareous earth is as equally and intimately mixed with it, as in the white iron ore.

IX. The following compounds of calcareous earth with different mineral substances are added from Mr Kirwan's Elements of Mineralogy.

1. A compound of calcareous and barotical earths: of this species are some yellowish stones found in Derbyshire, consisting of lumps of limestone interspersed with nodules of barofelenite. Many more may occur as compounds of gypsum and barofelenite, fluor and barofelenite, &c., &c.

2. Compounds of calcareous and magnesian earths; such as, a. The white marble, interspersed with spots of fleatites or soap-rock, either green or black, called by Cronstedt kalmord marble. This marble is of a fealy texture. b. The pietra takchina of the Italians, which consists of white spar with veins of talc. c. The verde antico of the Italians, which is a light green marble, with deep green, black, white, and purple spots. According to Mr Bayen, it contains 62 parts of mild calcareous earth, 30 of green talc, 1 of magnesia, and 1 of semiphlogisticated iron.

3. Compounds of calcareous and argillaceous earths; such as, a. The green Campan marble from the Pyrenees. It is flatly and somewhat magnetic. According to Mr Bayen, it contains 65 of mild calcareous earth, 32 of the argillaceous, and 3 of semiphlogisticated iron. b. The red Campan marble: this is not magnetic; it contains 82 parts of mild calcareous earth, 11 of argillaceous shistus, and 7 of dephlogisticated iron. c. Yellow figured marble from Florence: according to Mr Bayen, it contains 75 parts of mild calcareous earth, 13 or 14 of shistus, and 4 or 5 of dephlogisticated iron. d. Griotte marble from Autun of Burgundy in France: it contains 67 parts of mild calcareous earth, 26 of reddish shistus, 2 of iron, and 1 of magnesian earth. e. The Amandola, which is a green marble, honeycomb-like, with white spots. It contains 76 parts of mild calcareous earth, 20 of shistus, and 2 of semiphlogisticated iron. The cellular appearance proceeds from the shistus.

4. Compounds of calcareous earth and mica; such as, a. The cipolin from Autun in France: it is of a green colour, and consists of 83 parts of chalk, 12 of green mica, and 1 of iron. b. The micaceous limestone, is of a glittering appearance, of various degrees of hardness, and effervesces with acids. Such as the macigno of the Italians; their yellow pietra bigia; and their blue pietra columbina or turkina.

5. Compounds of calcareous and siliceous earths; such as, a. The calcareous quartz and pudding-stone: this consists of lumps of quartz, and sometimes of felt-spar in a calcareous cement. b. The limestone with veins of quarts; such as the saxum sablbergerse, and several marbles of Sweden and Siberia, which strike fire with steel.

6. Calcareous volcanic pudding-stone; such as, a. The cierchina, which consists of lumps of spar and lava in a calcareous cement, mentioned by Mr Ferber. b. The marble mixed with veins of black or green lava, mentioned by the same author.

7. Compounds of calcareous earth, mixed with two or more kinds of earth; such as, a. The cipolin from Rome, which is a green marble with white zones: it strikes, though difficultly, fire with steel: it contains 67,8 parts of mild chalk, 25 of quartz, 8 of shistus, and 0,2 of iron, besides the iron contained in the argillaceous shistus. b. The calcareous porphyry, which consists of quartz, felt-spar, and mica in separate grains, united by a calcareous cement. c. The limestone interspersed with shoerl and mica. d. To these compounds belongs the pyritaceous limestone called by the French Pierre de St. Ambroix. It is of an iron grey colour, interspersed with shining particles. Its texture is compact, and scarcely gives fire with steel. Its specific gravity is 2,7034. It is soluble in acids, and mostly with effervescence; calcines in a strong fire; makes nitre slightly detonate; and if distilled affords a small portion of vitriolic acid, and some sulphur sublimes. Its com- ponent parts are 75 of mild calcareous earth and 25 of pyrites; in which are contained 14 of argill, 7 of quartz and sulphur, and 4 of iron.

Order II. Ponderous Earth.

Ponderous earth, (Terra Ponderosa): Caulk, or chalk. See Earth, Art. I. This is a particular kind of earth (like chalk in appearance, but with some very different properties), discovered in Sweden about 1774, which by its results with other bodies has some similarity to the known alkalis. It has not yet been found pure, but mixed with other substances; however, its great specific weight easily distinguishes it from the others, it being the heaviest of all earths.

1. Its specific gravity when considerably purified by art is 3.773. 2. This earth combines with aerial acid: and in this case effervesces with stronger acids. 3. With vitriolic acid it forms the ponderous spar, which is insoluble in water. 4. Its crystallization, after being combined with the nitrous, or with the muriatic acids, is hardly soluble; 5. But with acetic acid, it becomes deliquescent. 6. When pure; viz. without any mixture of acid or alkali, it does not vitrify in the fire. 7. If deprived of the aerial acid (fixed air) by calcination, is then soluble in 900 times its weight of boiling water. This solution exposed to air, forms a cremor, like that of lime-water in the same circumstances, and like it changes also the vegetable colours. 8. Whilst combined with aerial acid, it is only soluble in about 1550 times its weight of water, chiefly if the water has been impregnated also with the same aerial acid. 9. It expels the caustic volatile alkali from ammoniacal salt. 10. Mixed with brimstone it produces a hepar fulphuris, whose solution in water is but incompletely decomposed either by the nitrous or the muriatic acid, on account of the great attraction between this earth and the acid of sulphur, which is so strong that it 11. Separates this acid (the vitriolic) from the vegetable alkali.

I. Combined with aerial acid; Terra ponderosa aerata. See Chemistry-Index.

It resembles alum, but is hard and striated, as if composed of radiating fibres coming from a centre. It is found in Allton-moor in England.

A. Spar-like gypsum. 1. Semitransparent, spatum Bononiense. The Bono-nian stone, or native phosphorus. 2. Opaque. a. White. b. Reddish.

B. Ponderous Drufan spar. 1. Jagged, cristatum. These resemble cock's combs, and are found in clefts and fissures accreted on the surfaces of balls of the same substance. 2. White. 3. Reddish.

II. United with phlogiston and the vitriolic acid.

Leberstein of the Germans and Swedes. Lapis Magnesium hepaticus.

This stone, in some specimens constantly, but in others only when rubbed, smells like the hepar sulphuris, or gun-powder.

It is found.

A. Scully. 1. With coarse scales. a. Whitish yellow. 2. With fine sparkling scales. a. Black.

Order III. Magnesian, Micaceous, and Asbestine Earths.

§ 1. Magnesian Earths.

Magnesia is a white, loose, and light earth, only known since the beginning of this century. It is generally found combined or mixed with other heterogeneous substances, as other simple earths are.

1. When pure its specific gravity is 2.330, and then 2. It neither hardens, contracts, nor melts by the application of heat, even by the solar rays. 3. But it melts easily with borax, or microcosmic salt; though it is scarcely affected by fixed alkalis or calces of lead. 4. Mixed with other earths, it produces by fire different hard masses. 5. It gives no causticity except to the volatile alkali; and 6. Does not effervesce with any acid. 7. When mixed with water it shows a very small degree of heat, but without any effervescence. And when the water exceeds the weight of magnesia about 7.692 times, it is totally dissolved. 8 and 9. Being put in water and afterwards dried, it contains 7.5 parts of its weight; though when saturated with aerial acid, it will absorb and retain after being dried 6.6 parts of water. 10. This earth combined with aerial acid is more soluble in cold than in hot water. 11. Combined with vitriolic acid it crystallizes into a bitter salt, known by the name of Epsom and Seydlitz or Seidlitzsalt, which is soluble in little more than its own weight of water. 12. With nitrous acid it forms a deliquescent salt. 13. With the muriatic or the acetic acids it does not crystallize; and the mass being dried, attracts humidity from the air. 14. It has a stronger attraction to the fluor acid than to any other (Berg.): and crystallizes with it into hexangular prisms whose ends are formed of two low pyramids, of three rhombs (Romé de Plisse). 15. It is not precipitated from other acids by the vitriolic, as calcareous earth is. 16. According to Lavoisier and Macquer, when magnesia is calcined, it becomes phosphorescent.

I. Magnesia combined with vitriolic and other acids.

A. When saturated with the vitriolic acid, it forms a bitter salt, called English or Epsom, Seydlitz or Seidlitz salt. The salts known under these different ferent names only differ from one another on account of some heterogeneous substance, which is combined in them; the vitriolated magnetia being the characteristic and principal ingredient in them all.

B. Magnesia is found not only combined with the vitriolic acid in the waters of Epsom, Sedlitz, &c., but also with the marine acid to a considerable quantity in sea-water and other salt springs.

C. It is contained frequently in fresh waters, where it is dissolved by means of a quantity of aerial acid.

II. Combined with other earths.

A. Magnesia, when combined with siliceous earth, is commonly unctuous to the touch, and more or less difficult to be cut or turned in proportion to its different degrees of hardness.

It is not dissoluble in water; grows hard, and is very refractory in the fire.

When pounded and mixed with water, it will not easily cohere into a paste; however, if it is managed with care, it may be baked in the fire to a mass, which being broken, shows a dull and porous texture.

It takes for the most part, and without much labour, a fine polish. It is found,

(1.) Compact and soft; Smectis, Briancon or French chalk. a. White, from the Lands-End, in Cornwall. b. Yellow. c. Red and white, from the Lands-End; the soap-earth, from Switzerland; it looks like Catilesoap.

(2.) Solid and compact; of impalpable particles; Steatites or soap-rock. a. White, or light green. b. Deep green — c. Yellow.

(3.) Solid, and of visible particles; serpentine stone. a. Of fibrous and coherent particles. This is composed, as it were, of fibres, and might therefore be confounded with the asbestos, if its fibres did not cohere so closely with one another, as not to be seen when the stone is cut and polished. The fibres themselves are large, and seem as if they were twisted. a. Deep green. It is sold for the lapis nephriticus, and is dug at some unknown place in Germany. b. Light green, from Skienhyttan, in Westmanland; is used by the plate-smiths instead of French chalk.

b. Of granulated particles; fine grained serpentine stone, the Zoebitz serpentine. a. Black. b. Deep green. c. Light green. d. Red. e. Bluish grey. f. White. These colours are all mixed together in the serpentine stone from Zoebitz, but the green is the most predominant colour.

B. Porcelain earth mixed with iron; terra porcellanea

This is,

A. Diffusible in water. a. Red, from Montmartre, and China. The water-clinkers which are imported from certain places in Germany seem to be made of this kind.

B. Indurated. 1. Martial soap earth. a. Red. 2. Martial soap rock. a. Black. b. Red.

C. The talcites of the Swedes; lapis ollaris. a. Light grey. b. Whitish yellow. c. Dark grey. d. Dark green.

The serpentine stone has many varieties; being found, (1.) Veined or spotted with green steatites. (2.) Red, with veins of asbestos. (3.) Red, green, yellow, or black with veins or spots of white calcareous spar, is called potzverda. The black is called nero di prato; the green verde di Suza; but these names are not restricted to this species. (4.) Veined or spotted with gypsum. (5.) Veined or spotted with barofenite. (6.) Veined or spotted with flint — And, (7.) With veins of quartz, feltspar, or shoerl. (Kirwan's Mineralogy.)

What is commonly called serpentine is a true lapis ollaris; but being variegated with green, yellowish, and brown spots, like the skin of some common serpents, it is called by that name. Great quantities of this stone are found in Italy and Switzerland, where it is often worked into the shape of dishes and other vases. (Fabroni.) And the gabbro of the Italians is nothing else but a kind of serpentine, (Kirwan.)

§ 2. Micaceous Earths.

These are known by the following characters:

1. Their texture and composition consist of thin flexible particles, divisible into plates or leaves, having a shining surface.

2. These leaves or scales exposed to the fire lose their flexibility and become brittle, and then separate into inner leaves; but in a quick and strong fire, they curl or crumple, which is a step towards fusion; though it is very difficult to reduce them into pure glass by themselves or without addition.

3. They melt pretty easily with borax, the microcosmic salt, and the alkaline salt; and may by means of the blow-pipe be brought to a clear glass with the two former salts. The martial mica is, however, more fusible than the uncoloured ones: its specific gravity is 3,000.

A. Colourless or pure mica; daze, glimmer, or glit.

1. Of large parallel plates; Mafcovy glass. This is transparent as glass; found in Siberia and Elfdalen in the province of Wermland.

2. Of small plates, from Silfverberget, at Runneby, in the province of Blekinge.

3. Of fine particles like chaff; chaffy mica.

4. Of twisted plates; crumpled mica.

B. Coloured and martial glimmer.

1. Brown, semi-transparent.

2. Of fine and minute scales. a. Brown. b. Deep green. c. Light green. d. Black.

3. Twisted or crumpled glimmer. a. Light green.

4. Chaffy glimmer. a. Black. § 3. Asbestos Earths.

There are only yet discovered in an indurated state; and their characters are as follows:

1. When pure, they are very refractory in the fire. 2. In large pieces they are flexible. 3. They have dull or uneven surfaces. 4. In the fire they become more brittle. 5. They do not strike fire with the steel. 6. They are not attacked by acids. 7. They are easily brought into fusion by borax or alkali.

In this section are included both those varieties which by fossilists have been mentioned under the names of amiantus and asbestos, and have often been confounded together.

I. Asbestos, which is compounded of soft and thin membranes; amiantus Wallerii.

A. Of parallel membranes: Corium, five caro montana; Mountain-leather. 1. Pure. a. White. 2. Martial. a. Yellowish brown.

B. Of twisted soft membranes; mountain-cork. 1. Pure. a. White. 2. Martial. a. Yellowish brown.

II. Of fine and flexible fibres: Earth-flax; asbestos Wallerii.

A. With parallel fibres: Buffet. 1. Pure and soft. a. Light green. b. White. 2. A little martial, and more brittle. a. Greenish, from Baftas Gruiva, at Ryddarhyttan in Westmanland. There it forms the greatest part of the vein out of which the copper ore is dug; a great part of it is consequently melted together with the ore, and is then brought to a pure semi-transparent martial flag or glass.

B. Of broken and recombined fibres. 1. Martial. a. Light green.

Order IV. Siliceous Earths.

Siliceous earth is, of all others, the most difficult to describe and to distinguish perfectly; however, it may be known by the following characters, which are common to all bodies belonging to this order.

1. In its indurated state it is hard, if not in regard to the whole, yet at least in regard to each particle of it, in a degree sufficient to strike fire with steel, and to scratch it, when rubbed against it, though the steel be ever so well tempered.

2. When pure, and free from heterogeneous particles, it does not melt by itself, neither in a reverberatory nor in a blast furnace.

3. After being burnt, it does not fall to a powder, neither in the open air nor in water, as the calcareous earth does, but becomes only a little looser and more cracked by the fire, unless it has been very slowly, and by degrees, heated.

4. It excites no effervescence with acids.

5. In the fire it melts easiest of all to a glass with the fixed alkaline salt; and hence it has got the name of vitreous, though this name is properly speaking, less applicable to this order than to a great many other earths.

To the above we may add the following properties, from Bergman.

6. It is not soluble in any of the known acids, the fluor-acid only excepted. But,

7. It may be dissolved by the fixed alkali, both in the dry and wet way.

8. If the fixed alkali is only half the weight of the siliceous earth, it produces a diaphanous and hard glass; but when it is in a double or triple proportion, then the glass deliquesces of itself by attracting the humidity of the atmosphere.

9. It melts easily with borax; but

10. With microcomic salt it is more difficult, and requires a longer time to melt.

11. This earth has a great analogy to acids, as it is perfectly dissolved in that wonderful natural hot-water-sprout above ninety feet high at Geyser, in Iceland, where by cooling it forms a siliceous mass.

§ 1. Gems, or precious stones.

I. Diamond. Adamas gemma. See DIAMOND.

1. Of all stones, it is the hardest. 2. Is commonly clear, or transparent; which quality, however, may, perhaps, only belong to its crystals, but not to the rock itself from which they have their origin. 3. Its specific gravity is nearest 3,500. When brought to Europe in its rough state, it is in the form either of round pebbles with shining surfaces, or of crystals of an octohedral form.

a. Colourless, or diaphanous, or the diamond properly so called.

But it also retains this name when it is tinged somewhat red or yellow. Being rubbed, it discovers some electrical qualities, and attracts the needle.

b. Red; Ruby. Adamas ruber; Rubinus.—Which, by lapidaries and jewellers, is, in regard to the colour, divided into,

1. The ruby of a deep red colour inclining a little to purple. 2. Spinell, of a dark colour. 3. The balas, pale red, inclining to violet. This is supposed to be the mother of the rubies. 4. The rubicell, reddish yellow.

However, all authors do not agree in the characters of these stones.

II Sapphire. Sapphirus gemma.

It is transparent, of a blue colour; and is said, to be in hardness next to the ruby, or diamond.

III. Topaz. III. Topaz. *Topaziæ gemma.*

a. The pale yellow topaz; which is nearly uncoloured.

b. The yellow topaz.

c. Deep yellow, or gold coloured topaz, or oriental topaz.

d. Orange-coloured topaz.

e. The yellowish green topaz, or chrysolite.

f. The yellowish green, and cloudy topaz, the chrysopeira (a).

g. Bluish green topaz, or the beryl.

This varies in its colours; and is called, when

1. Of a sea-green colour, the aqua-marine.

2. When more green, the beryl.

IV. Emerald. *Smaragdus gemma.*

Its chief colour is green and transparent. It is the softest of precious stones, and when heated it is phosphorescent like the fluors.

V. To the precious stones belong also the jacinths, or hyacinths; which are crystals harder than quartz crystals, transparent, of a fine reddish-yellow colour when in their full lustre, and formed in prisms pointed at both ends: these points are always regular, in regard to the number of the facets, being four on each point; but the facets seldom tally; the sides also which form the main body, or column, are very uncertain in regard both to their number and shape; for they are found of four, five, six, seven, and sometimes of eight, sides: further, the column or prism is in some also so compressed, as almost to resemble the face of a spherical faceted garnet.

Mr Cronstedt says, he got some jacinths of a quadrangular figure, which did not melt in the fire, but only became colourless.

VI. The amethyst is a gem of a violet colour, with great brilliancy, and as hard as the best kind of rubies or sapphires, from which it only differs by its colour. This is called the oriental amethyst; and is very rare; when it inclines to the purple, or rosy colour, it is more esteemed than when it is nearer to the blue.

These amethysts have the same figure, hardness, specific gravity, and other qualities, as the best sapphires or rubies; and come from the same places, particularly from Persia, Arabia, Armenia, and the West Indies.

The amethysts called occidental, are of the same nature as rock crystals, and have the same gradations, viz. of a violet inclining to the purple.

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(a) In the *Annals of Chemistry*, Vol. I. we have the following account of the method of digging for the chrysopeira, and of the earths and stones with which it is accompanied.

This precious stone is found in certain mountains in Silesea, which seem to begin those of Tradas, extending to within half a league of Glatz. These mountains appear, in general, to consist of a number of strata, horizontal or inclined, composed chiefly of substances containing magnesia, but likewise mixed with calcareous, argillaceous, and siliceous earths. The greatest part of these consist of serpentine, mixed with asbestos and anianthus, grey argillaceous earths, boles, and red or green ochres, stone marrow, steatites, or soapstone, and talc. In these mountains also we meet with quartz, petroflex, opal, and chalcedony, in detached fragments, and sometimes in continued veins. We also discover in them veins of sand, of the nature of granite. Sometimes the serpentine is met with at the surface; sometimes at the depth of 20 or 30 feet. The stone marrow seems here to be produced by the decomposition of a very milky species of opal agate named cacholong; for at the depth of 50 feet and upwards the veins of this soapy earth assume a degree of solidity, and we find nothing but hard and semitransparent cacholongs.

The above-mentioned strata are crossed by a great number of cracks filled with green-coloured earths and stones; but these frequent y do not contain a single true chrysopeira. They are sometimes found immediately under the vegetable mould, or at the depth of some feet, in shapeless masses, covered with a heavy clay, and sometimes enveloped by an unctuous earth of a beautiful green colour, which it derives from the calx of nickel. In other places, the chrysopeira has been found in uneven laminae of several yards in length and breadth, either immediately under the mould, or in the upper strata of serpentine, which have little solidity; and very beautiful ones have been found at the depth of seven or eight fathoms; and some have been met with in grey clay at the depth of four fathoms. In some places also they are met with in a kind of red ochre, which is attracted by the magnet; in others they are found in the crevices of rocks. The beautiful green chrysopeira is found most plentifully in the mountain of Glaffendorf. In another mountain named Kofsmutz, where it is also found, the pieces are so porous, and so much spotted with white, &c. that sometimes upwards of 1000 of them have not afforded one large enough for the use of the jewellers. The defects are frequently only discoverable on polishing, as the green opal, while rough, perfectly resembles the chrysopeira; but, on polishing the stones in which it is contained, it is detected by its want of lustre.

The quantity in which these stones are found is not sufficient to afford the expenses of regular mining; the most profitable way, therefore, of obtaining them is by making trenches in the earth from four to five feet deep. Almost all the mountain of Kofsmutz, however, has already been examined in this manner; so that they now dig for the chrysopeira in quarries by uncovering a bank of earth or stone, and descending to other banks by steps in the open air, so as to throw the rubbish back from bank to bank. This method, however, cannot be continued farther than 24 or 30 feet, otherwise the produce would not defray the expense. The only tools employed in digging for the chrysopeira are a spade and pick-axe; the former to remove the earth, the latter to detach the chrysopeira itself from the stones which surround it.

Various accounts have been given of the component parts of this precious stone. Lehmann thinks, that purple or rosy colour, or inclining to the blue; very often they are semi-transparent, without any colour in one end, and violet towards the other. The best are found in the Vic mountains of Catalonia in Spain, and at Wiesenthal in Saxony, as well as in Bohemia in Germany, in Italy, and in the province of Auvergne in France.

Crystals within the geodes, or hollow agate-balls, are very often found of an amethysty colour, and some are very fine.

What we call amethyst root, or mother of amethyst, is but a sparry fluor, of which we have plenty in Derbyshire; many fine ornamental pieces are made of this substance in different forms and shapes. These spars are found in insulated masses, sometimes pretty large; but never in the form of large rocks.

VII. The garnet, (Granat.) This stone, when transparent and of a fine colour, is reckoned among the gems; but it varies more than any, both in the form of its crystals and in its colour, some being of a deep and dark red, some yellowish and purplish, and some brown, blackish, and quite opaque. In general, their lustre is less than that of other gems, as well as their hardness, which yields to the file, although they may strike fire with steel. But as to their form, these crystals take almost all sorts of figures, as the rhombohedral, tetraededral, &c., and some are of an irregular form.

Their colour proceeds from the iron which enters into their composition; and, according to M. de Saussure, even the finest oriental garnets attract the magnetic needle at a small distance.

The Syrian garnet is the finest and best esteemed. It is of a fine red, inclining to the purple colour, very diaphanous, but less brilliant than the oriental amethyst. It seems to be the amethystizontas of Pliny; the Italians call it rubino di rocca,

the colour of it is owing to some ferruginous particles modified in a particular manner; but the experiments he adduces for this opinion are not satisfactory. Mr Sage attributes the colour to cobalt from the blue colour it imparts to glass. Mr Achard thinks the stone contains ca'x of copper as well as ca'x of iron; because a part of the metal separable from it may be dissolved in volatile alkali. The following are the experiments of M. Klaproth upon the subject.

1. On heating several pieces of very pure chrysoprasus red hot, and quenching them in water, the colour was changed from green to bluish grey; and, on repeating the operation, it became a white grey. They were found to have lost in weight one and a half per cent. and were easily pulverizable in a glass mortar.

2. Three hundred grains of chrysoprasus were mixed with double its weight of mild mineral alkali, and the mixture heated for some hours red hot, in a porcelain crucible. The mass was then powdered, and digested in distilled water. By filtration, a yellowish grey residuum was obtained, weighing 44 grains; the filtered liquor was limpid and colourless, a copious precipitate being formed with muriatic acid, which being washed and dried was found to be siliceous earth.

3. The 44 grains of yellowish grey residuum were digested in a retort, with 352 grains of aqua regia; a great part of which was evaporated. The acid which came over was returned into the retort, and filtered after a second digestion. The residuum was a very fine white siliceous earth, which, after being washed, dried, and heated red hot, weighed 20 grains.

4. The filtrated solution was of a pale green, but on supersaturation with volatile alkali immediately turned of a bluish colour, precipitating a small quantity of brownish gelatinous matter; which, when collected, twice distilled with nitrous acid, and afterwards strongly heated, yielded a brown ca'x of iron, weighing no more than a quarter of a grain: whence our author concludes, that iron does not contribute to the colour of the chrysoprasus, as we know many colourless stones which contain as great a quantity of that metal. This small quantity of calx was left after digesting the gelatinous residuum. On precipitating the soluble parts, they appeared to consist of aluminous earth, in an excessively divided state; which being washed and dried, weighed half a grain.

5. To find whether the solution contained calcareous earth or not, he mixed with that, supersaturated with volatile alkali, a saturated solution of mild mineral alkali, which precipitated four grains and an half of white and very pure calcareous earth.

6. Nothing more was precipitated from the solution, either by acids or alkalies, after the separation of the calcareous earth, though it still retained a bluish colour. It was poured into a retort, and evaporated to dryness; the residuum was of a yellowish colour, which became green on being dissolved in distilled water. Mild mineral alkali threw down only a little earth of a greenish white colour; which being re-dissolved in dephlogisticated nitrous acid, and precipitated with Prussian alkali, the liquor yielded 17 grains of a sea-green powder. This precipitate, in our author's opinion, is the colouring principle of the chrysoprasus; and this principle he afterwards found to be calx of nickel.

7. Our author likewise attempted to analyse the chrysoprasus in the moist way by concentrated vitriolic acid; in which process his chief view was to discover whether or not the stone contained any volatile particles or not. On an ounce of crude chrysoprasus, therefore, when put into a retort, he poured an equal quantity of rectified vitriolic acid, and two parts of distilled water. After the latter had passed over into the receiver, the fire was increased to force over the superabundant acid; a part arose in white vapours, and some fell into the receiver with a hissing noise. Boiling water, which had been distilled, was then poured upon the residuum, and the solution filtered. The powdered chrysoprasus left on the filter had not been perfectly dissolved, and... and is found in Syria, Calcutta, Cananor, Cambaya, and Ethiopia.

The fine garnet of a red inclining to a yellow colour, is the sorianus of the ancients, the vermeille of the French, and the giacinto guarnacino of the Italians. Its name is taken from Sorian, or Surian, a capital town of Pegu, from whence these gems are brought; when they have a brownish taint, they are then called hyacinths.

The occidental garnet is of a deep and dark red, and its hardness is lesser. However, some very fine hard garnets are found in Bohemia. Garnets are also found in Hungary, at Pyrna in Silesia, at S. Sapho in the canton of Berne, in Spain, and in Norway.

The garnet melts in the focus of a good burning glass into a brown mass, which is attracted by the loadstone; and this shows that iron enters considerably into its composition.

Some garnets are found, which contain a little gold. Those called zingraupen by the Germans contain tin.

VIII. Tourmalin; Lapis electricus.

This is a kind of hard stone, lately brought into notice by its electrical properties. See Siliceous Earths.

1. Its form is a prism of nine sides of different breadths, mostly truncated, and seldom terminating in a pyramid at each end, which is either composed of three pentagons, or of nine triangles.

2. When heated in the fire, it gives signs of contrary electricity on the two opposite ends of their prismatic form. But many of these stones are not in the least electric. However, on being rubbed, they become electric in their sides, like other diaphanous gems.

3. It is as hard almost as the topaz, and strikes fire with steel.

4. It melts by itself in a strong fire, though with difficulty.

5. With the microcosmic salt it melts perfectly; but only in part with borax.

6. With mineral alkali it is divided into a kind of powder.

7. The three mineral acids dissolve it when first reduced to a powder.

8. It bears a greater similarity to scheel than to any other stone; but its component parts show

in general, had undergone but little alteration, so that he could not by this method determine the component parts. M. Achard, however, was more successful, and by a similar method determined the component parts of this gem to be five grains of an earth, which, distilled with vitriolic acid, became volatile; eight grains of calcareous earth, six grains of magnesia, two grains of calx of iron, three grains of calx of copper, and 456 of siliceous earth.

M. Klaproth never met with any volatile earth or magnesia in his experiments on this gem; and therefore concludes, that the chrysopeirafus used by him had been essentially different from that made use of by M. Achard; and he seems not to give credit to the account of any copper being found in it.

8. One part of crude chrysopeirafus, well powdered and washed with two parts of mild vegetable alkali, yielded a violet-coloured glass, which in the atmosphere ran into a brownish coloured liquor.

9. Five parts of the gem, with four of mild alkali, gave a beautiful violet-coloured glass after being two hours in fusion.

10. Equal parts of crude chrysopeirafus and mild mineral alkali, yielded a transparent glass in thin laminae, of a brown colour, resembling that of the tourmalin, the surface being marked with fine reticulated veins, which veins arose from small grains of very fine reduced nickel placed in lines against one another.

11. Equal parts of crude chrysopeirafus and calcined borax, gave a clear, transparent, and brown glass, resembling the smoky topaz.

12. Equal parts of chrysopeirafus, extracted by vitriolic acid and calcined borax, yielded a similar glass of a clear brown colour; "which proves (says our author), that the vitriolic acid was incapable of perfectly analysing the chrysopeirafus, though I had used a double portion of the earth."

13. Eighty grains of prepared siliceous earth, sixty grains of mild fixed alkali, with three grains of calx of nickel procured from the chrysopeirafus, yielded a beautiful, clear, and violet-coloured glass.

14. On substituting three grains of calx produced from an ore of nickel, a glass was produced exactly like the former.

15. Sixty grains of prepared siliceous earth and calcined borax, with three grains of calx of nickel from the chrysopeirafus, yielded a transparent glass of a clear brown colour.

16. Sixty grains of prepared siliceous earth and vitrified phosphoric acid, with three grains of calx of nickel from the chrysopeirafus, gave a glass of the colour of honey.

17. Thus the attempts of M. Klaproth to recompose the chrysopeirafus proved abortive. From his experiments, however, he deduces the following conclusions: 1. The blue colour observable in the glass produced by fusing the chrysopeirafus with vegetable alkali, arises entirely from the nickel contained in the gem; and the experiment shows that the calx of nickel, when purified as much as possible, has the surprising property of tingling glasses prepared with vegetable alkali of a blue colour. "But (says he) why was not this colour also obtained with soda? and what is the cause of a difference so little to be expected?" 2. By these experiments the supposition of M. Sage is refuted, that the metallic matter which colours the chrysopeirafus is cobalt: "many metallic substances besides cobalt, it is well known, give by certain processes a blue glass; thus..." show that it may be ranged with propriety in this place, along with other precious stones; as the argillaceous earth is also the most prevalent in its composition.

a. The oriental tourmalines are found in the island of Ceylon. They are transparent, of a dark brown yellow; and their specific gravity is from 3062 to 3295.

b. From Brazil. Transparent. These are green for the most part; but there are also some red, blue, and yellow: their specific gravity is from 3075 to 3180.

c. From Tyrol. Of so dark a green as to appear opaque. Their specific gravity is about 3050. These are found in beds of steatites and lapis-lazuli, among the micaeous veins, talcs, and hornblende of Schneeberg, Jurzagi, and Zillerthal, in the mountains of Tyrol.

d. From the mountains of Old Castile in Spain. These are transparent, and have the same properties as the preceding ones.

IX. The opal, Opalus; the girasole of the Italians.—This is the most beautiful of all the flint kind, owing to the changeable appearance of its colours by reflection and refraction, and must therefore be described under both these circumstances.

1. The opal of Nonnius, the Sangonon of the Indians. This appears olive-coloured by reflection, and seems then to be opaque; but when held against the light, is found transparent and of a fine ruby red colour.

There is, however, another of the same kind in Sweden, which by reflection appears rather brown; but by refraction it is red, with violet veins.

2. The white opal. Its ground is white, of a glass-like complexion, from whence are thrown out green, yellow, purple, and bluish rays; but it is of a reddish or rather flame-colour when held against the light.

a. Of many colours; the oriental opal. b. Of a milky colour. c. Bluish, and semi-transparent. This is not so much valued as those which are more opaque, because it is easier to be imitated by art.

§ 2. Of Quartz.

This stone is very common in Europe, and easier to be known than described. It is distinguished from the other kinds of the siliceous order by the following qualities.

1. That it is most generally cracked throughout, even in the rock itself; whereby, 2. As well as by its nature, it breaks irregularly, and into sharp fragments. 3. That it cannot easily be made red-hot without cracking still more. 4. It never decays in the air. 5. Melted with pot-ashes, it gives a more solid and fixed glass than any other of the siliceous order. 6. When there has been no interruption in its natural accretion, its substance always crystallizes into hexagonal prisms pointed at one or both ends. 7. It occurs in clefts, fissures, and small veins in rocks. It very seldom forms large veins, and still seldom whole mountains, without being mixed with heterogeneous substances.

According to Mr Kirwan, quartz neither loses its hardness nor its weight by calcination. Its texture is lamellar. These stones are in general the purest of the siliceous kind, though most contain a slight mixture of other earths; the most obvious distinction among them arises from their transparency or opacity.

Quartz is found,

(i.) Pure. A. Solid, of no visible particles, with a glossy surface. Fat quartz. a. Uncoloured and clear. This has no crystallized form, but is nevertheless as clear as quartz crystals of the best water. b. White, the common fat quartz.

L

cobalt gives a blue colour to combinations of the mineral alkali with phosphoric acid, to mineral alkali itself, to potash, and to borax. The acid of tungsten (falsely so called) also gives a blue colour to frits made with phosphoric salts, but not to those made with borax; the calx of nickel gives a blue colour only to frits made with potash, brown to those with mineral alkali and borax, and yellow, like honey, to combinations of phosphoric acid with mineral alkali.

3. As the chrysoprasus gives a brown colour with borax, and the solution of this stone in muriatic acid gives no signs of cobalt dissolved in the same acid; this shows that there is no cobalt in the stone. Mr Sage, indeed, pretends, that he has obtained a blue glass from the chrysoprasus and borax; but this is contradicted by experience.

4. The mineralogical character of the chrysoprasus, therefore, is a quartz coloured green by nickel. Three hundred grains of it contain 288½ of siliceous earth calcined to redness, one quarter of a grain of pure alumious earth, two grains and an half of calcareous earth calcined to redness, three grains of calx of nickel, and one quarter of a grain of calx of iron. All these were extracted in the experiments; and there were besides five grains and an half of waste.

Our author mentions, that in the collections of chrysoprasus which have been brought to him, he has constantly observed green opal, in bits of vein from half an inch to an inch, and fixed in its borders: the reddish, yellow, and white opals, on the contrary, are generally met with on a green or brownish petroflex. But the white opal, which, as well as the green, is found in pieces of the nature of matrix, differs from the true opal, approaching the chalcedony and the opaque milky quartzes. This kind of transparent opal, radiated with a whitish blue, contains the following ingredients in its composition: Siliceous earth, 237 grains; alumious earth, a quarter of a grain; calx of iron, a quarter of a grain—in all, 2·7½ grains. In 240 grains were two and an half of waste. The colour of this stone, as well as the chrysoprasus, in our author's opinion, is derived from nickel. Part II.

Siliceous Earths.

Gem.

c. Blue. d. Violet.

B. Grained. a. White. b. Pale green.

C. Sparry quartz. This is the rarest; and ought not to be confounded with the white felt-pan, being of a smoother appearance, and breaking into larger and more irregular planes. a. Whitish yellow. b. White.

D. Crystallised quartz. Rock crystal. Quartz crystal. 1. Opaque, or semi-transparent. a. White, or of a milk colour. b. Red, or of a carnelian colour. c. Black. 2. Clear. a. Blackish brown, smoky topaz, or rauch topaz of the Germans. b. Yellow; found in Bohemia, and sold instead of topazes. c. Violet; the amethyst from Saxony, Bohemia, and Dammemore in Upland (b.) d. Uncoloured; rock crystal, properly so called. When these coloured crystals are not clear, they are called fluffs; for instance, topaz-fluffs, amethyst-fluffs, &c. (c.)

(1.) Impure quartz. a. Mixed with iron, in form of a black calx.— This is of a glossy texture, and contains a great quantity of iron. b. Mixed with copper in form of a red calx. a. Red.

§ 3. Of Flint.

The flint (Silex pyromachus, Lapis cornues, or the hornstein of the Germans) forms a kind of intermediate substance between quartz and jasper; both which, however, it so nearly resembles, that it is not easy to point out such characters as shall readily distinguish it from them. We can only, therefore, speak of its properties comparatively.

1. It is more uniformly solid, and not so much cracked in the mass as the quartz; and, 2. It is more pellucid than the jasper. 3. It bears being exposed to the air without decaying better than the jasper, but not so well as the quartz. 4. It is better for making of glass than the jasper, but is not quite so good as quartz for that purpose. 5. Whenever there has been an opportunity in this matter of its shooting into crystals, quartz crystals are always found in it; just as if the quartz made one of its constituent parts, and had in certain circumstances been squeezed out of it: this is to be seen in every hollow flint, and its clefts, which are always filled up with quartz. 6. It often shows most evident marks of having been originally in a soft and slimy tough state like glue or jelly.

The several varieties of this species have obtained more distinct names with respect to their colours than from any real difference in their substance; but these are still necessary to be retained, as the only names used by jewellers and others, who know how to value them accordingly.

I. Jade. Lapis nephriticus. Jaspachates. The true lapis nephriticus seems to belong to this siliceous order, as it gives fire with steel, and is semi-pellucid like flint; it does not harden.

(b) The most transparent are called false diamonds, Bristol, Kerry stones, and Alençon diamonds, &c. The coloured transparent crystals derive their tinge generally from metallic calces, though in exceeding small portions: they all lose their colours when strongly heated. These are what we call false gems, viz.

The red, from Oran in Barbary, false rubies. The yellow, from Saxony, false topazes. The green, from Dauphiny, (very rare) false emeralds, or prafes. The violet, from Vil in Catalonia, false amethysts. The blue, from Puy in Valay, France, false sapphires.

There are also opal, or rainbow crystals, some of which make a very fine appearance; the various colours of which are thrown out in zones across the surface, though they never shine like the oriental opal.

(c) M. Fourcroy makes a remarkable difference between the crystals and the quartz, by affirming that the former are unalterable in the fire, in which they neither lose their hardness, transparency, nor colour; whilst the quartz loses the same qualities, and is reduced by it to a white and opaque earth. He classes the rock crystals,

1st, According to their form, viz. 1. Infusilated-hexagonal-crystals, ending in two pyramids of six faces, which have a double refraction, or show two images of the same object when looked through. 2. Hexagonal crystals united, having one or two points. 3. Tetradral, dodecedral, flated crystals; and which, though hexagonal, have nevertheless their planes irregular. 4. Crystals in large masses, from the island of Madagascar, which have a simple refraction.

2dly, As to the colour, they are either diaphonous, reddish, smokey, or blackish.

3dly, As to accidental changes, some are hollow: some contain water within one or more cavities: some are cased, viz. one within the other: some are of a round form, as the pebbles of the Rhine: some have a crust of metallic calces, or of a pyrites: some are of a geological form, viz. crystallised in the inside of a cavity: some seem to contain amianthe, or asbestos, and others contain shirils.

The same author reckons among crystals, the oriental topaz, the hyacinth, the oriental sapphire, and the amethyst. Mr. Daubenton has always looked on this last as a quartzous crystal. den in fire, but melts by the solar heat in the focus of a burning lens into a transparent green glass with some bubbles. That called by the name of circoncision stone, which comes from the Amazon river, melts easier, in the same solar fire, into a brown opaque glass, which is far less hard than the stone itself. (Macquer.)

This stone is superior in hardness to quartz, though from its unctuousity to the touch, one would suspect it to contain a large portion of argillaceous earth, or rather of magnesian earth, as Mr Kirwan seems to suspect.

Its specific gravity is from 2,970 to 3,389.

It is of a granular texture, of a greasy look, and exceedingly hard; is scarcely soluble in acids, at least without particular management, and is infusible in the fire. M. Sauflaire seems to have extracted iron from it.

a. It is sometimes of a whitish milky colour, from China; but mostly

b. Of a greenish, or

c. Deep-green colour, from America,

d. Grey, yellowish, and olive colour: these are the vulgar lapis nephriticus, they being supposed to cure the nephritic pains by their external application to the loins.

The semi-pellucidity, hardness, and specific gravity, are the characters by which the lapis nephriticus may be distinguished from other stones.

II. Cat's eye; Pseudoporus. The sun-stone of the Turks, called gumeche.

This stone is opaque, and reflects green and yellowish rays from its surface: it is found in Siberia. It is very hard and semi-transparent, and has different points, from which light is reflected with a kind of yellow-brown radiation, somewhat similar to the eyes of cats, from whence it had its name. Jewellers do not fail to cut them round to the greatest advantage. The best of these stones are very scarce. One of these of one inch diameter was in the cabinet of the grand duke of Tuscany.

III. Hydrophanes, or Oculus Mundi; also called Lapis mutabilis.

The principal property which distinguishes this from all other stones, is that it becomes transparent by mere infusion in any aqueous fluid; but it gradually resumes its opacity when dry.

IV. The onyx. Onyx camehuja. Memphites. It is found of two sorts.

a. Nail-coloured onyx, having pale flesh-coloured and white lines.

b. With black and white lines. The oriental onyx.

V. The chalcedony, or white agate, is a flint of a white colour, like milk diluted with water, more or less

opaque: it has veins, circles, and round spots. It is said to be softer than the onyx, but much harder than those agates which are sometimes found of the same colour.

a. The white opaque chalcedony, or cablong, from the Buckharith Calmucks. This was first made known by one Renez, a Swedish officer, who for several years had been in that country. The inhabitants find this flint on the banks of their rivers, and work idols and domestic vessels out of it.

b. Of white and semi-transparent strata; from Ceylon.

c. Bluish grey; from Ceylon and Siberia.

VI. The carnelian. Carniolus.

Is of a brownish red colour, and often entirely brown. Its name is originally derived from its resemblance to flesh, or to water mixed with blood.

a. Red.

b. Yellowish brown, looks like yellow amber. It is said not to be so hard as the chalcedony.

VII. The fardonyx.

This is a mixture of the chalcedony and carnelian, sometimes stratumwise, and sometimes confusedly blended and mixed together.

a. Striped with white and red strata: this serves as well cut in cameo as the onyx.

b. White, with red dendritical figures. This very much resembles that agate which is called the mocha stone; but with this difference, that the figures are of a red colour in this, instead of black, as in that agate.

Between the onyx, carnelian, chalcedony, fardonyx, and agate, there seems to be no real difference, except some inexplicable degrees of hardness.

VIII. The agate; Achates.

This name is given to flints that are variegated with different colours, promiscuously blended together; and they are esteemed in proportion to their mixture of colours, their beauty, and elegance. Hence also they have obtained variety of names, mostly Greek, as if the business of the lapidary in cutting of them, and admiring their several beauties and figures, had been derived from that nation alone (p).

a. Brown opaque agate, with black veins, and dendritical figures; the Egyptian pebble.

b. Of a chalcedony colour; achates chalcedonians.

c. Semi-transparent, with lines of a blackish brown colour, and dendritical figures; the mocha stone.

d. Semi-transparent, with red dots; Gemma divi Stephani. When the points are very minute, so as to give the stone a red appearance, it is by some called Sardes.

(d) On the side of a hill near the church of Rothiemay Moray, is a quantity of fine agate of elegant red and white colours. It is very hard, heavy, of a smooth uniform texture, and of a considerable brightness; in which the red are remarkably clear, and finely mixed and shaded through the stone. Mr Williams says that this is the largest and most beautiful agate rock he ever saw; and so fine and hard as to be capable of the highest lustre in polishing. e. Semi-transparent, with clouds of an orange colour. f. Deep red or violet, and semi-transparent. g. Of many colours, or variegated. h. Black.

IX. Common Flint; Pyromachus. This, in reality, is of the same substance as the agate; but as the colours are not so striking or agreeable, it is commonly considered as a different substance. a. Blackish grey, from the province of Skone. b. Yellow semi-transparent, from France. c. Whitish grey. d. Yellow with brown.

When the flints are small, they are in England called pebbles; and the Swedish sailors, who take them as ballast, call them finger.

X. Chert; Petroflex, Lapis Cornues. The hornstein of the Germans. This is of a coarser texture than the preceding, and also less hard, which makes it consequently not so capable of a polish. It is semi-transparent at the edges, or when it is broke into very thin pieces. a. Chert of a flesh colour, from Carl-Schakt, at the silver-mine of Salberg, in the province of Westmanland. b. Whitish yellow, from Salberg. c. White, from Kriiftenberg, at Nya Kopparberget in Westmanland. d. Greenish, from Prekgrufvan, at Hellefors in Westmanland.

Chert runs in veins through rocks, from whence its name is derived. Its specific gravity is from 2590 to 2700. In the fire, it whitens and decrepitates like filex, but is generally so fusible as to melt per se. It is not totally dissolved in the dry way by the mineral alkali; but borax and microcosmic salt dissolve it without effervescence. Its appearance is duller and less transparent than common flint. The reddish Petro-flex used in the Count de Lauragar's porcelain manufacture, and called there felt spot, contained 72 per cent. of filex, 22 of argill, and 6 of calcareous earth.

There are not yet any certain characters known by which the cherts and jaspers may be distinguished from each other: by sight, however, they can easily be discerned, viz., the former (the cherts) appearing transparent, and of a fine sparkling texture, on being broken; whereas the jasper is grained, dull, and opaque, having the appearance of a dry clay. The chert is also found forming larger or smaller veins, or in nodules like kernels in the rocks; whereas the jasper, on the contrary, sometimes constitutes the chief substance of the highest and most extended chain of mountains. The chert is likewise found plentifully in the neighbourhood of scaly limestone, as flints in the strata of chalk. What connection there may be between these bodies, perhaps time will discover.

But flints and agates being generally found in loose and single irregular nodules, and hardly in rocks, as the chert, it is a circumstance very insufficient to establish a difference between them; for there is the agate-stone, near Constantinople, running vein-like across the rock with its country of the same hardness, and as fine and transparent as those other agates which are found in round nodules at Deux-ponts. We must, therefore, content ourselves with this remark concerning flints, viz. That they seem to be the only kind of stone hitherto known, of which a very large quantity has been formed in the shape of loose or separate nodules, each surrounded with its proper crust; and that the matter which constitutes this crust has been separated from the rest of the substance, in like manner as sandstone or glass-gall separates from, and swims upon, glass, during its vitrification; though sometimes the formation of this crust may be prevented by the too sudden hardening of the matter itself.

Other species of stones, which are found in loose pieces or nodules, except ores and some sorts of stalactites, show evidently by their cracks, angles, and irregular figures, that they have been torn from rocks, rolled about, and rubbed against one another in torrents, or by some other violent motions of water.

That flints had originally been in a soft state, M. Cronstedt observes, is easy to be seen in the Egyptian pebbles, which have impressions of small stones, sand, and sometimes, perhaps, grass; which, however, have not had any ingress into the very flint, but seem only to have forced the above agate-gall or crust out of the way.

§ 4. Of Jaspers.

Jasper, jaspii, (the dia/pro of the Italians), is a name given to all the opaque flints whose texture resembles dry clay, and which have no other known quality whereby they may be distinguished from other flints, except that they may be more easily melted in the fire; and this quality perhaps may proceed from the heterogeneous mixture, probably of iron.

I. Pure jasper; which by no means yet known can be decomposed. a. Green with red specks or dots; the heliotrope, or blood-stone. b. Green. c. Red. d. Yellow. e. Red with yellow spots and veins. f. Black.

II. Jasper containing iron; Jaspi maritatis Sinopel. A. Coarse-grained. a. Red and reddish brown; sinopel. B. Steel-grained, or fine grained. a. Reddish brown; looks like the red ochre or chalk used for drawing; and has partition veins, which are unctuous to the touch, like a fine clay, and other like kinds. C. Of a solid and shining texture, like a flag. a. Liver-coloured; and, b. Deep red. c. Yellow. This last mentioned, when calcined, is attracted by the lodestone; and being assayed, yields from 12 to 15 per cent. of iron. (R.)

(e) Near Portsoy in Banffshire is an extensive rock of jasper; some parts of which contain a beautiful mixture of green and red, which appear finely shaded and clouded through the body of the stone when polished. Mr Williams is of opinion that it would be a very valuable quarry if worked. § 5. Feltspars.

1. Rhombic quartz; Spatum scintillans. This has its name from its figure, but seems to be of the same substance as the jasper. We have not, however, ranked them together, for want of true marks to distinguish the different sorts of the flinty tribe from one another. This kind is found, a. Sparry. b. White. c. Reddish brown. d. Pale yellow. e. Greenish.

2. Crystalised. a. In separate or distinct rhomboidal crystals.

II. Labrador stone; Spatum rutilum versicolor. Its colour is commonly of a light or of a deep grey, and mostly of a blackish grey; but when held in certain positions to the light, discovers different varieties of beautiful shining colours, as lazuly-blue, grass-green, apple green, pea-green; and seldom a citron-yellow; some have an intermediate colour betwixt red-copper and tobacco-grey; besides other colours between grey and violet. These colours are seen for most part in spots; but sometimes in stripes, on the same piece.

III. White feltspar; Terra Silicea Magnesia & ferro intimè mixta. This stone has been described by Mr Bayen; and is found at St Marie aux mines in Lorraine.—It is of a white opaque colour, spotted with ochre on the outside.

§ 6. Of the Garnet Kinds.

The substances of this genus (which is considered by Cronstedt as an order) are analogous to gems; since all these are composed of the siliceous, calcareous, and argillaceous earths, with a greater or less proportion of iron. The opaque and black garnets contain about 20 hundredths of iron; but the diaphanous ones only two hundredths of their weight, according to Bergman. The garnets, properly so called, contain a greater quantity of siliceous earth than the thirils, and both are now justly ranked with the siliceous earths.

The species are, 1. Garnet; Granatus. This is a heavy and hard kind of stone, crystallising in form of polygonal balls, and mostly of a red, or reddish brown colour. A. Garnet mixed with iron; Granatus mariallis. 1. Coarse-grained garnet-stones, without any particular figure; in Swedish called Granatberg; in German, Granatstein. a. Reddish-brown garnet. b. Whitish-yellow. c. Pale yellow. 2. Crystalised garnet. a. Black. b. Red; semi-transparent, and cracked; transparent. c. Reddish-yellow; transparent; the jacinth, or hyacinth. d. Reddish brown. e. Green. f. Yellowish-green. g. Black.

B. Garnet mixed with iron and tin. 1. Coarse-grained, without any particular figure. a. Blackish-brown.

2. Crystalised. a. Blackish-brown. b. Light-green or white.

C. Garnet mixed with iron and lead. 1. Crystalised. a. Reddish-brown.

II. Cockle, or shirl. Corneous crystallisatus Wallerii; Stannum crystallis columnaribus nigris Linnaei. This is a heavy and hard kind of stone which shoots into crystals of a prismatical figure, and whose chief colours are black or green. Its specific gravity is the same as the garnets, viz. between 3000 and 3400, though always proportionable to their different solidity.

A. Cockle, or shirl, mixed with iron. 1. Coarse, without any determined figure. a. Green. 2. Sparry. a. Deep green, (the mother of the emeralds), from Egypt. b. Pale green. c. White. This occurs very frequently in the fealy limestones; and its colour changes from deep green to white, in proportion as it contains more or less of iron.

3. Fibrous, striated cockle, or shirl; it looks like fibres or threads made of glass. a. Of parallel fibres. a. Black. b. Green. c. White. b. Of concentrated fibres: The starred cockle, or shirl, from its fibres being laid stellarwise. a. Blackish green. b. Light green. c. White.

4. Crystalised cockle, or shirl. a. Black. To this variety belong most of those substances called imperfect abieti; and as the cockle perfectly resembles a flag from an iron furnace, both in regard to its metallic contents and its glassy texture, it is no wonder that it is not soft enough to be taken for an abietus. It has, however, only for the sake of its structure, been ranked among the abieti. The striated cockle, or shirl, compared to the abieti, is of a thinning and angular surface (though thus sometimes requires the aid of the magnifying glass to be discovered), always somewhat transparent, and is pretty easily brought to a glass with the blow-pipe, without being consumed as the pure abieti seem to be.

b. Deep green. c. Light green. d. Reddish brown. The taufstein is of this colour, and consists of two hexagonal crystals of cockle grown together in form of a cross; this the Roman Catholics wear as an amulet, and is called in Latin lapis crucifer, or the cross stone.

The figure of the cockle crystals is uncertain, but always prismatical; the cockle from Yxfio at Nya Kopparberg, is quadrangular; the French kind has nine sides or planes; and the taufstein is hexagonal.

The name cockle for these substances is an old Cornish mineral name; but is also given sometimes to other very different matters. We have not in England any great quantity of species of cockles; the chief are found in the tin mines of Cornwall, and some fine crystallized kinds have been brought from Scotland.

The English mineral name of call, has been used by some authors as synonymous with cockles, and they are confounded together at the mines; but the call, definitely speaking, is the substance called wolfram by the Germans, &c.

Garnets, though small, are often found in micaeous stones in England; but extreme good garnets are found in great plenty also in like stones in Scotland.

III. Rowley rag, (Kirwan.) This stone is of a dusty or dark grey colour, with numerous minute shining crystals. Its texture is granular: by exposure to the air it acquires an ochre crust. Its specific gravity is 2748. Heated in an open fire it becomes magnetic. In strong heat it melts per se, but with more difficulty than basaltes. According to Dr Withering's analysis, 100 parts of it contain 47.5 of siliceous earth, 32.5 of argil, and 20 of iron.

IV. Siliceous muriatic spar, (Id.) This stone is of a hard, solid, and sparry texture; of a grey, ochre, dull colour, but internally bright. It gives fire with steel: yet it effervesces with acids. In a strong heat it grows brown; but at last it melts per se. One hundred parts of this stone contain fifty parts of silic: the remainder is mild magnesia and iron; but in what proportion is not mentioned (See Journal de Physique, Supplement, vol. xiii. p. 216.)

V. Turkey stone; cos Turcica, (Id.) This stone is of a dull white colour, and often of an uneven colour, some parts appearing more compact than others, so that it is in some measure flattery. It is used as a whetstone: and those of the finest grain are the best bones for the most delicate cutting tools, and even for razors, lancets, &c. Its specific gravity is 2508. It gives fire with steel; yet effervesces with acids. Mr Kirwan found that 100 parts of it contains 25 of mild calcareous earth, and no iron. There probably are two sorts of stones known by this name, as Mr Wallerins affirms, that which he describes neither to give fire with steel nor effervescence with acids.

VI. Ragg stone. The colour of this stone is grey. Its texture is obscurely laminar, or rather fibrous, but the laminae or fibres consist of a congeries of grains of a quartz appearance, coarse and rough. Its specific gravity is 2729. It effervesces with acids; and gives fire with steel. Mr Kirwan found it to contain a portion of mild calcareous earth, and a small proportion of iron. It is used as a whet-stone for coarse cutting tools.

[The siliceous grit, cos arenarius, and other compounds of the siliceous earth, &c. will be found in a subsequent division of this article.]

Observations on the economical Uses of the Siliceous Order.

The Europeans have no farther trouble with the precious stones than either to cut them from their natural or rough figure, or to alter them when they have been badly cut in the East Indies; in which latter circumstances they are called labora: and it may be observed, that for cutting the ruby, spinell, ballas, and chrysolite, the oil of olive is required, instead of any other liquid, to be mixed with the diamond powder, in the same manner as for cutting the diamond itself.

If the petty princes in those parts of the Indies, where precious stones are found, have no other power nor riches proportionable to the value of these gems, the reason of it is as obvious as of the general weakness of those countries where gold and silver abound, viz. because the inhabitants, placing a false confidence in the high value of their possessions, neglect useful manufactures and trade, which by degrees produces a general idleness and ignorance through the whole country.

On the other hand, perhaps, some countries might safely improve their revenues by such traffic. In Saxony, for example, there might probably be other gems found besides aquamarines and topazes; or even a greater trade carried on with these than at present, without danger of bad consequences, especially under the direction of a careful and prudent government.

The half-precious stones, so called, or gems of less value, as the common opal, the onyx, the chalcedony, the cornelian, and the coloured and colourless rock crystals, have been employed for ornaments and economical utensils, in which the price of the workmanship greatly exceeds the intrinsic value of the stones. The ancients used to engrave concave and convex figures on them, which now-a-days are very highly valued, but often with less reason than modern performances of the same kind. These stones are worked by means of emery on plates and tools of lead, copper, and tin, or with other instruments; but the common work on agates is performed at Oberstein with grind-stones at a very cheap rate. When once such a manufactory is established in a country, it is necessary to keep it up with much industry and prudence, if we would wish it to surmount the caprice of fashions; since, howmuchsoever the natural beauties of these stones seem to plead for their pre-eminence, they will at some periods unavoidably sink in the esteem of mankind; but they will likewise often recover, and be restored to their former value.

The grindstones at Oberstein are of a red colour, and of such particular texture, that they neither become smooth, nor are they of too loose a composition.

Most part of the flinty tribe is employed for making glass, as the quartz, the flints, the pebbles, and the quartzose sands. The quartz, however, is the best; and if used in due proportion with respect to the alkali, there is no danger of the glass being easily attacked by the acids, as has sometimes happened with glass made of other substances, of which we had an instance of bottles filled with Rhineish and Moselle wines during the time of a voyage to China.

In the melting of copper ores, quartz is used, to render the slag glassy, or to vitrify the iron; quartz being more useful than any other stone to prevent the calcination of the metal.

The quartzose sand which constitutes part of many stones, and is also used in making crucibles and such vessels, Argillaceous vessels, contributes most of all to their power of resisting fire.

It appears likewise probable that the quartzose matter makes the grind and whetstone fit for their intended purposes. (Magellan.)

Order V. The Argillaceous Earths.

The principal character whereby these may be distinguished from other earths is, that they harden in the fire, and are compounded of very minute particles, by which they acquire a dead or dull appearance when broken.

1. Argilla aerata; lac lune.

This fanciful name was heretofore thought to denote a very fine species of calcareous earth; but Mr. Screber has lately shown, that the earth to which this name is given, is a very uncommon species of argill. It is generally found in small cakes of the hardness of chalk; and like that, it marks white. Its hardness is nearly as that of fleatites, and it does not feel so fat as common clay does. Its specific gravity is 1669; its colour snow white. When examined with a microscope, it is found to consist of small transparent crystals; and by his experiments it appears plainly to be an argill saturated with fixed air. It effervesces with acids, and contains a very small proportion of calcareous earth and sometimes of gypsum, besides some feeble traces of iron. It is found near Halles.

II. Porcelain clay; Terra porcellanea, vulgo Argylla apyra, very refractory; the kaolin of the Chinese.

(1.) Pure.

A Diffusible in water.

1. Coherent and dry. a. White. 2. Friable and lean. a. White.

(2.) Mixed with phlogiston

A. Diffusible in water.

a. White and fat pipe clay. b. Of a pearl colour. c. Bluith grey. d. Grey. e. Black. f. Violet.

These contain a phlogiston, which is discovered by exposing them to quick and strong fire, in which they become quite black interiorly, assuming the appearance of the common flints, not only in regard to colour, but also in regard to hardness: but if heated by degrees, they are first white, and afterwards of a pearl colour. The fatter they seem to be, which may be judged both by their feeling smooth and unctuous, and by their shining when scraped with the nail, they contain a larger quantity of the inflammable principle. It is difficult to determine, whether this strongly inherent phlogiston be the cause of the above-mentioned pearl-colour, or prevents them from being burnt white in a strong fire; yet no heterogeneous substance can be extracted from them, except sand, which may be separated from some by means of water; but which sand does not form any of the constituent parts of the clays. If they be boiled in aqua regis in order to extract any iron, they are found to lose their viscosity.

III. Stone-marrow; Lithomarga. Keffekil of the Tartars.

1. When dry, it is as fat and slippery as soap; Argillaceous but, 2. Is not wholly diffusible in water, in which it only falls to pieces, either in larger bits, or resembles a curd-like mass, 3. In the fire it easily melts to a white or reddish frothy flag, consequently is of a larger volume than the clay was before being fused. 4. It breaks into irregular scaly pieces.

A. Of coarse particles: Coarse stone-marrow.

a. Grey. b. Whitish yellow, from the Crim Tartary, where it is called koffkil, and is said to be used for washing instead of soap.

B. Of very fine particles; fine stone-marrow.

a. Yellowish brown; Terra Lemnia.—Is of a shining texture, falls to pieces in the water with a crackling noise; it is more indurated than the preceding, but has otherwise the same qualities.

IV. Bole, (iron clay.)

This is a fine and dense clay of various colours, containing a great quantity of iron, which makes it impossible to know the natural and specific qualities of the bole itself, by any easy method hitherto in use. It is not easily softened in water, contrary to what the porcelain and the common clays are, (I. & VI.) but either falls to pieces in form of small grains, or repels the water, and cannot be made ductile. In the fire it grows black, and is then attracted by the loadstone.

A. Loose and friable boles, or those which fall to a powder in water.

a. Flesh-coloured bole. b. Red.

1. Fine; Bolus Armenus. 2. Coarse; Bolus communis officinalis. 3. Hard; Terra rubrica. c. Green; Terre verte.

1. Fine. 2. Coarse.

d. Bluith-grey, is ductile as long as it is in the rock, but even then repels the water; it contains 40 per cent. of iron; which metal being melted out of it in a close vessel, the iron crystallises on its surface.

e. Grey.

1. Crystallised in a spherical polygonal figure. 2. Of an undetermined figure.

B. Indurated bole.

a. Of no visible particles.

This occurs very often in form of slate, or layers, in the earth; and then is made use of as an iron ore. However, it has usually been considered more in regard to its texture than to its constituent parts; and has been called flate, in common with several other earths which are found to have the same texture.

a. Reddish-brown; in most collieries, between the seams of coal. b. Grey.

b. Of scaly particles.—The hornblende of the Swedes. It is distinguished from the mastic glimmer, or mica, by the scales being less shining, thicker, and rectangular.

a. Black.—This, when rubbed fine, gives a green powder.

b. Greenish.

V. Zeolite.

This is described in its indurated state in the Transactions of the academy of sciences at Stockholm for the year 1756, and there arranged as a stone sui generis in regard to the following qualities.

1. It is a little harder than the fluors and the other calcareous spars; it receives, however, scratches from the steel, but does not strike fire with it.

2. It melts easily by itself in the fire, with a like ebullition as borax does, into a white frothy slag, which cannot without great difficulty be brought to a solidity and transparency.

3. It is more easily dissolved in the fire by the mineral alkali (sal soda), than by borax or the microcosmic salt.

4. It does not ferment with this last salt, as lime does; nor with the borax, as those of the gypseous kind.

5. It dissolves very slowly, and without any effervescence, in acids, as in oil of vitriol and spirit of nitre. If concentrated oil of vitriol be poured on pounded zeolites, a heat arises, and the powder unites into a mass.

6. In the very moment of fusion it gives a phosphoric light.

There have lately been discovered some of the zeolites, particularly at Adelors's gold mines in Smoland, in Sweden; of which some sorts do not melt by themselves in the fire, but dissolve readily in the acid of nitre, and are turned by it into a firm jelly.

The zeolite is found in an indurated state:

(1.) Solid, or of no visible particles.

A. Pure.

a. White.

B. Mixed with silver and iron.

a. Blue, Lapis lazuli.

(2) Sparry zeolite. This resembles a calcareous spar, though it is of a more irregular figure, and is more brittle.

a. Light red, or orange-coloured.

(3.) Crystalized zeolite. This is more common than the two preceding kinds; and is found,

A. In groups of crystals, in form of balls, and with concentrical points.

a. Yellow.

b. White.

B. Prismatical and truncated crystals.

a. White.

C. Capillary crystals, which are partly united in groups, and partly separate. In this latter accretion they resemble the capillary or feathery silver ore; and are perhaps sometimes called flus ferrari, at places where the nature of that kind of stone is not yet fully known.

a. White.

VI. Tripoli.

This is known by its quality of rubbing or wearing hard bodies, and making their surfaces to shine; the particles of the tripoli being so fine as to leave even no scratches on the surface. This effect, which is called polishing, may likewise be effected by other fine clays when they have been burnt a little. The tripoli grows somewhat harder in the fire, and is very refractory: it is with difficulty dissolved by borax, and still with greater difficulty by the microcosmic salt. It becomes white when it is heated: when crude, it imbibes water, but is not diffusible in it: it tastes like common chalk, and is rough or sandy between the teeth, although no sand can by any means be separated from it. It has no quality common with any other kind of earth, by which it might be considered as a variety of any other. That which is here described is of a yellow colour, and is sold by druggists. This kind of tripoli has been lately discovered in Scotland. But the rottenstone, so called, is another sort found in England, viz. in Derbyshire. It is in common use in England among workmen for all sorts of finer grinding and polishing, and is also sometimes used by lapidaries for cutting of stones, &c.

The tripoli is found,

1. Solid: of a rough texture.

a. Brown.

b. Yellowish.

c. Spotted like marble.

2. Friable and compact.

a. Granulated.

b. Brown.

c. Yellowish.

VII. Common clay, or brick clay.

This kind may be distinguished from the other clays by the following qualities:

1. In the fire it acquires a red colour, more or less deep.

2. It melts pretty easily into a greenish glass.

3. It contains a small quantity of iron and of the vitriolic acid, by which the preceding effects are produced.

It is found,

A. Diffusible in water.

1. Pure.

a. Red clay.

b. Flesh-coloured, or pale-red.

c. Grey.

d. Blue.

e. White.

f. Fermenting clay.

2. Mixed with lime. See Marle, above.

B. Indurated.

1. Pure.

a. Grey flaky.

b. Red flaky.

2. Mixed with phlogiston, and a great deal of the vitriolic acid. See Alum Orus, above.

3. Mixed with lime. See Lime, above.

VIII. Argillaceous fissile stones.

These and many other different kinds of earth have been comprehended under the denomination of schiffl but to avoid ambiguity we will confine this name to stones of the argillaceous kind.

1. The bluish purple schifflus, or common roof slate; schifflus tegularis. Its colour varies to the pale, to the slightly purple, and to the bluish. a. The dark-blue slate, schifflus scriptorius. 2. The pyritaceous schifflus. This is of a grey colour, brown, blue, or black. 3. The bituminous schifflus. This is generally black, of a lamellar texture, and of different degrees of hardness. 4. Flag stone. This is of a grey, yellowish, or reddish white colour. 5. The argillaceous grit. This is called also sand stone and free stone, because it may be cut easily in all directions. 6. Killas. This stone is of a pale grey or greenish colour; either lamellar, or coarsely granular. It is found chiefly in Cornwall. 7. Toadstone. Dr Withering, who has given an analysis of this stone, describes it as being of a dark brownish grey colour, of a granular texture, not giving fire with steel, nor effervescing with acids. It has cavities filled with crystal-lized spar, and is fusible per se in a strong heat. It is found in Derbyshire. See Toadstone.

For the economical uses of the argillaceous earths, see the article Clay.

[The compounds of this and other earths will fall to be mentioned under a subsequent division.]

Class II. Salts.

By this name those mineral bodies are called which can be dissolved in water, and give it a taste; and which have the power, at least when they are mixed with one another, to form new bodies of a solid and angular shape, when the water in which they are dissolved is diminished to a less quantity than is required to keep them in solution; which quality is called crystallization.

In regard to the principal known circumstances or qualities of the mineral salts, they are divided into

1. Acid salts, or mineral acids. 2. Alkaline salts, or mineral alkalies.

Order I. Acid Salts.

For the characters, properties, and phenomena of these, see the article Acid, and Chemistry-Index.

Till of late no more mineral acids were known than the vitriolic and marine; the boracic or sedative salt being reckoned as produced artificially; but later discoveries have proved that we may reckon at least eleven mineral acids; out of which only two or three have been found in an uncombined state. Those hitherto known are the following, viz. the vitriolic, the nitrous, the marine, the sparry, the arsenical, the molybdanic, the tungstic, the phosphoric, the boracic, the succinuous, and the aerial. See the article Acid, and Chemistry-Index.

I. The vitriolic acid. See Chemistry-Index. II. Nitrous acid. This acid is by some excluded from the mineral kingdom, because they suppose it to be produced from putrefaction of organic bodies. But these bodies, when deprived of life, are again received amongst fossils, from whence their more fixed parts were originally derived. For the nature of this acid, see Chemistry-Index.

III. Acid of common or sea-salt. See Chemistry-Index, at Acid and Marine. IV. The fluor acid, or sparry fluor acid. See Chemistry-Index. This acid is obtained by art, as it has never been found disengaged, but united, to calcareous earth, forming a sparly fluor*, called Derbyshire* See Fluor fluor, Cornish fluor, blue John, or amethyst root, Spar when of a purple colour. See p. 72. col. 2. concerning the substances arising from the combination of this acid with calcareous earth.

V. The acid of arsenic. See Chemistry-Index. VI. The acid of molybdena. Ibid. VII. The acid of tungsten. Ibid. VIII. The phosphoric acid. Ibid. IX. The boracic acid. Ibid. X. The succinuous or amber acid. Ibid. XI. Aerial acid, or fixed air. Ibid.

Order II. Alkaline Mineral Salts.

For the characters, properties, and phenomena of these, see the article Alkali; also Chemistry-Index, at Alkali and Alkalies.

New acids are daily detected; but no additions have been made to the three species of alkali long since known.

These alkaline salts are,

1. Vegetable fixed alkali (A.)

(A) With regard to the origin of the vegetable fixed alkali, there are sufficient proofs that it exists already formed in plants, and also that a portion is formed by combustion; but in each case, the alkali is obtained in an impure state through the admixture of other matters, which must be separated before it can be used for chemical purposes.

The cendres gravelees are made by burning the husks of grapes and wine lees. They contain the purest alkali met with in common, and are used by the dyers.

Pot-ash is made by burning wood and other vegetables. This alkali is much phlogisticated, and contains many foreign and saline matters, which, however, may be separated.

That which is obtained from the ashes of wood burned in kitchens is the most pure of all. On the contrary, Vegetable fixed alkali, deprived of every acid, is not found anywhere by itself; but it is sometimes met with in combination with the vitriolic acid or the muriatic, generally with the nitrous, rarely with the aerial (b).

The fixed vegetable alkali (or potaffe of Morveau), is of a powdery appearance, and of a dead white colour. When pure, it is much more caustic than the neutral salt; it forms with the aerial acid, and even corrodes the skin (c).

1. It changes the blue colours of vegetables into a deep green. 2. It has no smell when dry; but when wetted, it has a slight lixivious odour. 3. Its taste is strongly acid, burning, caustic, and urinous (d). This last sensation arises from the volatile alkaline diffractates from animal substances. 4. When exposed to the air, it attracts humidity, and is reduced into a transparent colourless liquor. According to Gellert, it attracts three times its own weight of water. 5. It likewise attracts sometimes the aerial acid from the atmosphere, and is thereby deprived of its property of deliquescent. 6. When it is dissolved in an equal weight of water, it has an oily feel, owing to its action on the fatty parts of the skin, whence it is, though improperly, called oil of tartar. 7. In a moderate heat it melts; but in a more violent fire, it is dispersed or volatilized. 8. It is a most powerful solvent by the dry way: in a proper heat, it dissolves calcareous, argillaceous, siliceous, and metallic earths: and when the alkali is nearly equal in quantity to the earth, it forms various kinds of hard, solid, and transparent glass. 9. But if the alkali be in quantity three or four times that of the earth, the glass is deliquescent. 10. The mild vegetable alkali unites with the vitriolic acid with a violent effervescence, and produces vitriolated tartar.

II. Fossil fixed alkalis.

A. Alkali of the sea, or of common salt (e.)

1. Pure.

This has nearly the same qualities with the lixivious salt, which is prepared from the ashes of burnt vegetables. It is the same with the sal soda, or kelp: for the kelp is nothing else than the ashes remaining, after the burning of certain herbs that abound in common salt; but which common salt, during the burning of those vegetables, has lost its acid (f).

The properties of the fossil alkali are as follows:

1. It 1. It effervesces with acids, and unites with them. 2. Turns the syrup of violets to a green colour. 3. Precipitates sublimate mercury in an orange-coloured powder. 4. Unites with fat substances, and forms soap. 5. Dissolves the siliceous earth in the fire, and makes glass with it, &c. It distinguishes itself from the salt of the potash by the following properties (a). 6. It shoots easily into rhomboidal crystals; which 7. Fall to powder in the air, merely by the loss of their humidity (h). 8. Mixed with the vitriolic acid, it makes the sal mirabile Glauberi. 9. It melts more easily, and is fitter for producing the sal commune regeneratum, nitrum cubicum, &c. Perhaps it is also more conveniently applied in the preparation of several medicines.

10. It is somewhat volatile in the fire.

III. Volatile mineral alkali.

This perfectly resembles that salt which is extracted from animals and vegetables, under the name of alkali volatile, or sal urinum, and is commonly considered as not belonging to the mineral kingdom; but since it is discovered, not only in most part of the clays, but likewise in the sublimations at Solfatara, near Naples, it cannot possibly be quite excluded from the mineral kingdom (i).

Its principal qualities are, a. In the fire it rises in forma fissa, and volatilizes in the air in form of corrosive vapours, which are offensive to the eyes and nose (k). b. It precipitates the solution of the mercurial sublimate in a white powder. c. It also precipitates gold out of aqua-regia, and detonates with it; because, d. It has a reaction in regard to the acids, though not so strongly as other alkalies.

M 2

acid; with which last it retains not only the name but many of the properties of a pure alkali, because this last acid is easily expelled.

It is easily known by its crystallisation and its solubility in two times and an half of its weight of water, at the temperature of 60 degrees.

One hundred parts of this alkali, when pure and recently crystallised, contain 20 of mere alkali, 16 of aerial acid, and 64 of water. (Macquer.)

Mineral alkali is found in Hungary, in marshy grounds, of an argillaceous or marly nature, either mixed with water or crystallised and efflorescing. It is found also in Egypt at the bottom of lakes, and dried up by the summer's heat; and also in the province of Suchena, 28 days journey from Tripoli, where it has the name of Trona; in Syria, Persia, as well as in the East-Indies, and China, where it is called kien. It sometimes germinates on walls, and is called by many aphronitron. In its native state, is frequently mixed with magnesian earth, common salt, muriatic magnesia, and marine felsnite. (Kirwan.)

(g) This mineral alkali likewise differs from the vegetable, 1. By its taste, which is less corrosive and burning. 2. By its not deliquescent. 3. By the small degree of heat it produces if calcined, and afterwards added to water. 4. By its property of crystallising, by evaporating the water from its solution, as is practised with neutral salts; whereas the vegetable alkali does not crystallise unless combined with a large portion of aerial acid.

(h) This alkali being a very useful commodity, and essentially necessary in a number of manufactories, many ingenious processes have been contrived and attempted to procure it at a cheap rate, by decomposing the sea-salt; but it is believed, that till lately none of these new manufactures have succeeded, except that of Mr Turner, mentioned by Mr Kirwan in the second part of the Philosophical Transactions for 1782.—The process is said to consist in mixing a quantity of litharge with half its weight of common salt, which, on being triturated with water till it assumes a white colour, is left to stand some hours; after which, a decomposition ensues, the alkali being left alone, whilst the acid unites to the metallic calx; and this last being urged by a proper degree of fire, produces a fine pigment of a greenish yellow colour, whose sale pays for the most part of the expenses.

Mr Kirwan says, in the place already quoted, that if common salt perfectly dry be projected on lead heated to incandescence, the common salt will be decomposed, and a horn-lead formed, according to Margraff. He adds also, that according to Scheele, if a solution of common salt be digested with litharge, the common salt will be decomposed, and a caustic alkali produced; and, finally, that Mr Scheele decomposed common salt, by letting its solution slowly pass through a funnel filled with litharge.

(i) It is easily known by its smell, though in a mild state, by its volatility, and by its action on copper; the solutions of which, in the mineral acids, are turned blue by an addition of this alkali. It is frequently found, though in small quantities, in mould, marl, clay, schistus, and in some mineral waters. It probably derives its origin, in the mineral kingdom, from the putrefaction or combustion of animal or vegetable substances. (Kirwan.)

The same is caustic when uncombined with any acid, not excepting even the aerial acid. It differs from the other two alkalies in many essential particulars. 1. By its aeriform or gaseous nature. For the volatile alkali, in a state of purity, is nothing more than an alkaline gas diffused in water, as Dr Priestley has demonstrated. 2. By its volatility. 3. By the nature of the salts it forms with acids, which are very different from those whose bases are formed either of the vegetable or mineral alkali. (Mongez.)

(k) Pure volatile alkali, in an aerial form, resembles atmospheric air, but is more heavy. Its smell is pene- It tinges the solution of copper blue, and dissolves this metal afresh if a great quantity is added (L).

f. It deflagrates with nitre, which proves that it contains a phlogiston.

It is never found pure.

Order III. Neutral Salts.

Acids united to alkalis form neutral salts. These dissolved in water are no ways disturbed by the addition of an alkali; and generally, by evaporation, concrete into crystals. If, by proper tests, they show neither acid nor alkaline properties, they are said to be perfect neutral's; but imperfect, when, from defect in quantity or strength of one ingredient, the peculiar properties of the other more or less prevail.

I. Vitriolated tartar, vitriolated vegetable alkali, or (as Morveau calls it) the vitriol of potash.

This is a perfectly neutral salt, which results from the combination of the vitriolic acid with the vegetable fixed alkali. According to Bergman, it seldom occurs spontaneously in nature, unless where tracks of wood have been burnt down; and Mr Bowles, quoted by Mr Kirwan, says it is contained in some earths in Spain. See Chemistry-Index.

It is easily obtained, by pouring the vitriolic acid on a solution of fixed vegetable alkali till it is saturated. Crystals of this neutral salt are then formed. This crystallisation succeeds better by evaporation than by cooling, according to Mongez.

The taste of this salt is disagreeable, though somewhat resembling common salt.

II. Common nitre, (Alkali vegetable nitratum).

This is known in commerce by the name of saltpetre, and is also called prismatic nitre, to distinguish it from the cubic nitre after-mentioned.—It is perfect neutral salt; resulting from the combination of the nitrous acid with the pure vegetable alkali.

According to Bergman, it is formed upon the surface of the earth, where vegetables, especially when mixed with animal substances, putrefy.—See Chemistry-Index, at Nitre.

III. Digestive salt, salt of Sylvius, (Alkali vegetable saltinum).

This neutral salt is sometimes, though rarely, met with on the earth, generated perhaps, as professed by Bergman observes, by the destruction of animal and vegetable substances.

According to Macquer, this salt has been very wrongly called regenerated marine salt; and the epithet of ferrugine has also been given to it, without any good reason, to evince that it has such a property. But M. de Morveau calls it muriate de potasse with great propriety.

This salt is produced by a perfect combination of the vegetable alkali with marine acid. It has been wrongly confounded with common salt.—It is found in some bogs in Picardy, and in some mineral waters at Normandy, according to Monnet, quoted by Kirwan. Mongez adds also the sea-water, as containing this salt, and that it is never found in large quantities, although its components parts are abundantly produced by nature. See Chemistry-Index, at Diggitive.

IV. Mild vegetable alkali, (alkali vegetable aeratium).

This salt was formerly considered as a pure alkali, known by the name of potash and salt of tartar; but since the discovery of the aerial acid, it is very properly classed among the neutral salts, and ought to be called aerated potasse.

It results from a combination of the vegetable alkali with the aerial acid, and is hardly ever found native, unless in the neighbourhood of woods destroyed by fire.

On being exposed on a piece of charcoal, urged by the blow-pipe, it melts, and is absorbed by the coal; but,

In the metallic spoon, it forms a glassy bead, which becomes opaque when cold.

V. Vitriolated acid saturated with mineral alkali; Glauber's salt. Alkali minerae vitriolatum.

This is a neutral salt, prepared by nature (as well as by art), containing more or less of iron, or of a calcareous earth; from which arises also some difference in its effects when internally used. It shoots easily into prismatic crystals, which become larger in proportion to the quantity of water evaporated before the crystallisation. When laid on a piece of burning charcoal, or else burnt with a phlogiston, the vitriolic acid discovers itself by the smell resembling the hepar sulphuris.

It is found in a dissolved state in springs and wells. Some of the lakes in Siberia and Astrakhan.

penetrating, and suffocates animals. Its taste is acrid and caustic. It quickly converts blue vegetable colours to green, and produces heat during its combination with water. But if the water be frozen, it melts, producing at the same time an extreme degree of cold. It has a remarkable action on most metals, particularly copper.

This substance is obtained by the putrefactive fermentation from animal and some vegetable matters. It is this salt which causes that strong smell which is perceived in drains and privies on a change of weather. (Mongez.)

Its volatility arises from a very subtile and volatile (or phlogistic) oil, which enters as a principle into its composition. (Macquer.)

(L.) The solution of copper by this alkali, which is of a fine blue, presents a remarkable phenomenon. For if it be kept in a well closed phial, the colour decays, and at length disappears, giving place to transparency. But on opening the phial, the surface or part in contact with the air becomes blue, and the colour is communicated through the whole mass. This experiment may be many times repeated with the same success. can; and many springs in other places, contain this salt, according to Bergman. It is found in the sea-water; also in the earth, at several parts of Dauphiné in France, and in Lorraine; and sometimes it germinates on the surface of the earth, according to Monet, quoted by Kirwan. It is found, in a dry form, on walls, in such places where aphronitrum has effloresced through them, and the vitriolic acid has happened to be present; for instance, where marcasites are roasted in the open air. This salt is often confounded with the aphronitum or mild mineral alkali.

VI. Cubic or quadrangular nitre. Alkali minerales nitratum.

This is the neutral salt which results from the combination of mineral alkali with nitrous acid. It has almost all the characters of prismatic or common nitre, from which it only differs on account of its base; and takes its denomination from the figure of its crystals, which appear cubic.

This salt rarely occurs but where marine plants putrify. According to Bowles, quoted by Kirwan, it is found native in Spain. See Chemistry, n° 741, &c.

VII. Common salt, or sea-salt; Alkali minerales salitum, sal commune.

This salt shoots into cubical crystals during the very evaporation; crackles in the fire, and attracts the humidity of the air. It is a perfectly neutral salt, composed of marine acid, saturated with mineral alkali. It has a saline but agreeable flavour. See Chemistry-Index, at Sea-salt.

A. Rock salt, fossile salt; Sal montanum. Occurs in the form of solid strata in the earth.

1. With scaly and irregular particles. a. Grey, and b. White. These are the most common, but the following are rarer: c. Red; d. Blue; and e. Yellow, from Cracow in Poland, England, Salzberg, and Tirol.

2. Crystalized rock salt; sal gemma. a. Transparent, from Cracow in Poland, and from Transylvania.

B. Sea-salt.

This is produced also from sea-water, or from the water of salt lakes by evaporation in the sun, or by boiling.

The seas contain this salt, though more or less in different parts. In Siberia and Tartary there are lakes that contain great quantities of it.

C. Spring sea-salt.

This is produced by boiling the water of the fountains near Halle in Germany, and other places.

Near the city of Lidköping, in the province of Westergotland, and in the province of Dal, salt-springs are found, but they contain very little salt; and such weak water is called salen by the Swedes.

VIII. Borax.

This is a peculiar alkaline salt, which is supposed to belong to the mineral kingdom, and cannot be otherwise described, than that it is diffusible in water, and vitreifiable; that it is fixed in the fire; and melts to a glass; which glass is afterwards diffusible in water. See the detached article Borax.

IX. Mild mineral alkali; Alkali minerales aeratum. Natron, the nitre of the ancients.

This neutral salt is a combination of the mineral alkali with the aerial acid or fixed air. It is found plentifully in many places, particularly in Africa and Asia, either concreted into crystallized strata, or fallen to a powder; or efflorescing on old brick walls; or lastly, dissolved in springs. It frequently originates from decomposed common salt.

This is an imperfect neutral salt, and was formerly considered as a pure alkali; but the discovery of the aerial acid has shown the mistake.

1. It has nearly all the properties of the pure mineral alkali N° II. A. i. (p. 90.), but with less energy.

2. The vegetable blue colours are turned green by this salt; it effloresces with acids, and has an urinous taste.

3. It is soluble in twice its weight of cold water; but if the water is hot, an equal weight is sufficient for its solution.

4. It effloresces when exposed to the action of the atmosphere.

5. It fuses easily on the fire, but without being decomposed.

6. Facilitates the fusion of vitreifiable earths, and produces glass more or less fine according to their qualities.

7. It is decomposable by lime and ponderous earth, which attract the aerial acid.

8. And also by the mineral acids; but these expel the aerial acid of this salt, by seizing its alkaline basis, (Mongez.)

Wallerius confounds this salt with the aphronitrum after-mentioned, and calls it halinitrum, when it contains some phlogiston. Mr Kulbel, quoted by Wallerius, showed that it exists in some vegetable earths, and takes it to be the cause of their fertility; but this (M. Magellan observes) can only be on account of its combination with the oily parts of them, and forming a kind of soap, which is miscible with the watery juices.

X. Vitriolic ammoniac, (Alkali volatile vitriolatum.)

This neutral salt was called secret salt of Glauber, and is a combination of the volatile alkali with vitriolic acid. According to Bergman, it is scarcely found anywhere but in places where the phlogisticated fumes of vitriolic acid arise from burning sulphur, and are absorbed in putrid places by the volatile alkali. Thus at Fahlun the acid vapour from the roasted minerals produces this salt in the necessary-houses. Dr Withering, however, observes, that as volatile alkali may be obtained in large quantities from pit-coal, and produced by processes not dependent upon putrefaction, there is reason to believe that the vitriolic ammoniac may be formed in several ways not noticed by the above author. It is said to have been found in the neighbourhood of volcanoes, particularly of Mount Vesuvius, where, indeed, it might well be expected; yet its existence seems dubious, since Mr Bergman could scarce find any trace of it among the various specimens of salts from Vesuvius which he examined. The reason (according to M. Magellan) probably is, that the vitriolic acid disengaged by the combustion of sulphur is in a phlogisticated state; and all its combinations in this state are easily decomposed by the marine acid, which plentifully occurs in volcanoes. It is also said to be found in the mineral lakes of Tuscany, which is much more probable, as the vitriolic acid when united to water easily parts with phlogiston, and recovers its superiority over other acids. It is said likewise that this neutral salt is found on the surface of the earth in the neighbourhood of Turin.

1. This salt is of a friable texture, and has an acid and urinous taste. 2. Attracts the moisture of the atmosphere. 3. Is very soluble in water, it requiring only twice its weight of cold water, or an equal weight of boiling water, to be dissolved. 4. It becomes liquid on a moderate fire; but if urged, 5. It becomes red hot, and volatilizes. 6. The nitrous and muriatic acid decompose this salt by seizing the volatile alkali. But 7. Lime, ponderous earth, and pure fixed alkali, set the volatile alkali free, and combine with the vitriolic acid. 8. According to Kirwan, 100 parts of this salt contain about 42 of real vitriolic acid, 40 of volatile alkali, and 18 of water.

This vitriolic ammonia is easily known; for if quicklime or fixed alkali be thrown into its solution, the smell of the volatile alkali is perceived; and if this solution be poured into that of chalk or ponderous earth by the nitrous acid, a precipitate will appear.

XI. Nitrous ammonia, (Alkali volatile nitratum.) This is a neutral salt, which results from the combination of the nitrous acid with the volatile alkali. It is frequently found in the mother-liquor of nitre. When mixed with a fixed alkali, the volatile betrays itself by its smell.

1. It is of a friable texture, of a sharp bitter, and of a nitrous or cooling taste. 2. According to Mongez, it attracts the moisture of the atmosphere; but Romé de l'Isle asserts, that its crystals are not deliquescent: the experiment may be easily tried, and the truth ascertained. 3. It is soluble in cold water; but half the quantity of water, if boiling, is sufficient for dissolving it. 4. It liquefies on the fire, and afterwards it becomes dry. 5. It detonates with a yellow flame before it is red hot; and what is peculiar to this salt, it needs not, like common nitre, the contact of any combustible matter for its detonation;

from whence it appears that the volatile alkali itself possesses a great share of phlogiston.

6. Its component parts, viz. the nitrous acid and the volatile alkali, are not very intimately united; and of course, 7. It is easily decomposed by all the substances that have any affinity to either of them. 8. Mixed with the muriatic acid—it makes aqua regia. 9. One hundred parts of this neutral salt contain 46 of nitrous acid, 40 of volatile alkali, and 14 of water, as Mr Kirwan thinks.

XII. Native sal ammoniac. The muriatic (or marine) acid saturated with a volatile alkali. This is of a yellowish colour, and is sublimed from the flaming crevices, or fire-springs, at Solfatara, near Naples.

XIII. Aerated or mild volatile alkali. This neutral salt results from the combination of volatile alkali united to the aerial acid. It was formerly considered as a pure alkali:—But the discovery of the aerial acid (or fixed air) has shown it to be a true neutral salt, though imperfect; as it retains still all the properties of an alkali, though in a weaker degree, on account of its combination with the aerial acid, which is itself the most weak of all acids, and of course other stronger acids easily dilute it from its base, and from various ammonial salts.

1. This imperfect neutral salt has an urinous taste, and a particular smell, which is very penetrating, though less pungent, than the pure volatile alkali; and in the same manner it turns the blue vegetable juices green. 2. But, 3. It effervesces with other acids stronger than the aerial one, which the pure or caustic volatile alkali does not. 4. It sublimes very easily with a small degree of heat; 5. And dissolves in twice its weight of cold water; but in a lesser quantity, when this last is boiling hot. 6. It acts on metallic substances, chiefly on copper, with which a blue colour is produced.

According to Bergman, this salt was found in a well in London (Phil. Trans. for 1767), at Frankfort on the Main, and at Lauchstadt.—Messrs. Hierne, Henkel, and Brandt, have found also this salt in the vegetable earth, in various kinds of argil, and in some stony substances. Mr Vozel found it also in some of the incrustations at Gottingen; and Mr Malouin in some acidulous waters of France.

M. Magellan observes, that the borax and the three aerated alkalis are called imperfect neutrals; whilst the other neutral salts have acquired the name of perfect, because these last do not exhibit any of the distinguishing properties of their component parts. The three aerated alkalis have a very distinct alkaline character, as they turn blue vegetable juices green, though not of so vivid a colour as the caustic alkali. alkali does; and the borax is capable of receiving almost an equal quantity of its sedative acid, without losing all its alkaline properties.

In general, those neutral salts, consisting of fixed alkalies combined with acids, are more saturated than those composed of volatile alkali called ammoniacal salts, or those called aerated; which last are only composed by the combination of the aerial acid, united to any alkaline or earthy base.

The aerated alkalis are called also by the name of mild alkalis, because they possess no longer that sharp corroding quality which they exhibit when deprived of the aerial acid or fixed air; in which case they are termed caustic alkalis.

These aerated alkalis differ also from the caustic ones, not only on account of the mildness of their taste, from which comes their epithet of mild alkalis, but also by their property of crystallizing, and by their effervescing with other acids, which expel the aerial one, the weakest of all acids we know.

Order IV, Earthy Neutral Salts.

The compounds of earths and acids which possess solubility are decomposed and precipitated by mild, but not by phlogisticated alkalis.

I. Calcareous earth combined with vitriolic acid.—Vitriolated calc; Selenite; Gypsum. See p. 72, col. 1, supra.

The gypsum, or plaster, is not only found dissolved in various waters, but also in many places it forms immense strata. It is placed by all mineralogists among the earths, which it greatly resembles; but it rather belongs to the saline substances of the neutral kind, as appears by its constituent parts. When burnt, it generates heat with water, but in a less degree than lime does.

Berg. Scig. § 59.

This salt has a particular taste, neither bitter nor astringent, but earthy, when applied to the tongue; and it is owing to it that some waters, chiefly from pumps and wells, are called hard waters, because they lie heavy on the stomach.

It is unalterable whilst kept in a dry place; but on being exposed to a moist air, it is much altered, and suffers a kind of decomposition.

When exposed to fire so as to lose the water off its crystallization, it assumes a dead white colour; and it is then what we call plaster of Paris; but if the fire is too strong, it melts and vitrifies, after losing the vitriolic acid with which it is saturated. See Gypsum.

The most famous quarries of gypsum in Europe, are those of Montmartre, near Paris. See Journal de Physique; 1780, vol. xvi p. 289 and 1782, vol. xix. p. 173.

It is found also in the vegetable kingdom.—Mr Model found that the white spots in the root of rhubarb are a selenitic or gypseous earth (Journal de Phys. vol vi p. 14).

What is called fossil flour (farine fossile in French), generally found in the fissures of rock and gypseous mountains, is very different from the agaricus mineralis p. 71, col. 1, and from the lac luna p. 87, col. 1.; as it is a true gypseous earth, already described p. 72, col. 1, which, according to Mongez, is of a white and shining colour, though sometimes it assumes a reddish or blueish colour, on account of some martial mixture.

II. Nitre of lime, (Calc nitrate.)

This earthy salt is sometimes found in water, but very sparingly. It is said that the chalk hills in some parts of France become spontaneously impregnated with nitrous acid, which may be washed out, and after a certain time they will become impregnated with it again. It is a combination of the nitrous acid with calcareous earth. (Berg. Scig.)

1. It is deliquescent; and is soluble in twice its weight of cold water, or in an equal weight of boiling water. 2. Its taste is bitter. 3. Is decomposed by fixed alkalies, which form the cubic and the prismatic nitres. 4. But caustic volatile alkali cannot decompose it. 5. It does not deflagrate in the fire; yet paper moistened with a saturated solution of it crackles in burning. 6. In a strong heat it loses its acid. 7. Its solution does not trouble that of silver nitrous acid. 8. The vitriolic acid precipitates its basis. 9. As does likewise the acid of sugar. 10. One hundred parts of it contain, when well dried, about 33 of nitrous acid, 32 of calcareous earth, and 35 of water.

It exists in old mortar, and in the mother liquor of nitre; and also in the chalk rocks near Roche Guyon, in France. (Kirwan.)

III. Muriatic chalk, or fixed salt ammoniac. Acidum salis communis terra calcarea saturatum.

This somewhat deliquesces, or attracts the humidity of the air. It is found in the sea water.

It is with great impropriety that this salt has obtained the name of ammoniac, on account only of its being formed in the chemical laboratories during the decomposition of the ammoniacal salt with lime, in the process for making the caustic volatile alkali. In this case, the muriatic acid unites to the calcareous basis, while this last gives its water to the volatile alkali; which, therefore, comes over in a fluid caustic state; but if chalk is employed instead of lime, the volatile alkali receives the aerial acid instead of water, and comes over in a concrete form. In neither case, the new combination of calcareous earth with muriatic salt has any volatile alkali to deserve the name of ammoniacal salt. (Macquer.)

1. This earthy salt has a saline and very disagreeable bitter taste. It is supposed to be the cause of that bitterness and nauseous taste of sea-water. 2. It fuses in the fire, and becomes phosphorescent, after undergoing a strong heat. 3. It becomes hard, so as to strike fire with steel. 4. It is then the phosphorus of Homberg. 5. It is decomposable by ponderous earth and fixed alkalies. 6. And also by the vitriolic or nitrous acid; which expel the muriatic acid, to unite with the calcareous balls. (Mongez.)

7. Its solution renders that of silver in the nitrous acid turbid, at the same time that

8. It makes no change in that of nitrous selenite.

9. It obstinately retains its acid in a red heat.

10. One hundred parts of this earthy salt contain, when well dried, about 42 of marine acid, 38 of calcareous earth, and 20 of water.

11. It is found in mineral waters, and in the salt works at Salzburg. (Kirwan.)

IV. Aerated chalk, (Calx aerata.)

Whenever calcareous earth is over saturated with the aerial acid, it becomes a true earthy neutral salt; becomes soluble in water, and has a slight pungent bitter taste. It is commonly found dissolved in waters, in consequence of an excess of the aerial acid. When this greatly abounds, the water is said to be hard (cruda). By boiling or by evaporation, it deposits streaks or crusts of calcareous matter.

But when the calcareous earth is only saturated with the aerial acid without excess, it is not easily soluble; it is then the calcareous spar p. 71. col. 2. and is properly referred to the clays of earths, p. 71. col. 1.

V. Vitriolated ponderous earth. Terra ponderosa vitriolata; barytes vitriolata.

This earthy salt, known by the name of ponderous spar, is a combination of the ponderous earth described in p. 75. col. 1. with the vitriolic acid; and has been already treated of.

The nitrous ponderous earth, according to Bergman, has not yet been found, although it may perhaps exist somewhere, and of course be discovered in nature.

VI. Muriatic barytes, marine baro-selenite. Barytes salina.

This earthy salt consists of marine acid united to the ponderous earth. It is said to have been found in some mineral waters in Sweden; and may be known by its easy precipitability with vitriolic acid, and by the great insolubility and weight of this resulting compound, which is the true ponderous spar of the preceding section.

VII. Aerated ponderous earth. Barytes aerata.

This earthy neutral salt was found by Dr Withering in a mine at Alltonmore in the county of Cumberland in England. He says that it is very pure, and in a large mass. This substance is a new acquisition to mineralogy, and may be turned to useful purposes in chemistry.

1. It effervesces with acids, and melts with the blow-pipe, though not very readily.

2. In a melting furnace, it gave some signs of fusion; but did not feel caustic when applied to the tongue, nor had it lost its property of effervescing with acids.

3. But the precipitated earth from a saturated solution of it in the marine acid, by the mild vegetable or mineral alkali being burned, and thrown into water, gave it the properties of lime-water, having an acrid taste in a high degree; and a single drop of it added to the solutions of vitriolated salts, as the Glauber's salt, vitriolated tartar, vitriolic ammonia, alum, Epsom salt, selenite, occasioned immediately a precipitation; from whence it appears to be the best test to discover the vitriolic acid. By it the marine acid may also be easily freed from any mixture of vitriolic acid, by means of this calx of ponderous earth. See Chemistry, p. 1049. et seq.

VIII. Vitriolated magnesia.

This earthy neutral salt is called by the English Epsom salt; Sel d'Angleterre by the French, and also sel de Scallia, de Seydeshuz, sel amer, sel cathartique amer, &c. These various names are given to it, either on account of its properties, it being a very mild purgative; or from the places where it is found, besides many others, as in the waters of Egrea, of Creutzbourg, Obernental, Umea, &c. It has also been found native, mixed with common salt and coaly matter, germinating on some free stones in coal mines. See Kirwan's Mineralogy, p. 183.

1. It has a very bitter taste.

2. It is soluble in one part and a half of its weight of cold water; but in hot water, a given weight of it dissolves the double of this salt.

3. It effloresces when exposed to a dry atmosphere, and is reduced to a white powder.

4. Exposed to the fire, it loses the water of its crystallisation, and is reduced into a friable mass.

5. This earthy salt is decomposed by fixed and volatile alkalies.

6. Lime-water precipitates the magnesia from its solution, the calcareous earth of lime-water combining itself with the vitriolic acid, and forming a selenite. N.B. By this test the vitriolated magnesia is easily distinguished from the vitriolated mineral alkali or Glauber's salt which it resembles.

7. But crude chalk, or aerated calcareous earth, has not such an effect in the same case; which shows how much the efficacy of this substance, viz. the calcareous earth, is diminished merely by its union with the aerial acid.

8. When urged by the flame with the blow-pipe, it froths; and may be melted by being repeatedly urged with that instrument.

9. With borax it effervesces, and also when burned with the microcosmic salt.

10. According to Bergman, 100 weight of this salt contains only 19 parts of pure magnesia, 33 of vitriolic acid; and 48 of water. But

11. According to Kirwan, 100 parts of it contain about 24 of real vitriolic acid, 19 of magnesian earth, and 57 of water.

IX. Nitrated magnesia; nitrous Epsom salt.

This earthy salt is usually found together with nitre. It is a combination of the nitrous acid with the magnesian earth.

1. It has an acrid taste, very bitter.

2. Attracts the moisture from the atmosphere, and deliquesces.

3. Is very soluble in water. 4. Is easily decomposable by fire. 5. The ponderous and calcareous earths decompose it, and also the alkalies. 6. On being urged by the blow-pipe, it swells up with some noise, but does not detonate. 7. If saturated solutions of nitrous felsparite and of this salt be mixed, a precipitate will appear; but, 8. Neither vitriolic acid, nor mild magnesia, will occasion any turbidness in its solution. 9. One hundred parts of this salt contain about 36 of real nitrous acid, 27 of magnesian earth, and 37 of water.

It exists in old mortar, and is found also in the mother liquor of nitre. As lime-water decomposes it, M. de Morveau has indicated the use of this process, not only to complete its analysis; but also to separate, in large quantities, and at a very cheap rate, the magnesian from the calcareous earth, as M. Mongez relates upon this subject.

X. Muriatic magnesia. Magnesia salina.

This earthy salt is a combination of magnesian earth with the muriatic acid. According to Bergman, it is found in the sea in greater plenty than any other salt except the sea-salt.

1. It has a very bitter taste; and being always mixed in the sea-water, it is the principal cause of its bitterness. 2. It is very deliquescent, and soluble in a small quantity of water. 3. All the alkalies, even the caustic volatile alkali and lime, decompose it by precipitating its basis. 4. The vitriolic, nitrous, and boracic acids expel the muriatic acid from the base of this neutral salt. 5. Its solution does not trouble that of nitrous or marine felsparite; but, 6. It causes a cloud in the nitrous solution of silver. 7. The vitriolic acid throws down no visible precipitate from the solution of this neutral salt. 8. It loses its acid in a red heat.

XI. Aerated magnesia.

Common magnesia, with an excess of aerial acid, is a true neutral salt, like the aerated felsparite of p. 96. col. I., and becomes soluble in cold water. Otherwise it is scarcely soluble at all; and is then clasped among the earths.

This neutral salt is decomposable by fire, by which its water and its acid are expelled; and it may become phosphoric.

When urged by fire, it agglutinates a little; and some pretended that it melts. But it must be in an impure state to vitrify at all.

The three mineral acids, and the alkalies, dissolve this salt with effervescence, by expelling the aerial acid.

XII. Argillaceous earth combined with vitriolic acid.

The alum kind. See Alums and Chemistry Index.

a. With a small quantity of clay; native or plumbose alum.

It is found on decayed alum ores in very small quantities; and therefore, through ignorance, the alabastrites and felsparites, both of which are found among most of the alum slates, are often substituted in its stead, as is also sometimes the albitus, notwithstanding the great difference there is between the alum and these both in regard to their uses and effects.

b. With a greater quantity of pure clay; white alum ore.

1. Indurated pale-red alum ore, (schilicus aluminis Romanus.) It is employed at Lumiini, not far from Civita Vecchia in Italy, to make the pale-red alum called roch alum. This is, of all alum ores, the most free from iron; and the reddish earth which can be precipitated from it, does not show the least marks of any metallic substance.

c. With a very large quantity of martial clay, which likewise contains an inflammable substance: Common alum ore. This is commonly indurated and flaky, and is therefore generally called alum slate.

It is found,

1. With parallel plates, having a dull surface; from Andrartum in the province of Skone, Hunneberg and Billingen in the province of Vellergotland, Rodoen in the province of Jemtland, and the island of Oeland, &c. In England, the great alum works at Whitby in Yorkshire are of this kind.

2. Undulated and wedge-like, with a shining surface. This at the first sight resembles pit-coal; it is found in great abundance in the parish of Nas in Jemtland.

XIII. Argillaceous earth saturated with muriatic acid.

Argilla salina.

Professor Bergman says, that the combinations of the argillaceous earth with the nitrous, muriatic, and aerial acids, had not yet been found naturally formed as far as he knew. But Dr Withering affirms, that he found the muriatic argil to exist in a considerable quantity, in the Nevis Holt water, when he analysed that mineral water about the year 1777; and he adds, that it is probably contained also in the Ballycastle water in Ireland.

XIV. Argillaceous earth mixed with volatile alkali.

[Although this mixture is by no means a neutral salt, this seems to be the place to treat of it according to the order of saline substances adopted in this article.]

The greatest part of the cays contain a volatile alkali, which discovers itself in the distillation of the spirit of sea-salt, &c.

Order V. Metallic Salts.

The native salts belonging to this division may be distinguished by the phlogisticated alkali, which precipitates them all. The few which have saline properties, according to the definition of salts formerly given, shall be mentioned here; referring the rest to the mineralised metals; as the luna cornea, the saline quicksilver or muriatic mercury, &c. I. Vitriol of copper; blue vitriol. Vitriolum veneris, seu cuprium.

This neutral metallic salt is a combination of the vitriolic acid with copper, and is found in all cement waters, as they are called. Its colour is a deep blue; and being long exposed to the air, it degenerates into a rusty yellow blue. Urged by the flame of the blow-pipe on a piece of charcoal, it froths at first with noise, giving a green flame, and the metallic particles are often reduced to a shining globule of copper, leaving an irregularly figured scoria. But with borax the scoria is dissolved, and forms a green glass.

This salt rarely occurs crystallised; but is often found naturally dissolved in water in Hungary, Sweden, and Ireland; from this water a blue vitriol is generally prepared. These natural waters are called cements or cementing ones. According to Monet, this concrete salt, when found naturally formed, only proceeds from the evaporation of such waters. It is also occasionally extracted from sulphurated copper ores after torrefaction. See Chemistry Index, at Vitriol.

II. Muriatic copper, or marine salt of copper. Cuprum salitum.

This salt has been found in Saxony, in the mine of Johngeorgenstadt. 1. It is of a greenish colour, and foliated texture. 2. It is moderately hard. 3. Sometimes it is transparent and crystallised.

It has been taken for a kind of mica; but Professor Bergman found it to consist of copper and marine acid, with a little argillaceous earth. Another specimen of a purer sort was deposited in the museum of Upsal. This is of a bluish green colour, and friable. It effervesces with nitrous acid, to which it gave a green colour; and by adding a proper solution of silver, a luna cornea was formed, by which the presence of the muriatic acid was ascertained. (Kirwan and Bergman)

III. Martial vitriol; vitriol of iron. Common green vitriol or copras.

This is the common green vitriol, which is naturally found dissolved in water, and is produced in abundance by decayed or calcined marcasites. This metallic neutral salt results from the combination of the vitriolic acid with iron.

1. It is of a greenish colour when perfectly and recently crystallised; but, 2. Effloresces by being exposed to the air, becomes yellowish, and is covered with a kind of rust. Sometimes it becomes white by long standing. 3. It requires six times its weight of water, in the temperature of 60 degrees, to be dissolved. 4. It has an astringent, harsh, and acidulous taste. 5. Exposed to a moderate heat, even to that of the sunshine, it falls into a yellowish powder; but, 6. On being exposed to a sudden heat, it melts; and on cooling, assumes a whitish brown colour. 7. When strongly urged by fire, it loses its acid, becomes of a dark red colour, and is then called colochar; a powder which is employed in polishing metals, and to which our artists have applied the improper name of crocus maris, though this name only belongs to the yellow preparations of the iron-calces, used in pharmacy and in enamelling, &c.

8. Pure fixed alkali precipitates the iron from its solution in deep green flakes; the mild alkali, in a greenish white colour; pure volatile alkali, in so deep a green, that it appears black; but the mild volatile alkali precipitates it in a greyish-green colour.

9. All vegetable astringents, as the tincture of tea, quinquina, gales, &c. precipitate the iron in a black colour; hence they are used as tests to discover its presence in chemical analyses; and it is from this black precipitate that the common writing ink is made, being diluted in water, and there suspended by the Arabic or Senegal gums.

10. One hundred parts of this salt, recently crystallised, contain 20 of real vitriolic acid, 25 of iron, and 55 of water.

11. Its acid is known by this, that its solution mixes without turbidity with the solutions of other salts that contain vitriolic acid; as Epsom, selenite, vitriolated tartar, &c.

12. And the basis of this metallic salt is known by the black colour produced by the solution of vegetable astringents.

13. On being urged by the flame thrown by the blow-pipe, it offers the same phenomena as the vitriol of copper, except that it does not colour the flame.

Green vitriol is frequently found native, either in coal mines or in the cavities of pyritaceous mines, or adhering to their scaffolds in a stalactitical form. It is found also in small round stones, called inkstones, of a white, red, grey, yellow, or black colour, which are almost soluble in water, and contain a portion of copper and zinc. Also sometimes in form of schilus or flaky pyritaceous stones. But the greatest part of that in use is prepared by art, from the martial pyrites or mundic. See Chemistry, n° 619.

IV. Acrated iron. Ferrum aeratum.

This metallic salt is a combination of the aerial acid with iron; and is found in the light chalybeate waters, where it is dissolved by an excess of this acid.

Mr Lane was the first who discovered in England the action of the aerial acid on iron, when the water is impregnated with that menstruum. The late M. Rouelle demonstrated the same phenomenon in France upon this and other metals. But Professor Bergman seems to have preceded them both nearly about the same time, though neither had any knowledge of each other's discoveries.

The great volatility of this acid is the cause why this neutral salt is not often found. For the mere evaporation of the ferruginous mineral waters, in order to analyse them, is sufficient to let loose the aerial acid; so that the iron which was there dissolved by its power falls down to the bottom in the form of a light ore, which amounts to nearly 10% of the weight of the water; and when... V. Vitriol of cobalt, or vitriolated cobalt.

This metallic salt results from the combination of the vitriolic acid with cobalt.

1. When found native, it is always in an efflorescent state; whence it arises that, in this case,

2. Its colour is greenish, mixed with a grey tint: but,

3. It is of a rosy colour when artificially made;

4. Effloresces when exposed to the action of the atmosphere; and,

5. Takes then a greenish colour mixed with a pale purple, or a Lilac colour, as the French call it.

6. It is difficultly soluble in water; and,

7. Its solution is of a red colour.

8. The phlogisticated alkali precipitates the cobalt from the solution of this salt, which with borax gives an azure glass.

By the above qualities, chiefly the rosy colour of the solution of this neutral salt, its basis is sufficiently distinguished. As to its acid, it is easily known by the same tests as those of the preceding vitriols.

It is said to be found native in small pieces, mixed with a greenish efflorescence in cobalt mines. (Kirwan and Mongez.)

VI. Vitriol of zinc, vitriolated zinc, or white vitriol.

This neutral metallic salt results from the combination of vitriolic acid with zinc.

1. Its colour is white. It,

2. Requires little more than twice its weight of water to dissolve it in the temperature of 60 degrees of Fahrenheit's thermometer, and deposits a greyish yellow powder.

3. Its specific gravity is 2000.

4. Its taste is very acetic.

5. It mixes uniformly with vitriolic neutral salts.

6. Precipitates nitrous or marine selenites from their solutions, by which its acid is ascertained.

7. It is precipitable in a whitish powder by alkalies and earths; but,

8. Neither iron, copper, nor zinc, precipitate it; by which circumstance its basis is sufficiently indicated.

9. If it contains any other metallic principle, this may be precipitated by adding more zinc to the solution; excepting iron, which will of itself precipitate by exposure to the air or boiling in an open vessel.

10. One hundred parts of this metallic salt contain 22 of vitriolic acid, 20 of zinc, and 58 of water.

11. Urged by fire, it loses a good part of its acid.

12. Treated with the blow-pipe, it exhibits nearly the same phenomena as other metallic vitriols; except only that the flame is brilliant when the zinc is reduced, and gives out white flocs called flowers of zinc.

This neutral metallic salt is sometimes found native, mixed with vitriol of iron, and in the form of white hairy crystals; or in a stalactite form in the mines of Hungary, or as an efflorescence on ores of zinc. It is also found dissolved in mineral waters, and generally with some proportion of vitriols of iron and copper. Bergman says, it is sometimes produced by the decomposition of pseudogalena, or black-jack; but this rarely happens, because this substance does not readily decompose spontaneously.

But that in common use is mostly prepared at Goslar, from an ore which contains zinc, copper, and lead, mineralised by sulphur and a little iron. The copper is first separated as much as possible: the remainder after torrefaction and distillation is thrown red-hot into water and lixiviated. It is never free from iron. (Kirwan, Mongez.)

VII. Vitriolated nickel, or vitriol of nickel.

This neutral metallic salt results from the combination of the vitriolic acid with nickel. It exists sometimes in consequence of the decomposition of the sulphureous ores of this semimetal. It is found native, efflorescing on Kupfer-nickel; and generally mixed with vitriol of iron.—It is of a green colour, as well as its solution. It is precipitated by zinc; but when joined with iron, this last is not precipitated by the same.

Its origin is perhaps owing to the decomposition of the pyritaceous and sulphureous ore of Kupfer-nickel, mentioned by Wallerius. This ore contains a great quantity of arsenic and sulphur, as well as cobalt, nickel, and iron. And if it comes to be decomposed in the bowels of the earth, it is natural to expect that the vitriolic acid of the sulphur will attack the nickel and the iron, with which it will form neutral metallic salts (Mongez, Kirwan).

VIII. Muriatic manganese. Mangansium fulcitum.

M. Hielm is the only person who has as yet found this middle salt in some mineral waters of Sweden. It is composed by the combination of the regulus of Manganese with muriatic acid.

1. It is precipitated of a whitish yellow colour, by the Prussian (phlogisticated) alkali; and of a brownish yellow, by the mineral alkali. 2. It does not crystallise in any distinct form. 3. It abstracts the moisture of the air. 4. To obtain its basis free from iron, it must be precipitated by the mineral alkali; redissolved in nitrous acid; then calcined until this acid is expelled; and the residuum is to be treated with distilled vinegar, which will then take up only the manganese. (Kirwan.)

Order VI. Triple Salts.

The neutral salts hitherto enumerated are such as are composed of two ingredients only; but sometimes three or more are so united as not to be separated by crystallization. The vitriols that we are acquainted with are hardly ever pure; and two or three of them sometimes are joined together.

Sometimes likewise it happens that neutral salts join earthy salts, and earthy salts metallic ones. Bergman generally distinguishes compound salts according to the number of their principles, whether the same acid be joined to several bases, or the same base to different acids; or, lastly, whether several menstrua and several bases are joined together. Hence arise salts triple, quadruple, &c., which the diligence of after-times must illustrate. The most remarkable examples of triple and quadruple native salts which have yet occurred are,

I. Mineral alkali, with a small quantity of calcareous earth. *Alkali salis communis.* Aphronitrum.

This is so strongly united with the calcareous earth, that the latter enters with it into the very crystals of the salt; though by repeated solutions the earth is by degrees separated from it, and falls to the bottom after every solution.

It grows in form of white frost on walls, and under vaults; and in places where it cannot be washed away by the rain.

Hence it would appear, that this is not only a triple, but a multiple salt; as these pieces of old mortar covered with this white frost, on ancient walls, are the very same from which the saltpetre makers extract the mother-water of nitre, after mixing therewith the vegetable ashes, to furnish the alkaline base to it. M. Fourcroy says in his seventeenth Lecture, that this mother-water contains not only nitre, but five other kinds of salt, viz. the marine salt, nitrous magnesia, calcareous nitre, magnesia nitra, and calx salis; to which the chemists of Dijon add the digestive salt of Sylvius, and in some cases various vitriols with alkaline or earthy bases.

When it contains any considerable quantity of the calcareous earth, its crystals become rhomboidal, a figure which the calcareous earth often assumes in shooting into crystals; but when it is purer, the crystals shoot into a prismatic figure.

This is a circumstance which necessarily must confuse those who know the salts only by their figure; and shows, at the same time, how little certainty such external marks afford in a true distinction of things.

This salt is very often confounded with the *sal mirabile Glauberi.*

II. Common salt with magnesia; or muriatic mineral alkali contaminated by muriatic magnesia.

This is a compound of the common salt with muriatic magnesia; and by the expression contaminated (quinquatum) of professor Bergman, we may suppose that the magnesian salt is not intimately united to the alkaline base.

This triple salt is very deliquescent; a quality it owes to its integrant part the muriatic magnesia, (p. 97, col. 1.) For the pure muriatic alkali does not deliquesce; but this degree of purity is seldom found, even in the native fossil or *sal gem,* (p. 93, col. 2.) In general all the earthy marine salts are very deliquescent, as the muriatic chalk, the muriatic barytes, and the muriatic magnesia, Bergman, Macquer, and Mongez.

III. Mineral alkali with succinuous acid and phlogiston. This substance will be afterwards mentioned among the inflammables.

IV. Vitriolated magnesia with vitriol of iron. Epsom salt contaminated with copperas.

Found in some mineral waters, according to Mr. Montet, (*Treatise on Mineral Waters*).

V. Native alum contaminated by copperas. Vitriolated argil with vitriol of iron.

Found in the aluminous schistus. It sometimes effloresces in a feathery form. Perhaps this is the *plumof alun* of the ancients.

VI. Native alum, contaminated by sulphur.

At the places about Wednesbury and Bilston, in Staffordshire, where the coal pits are on fire, this substance sublimes to the surface; and may be collected, in considerable quantity, during dry or frothy weather.

A similar compound substance sublimes at the Solfaterra near Naples.

VII. Native alum contaminated by vitriolated cobalt.

In the mines of Herregund and Idria this salt may be seen shooting out into long slender filaments. Perhaps this is the *tricrites* of the Greeks.

1. Dissolved in water, it immediately betrays the presence of vitriolic acid upon the addition of terra poderoza salta (muriatic acid saturated with heavy earth).

2. By the addition of phlogiticated alkali, a precipitate of cobalt is thrown down, which makes blue glais with borax or microcofomic salt. (*Berg. Scieg.*)

VIII. Vitriol of copper with iron.

This salt is of a bluish green colour. It is the *vitriolum ferro-cupreum cyanum* of Linnæus. Its colour varies, being sometimes more or less green, and sometimes more or less blue. It is found at Saltzberg and at Falun. This vitriol is called *vitriol of Hungary,* because it is found in the Hungarian mines of this kind. (*Mongez.*)

IX. Vitriol of copper, iron, and zinc.

This is the *vitriolum ferreo-zincico cupreum cyanum* of Linnæus. Its colour is of a blue inclining to green. If rubbed on a polished surface of iron, the copper is not precipitated thereby, as it happens to the blue vitriol; which shows that the vitriolic acid is perfectly saturated in this salt by the three metallic bases.

X. Vitriol of copper and zinc.

This is the blue vitriol from Goslar. According to Mongez it is the *vitriolum zinceo-cupreum caruclum* of Linnæus.

XI. Vitriol of iron and zinc.

This is the green vitriol from Goslar in the Hartz. According to Mongez, this is the *vitriolum zinceo-ferreum viride* of Linnæus, 105. 6. Its colour is a pale-green cast.

XII. Vitriol of iron and nickel.

This salt is of a deep-green colour, and is contained in the ochre, or decayed parts, of the nickel, at the cobalt-mines of Los, in the province of Helsingland.

**Class III. Mineral inflammable substances.**

To this class belong all those subterraneous bodies that are dissoluble in oils, but not in water, which they repel; repel; that catch flame in the fire; and that are electrical.

It is difficult to determine what constitutes the difference between the purer sorts of this class, since they all must be tied by fire, in which they all yield the same product; but those which in the fire show their differences by containing different substances, are here considered as being mixed with heterogeneous bodies: that small quantity of earthly substance, which all phlogiston leave behind in the fire, is, however, not attended to.

I. Inflammable air; fire damp.

This aeriform substance is easily known by its property of inflaming when mixed with twice or thrice its bulk of common atmospheric air; and it is asserted to be the real phlogiston almost pure. See Aerology-Index, and Inflammable Air.

It admits considerable varieties, according to the nature of the substances from which it is produced, and often gives different residua upon combustion, some of which are of the acid kind. If it is produced from charcoal, it yields aerial acid or fixed air; from solutions of metallic substances in the vitriolic, nitrous, or marine acids, it yields these respective acids, as M. Lavoisier asserts.

Ether, converted into vapour in a vacuum, gives a permanent elastic vapour, which is inflammable. The atmosphere, which floats round the fraxinella, is inflammable from the admixture of its vapours, which seem to be of the nature of an essential oil: so that on approaching the flame of a candle under this plant, in hot weather, it takes fire in an instant; although the essential oil, extracted from this plant by distillation, is not inflammable on account of the watery particles mixed with it, as M. Bomare asserts.

Mr Scheele is of opinion, that every inflammable air is composed of a very subtile oil. This coincides with the idea entertained by chemists of their phlogiston; and is confirmed by the fact, of its being naturally found in those springs from whence issues petrol, whose exhalations are very inflammable.

The residuum, which remains in the atmosphere after the combustion of inflammable air, is extremely noxious to animals. Doctor Priestley takes it to be a combination of phlogiston with pure air, and on this account calls it phlogisticated air. But M. Lavoisier, on the contrary, considers it to be a primitive substance of an unchangeable nature, and gives it the singular name of atmospheric mephitic.

II. Hepatic air.

This air seems to consist of sulphur, held in solution in vitriolic or marine air. It is inflammable when mixed with three quarters of its bulk of common air. Nitre will take up about half the bulk of this air; and when saturated with it, will turn silver black; but if strong dephlogisticated nitrous acid be dropped into this water, the sulphur will be precipitated.

One hundred cubic inches of this air may hold eight grains of sulphur in solution in the temperature of 60°; and more, if hotter.

Atmospheric air also decomposes hepatic air. It is found in many mineral waters, and particularly in the hot baths of Aix-la-Chapelle.

The cause and manner of their containing sulphur, which was long a problem, has at last been happily explained by Mr Bergman.

It plentifully occurs in the neighbourhood of volcanoes and in several mines.

Hepatic air is easily obtained by art, from all sorts of liver of sulphur, whether the base be an alkali, an earth, or a metal, if any acid is poured upon it; and the better, if it be made of the marine acid, because it contains phlogiston enough, and does not so strongly attract that of the hepatic sulphur. For this reason the nitrous acid is not fit for this process, as it combines itself with the phlogiston, and produces nitrous air. It may also be produced by distilling a mixture of sulphur and powdered charcoal, or of sulphur and oil, &c. See the detached article Hepatic Air, and Aerology-Index.

III. Phlogiston combined with aerial acid; black lead, or wadd. Plumbago. See the detached article Black Lead.

It is found,

a. Of a steel-grained and dull texture. It is naturally black, but when rubbed it gives a dark lead colour.

b. Of a fine scaly and coarse-grained texture; coarse black-lead.

IV. Mineral tallow. Serum minerae.

This was found in the sea on the coasts of Finland in the year 1736. Its specific gravity is 0.770; whereas that of tallow is 0.969. It burns with a blue flame, and a smell of grease, leaving a black viscid matter, which is with more difficulty consumed.

It is soluble in spirit of wine only when tartarised; and even then leaves an insoluble residuum; but expressed oils dissolve it when boiling.

It is also found in some rocky parts of Persia, but seems mixed with petrol, and is there called schelemaud, shemen, kodrei.

Dr Herman of Strasbourg mentions a spring in the neighbourhood of that city, which contains a substance of this sort distilled through it, which separates on ebullition, and may then be collected. (Kirawan).

V. Ambergris. Ambra grisea.

It is commonly supposed to belong to the mineral kingdom, although it is said to have doubtful marks of its origin (A).

(a) Ambergris, according to the assertion of M. Aublet (in his Histoire de la Guiane), is nothing more than the juice of a tree infiltrated by evaporation into a concrete form. This tree grows in Guyana, and is called... It has an agreeable smell, chiefly when burnt: b. Is consumed in an open fire: c. Softens in a slight degree of warmth, so as to stick to the teeth like pitch. d. It is of a black or grey colour; and of a dull or fine grained texture (b). The grey is reckoned the best, and is sold very dear. This drug is brought to Europe from the Indies. It is employed in medicine; and also as a perfume (c).

VI. Amber. *Ambra flava*, *succinum*, *eleo*rum, Lat. *Carabé*, French. *Agilem*, *Benzlein*, Germ. This substance is dug out of the earth, and found on the sea-coasts. According to the experiments of M. Bourdelin, it consists of an inflammable substance, united with the acid of common salt, which seems to have given it its hardness.

It is supposed to be of vegetable origin, since it is said to be found together with wood in the earth. By distillation it yields water, oil, and a volatile acid salt, which the above mentioned author has thought to be the acid of common salt united with a small portion of phlogiston. Insects, fish, and vegetables are often found included in it, which testify its having once been liquid. It is more transparent than most of the other bitumens; and is doubtless the substance which first gave rise to electrical experiments (on account of the power it possesses of attracting little bits of straw, or of other light substances, when rubbed). Its varieties are reckoned from its colour and transparency. It is found,

called *cuma*, but has not been investigated by other botanists. When some branches are broken by high winds, a large quantity of the juice comes out; and if it chances to have time to dry, various masses (some of which had been so large as to weigh 1200 pounds and more) are carried into the rivers by heavy rains, and through them into the sea; afterwards they are either thrown into the shore or eaten by some fish, chiefly the spermaceti whale, known by the name of *Physeter-macrocephalus* among ichthyologists. This kind of whale is very greedy of this gum-resin, and swallows such large quantities when they meet with it, that they generally become sick; so that those employed in the fishery of these whales, always expect to find some amber mixed with the excrements and remains of other food in the bowels of those whales who are lean. Various authors, among whom is Father Santos in his *Ethiopia Orientalis*, who travelled to various places of the African coast, and Borneo, say, that some species of birds are fond of eating this substance as well as the whales and other fishes. This accounts very well for the claws, beaks, bones, and feathers of birds, parts of vegetables, shells, and bones of fish, and particularly for the beaks of the cuttle fish or *Sepia officinalis*, that are sometimes found in the mass of this substance. Dr Swedler, however, attended only to these last, though he had mentioned also the other substances in his paper inserted in the Philosophical Transactions for 1783; wherein he attempts to establish an opinion, that the amber is nothing else but a supernaturally hardened dung, or feces, of the physeter whale. Dr Withering and Mr Kirwan have embraced this notion; as did also, inadvertently, the editors of this Work. See Ambergris.

(b) Mr Aublet brought specimens of this gum-resin, which he collected on the spot, from the cuma tree at Guiana. It is of a whitish brown colour with a yellowish shade, and melts and burns like wax on the fire. The singularity of this gum-resin is, that it imbibes very strongly the smell of the aromatic substances which surround it; and it is well known that perfumers avail themselves very considerably of this advantage. M. Rouelle examined very carefully this substance brought over by Mr Aublet, and found that it produced the very same results as in other good kind of amber. Besides Mr Aublet's authority, which is decisive, as being grounded upon direct proofs of fact, Rumphius, quoted by Bergman, long since mentioned a tree called *Nanarium*, whose infusorial juice resembles amber. It cannot therefore at present be doubted that the origin of this phlogistic substance is the vegetable kingdom, although it may be often found and reputed as a product of the fossile kind.

This substance being analysed by Mefris Geoffroy and Newman, quoted by M. Fourcroy, yielded them the same principles as the bitumens; viz. an acid spirit, a concrete acid salt, some oil, and a charry residuum; which evidently evinces, that all these fat and oily fossile substances have their origin from the other two kingdoms of nature.

(c) Ambergris is not only brought from the East Indies, but from the coasts of the Bahama Islands, Brasil, Madagascar, Africa, China, Japan, the Molucca islands, the coasts of Coromandel, Sumatra, &c. Dr Lippert, in a treatise he published at Vienna in 1782, entitled *Philosophia Mineralis*, has copied chiefly from Wallerius what he affirms of this substance. He affirms that there are eight known species of amber; five of a single colour, viz. the white and the black from the island of Nicobar, in the gulf of Bengal, the ash-coloured, the yellow, and the blackish; and two variegated, viz. the grey coloured with black specks, and the grey with yellow specks. This last he affirms to be the most esteemed on account of its very fragrant smell, and to come from the South coast of Africa and Madagascar, as well as from Sumatra; and that the black dark coloured amber is often found in the bowels of the cetaceous fishes. The same author adds also from Wallerius, that by distilling the oil of yellow amber (*succinum*) with three parts and a half of fuming nitrous acid, a residuum remains like rosin, which emits a perfect smell of musk; whence some conclude, that the ambergris belongs to the fossile kind: the contrary, however, is evinced in the preceding note. A. Opaque. a. Brown. b. White. c. Blackish.

B. Transparent. a. Colourless. b. Yellow.

The greatest quantity of European amber is found in Prussia; but it is, besides, collected on the sea coast of the province of Skone, and at Bjorko; in the lake Malaren in the province of Upland; as also in France and in Siberia. It is chiefly employed in medicine and for making varnishes (d).

VII. Rock oil. This is an inflammable mineral substance, or a thin bitumen, of a light brown colour, which cannot be decomposed; but is often rendered impure by heterogeneous admixtures. By length of time it hardens in the open air, and then resembles a vegetable resin; in this state it is of a black colour, whether pure or mixed with other bodies. It is found,

A. Liquid. 1. Naphtha. This is of a very fragrant smell, transparent, extremely inflammable, and attracts gold. It is collected on the surface of the water in some wells in Persia. See NAPHTHA.

2. Petrol. This smells like the oil of amber, though more agreeable; and likewise very readily takes fire. It is collected in the same manner as the Naphtha from some wells in Italy. See PETROLEUM.

B. Thick and pitchy; Petroleum tenax. Barbados-tar. This resembles soft pitch. It is found at the Dead Sea in the Holy Land; in Persia, in the chinks of rocks, and in strata of gypsum and limestone, or floating on water; also in Siberia, Germany, and Switzerland, in coal-pits; and in America; likewise in Colnebrookdale in England.

C. Elastic petrol. This is a very singular fossil, found of late in England. By its colour and consistence, it exactly resembles the Indian-rubber, or the gum-resin, from the north part of Brazil, called caoutchouc. It is of a dark brown colour, almost black; and some is found of a yellowish brown cast, like the same gum-resin. With respect to its elastic consistence, it hardly can be distinguished from it, except in the cohesion of its particles, which is weaker. It has the same property of rubbing off from paper the traces of black-lead pencils. It burns likewise with a smoky flame; and also melts into a thick oily fluid; but emits a disagreeable smell, like the foetid pitch, or Barbados tar.

(d) Amber, says M. Fourcroy, is found in small detached pieces, for the most part under coloured sands, dispersed in beds of pyritaceous earth; and above it is found wood, charged with a blackish bituminous matter. Hence it is strongly supposed that it is a resinous substance, which has been altered by the vitriolic acid of the pyrites, notwithstanding that we know that acids, when concentrated, always blacken and charry resinous substances. In fact, the chemical analysis of this substance rather confirms that supposition.

The singular opinion of Dr Curtanier, about the yellow amber being produced by a kind of ants, may be seen in Journal de Physique for March 1786, page 227. Or see the article AMBER in this Dictionary.

The colour, texture, transparency, and opacity of this substance, have shown some other varieties besides those mentioned in the text. The principal ones are the following:

6. The yellow succinum, 7. The coloured green or blue by foreign matter, 8. The veined succinum, 9. The white, 10. The pale-yellow, 11. The citron-yellow, 12. The deep red,

The golden yellow transparent amber, mentioned in the text, is what the ancients called chrysoleucrum, and the white opaque was called leucoleucrum.

But we must be cautious about the value of the specimens remarkable for their colour, size, transparency, and the well-preserved insects they contain internally; since there is a probability of deception, several persons professing the art of rendering it transparent and coloured, and of softening it, so as to introduce foreign substances, &c. into it at pleasure.

M. Fourcroy says, that two pieces of this substance may be united, by applying them to one another, after being wet with oil of tartar and heated. And Wallerius mentions, that pieces of yellow amber may be softened, formed into one, and even dissolved by means of oil of turnip-seed, in a gentle heat; and that according to some authors, it may be rendered pure and transparent, by boiling it in rape-seed oil, linseed oil, salt-water, &c.

Mr Macquer says, that for the purpose of making varnish, this substance must undergo beforehand a previous decomposition by torrefaction, in order to be dissolved by linseed-oil or essential oils. See VARNISH.

Besides the making of varnishes, this substance was much employed formerly in making various pieces of ornament and jewellery. The best pieces were cut, turned, carved, or planed, to make vases, heads of canes, collars, bracelets, snuff-boxes, beads, and other toys, small fine chests, &c. But after diamonds and beautiful hard stones were brought into use, these trinkets are little considered in Europe; nevertheless, they are still sent to Persia, China, and to various other eastern nations, who esteem them still as great curiosities. It is found in the same earthy and stony beds as petrol. Some specimens are of a cylindrical form, like bits of thin branches or stalks of vegetables, though much more flexible, being perfectly elastic.

M. Magellan observes, that this fossil seems to favour the opinion of those mineralogists, "who believe that these oily combustibles derive their origin from the vegetable kingdom." It seems worth trying, whether pieces of asphaltum, buried in damp beds of sparry rubbish, or other kind of earths, would take the same elastic consistence. But since many beds of shells and other fossile substances, both of the vegetable and animal kind, as impressions of various plants, and the remains of various quadrupeds, &c., have been found in different parts of the globe, whose individual species undoubtedly exist no longer alive unless in far distant climates, and in the most remote countries from the spot where their exuvia are dug out; why should we not allow that this new fossil may be the same original elastic gum, now growing naturally in Brazil, China, and other hot climates, only altered in its smell, and in the tenacity of its particles, by its long deposition during centuries in the bowels of the earth?"

This elastic petrol was found in 1785, near Casselton, in the county of Derbyshire in England, but in very inconsiderable quantities.

D. Hardened rock-oil; fossile pitch. Petroleum induratum, Pix montana.

1. Pure asphaltum.

This leaves no ashes or earthy substance when it is burnt.

It is a smooth, hard, brittle, inodorous, black or brown substance. When looked through in small pieces, appears of a deep red colour. It swims in water.

It breaks with a smooth shining surface. Melts easily; and, when pure, burns without leaving any ashes; but if impure, leaves ashes or a flag.

According to M. Monet, it contains sulphur, or at least the vitriolic acid.

It is slightly and partially acted on by alcohol and ether.

From this, or the preceding substance, it is probable the asphaltum was prepared that the Egyptians used in embalming their dead bodies, and which is now called mummia.

It is found also on the shores of the Red Sea, in the Dead Sea, in Germany, and France.—(Kirwan.)

And it comes likewise from Porto Principe, in the island of Cuba. (Brun.)

It is found also in many parts of China; and is employed as a covering to ships by the Arabs and Indians. (Feuerczy.)

2. Impure; Pix montana impura. Pissaphaltum.

This contains a great quantity of earthy matter, which is left in the retort after distillation, or upon the piece of charcoal, if burnt in an open fire; it coheres like a flag, and is of the colour of black-lead; but in a calcining heat, this earth quickly volatilises, so that the nature of it is not yet known.

N° 223.

It is found in Mossgrufvan in Norberg, and in Grengierberget, both in the province of Westmanland; and also in other places.

The pissaphaltum is of a mean consistence between the asphaltum and the common petroleum. It is the very bitumen which is collected in Auvergne in France in the well called de la Pege, near Clermont Ferrand.

VIII. Jet. Gagaz, Succinum nigrum.

This is a very compact bitumen, harder than asphaltum, always black, and susceptible of a good polish. It becomes electrical when rubbed; attracts light bodies like the yellow amber; and it swims on water.

It seems to be nothing else than a black amber, or succinum; but specifically lighter, on account of the greater portion of bitumen that enters into its composition. When burned, it emits a bituminous smell. See the article Jet.

IX. Mineral phlogiston united with earths.

A. With calcareous earth.

1. With pure calcareous earth. This is the fetid or wine spar formerly described.

B. United with calcareous, argillaceous, ponderous, and filaceous earth and vitriolic acid. Limestone: Lapis hepaticus.

C. With an argillaceous earth; Pit or Stone Coal.

1. With a small quantity of argillaceous earth and vitriolic acid. Lithanthrax. See the articles Coal and Pit-coal.

This is of a black colour, and of a shining texture; it burns with a flame, and is mostly consumed in the fire; but leaves, however, a small quantity of ashes.

a. Solid coal. b. Slaty coal.

2. Culm-coal, called kalm by the Swedes.

This has a greater quantity of argillaceous earth and vitriolic acid, and a moderate proportion of petrol.

It has the same appearance with the preceding one, though of a more dull texture; it burns with a flame; and yet is not consumed, but leaves behind a flag of the same bulk or volume as the coal was.

From England, and among the alum rock at Moltorp and Billingen in the province of Weitergottland.

3. Slate-coal.

This coal contains abundance of argillaceous earth. It burns with a flame by itself, otherwise it looks like other slates.

It is found at Gullerafen in the parish of Rettvik, in the province of Dalarna, and also with the coals at Boferup in Skone.

This seems to be the same with the bituminous schilus, already described among the argillaceous earths.

4. Cannel-coal.

Mr Kirwan has put together this variety of coal with that other called Killkenny-coal, though they have some different properties.

The cannel-coal is of a dull black colour; breaks easily in any direction; and, in its fracture, presents a smooth conchoidal surface, if broken transversely.

It contains a considerable quantity of petrol, in a less dense state than other coals; and burns with a bright lively flame, but is very apt to fly in pieces in the fire. It is said, however, to be entirely deprived of this property, by being previously immersed in water for some hours.

Its specific gravity is about 1270; and being of an uniform hard texture may be easily turned in the lathe, and receive a good polish.

It is from this kind of coal that small vases, as inkstands, various trinkets, and other curiosities, are made in England, which appear as if made of the finest jet.

5. Kilkenny-coal.

This contains the largest proportion of petrol or asphaltum; burns with less flame and smoke, and more slowly, though intensely, than the cannel-coal.

The quantity of earth in this coal does not exceed one twentieth of its weight. Its specific gravity is about 1400. It is frequently mixed with pyrites.

It is found in the county of Kilkenny, belonging to the province of Leinster in Ireland. The quality of this coal burning almost without smoke, is mentioned in a proverb by which the good qualities of this county are expressed.

6. Sulphureous coal.

This consists of the former kinds of coal, mixed with a notable proportion of pyrites; hence it is apt to moulder and break when exposed to the air. It contains yellow spots that look like metal; and burns with a sulphureous smell, leaving either red ashes, or a flag, or both. Water acts upon it, after it has mouldered. Its specific gravity is = 1500, or more.

Besides the above varieties, schistus, micaeous schistus, and gneiss, are frequently found in the neighbourhood of coal-mines, so penetrated with petrol bitumen as to constitute an inferior species of coal; but the bitumen being burnt, they preserve their form, and in some measure their hardness. Also some grey slates, that are so soft as to be scraped with the nail, and are greasy to the touch, burn like coal.

All the differences of coal arise from a mixture of the varieties already mentioned; and it is observable, that wherever coals exist, slates are generally found near them. Salt or mineral springs are also often found in their neighbourhood. (Kirwan.)

7. Bovey coal. Xylanthrax.

This is of a brown, or brownish black colour, and of a yellow laminar texture.

The laminae are frequently flexible when first dug, though generally they harden when exposed to the air.

It consists of wood penetrated with petrol or bitumen; and frequently contains pyrites, alum, and vitriol.

Its ashes afford a small quantity of fixed al-

kali, according to the German chemists; but according to Mr Mills they contain none.

By distillation it yields an ill-smelling liquor, mixed with a volatile alkali and oil, part of which is soluble in spirit of wine, and part insoluble, being of a mineral nature.

It is found in England, France, Italy, Switzerland, Germany, Ireland, &c. (Kirwan.)

8. Peat. Geanthrax.

There are two sorts of inflammable substances known by this name, viz.

The first of a brown, yellowish brown, or black colour, found in moorish grounds; in Scotland, Holland, and Germany. When fresh, it is of a viscid consistence, but hardens by exposure to the air. It consists of clay mixed with calcareous earth and pyrites; and sometimes contains common salt. While soft, it is formed into oblong pieces for fuel, after the pyritaceous and stony matters are separated. When distilled, it affords water, acid, oil, and volatile alkali. Its ashes contain a small proportion of fixed alkali. They are either white or red, according as it contains more or less ochre or pyrites.

The second is found near Newbury in Berkshire. It contains but little earth; but consists chiefly of wood, branches, twigs, roots of trees, with leaves, grass, straw, and weeds. (Kirwan.)

9. Stone-turf.

Cronstedt has ranged the turf among the fossils of his Appendix; but as that called in England by the name of stone-turf contains a considerable proportion of peat, it may be mentioned with propriety in this class.

Soon after it is dug out from the ground, where it keeps a soft consistence, it at first hardens; but afterwards it crumbles by long exposure to the air.

As to the other common turf, it only consists of mould interwoven with the roots of vegetables; but when these roots are of the bulbous kind, or in a large proportion, they form the worst kind of turf.

Although it may appear incredible, it is nevertheless a real fact, that in England pit-turf is advantageously employed in Lancashire to smelt the iron-ore of that county. Mr Wilkinson, brother-in-law to Dr Priestley, and famous for his undertakings in the extensive iron-works, perhaps the greatest in Europe, makes use of pit-turf in his large smelting furnaces of that province.

Those fossil substances, which furnish fuel for the various purposes of human life, are distinguished by the name of coals, on account of their being a succedaneum for wood and other vegetable productions, which, when dry or of an oleaginous kind serve for the same uses. If these vegetable substances are deprived of the access of air, by covering them after ignition, the half-consumed remainder, which is of a black colour, is called by the name of coal or charcoal; and from hence the fossil which affords fuel has also been called by the same name, though of a very different nature.

Pit-coal and earth-coal are synonymous, and mean coals dug out of a pit or from the earth. But the lithanthrax denotes stone-coal, and more properly indicates the cannel-coal, which has the greatest similarity to a stony substance, by the dull appearance of its fracture and by the uniform texture of its parts.

All these coals are in general a bituminous black or brown and dark substance; for the most part they have a lamellated texture, which breaks easily, and always with a shining surface.

The varieties of pit-coals above-mentioned are the most remarkable, by which they may be distinguished from one another. But they are far from being homogeneous in each kind; as the accidental qualities, and the various proportions of their component parts, produce a far greater number of properties, which renders them more or less fit for different purposes; though these are generally overlooked, and confounded with the common one of affording fuel for making fire to warm our rooms, or for culinary operations.

This fossil bitumen, as Fourcroy remarks, being heated in contact with a body in combustion, and a free access of air, kindles the more slowly, and with more difficulty, as it is more weighty and compact. When once kindled, it emits a brisk and very durable heat, and burns for a long time before it is consumed. If extinguished at a proper time, the remaining cinders may serve several times for a new firing with a final addition of fresh coals. The matter that is burned, and produces the flame, appears very dense, as if united to another substance which retards its destruction. Upon burning, it emits a particular strong smell, which is not at all sulphurous when the earth-coal is pure, and contains no pyrites.

When the combustible, oily, and most volatile parts, contained in the earth-coal, are dissipated and set on fire by the first application of heat; if the combustion is stopped, the bitumen retains only the most fixed and least inflammable part of its oil, and is reduced to a true charry state, in combination with the earthy and fixed base. Pit coals in this charry state are called coaks, which are capable of exciting the most intense heat; and are employed all over Britain in the melting of iron, copper, and other metallic ores, to the greatest advantage. See Coaks, Coal, Coalery, and Pit-coal (E).

(e) The coal-metals, or stone strata including coals, are very numerous. Mr Williams† gives the following general account of those in Scotland.

The sand-stones. Of these there is a great variety, distinguishable by colour, texture, and degrees of hardness, generally disposed into thick, middling, and thin strata. The only species our author takes notice of is the regular broad-bedded free-stone of a laminated texture. This commonly rises in thin or middling strata; appearing at the edges of a section, when broken or cut, to be formed of thin lamina or layers of sand, equally laid on the whole breadth of the stone, and well cemented together. A great deal of both red and white free-stone rise in layers of five or six inches, and so upwards, with regular streaks of a fifth or sixth part of an inch appearing the whole length of the stone, when the edge of a slab is polished, as if so many gentle waves of water had formed the layer. The regularity of the structure of this stone corresponds exactly with the regularity of its layers; and our author is of opinion, that the flaggy grey-strata of free stone, with many of the black and grey-strata of coal metals, the grey slate, as well as many other thin strata of the coal metal's, may be ranked with this free stone for perfect and regular stratification.

Along with these he classes some of the thin argillaceous strata. "Many of the grey regularly stratified mountain limestones (says he) are also streaked or striped; and the streaks in these appear more conspicuous when broken than the streaked free stones. Some of the hard regularly stratified mountain rocks are also stratified; and in all these three kinds of stones, the streaks are regularly and exactly parallel to the bed of the stone."

Another remarkable instance of regularity of strata is met with in the grey flaggy strata of Caithness.—Throughout all the low country of Caithness, a square of about 10 or 15 miles, there are bluish argillaceous strata, with generally a small quantity of lime in the composition of the stone, which is indurated to a greater degree than is common to such thin strata. The stone is strong and tough, everywhere disposed in thin broad-bedded, regular strata; and in several parts of the country the flags are so thin and regular, and are raised so light and broad, that they are used for covering houses; and three or four of them will cover the side of a small one. Our author mentions a gentleman who has an estate on the south side of the Pentland firth, and who in a bay there raises flags of any size and thickness he pleases; "so truly flat and smooth, that he has only to square the edges to make of them good loft-floors, partitions, chests, mangers, roofs of houses; in short, he does everything with them. The face of these flags are as smooth and true a plane, as if artificially finished by the best workman."

In most coal fields there are a great variety of strata of different kinds accompanying and lying between the seams of coal, of all sorts of colours, consistencies, and dimensions; all of them blended together without any certain order or regularity; so that if there be 20 seams of coal, it is possible that there may be as many different roofs; that is, the stratum which is the immediate roof of one seam of coal, shall differ from that of another seam in quality, thickness, and colour, so that perhaps no two of the twenty shall be in any respect alike.

The various kinds of coal-roofs (a) commonly met with are the following:

(a) The stratum which is placed immediately above a seam of coal, is called the roof of the coal, and that which is placed immediately below the seam, is called the pavement of the coal; which three, viz. the stratum of coal, and its roof and pavement, with the other concomitant strata lying above and below them, always preserve their stations and parallelism; that is, are all stretched out and spread one above another upon the same inclining plane, and have the same line of bearing and of declivity. X. The mineral phlogiston or bitumen, united with the vitriolic acid; sulphur or brimstone. See the article Sulphur.

This is very common in the earth, and discovers itself in many and various forms. It is found,

A. Native. Sulphur nativum.

In this the two constituent parts are mixed in due proportion in regard to each other, according to the rules of that attraction which is between them. It is easily known,

1. By its inflammability, and by its flame. 2. By its smell when burnt; and,

O 2

1. Bafaltes. This is very common in Scotland, where it is frequently called whin stone; and at Borrowstounness there are several thick beds of it between the seams of coal. One of them being the immediate roof of a seam of coal there at Hillhouse lime quarry, there is a thin seam of coal beneath a beautiful bed of columnar basaltes. In the Bathgate hills to the southward of Linlithgow, also, there are several strata of coal blended with those of basaltes. These basaltine strata are always very hard, frequently very thick, and generally of a black or blackish grey colour. "There are but few people (says Mr Williams) sufficiently versed in natural history, to know that they are basaltes, as this kind of rock, both in England and Scotland, goes by the name of whin rock. In the north of Scotland it is called furdy; and among the miners in Cornwall it has the name of cuckle (b)."

2. Strata of limestone of various thicknesses are met with in different coal-fields. Sometimes the lime is the immediate roof; but sometimes there is an argillaceous stratum of about the thickness of a foot between the coal stratum and that of lime. In the coal-fields at Gilmerton, near Edinburgh, are several beds of limestone, some of them very good, and of considerable thickness. At Blackburn in West Lothian, also, there is a stratum of limestone five or seven feet thick, which is the immediate roof of a seam of coal about five or six feet thick. At Carllops and Spittlehaugh in Tweedale, they have a seam of coal immediately below their lime quarries, which they work for burning their lime.

3. Pofflones, a kind of thick and solid stratum of free stone, is one of the roofs of coal, generally without the intervention of any argillaceous stratum, though sometimes a stratum of this kind is interposed. Frequently this kind of stone is rendered very hard by a mixture of iron or pyrites. In most coal fields, thinner strata of free stone are met with as the roofs of coal seams.

4. Dogger-band, as it is called by the Scots colliers, is frequently met with as the roof of coal seams. This name is applied to various substances. Sometimes they call strata of iron-stone dogger bands; sometimes the name is restricted to the ball iron-stone; sometimes to pyrites; and sometimes the dogger band is a kind of imperfect stone, composed of several heterogeneous mixtures, among which pyrites bears a considerable proportion, and by which the whole is so strongly bound together, that it is frequently very difficult to break through it.

5. Whinstone, properly so called, not of a basaltic nature. These roofs are always very hard, and of various colours, as black, blackish grey, brown, red, &c., sometimes not above two or three feet in thickness, but sometimes much more.

6. Pofflones, of a softer nature than that already mentioned. This has no mixture of ferruginous matter.

7. Regular strata of free stone, of various colours, textures, and thicknesses, but not sufficiently thick to deserve the name of pofflone, which our author thinks they do not, unless they are above three or four feet. These thin strata of free stone are very numerous in coal fields, and very frequently form the roofs of coal seams. Some of them are three or four feet thick, while others do not exceed three or four inches. They make good roofs, easily cut through, and may be readily quarried out for other purposes.

8. Grey-bands, or grey-coloured free-stone, frequently form the roofs of coal seams. A great number of them are generally arranged in one place, lying immediately above one another; and they are frequently found of all degrees of thickness from one to twenty inches, though the most common dimensions are from two to six. By the Scots colliers these are called grey fekes as well as grey bands. Frequently they are found of moderate hardness, and sufficiently strong to make good flags and covers for sewers. These roofs are strong and safe when the stone partakes of the nature of the coal, and has a black or blackish grey colour; but when they have a mixture of tilly or argillaceous matter, they are more friable.

9. Blaes, when hard, strong, and well stratified, are reckoned tolerably good coal-roofs. These are always of a bluish-black or black-grey colour, and are of great variety in respect to hardness and strength. Some of the strongest and hardest are either entirely black or greyish black; while some of the different shades of black are pretty thick, and others are but thin. The thickest, however, are not above 18 inches, and the thinnest two or three inches or less. The medium thickness is from one foot to three or four inches. Some of them are sufficiently hard to make a good and safe coal-roof; but they seldom acquire such a degree of hardness as to give any considerable obstruction in working. All of them seem to have a considerable quantity of black argillaceous matter in their composition; and the strongest blues have also a considerable quantity of sand; often also containing a large portion of empyreumatic oil, and sometimes have a considerable mixture of coaly matter. There is a great variety both in the thickness and quantity of these blues found above seams of coal. In some places the thinnest strata make the immediate roof; in others, the thickest. Sometimes we find only five or six inches of blues upon the coal; in others as many fathoms, or even much more; and it is common to find them of all intermediate thicknesses.

(b) We must observe, however, that according to Bergman and other eminent mineralogists, the cobbles or soils ought not to be confounded with bafaltes; which last name does not at all fit those substances. See Volcanic Products in the Appendix to this article. 3. By its producing a liver of sulphur, when mixed with a fixed alkali, like that made from artificial sulphur. It is found,

a. Pellucid, of a deep yellow colour.

b. Opaque, white, and greyish.

These are found in Siberia, at Bevieux in Switzerland, and at Salataura near Naples.

c. Crystallised in octohedral prisms, with blunted points.

d. Transparent. Mr Davila had been informed that this was brought from Normandy in France. (Brun.)

1. Native sulphur is found in different forms, viz., either in solid pieces of indeterminate figure, running in veins through rocks; or in small lumps, in gypsum and limestone; in considerable quantities at Solfatara, and in the neighbourhood of volcanoes; or crystallised in pale, transparent, or semitransparent, octagonal, or rhomboidal crystals, in the cavities of quartz; and particularly in the matrices of ores; or in the form of small needles over hot springs, or near volcanoes (Kirwan).

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10. White and ash-coloured argillaceous strata, of middling strength, are frequently found to be the immediate roofs of coal. Some of these are of middling thickness, others thin. They are commonly found from two inches to two feet in thickness. A great many of these roofs are very dangerous on account of their fragility; while others are quite safe, owing to the more perfect formation of their strata, or to some ingredient in their composition.

11. Streaked roofs. These are of two sorts: 1. Such as are composed chiefly of sand, with a very small mixture of clay and blaes; and, 2. Those composed principally of clay or blaes with a small quantity of sand. Some of these have large, others small, streaks or ribs. Mr Williams says that he has seen them so beautifully streaked as to resemble the finest striped cotton stuffs. These stripes or streaks always lie exactly parallel to one another, as well as to the bed of the stone, and are always spread out the whole breadth of the stratum. Their colours are various in different strata, some of the stripes being nearly black and white, others white and red, and others yellow and red. In some the stripes appear of a lighter and darker grey colour. Some of the finely striped stones have their streaks about a quarter of an inch in diameter; sometimes less; and it is common to see stripes from a quarter to three quarters of an inch broad; but in the finely striped stones it is rare to find them a full inch thick without some different shade on one side or other of the stripe. The second kind of these streaked roofs, viz. such as are composed of blaes, with a smaller mixture of sand, differ but little from the former; only the colours are not always so bright, nor the stripes so fine; neither is the roof quite so hard.

12. The soft blue roofs sometimes consist of pretty thick strata; others of such as are thin or of middling thickness. There are likewise arrangements or clastes of regularly stratified blaes, found immediately above seams of coal, from three or four inches to several fathoms in thickness, though some are even met with little exceeding one inch in thickness; though in the same place there might be a considerable thickness of blaes above the coal, taking in all the different strata, thick and thin, which lay above it. Some of these roofs have an oily appearance on the outside, and through all the fissures and joints of the strata; that is, they appear smooth and glossy, and are very slippery to the touch. Others have no appearance of this kind; but all of them are tender, weak, and fragile, so that they make a very indifferent and dangerous roof.

13. Another kind of coal-roof consists likewise of blaes, but such as are imperfectly stratified. It is altogether the same in quality and colour as the last, the only difference that can be distinguished being in the different degrees of stratification. The beds of this kind are not perfect, but unequal; whence it is a bad and dangerous roof, as great pieces of it are frequently apt to fall down by reason of the inequality and different joints of the strata. Some of these blaes appear in thick, and others in thin or middling thick beds; while some have an oily smoothness, called by the Scots colliers creasy (creasy) blaes. It is owing to this oiliness particularly that these kinds of roofs are so dangerous; for the oil pervades the joints, and rendering them slippery, makes the pieces more apt to fall out as soon as the coal is worked away from below them. Some of these have such a quantity of natural oil, that they will flame a little in the fire; and in some places there are hard blaes which will burn when fire is let to them, though they will not consume. At Pittsford in Fifeshire there is a species of this blae so inflammable, that when fire is let to one corner of a hillock it will burn throughout the whole; nevertheless it is not reduced in bulk by this combustion, nor does it produce any ashes. Instead of this it becomes considerably harder than before, and acquires a pale red colour. By reason of its hardness, it is proper for being laid upon horse and foot paths, but is not so for roads over which heavy wheel-carriages pass.

14. Soft blues not stratified at all. Of these there is no more than one bed from two or three inches to several fathoms in thickness, without any others either above or below it. They are as common as any above the coal seams; but their substance is not always uniform throughout the whole stratum. Some of them are found divided into small angular masses, and others into larger ones; but whether these are uniform or not, they always make a bad and dangerous roof. These argillaceous strata are sometimes called beds of till; the uniform sort are called daubs, and the glebous kind lipsey blaes, by the Scots colliers. Both the uniform and glebous soft blaes frequently contain a quantity of ball iron-stone, though some of it contains none at all. The regular continuous strata of iron-stone are commonly found in stratified soft blaes. There is a variety of soft coal-roofs of a grey colour, and of which some are regularly stratified, and some not. Sometimes it is formed in old privies; of this Mr Magellan saw some lumps that were found in a very old one at Paris.

2. United with clay in the alumino-ore of La Tolfa, and also at Tarnowitz in Silesia. This last resembles a light grey earth; when dry, bursts or cracks in the water like marl; and possesses a strong peculiar smell like camphor. If distilled, the sulphur sublimes. One hundred parts of this earth afford eight of sulphur, besides gypsum and a quantity of iron.

3. Mixed with clay, iron, and felspar. This compound is of a grey, brown, or black colour, found near Rome, Auvergne, Spain, and Iceland.

4. With limestone in the form of a calcareous hepar. This is found at Tivoli, near Rome, and elsewhere in Italy. It is sometimes dissolved in mineral waters, three pounds of which contain as much as 25 grains of sulphur. It often forms incrustations on the banks of these springs.

5. In the form of an alkaline hepar. This is said to be found in some waters in Russia; as will be hereafter noticed.

6. United to iron and clay of pyrites, &c., of which hereafter.

7. United to metallic substances, as hereafter specified.

B. Saturated with metals (r).

1. With iron. Pyrites, or copperas-stone; Pyrites.

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15. Regularly soft grey coal-roofs.—Of these there are several sorts. Some have a considerable quantity of sand in the composition of the strata; and many of these are as regularly stratified as any coal-metals whatever. Numbers are found very thin, and others of middling thicknesses; though in all cases they are so tender and friable, that they make very bad and dangerous roofs. Some of them indeed look pretty well at first but they soon crumble and come down, especially when they have been exposed to the air. This, in the opinion of Mr Williams, is owing partly to their having too much clay in their composition, and partly to the want of a sufficient quantity of natural cement to connect the several particles of the stone together.

16. Soft grey regular strata, or grey bands of an argillaceous kind; and of these there is likewise a considerable variety. Some are of a dark, others of a lighter grey; some thick, others thin: they are very numerous in coal-fields, and are frequently to be found as the immediate roofs of coal. These, as well as the black kinds, are found in all quantities or degrees of thickness above different coals, from a few inches up to several fathoms; but whether they be in great or small quantity, the roof they compose is generally very frail and tender.

17. Soft grey argillaceous bands, imperfectly stratified. These differ little or nothing in substance from the former; the only difference is in the stratification. Many of the strata of the former are of a middling thickness, or rather thin, finely and regularly spread out, and every part of each stratum of an equal thickness. But this sort, though it has the appearance of strata, is clumsy and irregular; that is, the several beds are unequal, and divided by many irregular joints into unequal misshapen masses, which makes this a very bad roof; the masses being apt to separate at the joints, and to fall down when the coal is worked out from below them.

18. Soft grey argillaceous beds of metal or coal roofs not stratified at all. These are of two kinds, viz. 1. Such as are found broken or formed in the stratum into glebes or masses; and, 2. Such as are found in one uniform mass throughout the whole bed, without any division into masses or strata. These grey soft roofs are of all degrees of thickness, from a few inches up to many fathoms, as well as the black; and there is but very little difference between them, in any respect excepting the colour. But in this, as well as in the black unstratified blues, and that both in the glebeous and uniform beds, ball or glebeous iron-stone is frequently found; and strata of iron-stone are also found in the stratified soft grey blues.

19. White and ash-coloured soft argillaceous coal-roofs; and of these there is also a great variety. Some of this kind are regularly stratified, others imperfectly, and some not at all. Some of the whitish argillaceous roofs are compounded of gritty sand and clay; others appear to be chiefly composed of pure clay; and some of a loamy clay. Those which are regularly stratified and mixed with sand, either coarse or fine, are of great variety with regard to thickness and the arrangements of the strata; but all of them are tender and fragile, and thus make very troublesome and dangerous roofs.

20. Whitish argillaceous roofs, stratified, and of a homogeneous quality, or not mixed with sand. Some of these are finely and perfectly stratified, and are of different degrees of hardness; but in general, make but a weak roof. Some of them are found in irregular strata, with all the other varieties and imperfections already mentioned.

21. White and ash-coloured argillaceous coal-roofs, not stratified at all. Sometimes these are found in very thick beds in the coal-fields; and some of these, as well as of the black soft roofs, rise in glebes and masses of different sizes; while others are homogeneous throughout the whole bed, however thick, from two or three inches to several fathoms. Some of these beds of white argillaceous marle-like matter are found to be a sandy or loamy clay; others a pure homogeneous clay, which does not feel gritty between the fingers nor in the mouth. The shades and varieties of this kind are as numerous as those of any of the foregoing; and all of them, by the Scots colliers, are called daub, whatever be their colour. Mr Williams informs us, that he has frequently taken some of these fine white clays to wash his hands, and has found them answer almost as well as soap.

(f) Sulphur is the most common mineraliser of metals; and therefore most of its combinations with these substances fall to be ranked hereafter among the metallic ores. This is the substance from which most sulphur is prepared, and is therefore ranked here with all its varieties. It is hard, and of a metallic shining colour.

A. Pale yellow pyrites; *Pyrites fulflavus*. Marcasite. This is very common, and contains a proportionable quantity of sulphur with respect to the iron; when once thoroughly inflamed, it burns by itself.

a. Of a compact texture; *Polita piedra del ynce*, *Hilspanorum*. b. Steel-grained. c. Coarse-grained. d. Crystallised. It shoots mostly into cubic and octoedal figures, though it also crystallises into innumerable other forms.

B. Liver-coloured marcasite. Its colour cannot be described, being betwixt that of the preceding marcasite and the azure copper ore. The iron prevails in this kind; it is therefore less fit to have sulphur extracted from it, and also for the smelting of copper ores. It is found,

a. Of a compact texture. b. Steel-grained. c. Coarse-grained.

C. Variously combined with iron and other metallic substances.

1. With iron and copper; forming yellow or marcasitical copper ore. 2. With iron, silver, and lead; potters lead ore. 3. With iron and zinc; mock lead, black jack or blende. 4. With iron and arsenic; arsenical pyrites. 5. With iron and cobalt. 6. With iron and bismuth. 7. With iron and nickel. 8. With iron and gold; pyritical gold ore. 9. With silver; glass silver ore. 10. With copper; grey or vitreous copper ore. 11. With lead; potters lead ore. 12. With bismuth. 13. With quicksilver; cinnabar. 14. With arsenic; orpiment, realgar.

XI. Mineral phlogiston mixed with metallic earths.

This is not found in any great quantity: in regard to its external appearance, it resembles pit-coal; and the fat substance contained in it, at times, partly burns to coal, and partly volatilises in a calcining heat.

The only known varieties of this kind are,

A. *Minera cupri phlogistica*.

When it has been inflamed, it retains the fire, and at last burns to ashes, out of which pure copper can be melted.

B. *Minera ferri phlogistica*.

This is not very different in its appearance from the pit-coal or fossil pitch, but it is somewhat harder to the touch. There are two varieties of this species:

1. Fixed in the fire; *Minera ferri phlogistica fina*.

Exposed to a calcining heat, it burns with a very languid though quick flame; it preserves its bulk, and loses only a little of its weight. It yields above 30 per cent. of iron.

a. Solid, which resembles black sealing-wax. b. Cracked, and friable.

2. Volatile in the fire.

This is unalterable in an open fire, either of charcoal, or even upon a piece of charcoal before the flame of the blow-pipe; but under a muffle the greatest part of it volatilises, so that only a small quantity of calx of iron remains. It is found,

a. Solid. b. Cracked.

This last kind leaves more ashes: these ashes, when farther exposed to the fire, become first yellowish-green, and afterwards reddish-brown; when, besides iron, they then also discover some marks of copper: it has, however, not been possible to extract any metallic substance from them, the effects of the loadstone, and the colour communicated to the glas of borax, having only given occasion to this suspicion.

Class IV. METALLIC SUBSTANCES.

Metals are those minerals which, with respect to their volume, are the heaviest of all known bodies. Some of them are malleable; and some may be decomposed; and, in a melting heat (g), be brought back again to their former state by the addition of the phlogiston they had lost in their decomposition. See Metallurgy, Part I. Sect. i. and Chemistry-Index at Metallic Calces and Metals.

All the metallic substances contain phlogiston; and when, to a certain degree, deprived of it, fall into a powder like an earth; but their attractions for phlogiston are different.

Most of them, when melted in a common way, and exposed to the air, have an earthy crust formed upon the surface, which cannot again be reduced to metal without the addition of some inflammable matter. The base metals have this property.

But the noble metals, viz., platina, gold, and silver, are so firmly united to the phlogiston, that they never calcine under fusion, however long continued; and, after being changed into a calx in the liquid way, when melted in the fire, they reassume their metallic form without any other phlogiston than what is contained in the matter of heat.

(g) The various degrees of heat required to reduce metals to a fluid state, are seen in the following table, which was extracted, for the most part, by Dr Withering, from the printed treatises of the late celebrated Professor Bergman. It exhibits, in a simple view, 1. The specific gravity of each metal; 2. The degree of heat by Fahrenheit's scale, in which it melts; 3. The quantity of phlogiston it requires for its saturation; and, Quicksilver holds a kind of middle place: for, like the base metals, it may be calcined, though not readily; and, like the noble ones, it may be reduced by heat alone.

We may therefore reckon four noble or perfect metals; viz., gold, platina, silver, and mercury; because, when calcined, they recover their phlogiston without the addition of any phlogistic substance.

But as tin, lead, copper, and iron, cannot be reduced without such addition, these are called ignoble and imperfect or base metals. Kirwan's Mineralogy.

However, all those eight metals (even mercury, when solid) are malleable to a considerable degree, and are called entire metals. But

Bismuth, zinc, antimony, arsenic, cobalt, nickel, manganese, molybdena, and wolfram, are scarce at all malleable, and hence they are called semifemalts. Nevertheless, zinc and purified nickel are more malleable than any of the other semifemalts; so that we have four perfect or noble metals, four imperfect or base, eight entire, and nine semifemalts(H).

Order

4. Its attraction to the same saturating phlogiston. We must, however, observe, that if the second column be compared with that of Wedgwood's thermometer, their great disagreements betray some fundamental error in the assumed data: for the degrees of heat assigned by Mr Wedgwood for melting gold, silver, and copper, are more than quadruple of those assigned by Bergman, and that for melting iron is more than eleven times greater; although they both nearly agree in the red heat of iron, which Bergman says to be 1050 degrees, and Wedgwood 1077. Mr Magellan is of opinion, that the fault lies in Mortimer's thermometer, which Bergman quotes with some diffidence (Sect. 197. of his Scieraphia); and thinks it probable, that the changes caused by heat, on this metallic thermometer, are in a much less increasing proportion by intense fire, than those indicated by the contraction of the pure clay, happily employed by Wedgwood in his thermometer. He therefore added another column to this table, marked Wedgwood, with the degrees of the melting heats already ascertained by this last thermometer, as being the nearest to truth.

| Metals | Specific Gravity | Melting Heat | Melting Heat | Saturating Phlogiston | Attraction to saturating Phlogiston | |--------|-----------------|--------------|--------------|----------------------|-----------------------------------| | Gold | 19640 | 1301 | 5237 | 394 | 1 or 2 | | Platina| 21000 | | | | | | Silver | 10552 | 1000 | 4717 | 100 | 3 | | Quicksilver | 14110 | -40 | -40 | 74 | 4 | | Lead | 11352 | 595 | | | | | Copper | 8876 | 1450 | 4587 | 312 | 8 | | Iron | 7800 | 1601 | 17977 | 312 | 11 | | Tin | 7264 | 415 | | | | | Bismuth| 9670 | 494 | | | | | Nickel | common | 7000 | 1301 | 156 | 11 | | | pure | 9000 | 1601 | 109 | 5 | | Arsenic| | 8308 | | | | | Cobalt | common | 7700 | 1450 | | | | | pure | | 1601 | | | | Zinc | 6862 | 669 | | | | | Antimony| | 6860 | 809 | | | | Manganese | | 6850 | Very great | | |

N.B. By saturating phlogiston, Professor Bergman means to express the proportionate quantities taken away from each metallic substance, when dissolved by means of acids, and of course reduced to a calciform state. The last column only expresses their attraction to this part of their phlogiston, not to that which still remains united to them in a calciform state. Withering.

(H) Mr Mongez remarks, that the following are the general properties of metals, when considered as physical bodies; viz., their opacity, great specific gravity, ductility, tenacity, crystallization, flavour, and even smell, at least in some of them.

It is from their density that their gravity and opacity proceed; this last being such, that, even reduced to the thinnest plates, no rays of light can pass through their particles, unless there remains an interstice or pore quite free from the metallic substance. Gold leaf must, however, be excepted, which exhibits a fine green by transmitted light.

As to their crystallization, it has been found to take place whenever they are pure, and left to cool very slowly by themselves, after having been perfectly fused. (See Journal de Physique for July 1781, p. 74.) The flavour and smell above mentioned are very perceptible in the reguline substances of arsenic and antimony, as well as in lead, copper, and iron.

All metals are conductors of electricity; and more perfectly so than any other bodies during their union with phlogiston. They Order I. Noble or Perfect Metals.

1. Gold; Aurum, sol elymicorum. See the articles Gold; also Chemistry-Index; and Metallurgy, Part II. sect. 1.

This is esteemed the principal and first among the metals; and that partly for its scarcity, but chiefly for the following qualities:

1. It is of a yellow thinning colour. 2. It is the heaviest of all known bodies, its specific gravity to water being as 19,440 to 1000. 3. It is the most tough and ductile of all metals; because one grain of it may be stretched out so as to cover a silver wire of the length of 98 yards, by which means a grain becomes visible to the naked eye. 4. Its softness comes nearest to that of lead, and consequently it is but very little elastic. 5. It is fixed and unalterable in air and water, and is indestructible by the common action of fire.

N° 223.

They are soluble either in nitrous acid and in dephtlogificated marine acid, or in aqua regia; and are precipitable in some degree by caustic alkalies; and except platina by the Prussian alkali.

When dephtlogificated, they communicate a tinge to borax and to microcosmic salt, or at least render them opaque.

They assume a convex surface when melted, and even a globular form, if in a small quantity; and though they mix for the most part with one another whilst fused, yet they refuse to unite with unmetallic substances, even their own calces, iron only excepted, which does to its own calx slightly dephtlogificated and to plum-bago. Nickel also, and some others, may contain sulphur in their reguline state.

Metals, when calcined, are capable of uniting with other calces and salts.

Three of the metallic calces have been found to be of an acid nature; viz., the arsenical, molybdenic, and tungstenic; from which, by analogy, the nature of other calces may be conjectured.

The phlogiston contained in metals is in a pure state; viz., without water and aerial acid, with which it is invariably accompanied in all other compounds except acids airs and sulphur.

When metallic substances are naturally found in the earth united to their full share of phlogiston, and consequently possessing their peculiar properties, they are called native.

But when they are found more or less deprived of their phlogiston and of their properties, combined with other substances, they are then called mineralised. This is the most common state of the mineral kingdom. The substance so combined with them is called the mineraliser, and the whole is called ore; by which name are also distinguished these earths and stones in which metallic substances are contained.

But if both metallic substances are mixed together in their metallic or reguline form, without the loss of phlogiston, they are then said to be alloyed.

When the mineraliser is of a saline nature, and renders the metallic combination soluble in less than 20 times its weight of water, the compound is ranged among salts. Thus the vitriols of iron, copper, and zinc, are rather clasped with salts than with ores.

The most common mineralisers are, sulphur, arsenic, and fixed air or aerial acid. The least common are the vitriolic and the marine acids. The phosphoric has been found only in two instances; viz., united to lead, discovered by Gahn; and to iron, in the siderite, as Mr Meyer believes.

Those metallic substances, mineralised by aerial acid, are called calciform ores.

M. Magellan observes, that if the new doctrine of the French chemists, who assert, that calces of metals are a compound of dephtlogificated or vital air with the metallic substance, were just, all calciform ores should produce this vital air instead of aerial acid, when they are reduced to their metallic form; which is not the case: neither should all the base metals and semimetals absolutely require the mixture of some phlogistic substance in order to their being reduced from the state of calces to their metallic form, which otherwise would be quite useless, if their reduction simply consisted in their separation from the vital or dephtlogificated air.

(1) Neither sulphur nor fixed alkali has any action on gold; but the liver of sulphur, which is a compound of both, can dissolve it in the dry way; so that if a proper quantity of gold-leaves be put in a crucible together with liver of sulphur, and it be melted in a brick fire, the gold is thoroughly dissolved; and if the whole be diluted in water, the gold will be kept in the solution, and even pass through the filter along with it.

(2) Antimony is used also to refine gold from its alloy, as it attenuates and carries off all other metallic substances. 11. The phosphorus is said to have ingress into gold (l).

12. If mixed with a less portion of silver, platina, copper, iron, and zinc, it preserves tolerably well its ductility. But,

13. When mixed with tin, it becomes very brittle; and it attracts likewise the smoke of that metal, so as to be spoiled if melted in an hearth where tin has been lately melted (m).

14. It requires a strong heat before it melts, nearly as much or a little more than copper.

15. It mixes or amalgamates readily with quicksilver. See Metallurgy, Part II, sect. i. (n).

16. It is not dissolved by the glass of lead, and therefore remains on the cupel.

A. Native gold. With respect to the figure or the quantity in which gold is found in one place, it is by miners divided into,

1. Thin superficial plated or leaved gold; which consists of very thin plates or leaves, like paper.

2. Solid or massive, is found in form of thick pieces.

3. Crystallized, consists of an angular figure.

4. Wash gold, or gold dust, is washed out of sands, wherein it lies in form of loose grains and lumps (o). See other distinctions of form under the article Gold.

B. Mineralized gold. This is an ore in which the gold is so far mineralized, or so entangled in other bodies, as not to be dissolved by the aqua-regia.

Vol. XII. Part I.

I. Mineralized with sulphur by means of iron. Perfect Marcafitical gold-ore; Pyrites aureus.

2. By means of quicksilver. It is found in Hungary.

3. By means of zinc and iron, or silver. The Schenmitz blende.

See other varieties of mineralized gold ores under the detached article Gold, already referred to.

II. Silver: Argentum, Luna. See the article Silver. See also Chemistry-Index; and Metallurgy, Part II, sect. iii. and Part III, sect. iii.

This metal is,

a. Of a white shining colour.

b. Its specific gravity to water is, according to Cronstedt, as 11,991 to 1000; according to Bergman, = 10,552; and according to Kirwan, 11,095.

c. It is very tough or ductile, so that a grain of it may be stretched out to three yards in length and two inches in breadth.

d. It is unalterable in air, water, and fire.

e. It dissolves in the acid of nitre, and also by boiling in the acid of vitriol.

f. If precipitated out of the acid nitre with the common salt, or with its acid, it unites so strongly with this last acid, that it does not part from it, even in the fire itself, but melts with it into a mass like glass, which is called luna cornea (p).

P

3. It

substances mixed with it, without excepting the silver; whilst lead leaves this last behind, and even adds some of its own to the gold. Paulson, p. 659.

(l) Gold, reduced into thin leaves, is not acted upon by the phosphoric acid in the humid way, though the fire be urged till luminous decrepitations take place; but when it passes that point which separates the humid from the dry way, Mr Margraaf observed that some purple scoria were formed, which is an indication that this concrete acid had partly calcined the gold during its fusion. Elements de Chymie de Dijon, Vol. III, p. 131.

Besides this, a drop of the phosphoric acid on the solution of gold by aqua-regia precipitates the metal in its revived state, as affected by the academicians of Dijon. Magellan.

(m) The fumes of a single grain of tin are capable of rendering hard eight ounces of gold; but it easily recovers its malleability by being melted on the fire. (Wallertus and Bomare's Mineralogy.) But when gold is mixed with arsenic, cobalt, nickel, bismuth, or with the regulus of antimony, it only loses great part of its malleability; and when in a certain proportion, it may be calcined and vitrified with them.—(Fabroni.)

(n) Bergman doubts if ever gold has been found perfectly pure; and Mr Kirwan says that it is very seldom found so, being generally alloyed with silver, copper, or iron, or all three. As to the gold commonly used in toys and other objects of luxury, every one knows that it is purposely debased by the artists with copper or other metals; and of late it has been employed in various pieces of jewellery, to form ornaments of various colours: thus a great alloy of silver (viz. one-third part), gives it a shade of a green colour; a similar quantity of copper, a reddish one; a mixture of arsenic, or filings of steel, in the proportion of one-fourth part, gives it a bluish cast; so that having the yellow naturally in the pure gold, and the white in pure silver, the jewellers have almost all the colours to diversify their work. Even in the currency of money, there is none coined out of pure gold, which, by common agreement, is called gold of 24 carats. The gold coin of England, France, and Portugal, only contains 22 parts of pure gold, and two of alloy, viz. it is only 22 carats, in the common saying: that of Spain is but of 21½ carats: but the ducat of Holland is of 23¾ carats; and the zecchino of Venice, of 23½ carats: which last therefore, it would seem, is the purest gold coin of Europe. (Paulson's Metallurgy.)

(o) M. Daubenton, in his Methodical Tables of Minerals, enumerates eight sorts of native gold, viz.

1. In powder; 2. In grains; 3. In small spangles; 4. In masses of lumps; 5. In filaments; 6. In branches like vegetables; 7. In lamella; and 8. In octoedral crystals.—He observes also, that gold, in its reguline state, is formed, either, 1. Into angular crystals, composed of yellow octoedres; or, 2. Into irregular yellow masses, which, being broken, show a granular substance.

(p) The marine acid attracts the calx of silver, but cannot remove its phlogiston; and therefore cannot dissolve g. It does not unite with the semi-metal nickel during the fusion.

h. It amalgamates easily with quicksilver.

i. It is in the dry way dissolved by the liver of sulphur.

k. It has a strong attraction to sulphur, so as readily to take a reddish yellow or black colour when it is exposed to liver vapours.

l. It has no attraction to arsenic; whence, when the red arsenical silver ore, or rothgulden erz of the Germans, is put into the fire, the arsenic flies off, and leaves the sulphur (which in this compound was the medium unitens, behind, united with the silver in form of the glaas silver ore, or glaas erz.

m. It is not dissolved by the glaas of lead, and consequently it remains on the cupel.

n. It is exhaled or carried off by volatile metals and acids; as by the vapours of antimony, zinc, and the acid of common salt.

o. According to Cronstedt, it melts more easily than copper; and this was a general opinion. But the contrary, as Mr Magellan remarks, has been proved by means of the nice thermometer lately invented by Wedgewood.—See Thermometer.

Silver is found,

A. Native or pure; which most generally is nearly of 16 carats standard (Q.)

1. Thin, superficial, plated or leaved.

2. In form, a. Of snaggs, and coarse fibres. b. Of fine fibres. Capillary silver. c. Arborelcent. d. Crystaline or figured. This is very rare: it has distinct fibres, with shining surfaces.

B. Mixed or alloyed with other metals.

The following are the known instances of these mixtures:

1. United to gold, (Bergman's Sciaigraphia, § 154.) 2. Mixed with copper; (Berg. Sc. § 155.) 3. United to gold and copper; (Berg. Sc. § 156.) 4. Amalgamated with mercury, found in the mines of Salberg; (Foster's notes to Brunnich.) 5. United to iron; (Berg. Sc. § 157.) 6. United to lead, sometimes in such quantities as to be worth the expenses attending the separation. 7. United to arsenic; (Journal de physique, 1778, p. 50.) 8. United to antimony; (Berg. Sc. § 159.) 9. Joined to the regulus of arsenic and iron; (Berg. Sc. § 160.) 10. Mixed with the alkaline limestone from Annaberg, described by Mr Justi; (Brunnich.)

11. Sandy silver-ore, without any metallic shining.

12. Silver-ore in a red-brown schistus, described by Lehman: it is composed of argillaceous earth, micaeous hematites, sulphur, calcareous spar, fluor mineralis, lead, and silver.—It contains about seven or eight ounces of silver on the hundred weight.

13. Soft silver-ore. It is found among the marles and argillaceous earths; and is of various colours, either singly or mixed.

C. Dissolved and mineralised.

(1.) With sulphur alone. Glaas silver-ore.

This is ductile, and of the same colour as lead; but, however, becomes blacker in the air. It has therefore, though very improperly, got the name of glaas-ore; for that name rather belongs to the minera argentii cornua, or horn silver ore, if indeed any silver ore can be considered as glaasy.

It is found,

1. In crusts, plates, or leaves.

2. Grown into a. Snaggs, and b. Crystaline figures.

It is generally either of a lamellar or a grained texture.

The glaas silver ore is the richest of all silver ores; since the sulphur, which is united with the silver in this ore, makes but a very small quantity of its weight.

(2.) Arsenico-martial silver ore, (Weill erz, Germ.)

This ore contains silver and iron mineralised by arsenic; the arsenic in a larger proportion than the iron. This is the Pyrites argenteus of Henckel.

1. It is a hard substance, of a white shining appearance, and of a compact, lamellar, or fibrous texture. (Kirwan, sp. 7.)

2. Of a yellowish white colour, and of a striated structure, resembling bismuth, but much harder. (Kirwan, sp. 3.)—It is found near Guadalcanal canal in Spain.

3. Near the same place is found also another ore of the same kind, which is very soft and easily cut; and when cut, has a brilliant metallic appearance. It consists of conchoideal laminae. The quintal contains only from four to six ounces of silver; but it is easily reduced by evaporating the arsenic, which then leaves the silver slightly contaminated with iron. (Kirwan, sp. 4.)

(3.) With

dissolve it in its metallic state, (Bergman.) However, the marine acid, if well concentrated, or rather reduced into an aerial form, dissolves silver in its metallic state, (Fabroni.)

Mr Scheele, and after him Mr Bertholet, assert positively, that the marine acid, being deplogilicated by its distillation over manganese in the form of a yellow air or gas, dissolves all the metals, without excepting gold, silver, or mercury. See Scheele's Essay 5. § 25. H.

The vitriolic acid being distilled also over the manganese, dissolves silver, gold, and mercury, as Dr Crell asserts, (Journal de Physique, Oct. 1785, p. 297.)

Silver is precipitated from the vitriolic and nitrous acids by the marine; and from the nitrous, in great measure, by the vitriolic, (Kirwan.)

(Q.) Wallerius distinguishes seven species of silver: (see the article Silver). Daubenton reckons eight varieties of native white silver, arising from their peculiar forms. (3.) With sulphur and arsenic. The red or ruby-like silver ore. The rothgulden of the Germans.

The colour of this ore varies as the proportion of the ingredients varies in the mixture, viz. from dark grey to deep red; but when it is rubbed or pounded, it always gives a red colour.

a. Grey arsenical silver ore. 1. Plated, crushed, or leaved. 2. Solid.

b. The red arsenical silver ore: 1. Plated, crushed, or leaved; 2. Solid or scaly. 3. Crystallised (r.)

In this last form it shows the most beautiful red colour, and is often semi-transparent. It contains about 60 per cent. in silver.

(4.) With sulphur, little arsenic, and iron.—(Schwarzertz, Schwartz guldén, Silber malm, Gern.)

This is a friable, weathered, decayed ore.

a. Of a black or footy colour; and is therefore called by the Germans filberfchwarzetz, or ruffigter-ertz.

(5.) With sulphurated arsenic and copper. The weiffgulden of the Germans.

This, in its solid form, is of a light grey colour, and of a dull and steel-grained texture. Its proportion of silver is from 10 to 30 per cent.

(6.) With sulphurated arsenic and iron. The weiflertz, or white silver ore of the Germans.

This is an arsenical pyrites, which contains silver; it occurs in the Saxon mines; and so exactly resembles the common arsenical pyrites, as not to be distinguished from it by sight alone, or without other means.

(7.) With sulphurated antimony.

a. Of a dark grey and somewhat brownish colour; the laberetz of the Germans.

b. Of a blackish blue colour. 1. In form of capillary crystals. Federertz, or plumose silver ore.

(8.) With iron, arsenic, and cobalt, mineralised by sulphur.

This ore looks like the weiffgulden described above; but is distinguished by the rose coloured particles of cobalt, dispersed through dark brown, blackish, or grey, and sometimes shining solid mass. It is to this species of ores that the silver goose dung ore belongs.

(9.) With sulphurated copper and antimony.—The Dal jah-lertz.

This resembles both in colour and texture the dark-coloured weiffgulden. When rubbed, it gives a red powder.

a. Solid. b. Crystallised.

(10.) With sulphurated zinc. The peebblende of the Germans.

This is a zinc ore, mock lead, or blende, which contains silver, and is found among rich silver and gold ores.

a. Of a metallic changeable colour. 1. Solid, and with fine scales. 2. In form of balls. The kugel-ertz, or ball ore.

b. Black mock lead, or blende, found in Saxony. This is also found, 1. Solid, and with fine scales; 2. And in form of balls.

(11.) With sulphurated lead; potters ore. Galena; bleiglanz.

(12.) With sulphurated lead and antimony, called flüterpertz.

(13.) With sulphurated iron. Silberhaligier kies; marcasite holding silver.

(14.) With sulphurated and arsenical cobalt; dendrites being sometimes found in the stone. These kinds keep well in water; but generally wither in the air, and lose the silver they contain.

(15.) Mineralized by sulphur, with regulus of antimony and barytes. The butter-milk ore. This is found in the form of thin particles, on granular spar, (Kirwan, sp. 13.)

(16.) Combustible silver ore.

This is a black and brittle substance, and leave about 6 per cent. of silver in its ashes. It is in fact a coal in which silver is found. (Kirwan, sp. 14.)

(17.) With the acid of common salt. Minera argenti cornea. Hornertz, or horn-silver ore.

This is the rarest silver ore; it is of a white or pearl colour, changeable or varying on the surface, semi-transparent, and somewhat ductile both when crude and when melted. It cannot be decomposed without some admixture of such substances as attract the acid of sea-salt.

III. Platina del Pinto; Juan blanca.

This metal is a recent discovery of our times; and is described with great accuracy by Scheffer, in the Acts of the Royal Academy of Sciences at Stockholm for the year 1752; as also by Dr Lewis, in the Philosophical Transactions for the year 1754, vol. xlviii., and by many other writers. By these descriptions we are convinced of the resemblance this metal bears to gold; and therefore we must allow it to be called white gold. It has, however, a variety of distinguishing qualities.

(r) Wallerius mentions the six following varieties of this notable ore in his Species 388, viz. 1. The red opaque, like cinnabar, from Andreasberg in the Hartz, and from Salberg in Weltmannia; 2. The bluish, from Freiberg and Annaberg; 3. The grey, from Freiberg and Andreasberg; 4. The red transparent amorphous, of the garnet colour, from Potofu and Ioachimital; 5. The red transparent, crystallised into prismatic decagons, or dodecahedrons, from Hungary, Alsace, and the Duchy of Deuxponts; 6. The only superficially red ore, from Salberg and Ehrenfriederichsdorf. lities besides its colour, which ascertain its peculiar nature: All which, with its history, uses, &c., are particularly described under the detached article Platina. See also Chemistry-Index; and Metallurgy, Part II, sect. ii.

1. It is of a white colour. 2. It is so refractory in the fire, that there is no degree of heat yet found by which it can be brought into fusion by itself, the burning-glass excepted. But, when mixed with other metals and semimetals, it melts very easily, and especially with arsenic, both in its metallic form and in form of a calx or glass.

IV. Quicksilver, mercury. Hydargyrum, Argentum vivum, Mercurius. See the article Quicksilver; Chemistry-Index, at Mercury; and Metallurgy, Part II, sect. viii.

Mercury distinguishes itself from all metals by the following qualities (s.)

a. Its colour is white and shining, a little darker than that of silver. b. It is fluid in the cold, and divisible by the least force; but, as it only sticks to a few bodies to which it has an attraction, it is said that it does not wet. c. It is volatile in the fire. d. It attracts the other semimetals and metals; and unites with them all except cobalt and nickel, with which it cannot by any means yet known be made to mix. This union is called amalgamation. This amalgamation, or mixture of metallic bodies, according to the readiness with which they unite or mix, is in the following progression, viz. gold, silver, lead, tin, zinc, bismuth, copper, iron, and the regulus of antimony; the three latter, however, do not very readily amalgamate. The iron requires a solution of the vitriol of iron, as a medium to promote the union. e. It dissolves in spirit of nitre, out of which it is precipitated by a volatile alkali, and common salt, in form of a white powder; but if a fixed alkali is used, a yellow powder or calx is obtained (t).

(s) It were almost superfluous, says Mr Kirwan, to mention any other character of quicksilver than its liquidity, to distinguish it from other metals. In regard to this property, Bergman observes, that mercury constitutes one extreme among the metals, and platina the other; since it requires to be melted only such a degree of heat as is rarely wanting in our atmosphere, and boils at the 6000 degrees nearly after lead melts. See the table at p. 111. Note. But when the cold is increased to the temperature denoted by 40 degrees below zero of Fahrenheit's and of the Swedish thermometer, which both coincide in that point (since 212 - 32 = 180 : 100 :: 32 + 40, or 72 : 40), this metal concretes like any other metal, and becomes quite solid; (see Philosophical Transactions for 1783, p. 303.) Mercury in its common state, therefore, according to Bergman (Treatise of Electricity), is to be considered as a metal in fusion; and since in its solid state it is nearly as malleable as lead, it by no means ought to be placed among the semimetals, otherwise every other entire metal should be considered as brittle, for none is malleable when in fusion.

(t) 1. Mercury is dissolved with great rapidity by nitrous acid: the liquor is of a greenish-blue colour, but loses it afterwards and becomes limpid. This solution, when made without heat, is used as a test for the analysis of mineral waters, and has different properties from that made with the help of heat. In the first case, says Bergman, very little phlogiston is lost, and the salt easily crystallizes, being white, and scarcely acrid. It is not precipitated by distilled water; but by caustic vegetable alkali, it is precipitated of a yellowish colour; by mild alkali, the precipitation is white; by mineral alkali, it is yellow, but it soon grows also white; by volatile alkali, it turns to a greyish-black colour; by Glauber's salt, or by pure vitriolic acid, the precipitation is white, granulated, and in a small quantity; nor, if this precipitant has been sparingly used, does this colour appear in less than an hour: by muriatic acid, or common salt, the precipitation is also white, but in a large quantity, and in curdles.

2. But if the mercurial solution be put over a sand-heat, it may be charged with a quantity of mercury equal almost to its weight. According to the chemists of Dijon, 10 ounces of nitrous acid may dissolve eight of mercury. The action of the solvent becomes stronger with the heat; emits great quantity of vapours; and if not taken from the fire, will be too far evaporated. Distilled water will precipitate from this solution a white calx, because it is more dephlogisticated, and the solvent is overcharged with it; and the water changing the density of the liquor, diminishes the adhesion of the calx, as Fourcroy remarks. This white calx will turn yellow, if boiling water be poured on it. The vegetable alkali precipitates it of a brownish-yellow, which by degrees assumes a pale-yellow tinge: the mild vegetable, and the mineral alkalies, produce nearly the same colour; though when this last is employed, the colour turns afterwards to white. The precipitation by volatile alkali is quite white also; that by the vitriolic acid is yellow; and, finally, a copious white mucilaginous matter is the precipitate by the marine acid.

3. This solution by nitrous acid is very caustic; corrodes and destroys animal substances; when it falls on the skin, stains it of a deep purple-brown colour, which appears black: the stains do not go off before the separation of the epidermis, which falls away in scales or kind of scars. It is used in surgery as a powerful elcharotic, and is called mercurial water.

4. The same solution, by cooling, is susceptible of forming crystals, which vary from one another according to circumstances: for the most part they are like needles; are very caustic; redden the skin; and detonate when put on burning coals, provided they be dry. They are called mercurial nitre, which fuses when heated in a crucible; exhales reddish fumes; assumes a deep yellow colour, which afterwards turns to orange, f. But it requires a boiling heat to dissolve it in oil of vitriol (v).

g. It is not affected by the acid of common salt, unless it be previously dissolved by other acids (v); in which case only they both unite with one another, and may be sublimed together; this sublimate is a strong poison.

h. It unites with sulphur by grinding; and then produces a black powder called *ethiops mineralis* (w), which sublimes into a red striated body called *fabulous cinnabar*.

i. The sulphur is again separated from the quicksilver, by adding iron or lime, to which the sulphur attaches itself, leaving the quicksilver to be distilled over in a metallic form; but if a fixed alkali be used, some part of the quicksilver will remain dissolved in the residuum, which is a liver of sulphur.

Quicksilver is found,

A. Native, or in a metallic state. *Mercurius nativus*, or *virginicus*.

This found in the quicksilver mines at Idra in Friuli, or the Lower Austria, in clay, or in a black flaky *lapis ollaris*, out of which it runs, either spontaneously, or by being warmed even in the hands.

B. United to gold or silver. *Hydrargyrum argento vel auro adunatum*.

Mr Kirwan asserts, on the authorities of Monet and Lin. Von Gmelin, that in Sweden and Germany mercury has been found united to silver in the form of a somewhat hard and brittle amalgam.

Romé de l'Isle had a specimen of this natural amalgam from Germany, which is imbedded in a quartzose mafs, and mixed with cinabars, as Mr Mongez asserts; and he adds, that in the royal cabinet, at the king's garden at Paris, is deposited another fine specimen of this mercurial ore, which was found crystallised in the mine called Carolina at Michel-ansberg in the duchy of Deux Ponts. M. de l'Isle speaks also very positively of a specimen of native gold from Hungary, which seems to be a natural amalgam of gold and mercury. It is composed of quadrangular prisms, of a greyish yellow colour, and of a brittle texture. This specimen is also in the king's cabinet at the royal garden at Paris.

Mr Kirwan, speaking of the method of examining the purity of gold by the moist way, supposes, with Sir Torbern Bergman, that there are natural amalgamations of mercury with gold and silver; and Neumann observes, that sometimes a mineral, containing gold or silver, is met with among mercurial ores, although this is a great rarity.

It is evident, therefore, that there naturally exist

and at last to a brilliant red: in this state it is called *red precipitate*, or *arcanum corallinum*. It must be made in a matras with a gentle heat if it is designed to be corrosive for chirurgical purposes.

(v) 1. The vitriolic acid, concentrated and boiling hot, seizes on mercury, and presently reduces it if urged by heat to a kind of white powder, which turns yellow by the affusion of hot water, but does not dissolve in it; this is called *turbit mineral*: but if cold water, instead of hot, was poured in the white mass, the powder would not change its white colour into yellow as was said above about the nitrous solution.

2. If Mercury be rarefied by heat into vapours, and these meet with those of marine acid in the same state, a corrosive sublimate will be formed. This metallic salt floats into crystals pointed like daggers, which are the strongest of all poisons. But there are various other processes found in chemical authors to make this salt with more or less trouble. See Chemistry, n° 814—818.

3. If corrosive sublimate be mixed with tin and distilled, a very smoking liquor is produced, called by the name of its inventor the *smoking liquor of Libavius*. See Chemistry, n° 810.

The muriatic acid in the sublimate is not saturated, and from hence proceeds its great corrosive power; for if a fresh quantity of mercury be added to it, and sublimed a second or third time, a sweet, or mixed sublimate, called *mercurius dulcis*, is produced, which is not poisonous, and is given internally as a purgative, or an emetic, according to the dose. See Chemistry, n° 819.

(v) Muriatic acid does not act upon quicksilver unless this last be previously deprived of as much phosphorus, as \( \frac{74}{105} \) of the quantity contained in the hundred of silver, or of \( \frac{80}{105} \) in the hundred of zinc. (See Bergman's *Sciagraphia*, and his treatise *De Phlogift quantitate*.)

(w) The academicians of Dijon say, that the true proportion to make this *ethiops*, is that of one part of brimstone with four of mercury. Fourcroy directs only one of mercury, with three of flowers of sulphur, to be triturated, till the mercury is extinguished. A black powder is then produced, which is the *ethiops* mineral. The combination is better effected when the mercury is mixed with the fused sulphur: by agitating this mixture, it becomes black, and easily takes fire; it should be then taken from the fire, and the flame should be extinguished a little after, stirring the mass till it becomes into solid clots. If this substance be exposed to a great degree of heat, it takes fire, the sulphur is consumed, and a substance remains which is of a violet colour when pulverised. This powder being put into matrasses, till their bottom become red by the force of fire, is sublimed after some hours, and artificial cinnabar is found in the top of the vessels crystallised into brown red needles.

Mercury, divided by means of a rapid and continual motion, as that of a mill-wheel, gradually changes itself into a very fine black powder, which is called *ethiops per se*, on account of its colour, in order to distinguish it from this *ethiops mineralis* mentioned in the text. ist various ores of quicksilver, amalgamated with silver, gold, and other minerals, although they be but seldom met with.

C. Mineralised,

[1.] With sulphur.

a. Pure cinnabar, *Cinnabaris nativa*. a. Loose or friable cinnabar like red ochre. b. Indurated or solid cinnabar. It is of a deep red colour; and, with respect to its texture, is either, 1. Steel-grained; 2. Radiated; 3. Composed of small cubes, or scaly; or 4. Crystallised, in a cubical form; it is transparent, and deep red like a ruby.

b. Impure cinnabars. 1.) A mercurial ore is found in Idria, says Gellert, where the mercury lies in an earth or stone, as if it were in a dead form; and has the appearance of a red-brown ironstone; but it is much heavier than that. It contains from three quarters to seven eighths of the purest mercury; leaves, after distillation, a very black strong earth behind; and gives some marks of cinnabar. 2.) Liver ore, which is most common in Idria, and has its name from its colour.—Outwardly it resembles an indurated ironclay; but its weight discovers that its contents are metallic. It yields sometimes 80 pounds of quicksilver per hundred weight. 3.) Burning ore; *brand-erz* in German. This ore may be lighted at the candle; and yields from nine to 50 pounds of quicksilver per hundred weight. *Brunnich.*

[2.] With iron by sulphur. Pyritous cinnabar.

Sir Torbern Bergman inferred this ore in the 17th section of his *Sciagraphia*, and seems doubtful whether this be a distinct species from the cinnabar; as the iron is perhaps, says he, only mechanically diffused therein. Mr Mongez remarks, that there are but a few instances of cinnabar in which iron is not found in its calcined form; though, in the act of the ore being reduced, it passes to its metallic state, and becomes capable of being acted on by the loadstone.

Another pyritous ore of cinnabar was found at Menidot, near St Lo in Lower Normandy. It consisted in grains of different sizes, of a red brown colour: they had a vitriolic taste and sulphurous smell. Found also at Almaden in Spain, and at Stahlberg in the Palatinate; though at this last place they are of imperfect a dodecaedral form.

[3.] With silver by the aerial acid, and sulphur.

This seems to be a native precipitate *per se*, or calx of mercury. It is said to have been lately found in Idria, in hard compact masses of a brownish-red colour; see *Journal de Physique* for January 1784, p. 61. If this account can be relied upon, it will prove, that quicksilver, even in a calciform state, is naturally found mineralised with silver by means of sulphur.

[4.] With sulphur and copper.

This ore is blackish grey, of a glaify texture, and brittle; crackles and splits excessively in the fire; and when the quicksilver and sulphur are evaporated, the copper is discovered by its common opaque red colour in the glats of borax, which, when farther forced in the fire, or diluted, becomes green and transparent. It is found at Mutschlandberg in the duchy of Deux Ponts.

[5.] Mineralised by the marine and vitriolic acids.

Mineralogy owes the discovery of this ore to Mr Woulfe, who published an account of it in the Philosophical Transactions for 1776. It was found in the duchy of Deux Ponts, at the mine distinguished by the name of Obermofchel. It had a spar-like appearance. This ore is either bright and white, or yellow or black. It was mixed with cinnabar in a flaky matrix: and being well mixed with one-third of its weight of vegetable alkali, afforded cubic and octagonal crystals; that is, salt of Sylvius and vitriolated tartar.

The marine salt of this mercury is in the state of sublimate corrosive.

Order II. IMPERFECT OR BASE METALS.

I. Tin. *Stannum*; *Jupiter*. (See the detached article *Tin: Also Chemistry-Index*; and *Metallurgy*, Part II., sect. vi. and Part III., sect. vi.)

This is distinguished from the other metals by the following characters and qualities. It is,

a. Of a white colour, which verges more to the blue than that of silver. b. It is the most fusible of all metals; and, c. The least ductile; that is, it cannot be extended or hammered out so much as the others (*x*).

(x) Tin is sufficiently ductile to be beaten into very thin leaves. But ductility and extensibility are two different properties, less connected with one another than is generally imagined. Iron and steel are drawn into exquisite fine wire, but cannot be beat into very thin leaves. Tin, on the other hand, is beat into fine leaves, and may be extended between rollers to a considerable surface. The tin-sheet used in various arts, is commonly about $\frac{1}{50}$th part of an inch; but may be extended twice as much in its dimensions without difficulty. Notwithstanding this extensibility, tin cannot be drawn into wire, on account of the weak cohesion of its particles. A tin wire, however, of one-tenth of an inch diameter, is able to support a weight of $49\frac{1}{2}$ pounds, according to Fourcroy. Gold and silver possess both properties of ductility and extensibility the most eminently of all metallic bodies; whilst lead, notwithstanding its flexibility and softness, cannot be made either into leaves or wire of any fineness. d. In breaking or bending, it makes a cracking noise.

e. It has a smell particular to itself, and which cannot be described.

f. In the fire it is easily calcined to white ashes, which are 25 per cent. heavier than the metal itself. During this operation, the phlogiston is seen to burn off in form of small sparkles among the ashes or calx.

g. This calx is very refractory; but may, however, with a very strong degree of heat be brought to a glass of the colour of colophony. But this calx is easily mixed in glass compositions, and makes with them the white enamel.

h. It unites with all metals and semimetals; but renders most of them very brittle, except lead, bitumen, and zinc.

i. It amalgamates easily with quicksilver.

k. It dissolves in aqua-regia, the spirit of sea-salt, and the vitriolic acid; but is only corroded into a white powder by the spirit of nitre. The vegetable acid, soaps, and pure alkaline salts, also corrode this metal by degrees.

l. Its specific gravity to water is as 7400 to 1000, or as 7321 to 1000.

m. Dissolved in aqua-regia, which for this purpose ought to consist of equal parts of the spirit of nitre and sea-salt, it heightens the colour of the cochineal, and makes it deeper; for otherwise that dye would be violet.

(1.) Native Tin.

The existence of native tin has long been questioned; but it has undoubtedly been found some years ago in Cornwall, as Mr Kirwan remarks.

1. Malleable tin, in a granular form, and also in a foliaceous shape, issuing out of a white hard matter like quartz; but which, after being properly assayed, proved to be arsenical crystals; a circumstance that evinces its being native tin, since the arsenic could not remain in this form if the tin had been melted. It appeared like a thick, jagged, or scolloped lace or edging; and was found near St Austell in Cornwall.

2. In the form of crystalline metallic laminae, or laminated crystals, rising side by side out of an edging, which shone like melted tin; they were almost as thin as flakes or scales of talc, intersecting each other in various directions, with some cavities between them, within which appeared many specks and granules of tin, that could be easily cut with a knife; this was also found in Cornwall.

3. In a massy form, more than one inch thick, in some places, and inclosed in a kind of quartzous stone; or rather in an hard crust of crystallised arsenic.

(2.) Calciform Ores of Tin.

A. In form of a calx, Stanum calciforme.

a. Indurated, or vitrified.

1. Mixed with a small portion of the calx of arsenic.

a. Solid tin ore, without any determinate figure. Tin-stone.

It resembles a garnet of a blackish brown colour, but is much heavier; and has been considered at the English tin-mines as a stone containing no metal, until some years ago it began to be melted to great advantage.

B. Crystallised.

a. Tin spar, or white tin ore. This is generally of a whitish or grey colour; sometimes it is yellowish, semi-transparent, and crystallised, either of a pyramidal form, or irregularly.

b. Tin-grains. This ore, like the garnets, is of a spherical polygonal figure; but seems more unctuous on its surface.

1. In large grains.

2. In small grains.

B. Mixed with metals.

1. With the calx of iron, as in the garnet.

2. With manganese. See the Semimetals.

C. Mineralised.

1. With sulphur and iron.

2. With sulphur. Aurum mufivum.

This was discovered by Professor Bergman, among some minerals which he received from Siberia. He observed two sorts of it, analogous to the two artificial combinations of tin with sulphur.

1. One nearly of the colour of zinc, and of a fibrous texture, which contained about 20 per cent. of sulphur, and the remainder tin.

2. The other enveloped the former like a crust; resembled aurum mufivum; and contained about 40 per cent. of sulphur, a small proportion of copper, and the remainder tin. Mem. Stockh. for 1721, p. 328.

At Huel Rock, in St Agnes in Cornwall, there has been found a metallic vein, nine feet wide, at 20 yards beneath the surface. Mr Rafae was the first who discovered this to be a sulphurated tin-ore: it is very compact, of a bluish white colour, approaching to grey steel, and similar to the colour of grey copper ore: it is lamellar in its texture, and very brittle. It consists of sulphur, tin, copper, and some iron. Mr Rafae proposes to call it bell-metal ore.

According to Mr Klaproth's analysis of this ore, 119 grains contain 30 of pure sulphur; 41 of tin; 43 of copper; two of iron; and three grains of the stony matrix. In another specimen of the same sulphurated tin-ore from Cornwall, there were in the hundred 25 parts of sulphur, 34 of tin, 36 of copper, three of iron, and two of the stony matrix.

II. Lead; Plumbum, Saturnus. (See the article Lead, and Chemistry Index; also Metallurgy, Part II, sect. v. and Part III, sect. vii.) The properties of lead are as follows.

a. It is of a bluish white colour when fresh broke, but soon dulls or fulfies in the air.

b. It is very heavy; viz. to water as 11,325 to 1000.

c. It is the softest metal next to gold; but it has no great tenacity, and is not in the least sonorous.

d. It is easily calcined; and, by a certain art in managing the degrees of the fire, its calx becomes white, yellow, and red.

e. This calx melts easier than any other metallic calx to a glass, which becomes of a yellow colour, and semitransparent. This glass brings other bodies, and the imperfect metals, into fusion with it.

f. It dissolves, 1st, In the spirit of nitre; 2dly, In a diluted oil of vitriol, by way of digestion; 3dly, In the vegetable acid; 4thly, In alkaline solutions; and 5thly, In expressed oils, both in the form of metal and of calx.

g. It gives a sweet taste to all solutions.

h. It amalgamates with quicksilver.

i. With the spirit of sea-salt it has the same effect as silver, whereby is produced a *saturnus cornues*.

k. It does not unite with iron, when it is alone added to it in the fire.

l. It works on the cupel, which signifies that its glass enters into certain porous bodies, destitute of phlogiston and alkaline salts.

m. It melts in the fire before it is made red-hot, almost as easily as the tin.

n. Its calx or glass may be reduced to its metallic state by pot-ashes.

[1.] Native Lead.

For proofs of lead being naturally found in its metallic state, see the article Lead.—It may be here added, that Henckel likewise affirms its existence, in his *Flora Saturnifans*; (see Kirwan's *Elements of Mineralogy*, p. 297, 298.) Wallerius asserts, that it has been so found in Poland, a specimen of which was kept in the collection of Richter; and adds, that a similar one found at Schneeberg, was seen in the collection of Spener. (*Mineralogy*, vol. ii. p. 301.)

Dr Lawson, in his English edition of Cramer's Art of Assaying Metals, says, that some pure native malleable lead had been lately found in New England; (p. 147.) And lastly, Professor Bergman did not hesitate to infer, by itself alone, the *plumbum nativum*, in Sect. 180. of his *Sciagraphia*.

[2.] Calciform Lead.

Lead is found,

A. In the form of a calx.

a. Pure.

b. Friable lead ochre, native ceruse.

c. Indurated lead spar, or spato lead ore.

i. Radiated, or fibrous.

ii. Crystallized in a prismatic figure.

1. White, from Mendip-hills, in England.

2. Yellowish green, from Zchopau in Saxony.

B. Mixed.

1. With the calx of arsenic, arsenical lead spar.

2. Indurated.

a. White. Mr Cronstedt has tried such an ore from an unknown place in Germany, and found that no metallic lead could be melted from it by means of the blow-pipe, as can be done out of other lead spars; but it must be performed in a crucible. (See the article Lead, par. iii.)

3. With a calcareous earth.

This ore effervesces with aqua-fortis, and contains 40 per cent. of lead; on which account it is placed here rather than among the calcareous earths.

B. Mineralized.

1. With sulphur alone: the *bley-schwefl*, or *bley-glanz*, of the Germans.

a. Steel-grained lead-ore.

b. Radiated, or antimoniated lead-ore.

c. Tessellated, or potter's lead-ore.

At Villach in Austria there is said to be found a potter's lead-ore, which contains not the least portion of silver.

2. Mineralized by the vitriolic acid.

This ore was discovered by Mr Monnet. It occurs sometimes, though rarely, in the form of a white ponderous calx; and seems to originate from the spontaneous decomposition of the sulphurated lead-ores above mentioned.

3. By the acid of phosphorus.

This ore was lately discovered by Gahn; and is of a greenish colour, by reason of a mixture of iron. See the article Lead, par. 6.

4. With sulphurated silver. Galena; also called *bleyglanz* by the Germans. Potter's ore.

a. Steel-grained.

b. With small scales.

c. Fine-grained.

d. Of a fine cubical texture; and,

e. Of coarse cubes. These two varieties are found in all the Swedish silver-mines.

f. Crystallized.

The steel-grained and scaly ores are of a dim and dull appearance when they are broken, and their particles have no determined angular figure; they are therefore in Swedish commonly called *bley-schwefl*; in opposition to the cubical ores, which are called *bleyglanz*. The most part of the ores called *bleyglanz* contain silver, even to 24 ounces per cent. of which we have instances in the mines of Salberg, where it has been observed, that the coarse cubical lead ores are generally the richest in silver, contrary to what is commonly taught in books; the reason of which may perhaps be, that, in making the essays on these two ores, the coarse cubical can be chosen purer or freer. freer from the rock than the fine cubical ores.

5. With sulphurated iron and silver. This is found, a. Fine-grained. b. Fine cubical. c. Coarse-cubical. When this ore is scorified, it yields a black flag; whereas the preceding lead-ores yield a yellow one, because they do not contain any iron.

6. With sulphurated antimony and silver; antimonated or radiated lead-ore. This has the colour of a byglanz, but is of a radiated texture.

It is found, a. Of fine rays and fibres; and, b. Of coarse rays or fibres. The lead in this ore prevents any use being made of the antimony to advantage; and the antimony likewise in a great measure hinders the extracting of the silver.

7. Mineralised by arsenic. This ore was lately discovered in Siberia.—Externally it is of a pale, and internally of a deep red, colour. See the article Lead, par. 10.

C. Mixed with earth; stony, or sandy lead ores. These consist either of the calciform or of the galena kind, intimately mixed and diffused through stones and earth, chiefly of the calcareous or of the barytic genus. See Lead, par. II.

Uses, &c. of Lead. See Lead, and the other articles above referred to.

III. Copper; Cuprum, Venus, &c. (See the article Copper: Also Chemistry-Index; and Metallurgy, Part II. sect. iv. and Part III. sect. iv.)

This metal is, a. Of a red colour. b. It is pretty soft and tough. c. The calx of copper being dissolved by acids becomes green, and by alkalies blue. d. It is easily calcined in the fire into a blackish blue substance, which, when rubbed to a fine powder, is red; when melted together with glass, it tinges it first reddish brown, and afterwards of a transparent green or sea-green colour. e. It dissolves in all the acids, and likewise in alkaline solutions. It is easier dissolved when in form of a calx than in a metallic state, especially by the acids of vitriol and sea-salt, and the vegetable acid. f. Vitriol of copper is of a deep blue colour; but the vegetable acid produces with the copper a green salt, which is verdigris. g. It can be precipitated out of the solutions in a metallic state; and this is the origin of the precipitated copper of the mines called Ziment copper. h. It is not easily amalgamated with quicksilver; but requires for this purpose a very strong trituration, or the admixture of the acid of nitre. i. It becomes yellow when mixed with zinc, which has a strong attraction to it, and makes brass, pinchbeck, &c.

k. When this metal is exposed to the fire, it gives a green colour to the flame in the moment it begins to melt, and continues to do so afterwards, without losing anything considerable of its weight.

[1.] Native copper. Copper found naturally in a metallic state, is called virgin or native copper. It is met with, 1. Solid. 2. Friable, in form of small, and somewhat coherent grains. Precipitated or ziment copper.

[2.] Calciform. Copper, in form of a calx, is found, 1.) Pure. a. Loose or friable; Ochra veneris. 1. Blue; Caruleum montanum. Very seldom found perfectly free from a calcareous substance. 2. Green; Viride montanum. Both this and the former colour depend on menstrua, which often are edulcorated or washed away. 3. Red. This is an efflorescence of the glaas copper ore.

2.) Indurated. Glaas copper-ore. a. Red. This is sometimes as red as sealing wax, and sometimes of a more liver-brown colour. It is always found along with native copper, and seems to have lost its phlogiston by way of efflorescence, and to be changed into this form. It is likewise found with the sulphurated copper, improperly called glaas copper-ore.

3.) Mixed. a. Loose or friable; Ochra veneris friabilis impura. 1. Mixed with a calcareous substance; Caruleum montanum. In this state copper-blue is mostly found. It ferments during the solution in aquafortis. 2. Mixed with iron. Black. It is the decomposition of the Fahlun copper ore.

4.) Indurated. 1. Mixed with gypsum, or plaster. Green. 2. Mixed with quartz. a. Red, from Sunnerflog in the province of Smoland. 3. Mixed with lime. a. Blue. This is the Lapis Armenus, according to the accounts given of it by authors.

5.) Cupreous stones. Analogous to the calciform copper ores, are, 1. The lapis armenus. See the detached article Copper, no 7. 2. The turquoise.

[3.] Dissolved and mineralised; Cuprum mineralisatum. a. With sulphur alone. Grey copper-ore; also called, improperly, glaas copper-ore. a. Solid, without any certain texture, and very soft, so that it can be cut with a knife almost as easily as black lead. b. Fine cubical. In Smoland this is sometimes times found decomposed or weathered, and changed into a deep mountain blue.

With sulphurated iron. *Minera cupri pyritacea*; yellow copper ore. Marcasitical copper ore; *Pyrites cupri*. This is various both in regard to colour and in regard to the different proportion of each of the contained metals; for instance,

a. Blackish grey, inclining a little to yellow; *Pyrites cupri griseus*. When decayed or weathered, it is of a black colour; is the richest of all the varieties of this kind of copper ore, yielding between 50 and 60 per cent. and is found in Spain and Germany.

b. Reddish yellow, or liver brown, with a blue coat on the surface; *Minera cupri laurina*. This ore yields between 40 and 50 per cent. of copper, and is commonly said to be blue, though it is as red, when fresh broken, as a red copper regulus.

c. Yellowish green; *Pyrites cupri flavo viridescens*. This is the most common in the north part of Europe; and is, in regard to its texture, found,

1. Solid, and of a shining texture. 2. Steel grained, of a dim texture. 3. Coarse-grained, of an uneven and shining texture. 4. Crystalized marcasitical copper ore.

a. Of long octohedral crystals.

b. Pale yellow. This cannot be described but as a marcasite, though an experienced eye will easily discover some difference between them. It yields 22 per cent. of copper.

c. Liver-coloured.

d. With sulphurated silver, arsenic, and some iron. Fallow copper-ore; which contains only a few ounces of silver. This ore is found in Hungary and Germany, where it is called black copper ore.

e. With sulphurated arsenic and iron. White copper ore.

f. Pyritous copper, with arsenic and zinc.

According to Mr Monnet, this ore is found at Catharineberg in Bohemia. It is of a brown colour; of a hard, solid, compact, granular texture; and contains from 18 to 30 per cent. of copper.

g. Dissolved by the vitriolic acid; *Vitriolum vesuvianum*. See the article copper, n° xiii.

h. With phlogiston. Copper coal ore, consisting of the calces of copper, mixed with a bituminous earth.

i. Mineralised by the muriatic acid. This ore was found in Saxony, and had been generally mistaken for a micaceous substance, which in fact it greatly resembles. It has not yet been found in large masses, but only in a superficial form, like a crust over other ores. It is moderately hard and friable; of a fine green colour, and sometimes of a bluish green, crystallised in a cubic form, or with a foliated texture, or in little scales resembling green mica or talc. This ore is easily dissolved by nitrous acid: the solution takes a green colour; and the metal may be precipitated on a polished plate of iron. If some drops of a nitrous solution of silver be mixed with it, a white powder of *luna cornea* will be precipitated, which discovers the presence of the muriatic acid in this ore.

The uses of copper are very numerous, although not thoroughly known to every one. Several of these have been mentioned under the detached article, and in Chemistry. Others of great importance may be here added. Its great ductility, lightness, strength, and durability, render it of very extensive utility. Blocks, or bars of copper, are reduced into flat sheets of any thickness, by being first heated by the reverberation of the flame, in a low-vaulted furnace, properly constructed for the purpose; and then immediately applied between large rollers of steel, or rather of cast-hardened iron, turned by a water-wheel or by the strength of horses, so that the hot metal is there quickly squeezed; and the operation is repeated, bringing the rollers every time nearer to one another, till the metallic sheet acquires the intended thickness.

These copper sheets are very advantageously employed in sheathing the bottoms of men of war and other vessels, which by this means are prevented from being attacked by the sea worms, and are kept clean from various marine concretions, so as to fail with considerably greater swiftness. Copper sheets are also employed to cover the tops of buildings instead of slates or earthen tiles, as is used in Sweden; and some architects have begun to introduce the use of copper covering into Great Britain, which is much lighter, and may be used with great advantage, although it must be much dearer in the prime cost.

Sundry preparations of copper are employed in painting, staining, and for colouring glazes and enamels. See Glass and Enamel.

The solution of copper in aqua-fortis stains marble and other stones of a green colour; when precipitated with chalk or whiting, it yields the green and the blue verditer of the painters. According to Lewis, a solution of the same metal in volatile spirits stains ivory and bones: when macerated for some time in the liquor, they become of a fine blue colour, which, however, tarnishes by exposure to the air, and becomes green afterwards.

The same author prepared elegant blue glasses, by melting common glass, or powdered flint and fixed alkaline salt, with blue vitriol, and with an amalgam of copper; fine green ones were made with green verditer, and with blue verditer, as well as with the precipitate of copper made by fixed alkalies, and with a precipitate by zinc; and a reddish glass was produced by the calx and scoria of copper made by fire alone. Even in this vitreous state, it seems as if a continuance of fire had the same effect in regard to colour, as air has upon copper in other forms; as some of the most beautiful blue glasses, by continued fusion, have changed changed to a green colour. See farther the article Brass in the Glass-trade.

Verdegris is a preparation of copper dissolved by the vegetable acids, which act on this metal, dissolving it very slowly, but in considerable quantities. It produces a fine green pigment for painting both in oil and water colours, inclining more or less to the bluish according to circumstances.

So great is the tenacity of copper, that a wire of a tenth of an inch in diameter is capable of supporting 299.5 pounds weight before it breaks.

Copper may be drawn into very fine wire, and beaten into extremely thin plates. The German artists, chiefly those of Nuremberg and Augsburg, are said to possess the best method for giving to these thin plates of copper a fine yellow colour like that of gold. See the articles Brass-Colour and Brass-Leaf.

The parings or shreds of these very thin leaves of yellow copper being well ground on a marble plate, are reduced to a powder similar to gold, which serves to cover, by means of some gum-water, or other adhesive fluid, the surface of various mouldings or other pieces of curious workmanship, giving them the appearance of real bronze, and even of fine gold, at a very trifling expense; because the gold colour of this metallic powder may be easily raised and improved by flaring it on a wide earthen bason over a slow fire.

In some of its states, copper is as difficultly extended under the hammer as iron, but proves softer to the file, and never can be made hard enough to strike a spark with flint or other stones; from whence proceeds the use that is made of this metal for chisels, hammers, hoops, &c., in the gun-powder works.

The vitriolic acid does not act on copper unless concentrated and boiling; during this solution a great quantity of sulphurous gas flies off; afterwards a brown thickish matter is found, which contains the calx of the metal partly combined with the acid. By solution and filtration, a blue solution is obtained, which being evaporated to a certain degree, produces after cooling long rhomboidal crystals of a beautiful blue colour, called vitriol of copper; but if this solution be merely exposed a long time to the air, it affords crystals, and a green calx is precipitated, a colour which all calces of this metal assume when dried by the air. Blue vitriol, however, is seldom formed by dissolving the metal directly in the vitriolic acid. That gold in the shops is mostly obtained from copper pyrites. It may also be made by stratifying copper-plates with sulphur, and cementing them together for some time; because the vitriolic acid of the sulphur being disengaged, attacks and corrodes the metal, forming a metallic salt, which by diffusion of water yields perfect crystals of blue vitriol. See Vitriol.

The nitrous acid, on the contrary, dissolves copper when cold with great rapidity; and a great quantity of smoking air or gas flies off, which, on being received in a pneumatic apparatus, and mixed in a glass tube with atmospheric air, shows its good or bad quality for the respiration of living animals, according as the common bulk is more or less diminished. This is one of the most important of Dr Priestley's discoveries; and various instruments known by the name of eudiometers have been since invented for making these experiments with ease and satisfaction. See Eudiometer.

But the most common use of copper is to make all sorts of large stills, boilers, pots, funnels, and other vessels employed by distillers, dyers, chemists, and various other manufacturers, who make use of large quantities of hot liquors in their various operations.

Although copper when pure is extremely valuable, on account of its ductility, lightness, and strength, it is, however, less useful on many occasions from the difficulty of forming large masses of work, as it is not an easy matter to cast copper solid, so as to retain all its properties entire. For if the heat be not sufficiently great, the metal proves deficient in toughness when cold; and if the heat be raised too high, or continued for a length of time, the copper blistered on the surface when cast in the moulds; so that the limits of its fusion are very contracted. And from these circumstances pure copper is rendered less applicable to several purposes.

We find, however, that the addition of a certain proportion of zinc removes almost all these inconveniences, and furnishes a mixed metal more fusible than copper, very ductile and tenacious when cold, which does not so readily scorchify in moderate heat, and which is less apt to rust from the action of air and moisture.

Copper is the basis of sundry compound metals for a great number of mechanical and economical uses of life, such as brass (v), prince's-metal, tombac, bell-metal, white copper, &c. See Chemistry, no. 1154, &c.

If the mixture is made of four to six parts of copper, with one part of zinc, it is called Prince's-metal. If more of the copper is taken, the mixture will be of a deeper yellow, and then goes by the name of tombac.

(v) Brass is frequently made by cementing plates of copper with calamine, where the copper imbibes one-fourth or one-fifth its weight of the zinc which rises from the calamine. The process consists in mixing three parts of calamine and two of copper with charcoal dust in a crucible, which is exposed to a red heat for some hours, and then brought to fusion. The vapours of the calamine penetrate the heated plates of copper, and add thereby to its fusibility. It is of great consequence for the success of this process to have the copper cut into small pieces, and intimately blended with the calamine. See Chemistry, no. 1154.

In most foreign foundries the copper is broken small by mechanical means with a great deal of labour; but at Bell-metal is a mixture of copper and tin, forming a compound extremely hard and honorous, and is less subject to alterations by exposure to the air than any other cheap metal. On this account it is advantageously employed in the fabrication of various utensils and articles, as cannons, bells, flat-ware, &c., in the composition of which, however, other metals are mixed in various proportions, according to the fancy and experience of the artist.

White-copper is prepared with arsenic and nitre, as mentioned under Chemistry, No. 1157.

But the principal kind of white-copper is that with which speculums of reflecting telescopes are made. See the article Speculum.

VII. Iron; Ferrum, Mars. This metal is,

a. Of a blackish blue shining colour. b. It becomes ductile by repeated heating between coals and hammering. c. It is attracted by the lodestone, which is an iron ore; and the metal itself may also be rendered magnetic. d. Its specific gravity to water is as 7.645, or 8000 : 1000. e. It calcines easily to a black scaly calx, which, when pounded, is of a deep red colour. f. When this calx is melted in great quantity with glass compositions, it gives a blackish brown colour to the glass; but in a small quantity a greenish colour, which at last vanishes if forced by a strong degree of heat.

It is dissolved by all salts, by water, and like imperfect wife by their vapours. The calx of iron is dissolved by the spirit of sea-salt and by aqua-regia.

The calx of the dissolved metal becomes yellow, or yellowish brown; and in a certain degree of heat it turns red.

The same calx, when precipitated from acids by means of the fixed alkali, is of a greenish colour; but it becomes blue when precipitated by means of an alkali united with phlogiston; in which last circumstance the phlogiston unites with the iron; these two precipitates lose their colour in the fire, and turn brown.

The vitriol of iron is brown.

Iron is found,

[1.] Native. See the detached article Iron. [2.] In form of calx.

A. Pure.

1. Powdery; Ochra ferri. This is commonly yellow or red, and is iron which has been dissolved by the vitriolic acid. 2. Concreted. Bog-ore. a. In form of round porous balls. b. More solid bars. c. In small flat pieces, like cakes or pieces of money. d. In small grains.

at Bristol the workmen employ an easier method. A pit is dug in the ground of the manufacture about four feet deep, the sides of which are lined with wood. The bottom is made of copper or brass, and is moveable by means of a chain. The top is made also of brass with a space near the centre, perforated with small holes, which are luted with clay; through them the melted copper is poured, which runs in a number of streams into the water, and this is perpetually renewed by a fresh stream that passes through the pit. As the copper falls down it forms itself into grains, which collect at the bottom. But great precaution is required to hinder the dangerous explosions which melted copper produces when thrown into cold water; which end is obtained by pouring small quantities of the metal at once. The granulated copper is completely mixed with powdered calamine, and fused afterwards. The process lasts eight or ten hours, and even some days, according to the quality of the calamine.

It is a wonderful thing, says Cramer, that zinc itself, being simply melted with copper, robs it of all its malleability; but if it be applied in form of vapour from the calamine, the sublimates, or the flowers, it does not cause the metal to become brittle.

The method mentioned by Cramer to make brass from copper, by the volatile emanations of zinc, seems to be preferable to any other process, as the metal is then preserved from the heterogeneous parts contained in the zinc itself, or in its ore. It consists in mixing the calamine and charcoal with moistened clay, and ramming the mixture to the bottom of the melting pot, on which the copper, mixed also with charcoal, is to be placed above the rammed matter. When the proper degree of heat is applied, the metallic vapour of the zinc contained in the calamine transpires through the clay, and attaches itself to the copper, leaving the iron and the lead which were in the calamine retained in the clay, without mixing with the upper metal. Dr. Watson says, that a very good metallurgist of Bristol, named John Champion, has obtained a patent for making brass by combining zinc in the vapourous form with heated copper plates; and that the brass from this manufacture is reported to be of the finest kind; but he knows not whether the method there employed is the same with that mentioned by Cramer.

Brass is sometimes made in another way, by mixing the two metals directly; but the heat requisite to melt the copper makes the zinc burn and flame out, by which the copper is defrauded of the due proportion of zinc. If the copper be melted separately, and the melted zinc poured into it, a considerable and dangerous explosion ensues; but if the zinc is only heated and plunged into the copper, it is quickly imbibed and retained. The union, however, of these two metals succeeds better if the flux composed of inflammable substances be first fused in the crucible, and the copper and zinc be poured into it. As soon as they appear thoroughly melted, they are to be well stirred, and expeditiously poured out, or else the zinc will be inflamed, and leave the red copper behind. In lumps of an indeterminate figure. All these are of a blackish brown, or a light brown colour.

**B. Indurated.** The blood-stone; *Hematites*.

1. Of an iron colour; *Hematites cara'gensis*. This is of a bluish grey colour; it is not attracted by the loadstone, yields a red powder when rubbed, and is hard. a. Solid, and of a dim appearance when broken. b. Cubical, and of a shining appearance when broken. c. Fibrous, is the most common *torsten* of Sweden. d. Scaly: the *eisenram* of the Germans. 1. Black. 2. Bluish grey. When this is found along with marcasite, it is not only attracted by the loadstone, but is itself really a loadstone. e. Crystallised. 1. In octohedral crystals. 2. In polyedrical crystals. 3. In a cellular form.

These varieties are the most common in Sweden, and are very seldom blended with marcasite or any other heterogeneous substance except their different beds. It is remarkable, that when these ores are found along with marcasite, those particles which have lain nearest to the marcasite are attracted by the loadstone, although they yield a red or reddish brown powder, like those which are not attracted by the loadstone; it is likewise worth observation, that they generally contain a little sulphur, if they are imbedded in a limestone rock.

2. Blackish brown bloodstone; *Hematites nigreflens*. Kidney ore. This yields a red or brown powder when it is rubbed; it is very hard, and is attracted by the loadstone. a. Solid, with a glassy texture. b. Radiated. c. Crystallised. 1. In form of cones, from Siberia. 2. In form of concentric balls, with a faceted surface. These are very common in Germany, but very scarce in Sweden.

3. Red bloodstone; *Hematites Ruber*. Red kidney ore. a. Solid, and dim in its texture. b. Scaly. The *eisenran* of the Germans. This is commonly found along with the iron-coloured iron glimmer, and smears the hands. c. Crystallised, in concentric balls, with a flat or faceted surface.

4. Yellow bloodstone; *Hematites flavus*. a. Solid. b. Fibrous.

The varieties of the colours in the bloodstone are the same with those produced in the calces of iron made by dry or liquid menstrua and afterwards exposed to different degrees of heat.

**B. Mixed with heterogeneous substances.**

A. With a calcareous earth. White spathose iron ore. The *flabelfein* of the Germans. B. With a filaceous earth. The martial jasper of Sinople. C. With a garnet earth. Garnet and cockle or thirl. D. With an argillaceous earth. The bole. E. With a micaeous earth. Mica. F. With manganese. G. With an alkali and phlogiston. Blue martial earth. Native Prussian-like blue. I. Loose or powdery. H. With an unknown earth, which hardens in water. Tarras; *Cementum*. J. Loose or granulated; *Terra Puzzolana*. This is of a reddish brown colour, is rich in iron, and is pretty fusible.

2. Indurated; *Cementum induratum*. This is of a whitish yellow colour, contains likewise a great deal of iron, and has the same quality with the former to harden soon in water when mixed with mortar. This quality cannot be owing to the iron alone, but rather to some particular modification of it occasioned by some accidental causes, because these varieties rarely happen at any other places except where volcanoes have been, or are yet, in the neighbourhood.

[3.] Dissolved or mineralised.

A. With sulphur alone. a. Perfectly saturated; *Ferrum sulphure saturatum*. Marcasite. b. With very little sulphur. Black iron ore. Iron stone.

This is either attracted by the loadstone, or is a loadstone itself attracting iron; it resembles iron, and yields a black powder when rubbed.

1.) Magnetic iron ore. The loadstone, *Magnes*. a. Steel-grained, of a dim texture, from Hogberget in the parish of Gagnef in Dalarne: it is found at that place almost to the day, and is of as great strength as any natural loadstones were ever commonly found. b. Fine grained, from Saxony. c. Coarse-grained, from Spetalfgrufvan at Norberg, and Kierrgrufvan, both in the province of Vastmanland. This loses very soon its magnetical virtue. d. With coarse scales, found at Sandswær in Norway. This yields a red powder when rubbed.

2.) Refractory iron ore. This in its crude state is attracted by the loadstone. a. Giving a black powder when rubbed; *Tritura atra*. Of this kind are, 1. Steel-grained. 2. Fine-grained. 3. Coarse grained.

This kind is found in great quantities in all the Swedish iron mines, and of this most part of the fusible ores consist; because it is commonly found in such kinds of rocks as are very fusible; and it is as seldom met with in quartz as the haematites is met with in limestone.

b. Rubbing into a red powder. These are real haematites, that are so far modified by sulphur or lime as to be attracted by the loadstone.

1. Steel-grained. 2. Fine-grained. Emery. This is imported from the Levant; it is mixed with mica, is strongly attracted by the loadstone, and smells of sulphur when put to the fire.

3. Of large shining cubes. 4. Coarse, scaly. The eisenklimmer or eisenron.

[4.] Mixed with various fossil substances. 1. With sulphur and clay; Pyrites. 2. With arsenic; called milpuckel by the Germans, and plate mundic in Cornwall. 3. With sulphurated arsenic. Arsenical pyrites. 4. With vitriolic acid. Martial vitriol. 5. With phlogiston. Martial coal ore. 6. With other sulphurated and arsenicated metals.

See these in their respective arrangements.

Uses and Properties of Iron. Iron is the most common metal in nature, and at the same time the most useful in common life; notwithstanding which, its qualities are perhaps very little known.

Iron has a particular and very sensible smell when strongly rubbed or heated; and a lyptic taste, which it communicates to the water in which it is extinguished after ignition. Its tenacity, ductility, and malleability, are very great. It exceeds every other metal in elasticity and hardness, when properly tempered. An iron wire of one-tenth of an inch thick is able to support 450 pounds weight without breaking, as Wallerius affirms.

Iron drawn into wire as slender as the finest hairs. It is more easily malleable when ignited than when cold; whereas other metals, though ductile when cold, become quite brittle by heat.

It grows red-hot sooner than other metals; nevertheless it melts the most difficulty of all, platina and manganese excepted. It does not tinge the flame of burning matters into bluish or greenish colours, like other imperfect metals, but brightens and whitens it; hence the filings of iron are used in compositions of fire-works, to produce what is called white-fire.

Iron, or rather steel, expands the least of all hard metals by the action of heat; but brass expands the most; and on this account these two metals are employed in the construction of compound pendulums for the best sort of regulating clocks for astronomical purposes.

Iron, in the act of fusion, instead of continuing to expand, like the other metals, shrinks, as Dr Lewis observes; and thus becomes so much more dense as to throw up such part as is unmelted imperfect to the surface; whilst pieces of gold, silver, copper, lead, and tin, put in the respective metals in fusion, sink quickly to the bottom. But in its return to a consistent state, instead of shrinking, like other metals, it expands; sensibly rising in the vessel, and assuming a convex surface, whilst the others subside, and appear concave. This property of iron was first taken notice of by Reamur, and excellently fits it for receiving impressions from the moulds into which it is cast, being forced into their minutest cavities. Even when poured thick into the mould, it takes, nevertheless, a perfect impression; and it is observed, that cast iron is somewhat larger than the dimensions of the mould, whilst cast figures of other metals are generally smaller.

The vitriolic acid dissolves iron readily, and forms green vitriol.

This acid requires to be diluted with 304 times its quantity of water, to enable it effectually to dissolve iron; and, during the dissolution, a strong acrid fluid arises, called inflammable air, which, on being mixed with atmospheric air, takes fire at the approach of the flame of a candle. A glass phial, of about two ounces measure, with one third of inflammable air, and the rest of common air, produces a very loud report if opened in the same circumstance; and if it be filled with two-thirds of inflammable air, mixed with one of dephlogisticated air, the report will be as loud as the explosion of a pistol with gunpowder.

Dilute nitrous acid dissolves iron; but this saline combination is incapable of crystallising. Strong nitrous acid corrodes and dephlogisticates a considerable quantity of iron, which falls to the bottom.

Marine acid likewise dissolves iron, and this solution is also incrustifiable.

The Prussian acid precipitates iron from its solutions in the form of Prussian blue.

This metal is likewise sensibly acted upon by alkaline and neutral liquors, and corroded even by those which have no perceptible saline impregnation; the oils themselves, with which iron utensils are usually rubbed to prevent their rusting, often promote this effect in some measure, unless the oils had been previously boiled with litharge or calces of lead.

Galls, and other astringent vegetables, precipitate iron from its solutions, of a deep blue or purple colour, of so intense a shade as to appear black. It is owing to this property of iron that the common writing ink is made. The infusion of galls, and also the Prussian alkali, are tests of the presence of iron by the colours they produce on any fluid. Acids, however, dissolve the coloured precipitates by the former; and hence it arises that the marine acid is successfully applied to take off ink spots and iron stains from white linens. Alkalis, however, convert these iron precipitates into a brown ochre.

Iron has a strong affinity with sulphur. If a bar of iron be strongly ignited, and a roll of brimstone be applied to the heated end, it will combine bine with the iron, and form a fusible mass, which will drop down. A vessel of water ought to be placed beneath for the purpose of receiving and extinguishing it, as the fumes would otherwise be very inconvenient to the operator.

A mixture of iron-filings and sulphur in powder, moistened with water, and pressed so as to form a paste, will in a few hours swell, become hot, fume, and even burst into a flame, if the quantity is large. The residue furnishes martial vitriol. This process is similar to the decomposition of martial pyrites; from which some philosophers account for hot spring-waters and subterranean fires. The mixture of water in this paste seems to be necessary to enable the vitriolic acid of the sulphur to act on the iron.

For other chemical properties of this metal, see Chemistry-Index; for its electrical and magnetic properties, see Electricity and Magnetism. For a more particular account of its nature and uses, and the methods of making and manufacturing it, see the articles Iron and Steel; also Metallurgy, Part II, sect. vii., and Part III, sect. v.

Order III. SEMIMETALS.

I. Bismuth; tin-glass. *Vifmutum*, *Bismutum*, *Marcasita officinalis*. It is,

a. Of a whitish yellow colour. b. Of a laminated texture, soft under the hammer, and nevertheless very brittle. c. It is very fusible; calcines and scorifies like lead, if not rather easier; and therefore it works on the cupel. It is pretty volatile in the fire. d. Its glaze or slag becomes yellowish brown, and has the quality of retaining some part of the gold, if that metal has been melted, calcined, and vitrified with it. e. It may be mixed with the other metals, except cobalt and zinc, making them white and brittle. f. It dissolves in aquafortis, without imparting to it any colour; but to the aqua-regia it gives a red colour, and may be precipitated out of both these solutions with pure water into a white powder, which is called *Spanische Weisse*. It is also precipitated by the acid of sea-salt; which last unites with it, and makes the *vifmutum cornicum*. g. It amalgamates easily with quicksilver. Other metals are so far attenuated by the bismuth, when mixed with it, as to be strained or forced along with the quicksilver through skins or leather.

Bismuth is found in the earth.

A. Native. This resembles a regulus of bismuth, but consists of smaller scales or plates. 1. Superficial, or in crusts. 2. Solid, and composed of small cubes.

B. In form of calx.

1. Powdery or friable; *Ochra vifmuti*. This is of a whitish yellow colour; it is found in form of an efflorescence.

It has been customary to give the name of *flowers of bismuth* to the pale red calx of cobalt, but it is wrong; because neither the calx of bismuth, nor its solutions, become red, this being a quality belonging to the cobalt.

C. Mineralised bismuth. This is, with respect to colour and appearance, like the coarse tessellated potter's lead ore; but it consists of very thin square plates or flakes, from which it receives a radiated appearance when broken crosswise.

1. With sulphur. a. With large plates or flakes. b. With fine or small scales. 2. With sulphurated iron. a. Of coarse wedge-like scales.

This mineralised bismuth ore yields a fine radiated regulus; for which reason it has been ranked among the antimonial ores by those who have not taken proper care to melt a pure regulus ore destitute of sulphur from it; while others, who make no difference between regulus and pure metals, have still more positively asserted it to be only an antimonial ore.

3. With sulphur and arsenic. a. Of a whitish yellow or ash colour. It has a shining appearance; and is composed of small scales or plates, intermixed very small yellow flakes. It is of a hard and solid texture: Sometimes strikes fire with hard steel: Has a disagreeable smell when rubbed: Does not effervesce with aqua-fortis; but is partially dissolved by the same acid (z). b. Grey, of a striated form; found at Helsingland in Sweden, and at Annaberg in Saxony. c. With variegated colours of red, blue, and yellow grey; found at Schneeberg in Saxony. d. With green fibres like an amianthus; at Milnau in Germany, and at Gillebeck in Norway. e. With yellow red shining particles, called *mines de bismuth Tigrees* in French, at Georgenstadt in Germany, and at Annaberg in Saxony. f. The *minera bismuthi arenacea*, mentioned by Wallerius and Bomare, belongs also to the same kind of the arsenicated ores.

4. By vitriolic acid. This ore is called *vifmut bluth* by the Germans. It is said to be of a yellowish, reddish, or variegated colour; and to be found mixed with the calx of bismuth, incrusting other ores. Kirwan, p. 334.

Uses, &c., of Bismuth. See the article Bismuth. Also Chemistry-Index; and Metallurgy, Part II, sect. x., and Part III, sect. viii.

---

(z) This solution, being diluted with water, becomes a kind of sympathetic ink; as the words written with it on white paper, and dried, are not distinguished by the eye; but on being heated before the fire, they assume a yellowish colour. II. Zinc; Spelter. Zincum.

a. Its colour comes nearest to that of lead, but it does not so easily tarnish.

b. It shows a texture when it is broken, as if it were compounded of flat pyramids (A).

c. Its specific gravity to water is about 6,900 or 7,000 to 1,000.

d. It melts in the fire before it has acquired a glowing heat; but when it has gained that degree of heat, it burns with a flame of a changeable colour, between blue and yellow. If in an open fire, the calx rises in form of soft white flowers; but if in a covered vessel, with the addition of some inflammable, it is distilled in a metallic form; in which operation, however, part of it is sometimes found vitrified.

e. It unites with all the metals (B) except bismuth and nickel, and makes them volatile. It is, however, not easy to unite it with iron without the addition of sulphur. It has the strongest attraction to gold and copper, and this last metal acquires a yellow colour by it; which has occasioned many experiments to be made to produce new metallic compositions.

f. It is dissolved by all the acids: of these the vitriolic acid has the strongest attraction to it; yet it does not dissolve it, if it is not previously diluted with much water.

g. Quicksilver amalgamates easier with zinc than with copper; by which means it is separated from compositions made with copper.

h. It seems to become electrical by friction.

Zinc is found,

A. Native.

Zinc has been met with native, though rarely, in the form of thin and flexible filaments, of a grey colour, which were easily inflamed when applied to a fire. And Bomare affirms that he has seen many small pieces of native zinc among the calamine-mines in the duchy of Limbourg and in the zinc-mines at Goeßlar, where this semimetal was always surrounded by a kind of ferruginous yellow earth, or ochraceous substances. See the detached article Zinc.

B. In form of calx.

No 224.

(A) It cannot be reduced into powder under the hammer like other semimetals. When it is wanted very much divided, it must be granulated, by pouring it while fused into cold water; or filed, which is very tedious, as it stuffs and fills the teeth of the file. But if heated the most possible without fusing it, Macquer affirms, that it becomes so brittle as to be pulverized in a mortar.

(B) It brightens the colour of iron almost into a silver hue; changes that of copper to a yellow or gold colour, but greatly debases the colour of gold and destroys its malleability. It improves the colour and lustre of lead and tin, rendering them firmer, and consequently fitter for sundry mechanic uses. Lead will bear an equal weight of zinc, without losing too much of its malleability.—The process for giving the yellow colour to copper, by the mixture of zinc, and of its ore called calamine, has been described above under the Uses of Copper.

(C) The varieties of pseudo-galena, or black-jack, are in general of a lamellar or scaly texture, and frequently of a quadrangular form, resembling galena. They all lose much of their weight when heated, and burn with a blue flame; but their specific gravity is considerably inferior to that of true galena. Almost all contain a mixture of lead-ore. Most of them exhale a sulphurous smell when scraped; or at least when vitriolic or marine acid is dropped on them.

(1.) Pure.

a. Indurated.

1. Solid

2. Crystallized.

This is of a whitish-grey colour, and its external appearance is like that of a lead spar; it cannot be described, but is easily known by an experienced eye.—It looks very like an artificial glass of zinc; and is found among other calamines at Namur and in England.

(2.) Mixed.

A. With a martial ochre.

1. Half indurated. Calamine; Lapis calaminaris.

a. Whitish yellow.

b. Reddish brown. This seems to be a mouldered or weathered blende.

B. With a martial clay or bole.

C. With a lead ochre and iron.

D. With quartz: Zeolite of Friburgh.

The real contents of this substance were first discovered by M. Pelletier. It was long taken for a true zeolite, being of a pearl colour, crystallized, and semitransparent. It consists of laminae, diverging from different centres, and becoming gelatinous with acids. Its contents are 48 to 52 per cent. of quartz, 36 of calx of zinc, and 8 or 12 of water. (Kirwan, p. 318.)

C. Mineralized.

(1.) With sulphurated iron. Blende, mock-lead, black-jack, mock-ore; pseudogalena and blendé of the Germans.

A. Mineralized zinc in a metallic form. Zinc ore. This is of a metallic bluish-grey colour, neither perfectly clear as a potter's ore, nor so dark as the Swedish iron ores.

1. Of a fine cubical or scaly texture.

2. Steel-grained.

B. In form of calx. Blende. Mock-lead; Sterile nigrum. Pseudo-galena (c). This is found,

1. With coarse scales.

a. Yellow; semi-transparent.

b. Greenish.

c. Greenish-

(A) It cannot be reduced into powder under the hammer like other semimetals. When it is wanted very much divided, it must be granulated, by pouring it while fused into cold water; or filed, which is very tedious, as it stuffs and fills the teeth of the file. But if heated the most possible without fusing it, Macquer affirms, that it becomes so brittle as to be pulverized in a mortar.

(B) It brightens the colour of iron almost into a silver hue; changes that of copper to a yellow or gold colour, but greatly debases the colour of gold and destroys its malleability. It improves the colour and lustre of lead and tin, rendering them firmer, and consequently fitter for sundry mechanic uses. Lead will bear an equal weight of zinc, without losing too much of its malleability.—The process for giving the yellow colour to copper, by the mixture of zinc, and of its ore called calamine, has been described above under the Uses of Copper.

(C) The varieties of pseudo-galena, or black-jack, are in general of a lamellar or scaly texture, and frequently of a quadrangular form, resembling galena. They all lose much of their weight when heated, and burn with a blue flame; but their specific gravity is considerably inferior to that of true galena. Almost all contain a mixture of lead-ore. Most of them exhale a sulphurous smell when scraped; or at least when vitriolic or marine acid is dropped on them. Greenish-black; pechblende, or pitch blende of the Germans.

d. Blackish-brown.

2. With fine scales, a. White. b. Whitish-yellow. c. Reddish-brown.

3. Fine and sparkling; at Goslar called braun blyertz. Its texture is generally scaly; sometimes crystallized and semitransparent. It gives fire with steel; but does not decrepitate, nor smoke when heated; yet it loses about 13 per cent. of its weight by torrefaction. a. Dark-brown. b. Red, which becomes phosphorescent when rubbed; found at Scharfenberg in Münsteria. (Brunich). c. Greenish, yellowish-green, or red. It has different degrees of transparency, and is sometimes quite opaque. When scraped with a knife in the dark, it emits light, even in water; and after undergoing a white heat, if it is distilled per se, a filaceous sublimate rises, which shows it contains the sparry acid, probably united to the metal, since it sublimes.

4. Of a metallic appearance; glanz blende.

This is of a bluish-grey, of a scaly or steel-grained texture, and its form generally cubical or rhomboidal. It loses nearly one sixth of its weight by calcination; and after calcination it is more soluble in the mineral acids.

100 parts of this ore afforded to Bergman about 52 of zinc, 8 of iron, 4 of copper, 26 of sulphur, 6 of filex, and 4 of water.

5. Cryalline. a. Dark-red, very scarce; found in a mine near Freyberg. Something like it is found at the Morgenstern and Himmelsfute. b. Brown. In Hungary and Transilvania. c. Black. Hungary.

These varieties may easily be mistaken for rock crystals; but by experience they may be distinguished on account of their lamellated texture and greater softness. Their transparency arises from a very small portion of iron in them.

(2.) Zinc mineralized by the vitriolic acid.

This ore has been already described among the middle Salts, at Vitriol of zinc.

Uses, &c. of zinc. See the detached article Zinc; also Chemistry-Index; and Metallurgy, Part II. sect. xii. and Part III. under sect. iii.

III. Antimony; Antimonium Stibium. This semimetal is, a. Of a white colour almost like silver. b. Brittle; and, in regard to its texture, it consists

of shining planes of greater length than breadth.

c. In the fire it is volatile, and volatilizes part of the other metals along with it, except gold and platinum. It may, however, in a moderate fire, be calcined into a light-grey calx, which is pretty refractory in the fire; but melts at last to a glasa of a reddish-brown colour.

d. It dissolves in spirit of sea-salt and aqua regia, but is only corroded by the spirit of nitre into a white calx; it is precipitated out of the aqua regia by water.

e. It has an emetic quality when its calx, glasa, or metal, is dissolved in an acid, except when in the spirit of nitre, which has not this effect.

f. It amalgamates with quicksilver, if the regulus, when fused, is put to it; but the quicksilver ought for this purpose to be covered with warm water; it amalgamates with it likewise, if the regulus of antimony be previously melted with an addition of lime.

Antimony is found in the earth.

A. Native. Regulus antimonii nativus.

This is of a silver colour, and its texture is composed of pretty large shining planes.

This kind was found in Carls Ort, in the mine of Salberg, about the end of the last century; and specimens thereof have been preserved in collections under the name of an artificial pyrites, until the mine-master Mr Von Swab discovered its real nature, in a treatise he communicated to the Royal Academy of Sciences at Stockholm in the year 1748. Among other remarkable observations in this treatise, it is said, first, That this native antimony easily amalgamated with quicksilver; doubtless, because it was imbedded in a limestone; since, according to Mr Pott's experiments, an artificial regulus of antimony may, by means of lime, be disposed to an amalgamation; Secondly, That when brought in form of a calx, it shot into crystals during the cooling.

B. Mineralized antimony.

(1.) With sulphur.

This is commonly of a radiated texture, composed of long wedge-like flakes or plates; it is nearly of a lead-colour, and rough to the touch.

a. Of coarse fibres. b. Of small fibres. c. Steel-grained, from Saxony and Hungary. d. Crystalized, from Hungary.

1. Of a prismatical, or of a pointed pyramidal figure, in which last circumstance the points are concentrical.

Cronstedt mentions a specimen of this, in which the crystals were covered with very minute crystals or quartz, except at the extremities, where there was always a little hole; this specimen was given for a flox ferri spar.

(2.) With sulphur and arsenic. Red antimony ore; Antimonium solare.

This is of a red colour, and has the same texture with the preceding, though its fibres are not so course.

R a. With small fibres. b. With abrupt broken fibres, from Braunf- dorff in Saxony; and from Hungary.

All antimonial ores are somewhat arse- nical, but this is more so than the preceding kinds.

(3.) With sulphurated silver. Plumose silver- ore, or federitz of the Germans.

(4.) With sulphurated silver, copper, and arse- nic; the dal fahleritz of the Germans.

(5.) With sulphurated lead; radiated lead-ore.

(6.) By the aerial acid.

This ore was lately discovered by Mongez, among those of native antimony from the mine of Chalanges in Dauphiny. It consists of a group of white crystallised filaments of a needle-form appearance, diverging from a com- mon centre, like zeolite. They are insoluble in nitrous acid; and, on being urged by the flame of a blow-pipe, upon a piece of charcoal, they are dissipated into white fumes, or anti- monial flowers, without any smell of arsenic; from whence it follows, that these needle-form- ed crystals are a pure calx of antimony, form- ed by its combination with, or mineralised by, the aerial acid. See Kirwan, p. 325, and Journal de Physique for July 1787, p. 67.

Uses, &c. By the name of antimony is commonly understood the crude antimony (which is com- pounded of the metallic part and sulphur) as it melted out of the ore; and by the name of regu- lus, the pure semimetal.

1. Though the regulus of antimony is a metallic substance, of a considerably bright white colour, and has the splendour, opacity, and gravity of a metal, yet it is quite unworkable, and falls into powder instead of yielding or expanding under the hammer; on which account it is clasped among the semimetals.

2. Regulus of antimony is used in various metallic mixtures, as for printing types, metallic specu- lums, &c. and it enters into the best sort of pew- ter ware.

3. It mixes with, and dissolves various metals; in particular it affects iron the most powerfully; and, what is very remarkable, when mixed toge- ther, the iron is prevented from being attracted by the loadstone.

4. It affects copper next, then tin, lead, and silver; promoting their fusion, and rendering them all brittle and unworkable; but it will neither unite with gold nor mercury; though it may be made to combine with this last by the interpolation of sulphur. In this case it resembles the common Ethiops, and is thence called antimonial Ethiops.

5. Regulus of antimony readily unites with sulphur, and forms a compound of a very faint metallic splendour; it assumes the form of long needles ad- hering together laterally: it usually formed na- aturally also in this shape. This is called crude antimony.

6. But though antimony has a considerable affinity to sulphur; yet all the metals, except gold and mercury, have a greater affinity to that com-

If therefore iron, copper, lead, silver, or tin, be melted with antimony, the sulphur will unite with the metal, and be separated from the regulus, which, however, takes up some part of the metal, for which reason it is called martial re- gulus, regulus veneris, &c.

7. When gold is mixed, or debased by the mixture of other metals, it may be fused with antimony; for the sulphur combines with the base metals, which, being the lighter, rise up into scoria, while the regulus remains united at the bottom with the gold; which being urged by a stronger degree of heat, is freed from the semimetal, which is very volatile. This method of refining gold is the easiest of all.

8. But the most numerous purposes to which this metal has been applied are those of the chemical and pharmaceutical preparations. Lemery, in his Treatise on Antimony, describes no less than 200 processes and formulae; among which there are many good and many useless ones. The following deserve to be mentioned on account of their utility.

9. Antimony melts as soon as it is moderately red hot, but cannot sustain a violent degree of fire, as it is thereby dissipated into smoke and white vapours, which adhere to such cold bodies as they meet with, and are collected into a kind of farina or powder, called flowers of antimony.

10. If it be only moderately heated, in very small pieces, so as not to melt, it becomes calcined in to a greyish powder destitute of all splendour, called calx of antimony. This calx is capable of enduring the most violent fire; but at last it will run into a glaze of a reddish-yellow colour, similar to that of the hyacinth. The infusion made of this col- oured antimonial glass, in acidulous wine (such as that of Bourdeaux) for the space of 5 or 6 hours, is a very violent emetic.

11. If equal parts of nitre and regulus of antimony be deflagrated over the fire, the grey calx which remains is called liver of antimony.

12. If regulus of antimony be melted with two parts of fixed alkali, a mass of a reddish-yellow colour is produced, which being dissolved in water, and any acid being afterwards added, a precipitate is formed of the same colour, called golden sulphur of antimony.

13. Fixed nitre, viz. the alkaline salt that remains after the deflagration of nitre, being boiled with small pieces of regulus of antimony, the solution becomes reddish; and, on cooling, deposits the antimony in the form of a red powder, called mineral kerme.

14. Equal parts of the glaze, and of the liver of an- timony, well pulverised and mixed with an equal quantity of pulverised cream of tartar, being put into as much water as will dissolve the cream of tartar, and boiled for 12 hours, adding now and then some hot water to replace what is evaporated, the whole is to be filtered while hot; then being evaporated to dryness, the saline matter that remains is the emetic tartar.

15. The regulus of antimony being pulverised, and distilled distilled with corrosive sublimate of mercury, a thick white matter is produced, which is extremely corrosive, and is called butter of antimony. This thick substance may be rendered limpid and fluid by repeated distillations.

16. On mixing the nitrous acid with this butter of antimony, a kind of aqua regia is distilled, called bezoardic spirit of nitre.

17. The white matter that remains from this last distillation may be redistilled with fresh nitrous acid; and the remainder being washed with water, is called bezoard mineral, which is neither so volatile nor so caustic as the antimonial butter. This butter being mixed with water, a precipitate falls to the bottom, which is very improperly called mercurius vitae, for it is in fact a very violent emetic.

18. But if, instead of the regulus, crude antimony be employed, and the same operation be performed, the reguline part separates from the sulphur, unites to the mercury, and produces the substance which is called cinnabar of antimony.

19. Crude antimony being projected in a crucible, in which an equal quantity of nitre is fused, detonates; is calcined, and forms a compound called by the French fondant de Retrou, or antimoine diaphorétique non lavé. This being dissolved in hot water, falls to the bottom after it is cold; and after decantation is known, when dry, by the name of diaphoretic antimony. This preparation excites animal perspiration, and is a good sudorific. The same preparation may be more expeditiously made by one part of antimony with two and a half of nitre, mixed together and deflagrated: the residue of which is the mere calx of antimony, void of all emetic power.

20. And if the detonation be performed in a tubulated retort, having a large receiver, containing some water adapted to it, both a clystus of antimony and the antimonial flowers may be obtained at the same time, as Neumann affirms.

21. When nitre is deflagrated with antimony over the fire, the alkaline basis of the nitre unites with the calx of the semimetal, which may be separated by an acid, and is called materia perlata. See farther the article Antimony; also Metallurgy, Part II. sect. ix.

IV. Arsenic. In its metallic form, is,

a. Nearly of the same colour as lead, but brittle, and changes sooner its shining colour in the air, first to yellow, and afterwards to black.

b. It appears laminated in its fractures, or where broken.

c. Is very volatile in the fire, burns with a small flame, and gives a very disagreeable smell like garlic.

d. It is, by reason of its volatility, very difficult to be reduced, unless it is mixed with other metals: However, a regulus may be got from the white arsenic, if it is quickly melted with equal parts of potashes and soap; but this regulus contains generally some cobalt, most of the white arsenic being produced from the cobalt ores during their calcination. The white arsenic, mixed with a phlogiston, sublimes likewise into octahedral crystals of a metallic appearance, whose specific gravity is $8.358$.

e. The calx of arsenic, which always, on account of its volatility, must be got as a sublimation, is white, and easily melts to a glaas, whose specific gravity is $5.000$. When sulphur is blended in this calx, it becomes of a yellow, orange, or red colour; and according to the degrees of colour is called orpiment or yellow arsenic; sandarach, realgar, or red arsenic; and also rubinus arsenici.

f. This calx and glaas are dissoluble in water, and in all liquids; though not in all with the same facility. In this circumstance arsenic resembles the salts; for which reason it also might be ranked in that class.

g. The regulus of arsenic dissolves in spirit of nitre; but as it is very difficult to have it perfectly free from other metals, it is yet very little examined in various menitria.

h. It is poisonous, especially in form of a pure calx or glaas: But probably it is less dangerous when mixed with sulphur, since it is proved by experience, that the men at mineral works are not so much affected by the smoke of this mixture as by the smoke of lead, and that some nations make use of the red arsenic in small doses as a medicine.

i. It unites with all metals, and is likewise much used by nature itself to dissolve, or, as we term it, to mineralise, the metals, to which its volatility and dissolubility in water must greatly contribute. It is likewise most generally mixed with sulphur.

k. It absorbs or expels the phlogiston, which has coloured glaases, if mixed with them in the fire.

Arsenic is found,

[1.] Native; called Scherbencobolt and Fliegenstein by the Germans.

It is of a lead colour when fresh broken, and may be cut with a knife, like black lead, but soon blackens in the air. It burns with a small flame, and goes off in smoke.

A. Solid and tellaceous; Scherbencobolt.

B. Scaly.

C. Friable and porous; Fliegenstein.

(1.) With shining fissures.

This is by some called Spigel cobalt.

[2.] In form of a calx.

A. Pure, or free from heterogeneous substances.

1. Loose or powdery.

2. Indurated, or hardened. This is found in form of white semi-transparent crystals.

B. Mixed.

a. With sulphur.

1. Hardened.

a. Yellow. Orpiment; Auripigmentum.

b. Red. Native realgar, or sandarach.

b. With the calx of tin, in the tin-grains.

c. With sulphur and silver; in the rothgulden or red silver ore.

d. With calx of lead, in the lead-spar.

e. With calx of cobalt, in the efflorescence of cobalt.

R 2

[2.] Mi- [3.] Mineralised.

A. With sulphur and iron. Arsenical pyrites or marcasite. These kinds in Cornwall are called silvery or white mundics and plate mundics.

This alone produces red arsenic when calcined. It is of a deeper colour than the following.

B. With iron only. This differs with regard to its particles; being,

1. Steel-grained. 2. Coarse-grained. 3. Crystallised.

a. In an octahedral figure. This is the most common kind.

b. Prismatical. The sulphureous marcasite is added to this kind when red arsenic is to be made; but in Sweden it is scarcer than the sulphureous arsenical pyrites.

C. With cobalt, almost in all cobalt ores.

D. With silver. See under Silver, Copper, and Antimony, supra.

E. With copper.

F. With antimony.

For the Uses of Arsenic, see the detached article Arsenic, and Chemistry Index; also Metallurgy, Part II. Sect. xiii. and Part III. Sect. viii.

V. Cobalt.

This semimetal is,

a. Of a whitish grey colour, nearly as fine-tempered steel.

b. Is hard and brittle, and of a fine-grained texture; hence it is of a dusky, or not shining appearance.

c. Its specific gravity to water is 6000 to 1000.

d. It is fixed in the fire, and becomes black by calcination; it then gives to glass a blue colour, inclining a little to violet, which colour, of all others, is the most fixed in fire.

e. The concentrated oil of vitriol, aquafortis, and aqua-regia, dissolve it; and the solutions become red. The cobalt calx is likewise dissolved by the same menstrua, and also by the volatile alkali and the spirit of sea salt.

f. When united with the calx of arsenic in a slow (not a brisk) calcining heat, it assumes a red colour: the same colour is naturally produced by way of efflorescence, and is then called the bloom or flowers of cobalt. When cobalt and arsenic are melted together in an open fire, they produce a blue flame.

g. It does not amalgamate with quicksilver by any means hitherto known.

h. Nor does it mix with bismuth, when melted with it, without addition of some medium to promote their union.

[1.] Native cobalt. Cobalt with arsenic and iron in a metallic form.

Pure native cobalt has not yet been found: that which passes for such, according to Kirwan, is mineralised by arsenic. Bergman, however, in his Sciagraphia, has entered this prevalent ore under the denomination of native cobalt: and certain it is, that among all the cobaltic ores, this is the nearest to the native state of this semimetal. It always contains a small quantity of iron, besides the arsenic, by which it is mineralised.

This is of a dim colour when broken, and not unlike steel. It is found,

a. Steel-grained, from Loos in the parish of Farila in the province of Helsingeland, and Schneeberg in Saxony.

b. Fine-grained, from Loos.

c. Coarse-grained.

d. Crystallised:

1. In a dendritical or arboreal form; 2. Polyhedral, with shining surfaces; 3. In radiated nodules.

[2.] Calciform cobalt. Cobalt is most commonly found in the earth mixed with iron.

A. In form of a calx.

1.) With iron without arsenic.

a. Loose or friable; cobalt ochre. This is black, and resembles the artificial zaffire.

b. Indurated: Minera cobalti vitrea. The schlocken or flag cobalt. This is likewise of a black colour, but of a glassy texture, and seems to have lost that substance which mineralised it, by being decayed or weathered.

2.) With arsenical acid; cobalt-blut, Germ. Ochra cobalti rubra; bloom, flowers, or efflorescence of cobalt.

a. Loose or friable. This is often found of a red colour like other earths, spread very thin on the cobalt ores; and is, when of a pale colour, erroneously called flowers of bismuth.

b. Indurated. This is commonly crystallised in form of deep red semitransparent rays or radiations: It is found at Schneeberg in Saxony.

B. Mineralised.

1.) With sulphurated iron.

This ore is of a light colour, nearly resembling tin or silver. It is found crystallised in a polygonal form.

a. Of a flaky texture.

b. Coarse-grained.

This ore is found in Bastnäsgrufva at Raddarshyttan in Westmanland, and discovers not the least mark of arsenic. The coarse-grained becomes flimsy in the fire, and sticks to the flinting hook during the calcination in the same manner as many regules do: It is a kind of regule prepared by nature. Both these give a beautiful colour.

2.) With sulphur, arsenic, and iron. This resembles the arsenicated cobalt ore, being only rather of a whiter or lighter colour. It is found,

a. Coarse-grained.

b. Crystallised;

1. In a polygonal figure, with shining surfaces, or glanzcobalt. It is partly of a white or light colour, and partly of a somewhat reddish yellow.

3.) With VI. Nickel; Niccolum. This is the latest discovered semimetal. It was first described by its discoverer Mr Cronstedt, in the Acts of the Royal Academy of Sciences at Stockholm for the years 1751 and 1754, where it is said to have the following qualities:

1. It is of a white colour, which, however, inclines somewhat to red. 2. Of a solid texture, and shining in its fractures. 3. Its specific gravity to water is as 8,500 to 1000. 4. It is pretty fixed in the fire; but, together with the sulphur and arsenic, with which its ore abounds, it is so far volatile as to rise in form of hairs and branches, if in the calcination it is left without being stirred. 5. It calcines to a green calx. 6. The calx is not very fusible, but, however, tinged glas of a transparent reddish-brown or jacinth colour. 7. It dissolves in aquafortis, aqua-regia, and the spirit of sea-salt; but more difficultly in the vitriolic acid, tinging all these solutions of a deep green colour. Its vitriol is of the same colour; but the colcotar of this vitriol, as well as the precipitates from the solutions, become by calcination of a light green colour. 8. These precipitates are dissolved by the spirit of sal ammoniac, and the solution has a blue colour; but being evaporated, and the sediment reduced, there is no copper, but a nickel regulus is produced. 9. It has a strong attraction to sulphur; so that when its calx is mixed with it, and put on a scorifying test under the muffel, it forms with the sulphur a regulus; this regulus resembles the yellow steel-grained copper-ores, and is hard and shining in its convex surface. 10. It unites with all the metals, except quicksilver and silver. When the nickel regulus is melted with the latter, it only adheres close to it, both the metals lying near one another on the same plane; but they are easily separated with a hammer. Cobalt has the strongest attraction to nickel, after that to iron, and then to arsenic. The two former cannot be separated from one another but by their scoriafication; which is easily done, since,

11. This semimetal retains its phlogiston a long time in the fire, and its calx is reduced by the help of a very small portion of inflammable matter; it requires, however, a red heat before it can be brought into fusion, and melts a little sooner, or almost as soon, as copper or gold, consequently sooner than iron.

Nickel is found,

A. Native. This is mentioned by Mr Rinman to have been lately met with in a mine of cobalt in Hesse.

It is very heavy, and of a liver colour, that is, dark red. When pulverised and roasted under a muffel, it forms green excrescences, and smokes; but its smoke has no particular smell; and no sublimate, whether sulphureous or arsenical, can be caught. It is soluble in acids, and the solution is green; but a polished iron plate discovers no copper.

B. In form of a calx. Nickel ochre, aerated nickel.

1. Mixed with the calx of iron. This is green, and is found in form of flowers on kupfer-nickel.

C. Mineralised.

1. With sulphurated and arsenicated iron and cobalt; Kupfernickel. This is of a reddish yellow colour; and is found, a. Of a flaky texture. b. Fine-grained; and c. Scaly. These two are often from their colour confounded with the liver-coloured marcalite.

2. With the acid of vitriol. This is of a beautiful green colour, and may be extracted out of the nickel ochre, or efflorescence of the Kupfernickel.

For a full account of this semimetal, see the article Nickel, and Chemistry-Index.

VII. Manganese. Manganium.

The ores of this kind are in Swedish called brunsten; in Latin sydereus, or magnesia nigrae, in order to distinguish them from the magnesia alba officinalis; and in French manganèse, &c.

1. Manganese consists of a substance which gives a colour both to glasses and to the solutions of salts, or, which is the same thing, both to dry and to liquid menstrua, viz.

a. Borax, which has dissolved manganese in the fire, becomes transparent, of a reddish brown or hyacinth colour.

b. The microcosmic salt becomes transparent with it, of a crimson colour, and moulders in the air.

c. With the fixed alkali, in compositions of glass, it becomes violet; but if a great quantity of manganese is added, the glass is in thick lumps, and looks black.

d. When scorified with lead, the glass obtains a reddish brown colour.

e. The lixivium of deslagrated manganese is of a deep red colour.

2. It deflagrates with nitre, which is a proof that it contains some phlogiston.

3. When reckoned to be light, it weighs as much as an iron ore of the same texture.

4. When melted together with vitreous compositions, it ferments during the solution; but it ferments in a still greater degree when it is melted with the microcosmic salt.

5. It does not excite any effervescence with the nitrous acid; aqua-regia, however, extracts the colour out of the black manganese, and dissolves likewise a great portion of it, which by means of an alkali is precipitated to a white powder.

6. Such 6. Such colours as are communicated to glasses by manganese, are easily destroyed by the calx of arsenic or tin; they also vanish of themselves in the fire.

7. It is commonly of a loose texture, so as to colour the fingers like foot, though it is of a metallic appearance when broken.

Manganese is found,

[1.] Native; of the discovery and qualities of which, an account is given under the article Manganese in its alphabetical order. See also Chemistry-Index.

[2.] Calciform.

A. Loose and friable. a. Black; which seems to be weathered or decayed particles of the indurated kind.

B. Indurated. 1.) Pore, in form of balls, whose texture consists of concentric fibres. Pura sphaerica radis concentrae. a. White; very scarce. 2.) Mixed with a small quantity of iron. a. Black manganese, with a metallic brightness. This is the most common kind, and is employed at the glass-houses and by the potters. It is found, 1. Solid, of a flaggy texture. 2. Steel-grained. 3. Radiated. 4. Crystallised, in form of coherent hemispheres.

VIII. Molybdena.

A. Lamellar and shining, its colour similar to that of the potter's lead-ore.

This substance resembles plumbago or black-lead; and has long been confounded with it, even by Cronstedt. But it possesses very different properties; in particular,

1. Its laminae are larger, brighter; and, when thin, slightly flexible. They are of an hexagonal figure. 2. It is of a lead colour, and does not strike fire with hard steel. 3. Its specific gravity is = 4.569, according to Kirwan; and 4.7385, according to Briffon. 4. When rubbed on white paper, it leaves traces of a dark brown or bluish colour, as the plumbago or black lead does; but they are rather of an argentine gloo; by which circumstance the molybdena, according to Dr d'Arcet, may be easily distinguished from black-lead, as the traces made by this last are of less brilliant, and of a deeper tinge. 5. In an open fire, it is almost entirely volatile and insensible. Microcosmic salt or borax scarcely affect it; but it is acted upon with much effervescence by mineral alkali, and forms with it a reddish mass, which smells of sulphur. 6. It consists of an acid of peculiar nature (see Chemistry-Index) united to sulphur. A small proportion of iron is commonly found in it, but this seems merely fortuitous: 100 parts of molybdena contain about 45 of this acid and 55 of sulphur.

7. It is decomposed either by detonation with nitre, or by solution in nitrous acid.

8. This acid is soluble in 570 times its weight of water in the temperature of 60°; the solution reddens that of litmus, precipitates sulphur from the solution of liver of sulphur, &c. The specific gravity of the dry acid is 3.460.

9. This acid is precipitable from its solution in water by the Prussian alkali, and also by tincture of galls: the precipitate is reddish brown.

10. If this acid be distilled with three times its weight of sulphur, it reproduces molybdena.

11. The solution of this acid in water unites to fixed alkalies, and forms crystallisable salts; as it also does with calcareous earth, magnesia, and argil: these last combinations are difficultly soluble. It acts also on the base metals, and with them affumes a bluish colour.

12. This solution precipitates silver, mercury, or lead, from the nitrous acid, and lead from the marine, but not mercury.

13. It also precipitates barytes from the nitrous and marine acids, but no other earth. Molybdenous barofelenite is soluble in cold water.

14. This acid is itself soluble in the vitriolic acid by the affluence of heat; and the solution is blue when cold, though colourless while hot; it is also soluble in the marine acid, but not in the nitrous.

15. Molybdena tartar and ammoniac precipitate all metals from their solutions by a double affinity. Gold, sublimate corrosive, zinc, and manganese, are precipitated white; iron or tin, from the marine acid, brown; cobalt, red; copper, blue; alum and calcareous earth, white.

16. This acid has been lately reduced by Mr Hielm; but the properties of the regulus thus obtained are not yet published.

17. Mr Pelletier obtained also the regulus or molybdena, by mixing its powder with oil into a paste, and exposing it with powdered charcoal in a crucible to a very violent fire for two hours. See Chemistry-Index, n° 14, 97.

18. This semi-metal being urged by a strong fire for an hour, produces a kind of silvery flowers, like those of antimony.

19. Molybdena is said to be soluble in melted sulphur; which seems highly probable, as sulphur is one of its component parts.

See farther the article Molybdena, and Chemistry-Index.

IX. Wolfram. Wolfranum, Stuma Lupi, Lat. See the detached article Wolfram.

This mineral has the appearance of manganese, blended with a small quantity of iron and tin.

1. With coarse fibres. a. Of an iron-colour, from Altenberg in Saxony. This gives to the glass compositions, and also to borax and the microcosmic salt, an opaque whitish yellow colour, which at last vanishes.

X. Siderite. See those words in the order of the alphabet.

XI. Saturnite. THOUGH the Saxa, and fossils commonly called Petrifications, cannot, in strictness, be ranked in a mineral system, for the reasons formerly given; yet as these bodies, especially the latter, occupy so considerable a place in most mineral collections, and the former must necessarily be taken notice of by the miners in the observations they make in subterranean geography, it appeared proper to subjoin them in such an order as might answer the purpose for which they are regarded by miners and mineralogists.

Order I. Saxa. Petra.

These may be divided into two kinds.

1. Compound Saxa, are stones whose particles, consisting of different substances, are so exactly fitted and joined together, that no empty space, or even cement, can be perceived between them; which seems to indicate, that some, if not all, of these substances have been lost at the instant of their union.

2. Conglutinated stones, are stones whose particles have been united by some cementitious substance, which, however, is seldom perceivable, and which often has not been sufficient to fill every space between the particles: in this case the particles seem to have been hard, worn off, and in loose, single, unfigured pieces, before they were united.

I. Compound Saxa.

A. Ophites. Scaly limestone with kernels or bits of serpentine stone in it.

1. Kolmord marble. It is white and green. 2. Serpentino antico, is white, with round pieces of black fleatites in it. This must not be confounded with the serpentino verde antico. 3. The Haraldso marble. White, with quadrangular pieces of a black fleatites. 4. The marmor pozzerona di Genova. Dark green marble, with white veins. This kind receives its fine polish and appearance from the serpentine stone.

B. Stellifer or geleifstein. Granitello.

1. Of distinct particles. In some of these the quartzose particles predominate, and in others the micaceous: in the last case it is commonly flatly, and easy to split.

2. Of particles which are wrapped up in one another.

a. Whitish grey. b. Greenish. c. Reddish.

C. Norrka. Murlsten of the Swedes. Saxum Appendix.

compositum mica, quartzo, et granato.

1. With distinct garnets or shirl.

a. Light grey. b. Dark grey. c. Dark grey, with prismatical, radiated, or fibrous cockle or shirl.

2. With kernels of garnet-stone.

a. Of pale red garnet stone.

The first of this kind, whose flatly strata makes it commonly easy to be split, is employed for mill-stones, which may without difficulty be accomplished, if sand is first ground with them; because the sand wearing away the micaceous particles on the surfaces, and leaving the garnets predominant, renders the stone fitter for grinding the corn.

D. The whetstone, Cot. Saxum compositum mica, quartzo, et forsan argilla maritimi in non-nullis speciesbus.

1. Of coarse particles.

a. White. b. Light grey.

2. Of fine particles.

a. Liver-brown colour. b. Blackish grey. c. Light grey. d. Black. The table-plate, or that kind used for large tables and for school plates.

3. Of very minute and closely combined particles. The Turkey-stone*. This is of an olive colour, and seems to be the finest mix-(p.86.) ture of the first species of this genus. The col. t.) best of this sort come from the Levant, and are pretty dear. The whetstone kinds, when they split easily and in thin plates, are very fit to cover houses with, though most of them are without those properties.

F. Porphyry; Porphyrites. Italorum porfido. Saxum compositum jalpide et feltspato, interdum mica et basalt (v). See the article Porphyry.

a. Its colour is green, with light-green feltspat, Serpentino verde antico. It is said to have been brought from Egypt to Rome, from which latter place the specimens of it now come.

b. Deep red, with white feltspat. c. Black, with white and red feltspat. d. Reddish brown, with light red and white feltspat. e. Dark grey, with white grains of feltspat also. The dark red porphyry has been most employed for ornaments in building; yet it is not the only one known by the name

(d) Great part of the hill of Bineves in Lochaber is composed of a kind of porphyry. It is remarkably fine, beautiful, and of an elegant reddish colour; "in which (says Mr Williams) the pale rose, the blush, and the yellowish white colours, are finely blended and shaded through the body of the stone; which is of a jelly-like texture, and is undoubtedly one of the finest and most elegant stones in the world. On this hill also is found a kind of porphyry of a greenish colour, with a tinge of brownish red. It is smooth, compact, and heavy; of a close uniform texture, but has no brightness when broken. It has angular specks in it of a white quartzy substance." name of porfido, the Italians applying the same name also to the black kind.

G. The trapp of the Swedes. Saxum compositum jaspide martialis mollis, seu argilla martialis indurata. See the article TRAPP.

This kind of stone sometimes constitutes or forms whole mountains; as, for example, the mountain called Hummelberg in the province of Wettergottland, and at Drammen in Norway; but it is oftener found in form of veins in mountains of another kind, running commonly in a serpentine manner, contrary or across to the direction of the rock itself. It is not homogeneous, as may be plainly seen at those places where it is pressed close together; but where it is pressed close, it seems to be perfectly free from heterogeneous substances.—When this kind is very coarse, it is interspersed with feltspat; but it is not known if the finer sorts likewise contain any of it. Besides this, there are also some fibrous particles in it, and something that resembles a calcareous spar; this, however, does not ferment with acids, but melts as easy as the stone itself, which becomes a black solid glass in the fire. By calcination it becomes red, and yields in assays 12 or more per cent. of iron. No other sort of ore is to be found in it, unless now and then somewhat merely superficial lies in its fissures; for this stone is commonly, even to a great depth in the rock, cracked in acute angles, or in form of large rhomboidal dice. It is employed at the glass-houses, and added to the composition of which bottles are made. In the air it decays a little, leaving a powder of a brown colour; it cracks commonly in the fire, and becomes reddish brown if made red-hot.

It is found,

1. Of coarse chaffy particles. a. Dark grey. b. Black.

2. Coarse-grained. a. Dark grey. b. Reddish.

c. Deep brown.

3. Of fine imperceptible particles. a. Black. The touchstone; Lapis lydius. b. Bluish. c. Grey. d. Reddish.

The black variety (3.a) is sometimes found so compact and hard, as to take a polish like the black agate; it melts, however, in the fire to a black glass; and is, when calcined, attracted by the load-stone.

H. Amygdaloides. The carpolithi or fruit-stone rocks of the Germans.

It is a martial jasper, in which elliptical kernels of calcareous spar and serpentine stone are included.

a. Red, with kernels of white limestone, and of a green fleatites. This is of a particular appearance, and when calcined is attracted by the loadstone; it decays pretty much in the air, and has some affinity with the trapp, and also with the porphyry. There are sometimes found pieces of native copper in this stone.

I. The granjen of the Swedes.

Its basis is hornblende, interspersed with mica. It is of a dark green colour, and in Smoland is employed in the iron furnaces as a flux to the bog-ore.

K. The granite. Saxum compositum feltspata, mica et quarizo, quibus accidentaliter interdum hornblende fleatites, granatus et basaltes immixti sunt. Its principal constituent parts are felt-spat, or rhombic quartz, mica, and quartz. See the article GRANITE.

It is found,

(1.) Loofe or friable. This is used at the Swedish brass-works to cast the brass in, and comes from France.

(2.) Hard and compact. a. Red. 1. Fine-grained; 2. Coarse-grained. b. Grey, with many and various colours (E).

(e) Mr Wiegleb has analysed a species of green granite found in Saxony. The crystals are heaped together, and form very compact layers; the colour sometimes an olive green, sometimes resembling a pear, and sometimes of a reddish brown; some of them being perfectly transparent, and others nearly so. According to Mr Warren, they contain 25 per cent. of iron; whence they have been called green ore of iron. An ounce of these crystals heated red hot in a crucible lost two grains in weight, and became of the colour of honey. The remainder was put into a retort, and distilled with marine acid, with which it evidently effervesced. The residuum was lixiviated with distilled water, fresh muriatic acid added, and the distillation and lixiviation repeated. The iron precipitated from this lixivium, and reduced partly to its metallic state, weighed two drachms. M. Wiegleb concludes, that the specimen contained two drams 26½ grains of lime. From further experiments he concludes, that 100 parts of the substance contained 36.5 of siliceous earth; lime 30.8; iron 28.7; and water and fixed air 4.0.

Scotland is remarkable for a great number of excellent granites, little or nothing inferior to porphyry. Of these the following kinds are mentioned by Mr Williams.

1. The grey granite, or moor-stone as it is called in Cornwall, is very common in this country. In some places it shows no marks of strata; and in others it is disposed in thick unwieldy irregular beds, which are commonly broken transversely into huge masses or blocks of various sizes and shapes. There is a great variety in this kind of stones; some of them differing but little in appearance from basaltes; others are composed of almost equal parts of black and white grains, about the size of small peas, whence it is called peasy-whin by the Part II.

Appendix II. Conglutinated Saxa.

SAXA.

A. Of larger or broken pieces of stones of the same kinds conglutinated together. Breccia.

1. Of limestone cemented by lime.

a. Calcareous breccia; the marmi brecciati of the Italians.

When these kinds have fine colours, they are polished and employed for ornaments in architecture and other economical uses.

b. The lumachella of the Italians, or shell marbles. These are a compound of shells and corals, which are petrified or changed into lime, and conglutinated with a calcareous substance. When they have many colours, they

the common people. In Galloway and other places it frequently has a longitudinal grain, as if the component parts had been all moved one way by a gentle flow of water. When this kind of granite begins to undergo a spontaneous decomposition by exposure to the atmosphere, we observe that it is composed of pretty large grains of the figures of cubes, rhomboids, &c., some of them so large as to deserve the name of fragments; and the largest of these are always of quartz or feldspar, and talc.

2. Reddish granite, of a gellied texture, which, Mr Williams says, is one of the finest and most elegant stones in the world. The mountains of Bineves, he says, are principally composed of this stone; and it is found in great abundance in many other parts of Scotland, but he never saw it exhibit any marks of stratification.

3. The fine reddish granites, in which several fine shades of colours are blended together, not spread out in tints as in the former. Neither this nor the former are stratified: "On the contrary (says our author), both exhibit such a degree of uniform regularity, that in some places there is no difference between a stone and a mountain, excepting only in magnitude; as many mountains of granite are nothing more than one regularly uniform mass throughout, in which not the least mark of a bed is to be seen, nor hardly a crack or fissure, unless it be at the edge of some precipice or declivity. These two varieties of elegant red granite are met with in the Highlands and Lowlands of Scotland, in Galloway, and many other places. We often find masses of talc so large in this second variety, that some of them may be called fragments, not disposed in any order, but higgledy-piggledy through the body of the stone.

4. Stratified reddish granite, resembling the third in colour and quality, but not always quite so pure or free from admixture of other stony matter of a different quality. This variety frequently contains larger and smaller fragments of fine laminated talc. Mr Williams, however, has seen this kind of granite disposed in pretty regular strata in the shires of Moray and Nairn, and other parts of Scotland.

5. Granite of a white and whitish colour, generally of a granulated texture, containing a great quantity of mica, or small-leaved talc, and the grains of quartz sometimes large and angular. This variety is subject to spontaneous decomposition; part frequently dissolves and falls into lakes, in such an exceedingly fine and attenuated state, that it does not sink in the water. "I have found (says Mr Williams) this substance in many places where water had been accidentally drained off, resembling fine shell marle, only much lighter. When thoroughly dry, it is the lightest fossil substance I ever handled; and, when blanched with rain, it is as white as snow. This variety of granite is either not stratified, or exhibits thick irregular beds. It frequently contains a considerable quantity of talc, in masses and scales too large to be called mica."

Our author is of opinion, that this fine white substance produced from the decomposition of the granite, is the true kaolin of the Chinese, one of the component parts of porcelain ware. "The authors of the History of China (says he) informs us, that the fine porcelain ware is composed of two different fossil substances, called by them petuntse and kaolin. We are further told, that the petuntse is a fine white vitreous stone, compact and ponderous, and of considerable brightness in the inside when broken, which they grind to a fine powder; and that the kaolin is not a stone, but a fine white earthy substance, not vitreous, at least not in the heat of a common potter's furnace; that they mix the kaolin and the flour of the petuntse together, and form a paste of this mixture, which they mould into all sorts of porcelain vessels. Now, from the best accounts of this matter which I have been able to obtain, after a good deal of search and inquiry, it appears to me, that the sediment which I have mentioned above is the true kaolin; and that as the fine white glassy quartz, which is found in irregular masses, and in irregular discontinuous veins or ribs, in some of the rocks of schistus, is the true petuntse; and if this observation is really true, it deserves to be remarked, that Scotland is as well furnished with the best materials for making fine porcelain as most countries in the world. The species of quartz which I suppose to be petuntse is of a pure fine uniform glassy texture, semitransparent, and of a pure snowy whiteness. A broken piece of this stone, and a newly broken piece of fine porcelain, are very like one another. There is a great quantity of petuntse, or pure white quartz, in many places of Scotland, particularly in the north and Highlands. There is a considerable quantity of it upon the shore and washed by the tide between Banff and Cullen, generally in pretty large masses in rocks of bluish schistus; and to the best of my memory it is very fine of the kind. There is also a considerable quantity of it in discontinuous ribs and masses, in rocks of blue schist, about three or four miles north of Calendar in Montteil, upon the side of the high road which runs parallel to Lochleodunich, which I think also very fine. In some places this sort of quartz is tinged with a flesh colour from the neighbourhood of iron, which renders it unfit for porcelain; but there is plenty to be found of a pure white in almost all parts of Scotland, without any mineral tinge whatever. The kaolin is perhaps as plentiful in Scotland as the petuntse, there being many extensive lakes easily drained, which contain a considerable depth of it; and moreover, it is to be found in many places that have been lakes, which are now laid dry by accident. There is a quantity of kaolin about they are called marbles, and employed for the same purposes as the preceding (f).

2. Of kernels of jasper cemented by a jaspery substance. Brecia jaspidea. Diaspro brecciato of the Italians.

Of this kind specimens from Italy are seen in collections. A coarse jasper breccia is said to be found not far from Frejus in Provence in France.

3. Of siliceous pebbles, cemented by a jaspery substance,

100 yards below the high road upon the south side of a bridge, about a mile and a half or two miles south of the inn of Aviemore in the Highlands. It lies beneath a stratum of peat bog, in a place which has been a lake, but is now drained by the river Spey cutting through one side of the mound which formed the lake.—There is more than one stratum of the kaolin in this place, and some of it is exceeding white, especially when blanched by the rain; and there is a white granite rock up the rivulet, at some distance above the bridge, the decomposition and dissolution of which is supposed to produce this fine and curious sediment. Several lakes in the Highlands of Scotland are nearly full of kaolin. One of them is situated in the country of Stratherrick in Inverness-shire, less than a mile north of the public road, and upon the west side of the farm of Drimin. It is a pretty long lake, and there is a considerable depth of kaolin in it, which may be drained at a moderate expense; and, if I remember well, the granite rocks which surround it are pretty white and fine. If the kaolin originates from coloured granite, it is good for nothing, especially if it contains the least tinge of iron, because this will discolour and spoil the beauty of the porcelain; but wherever white granite is found composed of quartz, feldspar, and mica, without any admixture of shirl, and especially iron, the kaolin should be diligently sought after in that neighbourhood. Lochdoon, in Galloway, is said to contain a great quantity of kaolin. It was drained some years ago on the supposition of its containing shell marle; but on trying the substance contained in it, it was found not to be marle but kaolin. These substances may easily be mistaken for one another at first; but they are easily distinguished by trying them with acids, the marle readily effervescing with the weakest, and the kaolin not at all with the strongest acid liquors."

6. Grey composite granite is a very beautiful stone, and when broken looks as if composed of small fragments of various sizes and shapes, not unlike calve's-head jelly. When polished, the fragments appear as if set or inlaid in a fine pellucid or water-coloured matter. There is a single stratum of very curious composite granite, a little to the west of Lossiemouth, in the county of Moray, in Scotland of about six or eight feet thick. It is composed chiefly of grains and fragments of various bright and elegant colours, most of which are as large as peas and beans, all fine, hard, and semipellucid; there is about an eighth part of good lead ore in the composition of this stone, of the kind commonly called potter's ore; and it is likewise remarkable, that there is no other granite in that neighbourhood but this single stratum, all the strata above and below it being mostly a coarse, imperfect, grey sand-stone.

7. Granite of a loose friable texture, subject to spontaneous decomposition, and reduction to granite gravel. There is a remarkable rock of this kind near the Queen's ferry in Scotland, on the road to Edinburgh, which appears in prodigious thick irregular strata. This rock seems to be composed chiefly of quartz, shirl, and some iron; and produces excellent materials for the high roads.

8. In many parts of the north of Scotland, in the Highlands, and in Galloway, there is found an excellent species of grey granite, composed chiefly of red and black coloured grains. This is a fine and very durable stone, very fit for all kinds of architecture.

In speaking of these stones, Mr Williams observes, that the finer and most elegant red granites, and the finest granite-like porphyries, so much resemble one another, that he does not attempt to distinguish them; and Scotland is remarkable for a great number and variety of them. "The elegant reddish granite of Bineves, near Fort William (says he), is perhaps the best and most beautiful in the world; and there is enough of it to serve all the kingdoms on earth, though they were all as fond of granite as ancient Egypt. There are extensive rocks of red granite upon the sea-shore to the west of the ferry of Ballachulish in Appin, and likewise at Strontian, as well as many other parts of Argyleshire. I have seen beautiful red granite by the road side, near Dingwall, and in several other parts of the north of Scotland, which had been blown to pieces with gunpowder, and tuned off the fields. There are extensive rocks of reddish granite about Peterhead and Slains, and both of red and grey granite in the neighbourhood of Aberdeen. The hill of Cruffel in Galloway, and several lower hills and extensive rocks in that neighbourhood, are of red and grey granite, where there are great varieties of that stone, and many of them excellent. Upon the sea shore near Kinneodore, west of Lossiemouth, in Moray, there is a bed of stone about eight feet thick, which I think should be called a composite granite. It is composed of large grains, or rather small pieces of bright and beautiful stones of many different colours; and all the stony parts are exceedingly hard, and fit to receive the highest polish. About a fifth or eighth part of it also consists of lead ore, of that species called potter's ore. The separate stony parts composing this stratum are all hard, fine, solid, and capable of the most brilliant polish; and if solid blocks can be raised free from all cracks and blemishes, I imagine, from the beauty and variety of colours of the stony part, and the quantity of bright lead ore which is blended through the composition and body of the stone, that this would be a very curious and beautiful stone when polished."

(f) The stones called Ludi Helmontii or Paracelsi, have some similarity in their form to the breccia, a.b.; for they are composed of various lumps of a marly whitish-brown matter, separated into a great number of polygonous compartments, of various sizes, formed of a whitish-yellow crust of a red calcareous spar, sometimes... substance, or something like it. The plum-pudding stone of the English; *Brecia silicea*. Its basis, which at the same time is the cement, is yellow; wherein are contained single flinty or agaty pebbles, of a grey colour or variegated. This is of a very elegant appearance when cut and polished; it is found in England and Scotland (e).

4. Of quartzose kernels combined with an unknown cement. *Brecia quartzosa*.

5. Of kernels of several different kinds of stones. *Brecia saxo/a*.

a. Of kernels of porphyry, cemented by a porphyry or coarse jaspery substance; *Brecia porphyrea*.

b. Of kernels of several saxa; *Brecia indeterminata*.

c. Of conglutinated kernels of sandstone; *Brecia arenacea*. This kind consists of sandstone kernels, which have been combined a second time together.

The above mentioned brecciae of themselves must demand the distinctions here made between, but which perhaps may seem to be carried too far,

times pyritous, which often rise a little above the external surface, and inclose each of them on the inside. According to Bomare, the *ludus flottatus helmontii*, found in the county of Kent, is covered with a kind of striated selenite resembling the zeolite. They are for the most part of a globular figure, seldom flat, but often convex on the outside; and sometimes with a concave surface.

According to Wallerius, the *ludus helmontii* loses by calcination about half of its weight; and, on being urged by fire, is melted into a black glassy slag. It effervesces strongly with aqua-fortis, and this solution is of a yellow colour. But what seems very extraordinary, by adding to it some oil of tartar per deliquium, bubbles are produced, from which a great number of slender black threads or filaments are produced, sticking like a cobweb to the sides and bottom of the vessel.

These stones are found quite separate by themselves, as well as various stalagmites and crustaceous bodies, on the strata of argillaceous earth, in various parts of Europe, chiefly in Lorraine, Italy, England (in the counties of Middlesex and Kent), and elsewhere.

Wallerius ranges the *ludus helmontii* among the *tophi*, in the Spec. 425, of his System of Mineralogy. Paracelsus had attributed to these stones a lithontriptic power, and Dr Grew says that they are diuretic; but there is not the least proof of their really possessing such qualities.

(g) The breccia stratum, or plum pudding rock, exhibits a singular appearance as it lies in the ground; being composed of water-rounded stones of all qualities and of all sizes, from small gravel up to large rounded stones of several hundreds weight each; the interstices being filled up with lime and sand. It frequently also contains lime and iron. Sometimes it exhibits a grotesque and formidable appearance; containing many large bullets of various sizes and shapes, without any marks of regular stratification, but looking like one vast mass of bullets of unequal thickness; and in this manner frequently swelled to the size of a considerable mountain. It is frequently cemented very strongly together; so that parts of the hills composed of it will frequently overhang in dreadful precipices, less apt to break off than other rocks in the same situation; one reason for which, besides the strength of the cement, is, that the breccia, when composed of bullets, is less subject to fissures and cutters than other rocks; being frequently found in one solid mass of great extent and thickness. Some of the plum pudding rocks are made up of smaller parts, coming near to the size of coarse gravel. It is evident, however, that all the parts of the breccia, whether coarse or fine, have been rounded by agitation in water, as the rocks differ nothing in appearance from the coarser and finer gravel found upon the beach of the sea, excepting only that the parts are strongly cemented together in the rocks, and are loose upon the shores of the ocean.

Some of the breccia is composed of finely rounded stones of various and beautiful colours, about the size of plums or nuts, all very hard and fine. Were this species sawed and polished, it would appear as beautiful and elegant as any stone in Europe; much resembling mosaic work in small patterns.

In general, the breccia is regularly stratified or not according to the size of the component parts of the stone. Such rocks as are composed of round gravel and small bullets are generally very regular in their stratification, while those which contain bullets somewhat larger in size are commonly disposed in thick and coarse beds, and such rocks as are made up of the largest kind of bullets seldom show any marks of stratification at all.

Among many other places in Scotland, where breccia or pudding-stone abounds, there are extensive rocks and high cliffs of it upon the south shore at the west end of the Pentland Frith, to the westward of Thurso in Caithness, which stretch quite across the county of Caithness into Sutherland; and in Sutherland, as well as Caithness, this rock is of a rough texture, and appears in pretty high hills, deep glens, overhanging rocks, and frightful precipices, to the west of Brora, Dunrobin, and Dornoch, which gives it a grotesque and formidable appearance in that country. This range of breccia stretches also quite through Sutherland, and likewise through Ross-shire, the west side of Ferniehall, and Dingwall, where it exhibits the very same phenomena as in Sutherland and Caithness. It continues the same longitudinal line of bearing, which is nearly from north-east to south-west, quite through the highland countries of Inverness and Perthshire; and it forms considerable hills, and very high and rugged rocks, upon both sides of that beautiful piece of fresh water Loch Ness. Much of the stone here, as well as in other places in this range, is composed of large bullets; the rock is very hard and strong, and it hangs in frightful precipices upon both sides of the lake, through which rock General far; since their particles are so big and plain as to be easily known from one another. These stones are a proof both of the subversions which the mountains in many centuries have undergone, and of some hidden means which nature makes use of in thus cementing different kinds of stones together. Any certain bigness for the kernels or lumps in such compounds, before they deserve the name of breccia, cannot be determined, because that depends on a comparison which every one is at liberty to imagine. In some places, the kernels of porphyry have a diameter of six feet, while in others they are no bigger than walnuts. Sometimes they have a progressive size down to that of a fine sandstone. Most of this kind of stone is fit for ornaments, though the workmanship is very difficult and costly.

B. Conglomerated stones of granules or sands of different kinds. Sandstone; Lapis arenaceus.

In this division are reckoned those which consist of such minute particles, that all of them cannot easily be discovered by the naked eye. The greatest part, however, consist of quartz and mica; which substances are the most fit to be granulated, without being brought to a powder.

1. Cemented by clay. a. With an impure or refractory clay. This is of a loose texture; but hardens, and is very refractory in the fire. b. With common clay.

2. With lime; resembles mortar made with coarse sand. a. Consisting of transparent and greenish grains of quartz and white limestone. b. Of no visible particles. This is of a loose texture, and hardens in the air.

3. With an unknown cement. a. Loose. b. Harder. c. Compact. d. Very hard.

4. Cemented by the rust or ochre of iron. Is found in form of loose stones at several places, and ought perhaps to be reckoned among the minerals arenaceae or sand ores; at least when the martial ochre makes any considerable portion of the whole.

5. Grit-stone. This is of greater or less hardness, mostly of a grey, and sometimes of a yellowish colour; composed of a siliceous and micaceous sand, and rarely of a sparry kind, with greater or lesser particles closely compacted and united by an argillaceous cement. It gives some sparks with steel, is indissoluble for the most part in acids, and vitrifiable in a strong fire. It is used for millstones and whetstones, sometimes for filtering stones and for building. Fa-broin.

N.B. The argillaceous grit has been before described, p. 86, col. 1.

6. Elastic. A singular species of sandstone, of which a specimen was shown some years ago to the Royal Academy of Sciences at Paris by the Baron de Dietrich. It is flexible and elastic; and consists of small grains of hard quartz, that strike fire with tempered steel, together with some micaceous mixture. The elasticity seems to depend on the micaceous part, and softness of the natural gluten between both. It is said, that this elastic stone was found in Brazil, and brought to Germany by his excellency the Marquis de Lavradio.

There are also two tables of white marble, kept in the palace Borghese at Rome, which have the same property. But the sparry particles of their substance, though transparent, are rather soft; may be easily separated with the nail, and effervescence with aqua fortis; and there is also in it a little mixture of small particles of tale or mica. See Journ. de Phys. for Oct. 1784, p. 275. See also the article Marble (Elastic.)

C. Stones and ores cemented together; Minera arenaceae.

1. Of larger fragments. a. Mountain green, or viride montanum cupri, and pebbles cemented together, from Siberia. b. Potters lead-ore, with limestone, flake-kernels, and shells. c. Yellow or marcasitical copper ore, with small pebbles.

2. Of smaller pieces. a. Potter's lead-ore with a quartzose sand. b. Mountain green with sand from Siberia. c. Cobalt ore with sand. d. Martial ochre with sand.

Order II. Mineral changes, or Petrifications.

These are mineral bodies in the form of animals or vegetables, and for this reason no others belong to this order than such as have been really changed from the subjects of the other two kingdoms of nature.

I. Earthly changes; Terra larvatae.

A. Extraneous bodies changed into a lime substance, or calcareous changes; Larvae calcareae.

(1.) Loose or friable. Chalky changes; Crete larvatae.

General Wade cut a fine military road upon the south side of the lake, at a great expense of time, labour, and gunpowder. These rocks are seen stretching through the mountains of Stratherrick into Badenoch, where it forms a remarkable rock and recipice called Craigdow or the Black Rock. The same range is again seen farther towards the south-west, in several places to the south of the Black Mount, and in the country of Glenorchy in Argyleshire; and Mr Williams supposes, that the longitudinal line of this rock, so far as it has been just pointed out, is little less than 200 miles, and in some places it spreads eight or ten miles in what may be called the latitudinal line across the bearing of the rocks. Part II.

Appendix.

Petrifactions.

a. In form of vegetables. b. In form of animals. 1. Calcined or mouldered shells; Humus conchaceus. (2.) Indurated; Petrifaction calcarea. a. Changed and filled with solid limestone. 1. In form of animals. 2. In form of vegetables. b. Changed into a calcareous spar; Petrifaction calcarea spatoidea. 1. In form of animals. 2. In form of vegetables.

B. Extraneous bodies changed into a flinty substance. Siliceous changes; Larvae silicis. These are, like the flint, (1.) Indurated. a. Changed into flints. 1. Carnelians in form of shells, from the river Tomm in Siberia. 2. Agat in form of wood. Such a piece is said to be in the collection of Count Teffin. 3. Coralloids of white flint, (Millepora.) 4. Wood of yellow flint.

C. Extraneous bodies changed into clay. Argillaceous changes; Larvae argillacea. A. Loose and friable. 1. Of porcelain clay. a. In form of vegetables. A piece of white porcelain clay from Japan, with all the marks of the root of a tree, has been observed in a certain collection. b. Indurated. 1. In an unknown clay. a. In form of vegetables. Offecolla. It is said to be changed roots of the poplar tree, and not to consist of any calcareous substance. A sort of fossil ivory is said to be found, which has the properties of a clay; but it is doubtful if it has been rightly examined.

II. Saline extraneous bodies, or such as are penetrated by mineral salts. Corpora peregrina salinae. Larvae salinae.

A. With the vitriol of iron. 1. Animals. a. Human bodies have been twice found in the mine at Falun in Dalarna; the last was kept a good many years in a glass-case, but began at last to moulder and fall to pieces. 2. Vegetables. a. Turf, and b. Roots of trees. These are found in water strongly impregnated with vitriol. They do not burn with a flame, but only like coal in a strong fire; neither do they decay in the air.

III. Extraneous bodies penetrated by mineral inflammable substances, or mineral phlogiston. A. Penetrated by the substance of pit-coals. 1. Vegetables, which commonly have been woods, or appertaining to them.

a. Fully saturated. Gogat, Jet. (See p. 104, Appendix col. 2.) The jet is of a solid shining texture. b. Not perfectly saturated; Mumia vegetabilis. It is loose; resembles umber, and may be used as such.

B. Penetrated by rock-oil or asphaltum. 1. Vegetables. a. Turf. The Egyptian mummies cannot have any place here, since art alone is the occasion that those human bodies have in length of time been penetrated by the asphaltum, in the same manner as has happened naturally to the wood in pit coal strata. See Mummy.

C. Penetrated by sulphur which has dissolved iron, or by marcasite and pyrites. Pyrite impregnata. Petrifaction pyritacea. 1. Animals. a. Human. b. Bivalves. c. Univalves. d. Insects.

IV. Metals in form of extraneous bodies; Larvae metallicae.

A. Silver; Larvae argentifera. (1.) Native. a. On the surfaces of shells. (2.) Mineralised with copper and sulphur. a. Fahlertz, or grey silver ore in form of ears of corn, &c. and supposed to be vegetables, are found in argillaceous slate at Frankenberg and Tahitteren in Hesse.

B. Copper; Larvae cupriferæ. (1.) Copper in form of calx. a. In form of animals, or of parts belonging to them. 1. Ivory and other bones of the elephant. The Turcois or Turquoise; which is of a bluish green colour, and much valued in the east. At Simore in Languedoc bones of animals are dug, which during the calcination assume a blue colour; but it is not probable that the blue colour is owing to copper. (2.) Mineralised copper, which impregnates extraneous bodies; Cuprum mineralisatum corpora peregrina ingredium. A. With sulphur and iron. The yellow or marcasitical copper ore that impregnates, 1. Animals. a. Shells. b. In form of fish. B. With sulphur and silver. Grey silver ore or fahlerete, like ears of corn, from the slate-quarries in Hesse.

C. Changes into iron; Larvae ferrifera. (1.) Iron in form of calx, which has assumed the place or the shape of extraneous bodies; Ferrum calciforme corpora peregrina ingredium. a. Loose; Larvae ebracce. 1. Of vegetables. Roots of trees, from the lake Langelma in Finland. See the acts of the Swedish Academy of Sciences for the year 1742. **MINERALOGY**

**Part II.**

**Appendix.**

**Volcanic Products**

**I. Indurated; Larvae hematiticae.**

1. Of vegetables.

(z.) Iron mineralised, assuming the shape of extraneous bodies.

a. Mineralised with sulphur. Marcasite. Larvae pyritacea.

V. Extraneous bodies decomposing, or in a way of destruction; Corpora peregrina in gradibus destructio confederata. Mould; Humus; Turf; Turba.

A. From animals. Animal-mould; Humus animalis.

1. Shells. Humus conchaceus.

2. Mould of other animals; Humus diversorum animalium.

B. Vegetable mould; Humus vegetabilis.

1. Turf; Turba.

a. Solid, and hardening in the air; Turba folida acre indurascens. This is the best of the kind to be used for fuel, and comes nearest to the pit-coals. It often contains a little of the vitriolic acid.

b. Lamellated turf; Turba foliata. This is in the first degree of destruction.

2. Mould of lakes; Humus lacustris. This is a black mould which is edulcorated by water.

3. Black mould; Humus ater. This is universally known, and covers the surface of that loose earth in which vegetables thrive best.

**Order III. Volcanic Products (h).**

I. Slags; Scoria vulcanorum.

Slags are found in great abundance in many places of the world, not only where volcanoes yet exist, but likewise where no subterranean fire is now known: Yet, in Mr Cronstedt's opinion, they cannot be produced but by means of fire. These are not properly to be called natural, since they have marks of violence, and of the last change that mineral bodies can suffer without the destruction of the world; nor are they artificial, according to the universally received meaning of this word. We cannot, however, avoid giving them a place here, especially after having admitted the petrifications; and shall therefore arrange the principal of them, according to their external marks.

A. Iceland agate; Achates islandicus niger.

It is black, solid, and of a glassy texture; but in thin pieces it is greenish and semitransparent like glass-bottles, which contain much iron. The most remarkable circumstance is, that such large solid masses are found of it, that there is no possibility of producing the like in any glasshouse.

It is found in Iceland, and in the island of Ascension: The jewellers employ it as an agate, though it is too soft to resist wear.

B. Rhemith millstone; Lapis molaris Rhenanus.

Is blackish-grey, porous, and perfectly resembles a sort of slag produced by mount Vesuvius. A variety of lava, according to Kirwan.

C. Pumice-stone; Pumex.

It is very porous and blistered, in consequence of which it is specifically very light. It resembles that frothy slag which is produced in our iron furnaces.

1. White.

2. Black.

The colour of the first is perhaps faded or bleached, because the second kind comes in that state from the laboratory itself, viz. the volcanoes.

D. Pearl slag; Scoriae conflantes globulis vitreis conglomeratis.

It is compounded of white and greenish glass particles, which seem to have been conglutinated while yet soft or in fusion. Found on the Isle of Ascension.

E. Slag-pan; ashes; Scoria pulverulentæ, cineræ vulcanorum.

This is thrown out from volcanoes in form of larger or smaller grains. It may perhaps be the principle of the Terra Puzzolana; because such an earth is said at this time to cover the ruins of Herculaneum near Naples, which history informs us was destroyed by a volcano during an earthquake.

II. Lavas.

Lava has been generally understood to denote the aggregate mass of melted matters which flow out of the mouths, or burst out from the sides, of burning mountains. According to Mr Kirwan, however, lavas are the immediate produce of liquefaction or vitrification by the volcanic fires, and "should carefully be distinguished from the subsequent productions affected by the water either in a liquid or fluid state, which generally is ejected at the same time." And of lavas, so distinguished, he describes several varieties. See the article Lava, in the order of the alphabet; where the nature, origin, kinds, and phenomena of lavas, are copiously described and explained.

III. Basaltes.

This sort of stone was by Cronstedt, in the first edition of his Mineralogy, ranked among the garnet earths, and confounded with the shoers; an impropriety which was pointed out by Bergman in his Sciarographia, sect. 120.—Mr Kirwan considers basaltes as an imperfect lava, and ascribes its origin both to fire and water. He describes it as found, either, 1. In opaque triangular or polyangular columns; which is the proper basaltes: Or, 2. In amorphous masses of different magnitudes; forming solid blocks, from the smallest size to that of whole mountains; which kind is called trapp. See the detached article Basaltes (1); where its species and varieties

(h) For the nature, history, theory, &c. of volcanoes, see the article Volcano.

(1) In that article, p. 46, col. 1. l. 9, dele the words, "The English miners call it cockle, the German scheerl."—P. 47, col. 2. l. 28, for "a kind of marble," read "a volcanic production." The Lapis Lydus, or Touchstone, mentioned in the same paragraph, should have been specified to be of the sort called Trapp. There is a great variety of basaltes in Scotland, particularly of the grey kind; some of which are capable of the highest degree of polish. A good black kind is met with on the south side of Arthur's Seat near Edinburgh, where it forms a smooth perpendicular rock, with several of the columns broken off, and the suspended pieces threatening to fall down upon the passengers below. This stone is capable of receiving a fine polish; and, in the opinion of Mr Williams, would be fit for all sorts of ornaments about sepulchral monuments. It will polish to a bright and beautiful black, which will be unfading.

There is another kind, heavy and hard, of a black or blackish-grey colour; of which great quantities have been carried from the Firth of Forth to pave the streets of London. This, for the most part, is coarsely granulated in the inside, though sometimes the grain is pretty fine. Sometimes it is bright in the inside when broken. It is composed of grains of quartz and flint of different sizes, and commonly contains some iron. It always appears in thick, irregular, beds, some of which are enormously thick; and seldom or ever equally so; on the contrary, where it is found uppermost, it frequently swells into little hills of various sizes. Most of the small islands in the Firth of Forth are composed of this kind of stone; as well as some hills in the neighbourhood of Inverkeithing and of Edinburgh.

The known characteristic of the basaltes is to form itself into balls, columns, and other regular figures. The columnar kind assumes a pentagonal, hexagonal, or heptagonal figure; but quadrangular columns are not common. They are all smooth on the outside, and lie parallel and contiguous to one another; sometimes perpendicular, sometimes inclining, in proportion to the position of the stratum which is thus divided: If the stratum lies horizontal, the columns are perpendicular; if inclining, the pillars also incline in exact proportion to the declivity of the strata, being always broken right across the stratum. Some are of one piece from top to bottom; others divided by one or more joints laid upon one another, which form a column of several parts. The rock called the Giant's Causeway in Ireland is a pretty good specimen of the jointed columnar basaltes: but there is a more beautiful species above Hillhouse lime-quarry, about a mile south of Linlithgow in Scotland; and a coarser one near the toll bar north side of Queen's Ferry, and several other places in Fife. In some places the basaltes are formed into magnificent columns of great length; and in others afford an assemblage of small and beautiful pillars resembling a range of ballustrades or organ pipes. Some of the columns on the south side of Arthur's Seat already mentioned are very long; and there are likewise magnificent columns of great length in the island of Egg, and others of the Hebrides. These columns, when broken, are frequently of a black, or blackish grey, in the inside; some of them being composed of small grains, which gives them an uniform and smooth texture; but much of this species of stone has larger grains in its composition, rough, sharp, and unequal, when broken. All the grains, however, are fine, hard, and bright; and the stone in general is capable of a fine polish.

The other species of basaltes which forms itself into distinct masses, assumes sometimes a quadrangular, sometimes an oval, globular, or indeterminate figure. They are found of all sizes from the size of an egg to that of an house: but though they differ in shape from the columnar basaltes, they agree in almost every other respect; whence Mr Williams thinks that they are only to be accounted a variety of the columnar kind. It is common to see one stratum of the basaltine rocks exhibiting, in one place, regular pillars or globes; and near these, very irregular ones, differing very little from the common cutters found in all rocks; and at no great distance, the same rock is found to run into one entire mass, exhibiting no tendency to be broken or divided into any columns whatever. Of this the rock of Arthur's Seat is an instance. Some of these only produce solid masses of different figures and sizes; while others produce quantities of a softer, friable, stony matter, of the same quality in which the hard masses of different figures are found imbedded. Pretty good specimens of the second kind or variety of basaltes are met with on the road-side between Cremond bridge and the Queen's Ferry, and in several other places in the Lothians and in Fife.

The crustated basaltes are of two kinds; 1. Such as have the crusts more dry and friable than the internal parts; and, 2. Such as are dry and friable throughout the whole mass.

The first of these has not only a crust of the friable matter adhering to it, but is likewise imbedded in a quantity of the same. Our author has seen many quarries of this kind of basaltes dug for the high roads, in which the quantity of soft friable matter greatly exceeded that of the hard masses, and in which incrustated stones of various sizes and shapes appeared. In such quarries, some of the largest masses have only a few coats of penetrable friable matter, surrounding a nucleus which varies in size, but is uniformly hard throughout; and we shall find other yolks in the same quarry imbedded in the softer matter, which, when broken, exhibit a nest of stones including one another like the several coats of an onion. These crustated basaltes which envelope one another are a curious species of stone. The several coats of surrounding matter differ nothing in quality from the stones contained in them, and some of the inner crusts are often very hard; but the nucleus within, though small, is always the hardest. The decomposition by the weathering of the softer matter found surrounding and enveloping the harder masses of stone in this and the second species... Appendix of basaltine rocks, has produced a phenomenon frequently met with in Great Britain, especially in Scotland, which greatly puzzles many. It is very common in low grounds, and upon some moderate eminences, to see a prodigious multitude of stones of all shapes and sizes, very hard, and pretty smooth on the outside. These stones are sometimes so numerous and large, that it is often found impracticable to clear a field of them. Where these stones are a species of basaltes, which they commonly are, and of the second species of basaltes described above, they always originate from a decomposition of the more soft or friable parts of those rocks, which moulder or fall away, and leave the harder stones detached and scattered about, and the decomposed matter dissolves by degrees, and becomes good corn mould.

Here Mr Williams takes occasion to contest the opinion of those who think that stones grow or vegetate like plants. He owns indeed that they increase in bulk; but this, he says, is only in such situations as are favourable for an accretion of matter carried down and deposited by the water; in all other situations they grow less and less. "Others (says he) imagine, that these stones (on which this extraneous matter has been deposited) were rolled about; that the asperities and sharp angles were by that means worn off; and that they were all at last deposited as we see them, by the waters of the universal deluge: and, having their obtuse sides and angles, as if they had been rounded by rolling in water, makes these gentlemen confident that they are right; and if we did not frequently find stones exactly of the same figure, size, and quality in the rock, it would be very difficult to overthrow this hypothesis. I have taken great pains to investigate this point, having frequently examined circumstances; and never failed to discover the stratum of rock which those detached stones originally belonged to. "The strata or beds of the several species of basaltes spread as wide, and stretch as far, as the other concomitant strata in the neighbourhood where they are found: but they often lie very flat, or with a moderate degree of declivity; and consequently, when the softer and more friable matter found in the interstices of these rocks, which incloses and binds the harder masses in their native beds, is decomposed, the harder stones must then lie scattered wide upon the face of the ground."

The second species of the crusted basaltes, viz. that which is dry and friable throughout the whole mass, is generally of a coarse and granulated texture, and of all the various shades of grey colours; from a rusty black to a light-coloured grey. This kind of crusted basaltes is developed when the masses are either broken or in a state of decomposition; and there are masses of it of all sizes and shapes found in the rocks, resembling the second and third species of the basaltes; appearing alike smooth on the outside, with obtuse angles; in short, resembling the basaltes in every respect: but when they are exposed to the external air and weather for any considerable time, the several incrustations decay, decompose, and crumble down by degrees. When they quarry this species of basaltes for the roads, they are able to break and pound them small with ease; but the harder species are so hard and cohesive, that they are with the greatest difficulty broken into sufficiently small parts.

Composite basaltes resembles the three last species, in figure, colour, and all other external appearances; being distinguishable from them only in the internal structure or grain of the stone. It resembles some of the granites, as consisting of much larger grains than the other basaltes. Many of the larger grains in the composite basaltes are more than an eighth part of an inch over, and some more than a fourth; appearing with smooth flat surfaces, and of a tabulated texture, exactly resembling the quartzy grains so commonly found in the composition of most of the granites. The chief, if not the only, distinguishable difference between the grains in each of them is the colour. They are evidently large grains of quartz, &c. which exhibit flat shining surfaces in both. Those grains or fragments are commonly white, yellowish, red, or black, in the composition of most of the granites; whereas they are often seen of a pale blue, or a bluish grey colour, in the composite basaltes, and some of them approaching to white. It is only in the internal structure, however, that these basaltes have any resemblance to the granites; in all the external characters, they differ nothing from the rest of their own genus.

A fifth species of basaltes is indurated through the whole stratum, solid and uniform through all its parts, and exhibiting only such cracks and fissures or cutters as are commonly met with in other hard beds of stones. Many beds of this species are frequently met with in the coal-fields, and the miners are often obliged to sink through them in their coal-pits. "The Salisbury craigs at Edinburgh (says our author) might be singled out as a good example of this species of stone, were it not that part of the same stratum is formed into columns on Arthur's seat; though, I believe, this is no good exception, as it evidently appears that the beds of basaltes which are formed into columns, glebes, &c. only assume these figures where they are exposed to the influence of the external air, or have but little cover of rock above them. When any of these beds strike deep under the cover of several strata, they are not found in columns, &c. Nothing but an uniform mass then appears, although the same bed is regularly formed near the surface; which proves that the columnar and other basaltes are formed by shrinking and chapping.

"The strata of basaltes spread as wide, and stretch as far in the longitudinal bearing, as the other different strata which accompany them in the countries where they are found. The rocks of basaltes also are generally found in very thick strata; and that generally in places where no other rock is found above the basaltes, the strata of it are often very unequal in thickness. But this, in general, is only in situations where no other rock is found above it; for when it fairly enters into the surface of the earth, so as to have other regular strata above it, which is seen in a hundred places in the Lothians, Fife, and other parts of Scotland, it then appears pretty equal in thickness, as equal as most other beds of such great thickness are; and yet it is remarkable, that although most of the strata of basaltes are of great thickness, there are frequently thin strata..." Appendix. Strata of various kinds found both above and below it. We have numerous examples of this in all the parts of Scotland where basaltic strata is found; as for instance, there are thin and regular strata seen and quarried both above and below the thick bed of that rock in the Salisbury crags near Edinburgh. In the Bathgate hills, south of Linlithgow, and in many other parts of Scotland, there are several strata of basaltic, and likewise of coal, limestone, freestone, and other concomitants of coal blended promiscuously stratum super stratum; and the basalt is frequently found immediately above, and immediately below regular strata of coal; of course basaltic is not the lava of volcanoes. We can prove to ocular demonstration, from the component parts, and from the situation, stretch, and bearing of the strata of basaltic, that they are real beds of stone, coeval with all the other strata which accompany them; and are blended with them in the structure of that part of the globe where they are found, as they dip and stretch as far every way as the other strata found above and below them. If basaltic, therefore, be a volcanic production, the other strata must of necessity be so likewise. But how volcanoes should produce coal, and how that coal should come into contact with burning lava, is not a little problematical; or rather it is strangely absurd to imagine that burning lava can come into contact with coal without destroying it.

The regularly stratified quartzy white-mountain rock is scarce or rather not to be found in most parts of Britain. In the Highlands, however, it is very common; and in some places of them Mr Williams has seen it stratified as regularly as any of the sand-stones, with other regular strata of different qualities immediately above and below it; and sometimes composing large and high mountains entirely of its own strata. This stone is exceedingly hard, dry, and brittle, full of cracks and sharp angles; the different strata sometimes moderately fold, but often naturally broken into small irregular masses, with angles as sharp as broken glass, and of an uniformly fine and granulated texture, resembling the finest sugar-loaf. There are large and high mountains of this stone in Rossshire and Invernesshire, which, in a clear day, appear at a distance as white as snow, without any sort of vegetation on them except a little dry heath round the edge of the hill.