in Natural History, have been defined bodies which are insipid, not ductile, nor inflammable, nor soluble in water. For a view of the classification of stones, and of their distribution, see MINERALOGY and GEOLOGY.

Here we shall make a few observations on some speculative discussions relative to their natural history.

As philosophers have perplexed themselves much about the origin and formation of the earth (a subject certainly far beyond the ken of the human intellect, at least if we believe that it was made by the almighty power of God), so they have also proposed theories to explain the origin of stones. When philosophers limit their inquiries within the boundaries of science, where they are led by the sober and safe conduct of observation and experiment, their conclusions may be solid and may be useful; but when, throwing experiment and observation aside, they rear a theory upon an airy nothing, or upon a single detached fact, their theories will vanish before the touch of true philosophy as a romantic palace before the rod of the enchanter. Sometimes from whim, or caprice, or vanity, they attempt to confound every thing: they wish to prove that the soul is mere matter, that plants are animals, and that fossils are plants, and thus would banish two substances, spirit and dead matter, entirely from the world; as if the Author of Nature were actuated by sordid views of parsimony in the works of creation, though we evidently see that a generous profusion is one of the characteristic marks of these works. We leave the task of confounding the different classes of being to those philosophers whose minds are too contracted to comprehend a great variety of being at one view, or who prefer novelty to everything else. We content ourselves with the old opinion, that the soul is a spiritual substance; that plants are plants, and that stones are stones.

We have been led into these remarks by finding that some philosophers say that stones are vegetables; that they grow and increase in size like a plant. This theory, we believe, was first offered to the world by M. Tournefort, in the year 1702, after returning from his travels in the east. It was founded on a curious fact. In surveying the labyrinth of Crete, he observed that the names which visitors had engraved upon the rock were not formed of hollow but of prominent letters like basso relievo. He supposes that these letters were at first hollowed out by knives; that the hollows have since been filled up by the growth of the stone; and hence he concludes that stones vegetate. We wish we were fully assured of the fact that the letters were at first hollowed, before we attempt to account for their promiscuity. But even allowing the supposition to be true that they were at first hollow, we reply it is only a single fact, and that it is altogether unphilosophical to deduce a general system from a single fact.

In the second place, this protuberancy of the characters is very improperly called vegetation, for it is not produced by a process in any respect like the vegetation of a plant. Vegetation supposes vessels containing fluids and growth by expansion; but whoever heard of vessels in a stone, of fluids moving in them, or of the different parts expanding and swelling like the branch or trunk of a tree? Even the fact which Tournefort mentions proves nothing. He does not pretend to say, that the rock itself is increasing, but only that a few small hollows are filled with new stony matter, which rises a little above the surrounding surface of the rock. This matter evidently has been once liquid, and at length has congealed in the channel into which it had run. But is not this easily explained by a common process, the formation of stalactites? When water charged with calcareous matter is exposed to the action of air, the water evaporates, and leaves the calcareous earth behind, which hardens and becomes like a stone.

Having thus examined the principal fact upon which M. Tournefort founds his theory, it is unnecessary to follow him minutely through the rest of his subject.—He compares the accretion of matter in the labyrinth to the consolidation of a bone when broken, by a callus formed of the extravasated nutritious juice. This observation is thought to be confirmed, by finding that the projecting matter of the letters is whitish and the rock itself grayish. But it is easy to find comparisons. The difficulty, as Pope says, is to apply them. The resemblance between the filling up of the hollow of a stone, and the consolidation of a broken bone by a callus, we confess ourselves not philosophers enough to see. Were we writing poetry in bad taste, perhaps it might appear. The circumstance, that the prominent matter of the letters is whitish, while the rock is grayish, we flatter ourselves strengthens our supposition that it consists of a deposition of calcareous matter. Upon the whole, we conclude, we hope logically, that no such theory as this, that stones are vegetables, can be drawn from the supposed fact respecting the labyrinth. We have to regret, that the account which we have seen of the subject is so imperfect, that we have not sufficient materials for a proper investigation. Tournefort has not even told us of what kind of stone or earth the accretion consists; yet this single information would probably have decided the question (A).

(A) To give a more distinct notion of Tournefort's theory, we shall subjoin his conclusions: From these observations (he says) it follows, that there are stones which grow in the quarries, and of consequence that are fed; that the same juice which nourishes them serves to rejoin their parts when broken; just as in the bones of animals, and the branches of trees, when kept up by bandages; and, in a word, that they vegetate. There is, then (he says), no room to doubt but that they are organized; or that they draw their nutritious juice from STONES AND EARTHS, Analysis of.

At the close of our article Mineralogy, we referred to this place for an account of the method of examining the chemical constitution of earths and stones. In the article Ores, we have given a pretty full detail of the method of analysing that class of minerals. In this place we propose briefly to point out the most improved processes for the analysis of the other three classes of mineral bodies, viz. earths and stones, salts, and combustibles; to which we shall add some account of the method of examining soils.

But before proceeding to the immediate object of this treatise, it may be useful to make some observations on some preliminary processes connected with the subject under consideration.

In the first place, it is necessary that the mineral to be examined be reduced to a fine powder. To effect this with very hard stones, they are made red hot, and in this state thrown into cold water. By the sudden change of temperature in the different parts of the stone, it cracks, and falls to pieces. If the pieces be not sufficiently small, the same process is to be repeated. The fragments are then to be reduced to smaller pieces in a polished steel mortar, and the cavity of this mortar ought to be cylindrical. A pestle of the same metal should be made to fit it exactly, that no part of the stone may escape during the operation of pounding. The stone being in this way reduced to powder, a determinate quantity is taken, 100 or 200 grains, for example, and this is to be reduced to as fine a powder as possible; or, as it is called, to an impalpable powder. This operation is most successfully performed in an agate mortar, with a pestle of the same mineral; a mortar of about four inches in diameter, and rather more than one inch deep, is found to answer the purpose very well. It is found most convenient to operate on small quantities only at a time; not more than five or six grains. When the powder feels soft, adheres, and appears under the pestle in the form of a cake, it is then as fine as possible. It is now to be accurately weighed, and it is usually found to have acquired some additional weight, arising from part of the mortar being worn off during the pounding. This additional weight must be attended to, and after the analysis is completed, a part of the substance of the mortar must be subtracted. In the case of an agate or flint mortar being used, the portion rubbed off, which increases the weight, may be regarded as pure siliceous earth.

The chemical vessels necessary for the analysis of minerals are crucibles for exposing the substances to heat; preliminary glasses and shallow dishes for solutions and evaporations. The crucibles should be of platina or pure silver, and of such a capacity as to hold from seven to eight cubic inches of water. The vessels in which the solutions, evaporations, and other processes are performed, should be of glass or porcelain; the glass vessels, as being more brittle, and therefore more apt to break, are found to be less economical than those of porcelain. Some chemists employ porcelain vessels which are in the form of sections of spheres, and are glazed both in the inside and outside, excepting part of the bottom, which comes into immediate contact with the fire. Wedgwood's glazed vessels for evaporations, are found to answer very well; the glaze is thin, and the vessels are not very apt to crack; but it is supposed by some chemists, that it is occasionally acted on by strong acids. It is scarcely necessary to add, that an accurate balance is a necessary instrument in the hands of the analyst.

I. Of the Analysis of Earths and Stones.

The ingredients which have been discovered by means of analysis, in the composition of simple stones are silica, alumina, lime, magnesia, zirconia, and glucin, with some of the metallic oxides, as those of iron, copper, manganese, chromium, and nickel; but it never happens that the whole of these substances are found in combination; and indeed it is a rare circumstance to meet with more than four or five in the same stone. With a view of discovering the different substances which enter into the composition of stones, the following method is recommended.

Take 200 grains of the stone to be examined, or, if it be inconvenient to procure this quantity, 100 grams will be sufficient. Let it be reduced to a fine powder, mixed with three times its weight of pure potash, and a small portion of water, and then subjected to heat in a crucible of silver. The heat must be applied slowly at first, and the matter is to be constantly stirred, that no part of it may be thrown out of the crucible by the swelling of the potash. The water being evaporated, the mixture is to be kept at a red heat for half an hour; and being removed from the furnace, some notion may be formed of the nature of the ingredients, by examining the contents; for, if the mixture be in a liquid state, the stone is chiefly composed of siliceous earth; if it be of the consistence of paste, and have an opaque appearance,

the earth. This juice must be first filtrated and prepared in their surface, which may be here esteemed as a kind of bark; and hence it must be conveyed to all the other parts. It is highly probable the juice which filled the cavities of the letters was brought thither from the bottom of the roots; nor is there any more difficulty in conceiving this than in comprehending how the sap should pass from the roots of our largest oaks to the very extremities of their highest branches. Some stones, then (he concludes), must be allowed to vegetate and grow like plants: but this is not all; he adds, that probably they are generated in the same manner; at least, that there are abundance of stones whose generation is inconceivable, without supposing that they come from a kind of seeds, wherein the organical parts of the stones are wrapped up as those of the largest plants are in their seeds. But there are some stones on which potash has a very feeble action, and in this case borax has been substituted for the alkali. This is the method which was followed by Mr Chenevix in analysing aluminous stones. A hundred grains of sapphire in powder were mixed with 250 grains of calcined borax, and subjected to a strong heat in a crucible of platinum for two hours. When the mass was cold, it exhibited the appearance of a greenish blue glass, which adhered strongly to the crucible; but the whole being boiled for some hours in muriatic acid, it was completely dissolved; the earthy matter was then precipitated by means of sub-carbonate of ammonia, and the precipitate, after being well washed, was again dissolved in muriatic acid; and in this way the borax was separated. The remaining part of the analysis was nearly similar to that directed for other stones, excepting only that the alumina was separated from the potash by means of muriate of ammonia.

But to return to the examination and farther treatment of the mass in the silver crucible, which after being removed from the furnace, and wiped on the outside, is to be placed in a porcelain capsule; it is then filled with water, and this water is renewed occasionally, till the whole matter is separated from the crucible. By this means a part of the compound of the alkali with the siliceous and aluminous earths, is dissolved, and with a sufficient quantity of water the whole may be dissolved. Muriatic acid is now to be added till the whole of the mass is brought to a state of solution. This, however, will not be the case, if the stone be composed chiefly of silica. On the first addition of the acid, a flaky precipitate is produced, because the acid unites with the alkali, which held the mass in solution. An effervescence afterwards takes place, which arises from the decomposition of a portion of carbonate of potash, formed during the fusion; and the flaky precipitate is again dissolved, as well as the matter which remained in the form of powder at the bottom of the vessel. If the powder be silica and alumina, there is no effervescence; but if it contain lime, an effervescence is produced. The solution in the muriatic acid being formed, if it shall appear colourless, it may be inferred that it contains no metallic oxide, or at least a very small portion. An orange red colour shows that it contains iron, a purplish red indicates manganese, and a golden yellow, chromium.

The solution is now to be introduced into an evaporating dish of porcelain, and being covered with paper, is to be placed on a sand bath, and evaporated to dryness. Towards the end of the evaporation, as the liquid assumes the form of a jelly, it must be constantly stirred with a rod of silver or porcelain, to permit the acid and water to pass off, and to allow the whole mass to be equally dried; for it is in this way that the silica and alumina are separated from each other. The matter being reduced to a dry powder, add to it a large quantity of pure water, expose it to a moderate heat, and pour it on a filter. This solution may be denominated A. Wash repeatedly the powder which remains upon the silver, till the water with which it is washed no longer precipitates silver from its solutions. The powder remaining is silicious earth, which is first to be dried between folds of blotting paper, and then made red hot in a crucible of platinum or silver; and when it is cold, it is to be accurately weighed. If it be pure silicious earth, it is in the form of a white powder, is of a white colour, does not adhere to the fingers, and is insoluble in acids. If it be at all coloured, it shows that it contains some metallic oxide, and is a proof that the evaporation has been carried on with too great a heat. To separate the oxide, boil the silica with an acid, and then wash and dry it as before. This acid solution is to be added to the solution A, and the whole is to be evaporated to about the quantity of an English pint; then add to it a solution of carbonate of potash, till the precipitation ceases; and it may be necessary to boil it a few moments, to allow the whole of the precipitate to fall to the bottom. The whole of the precipitate being collected at the bottom, the supernatant liquid is decanted off, and the water being put in its place, the precipitate and water are thrown on a filter; and when the water has run off, the filter with the precipitate upon it is placed on the folds of blotting paper. After the precipitate has acquired some degree of consistence, collect it carefully with an ivory knife, mix it with a solution of pure potash, and boil it in a capsule of porcelain. The potash dissolves the alumina or glucina, and the other substances remain in the form of a powder. This powder may be called B.

Add to the solution of potash as much acid as will saturate the potash, and also redissolve any precipitate which at first appeared; and then add carbonate of ammonia till the taste of it be perceptible in the liquid. The whole of the alumina is now precipitated in the form of white flakes, while the glucina remains dissolved, if a sufficient quantity of carbonate of ammonia had been employed. Filter the liquid; and the alumina remaining on the filter being washed and dried, and after being made red hot, and allowed to cool, is weighed. To prove its being alumina, dissolve it in sulphuric acid, and a sufficient quantity of sulphate or acetate of potash being added, the whole of it will be converted into alum crystals, if the earth employed be aluminous earth.

To separate the glucina, the liquid which passed through the filter is to be boiled for some time, and if the solution contain any of this earth it will be precipitated in the form of a light powder, which may be dried in the usual manner, and weighed. It is a fine, soft, light, tasteless powder, when in a state of purity; and the application of heat does not make it concrete, as happens to alumina.

We now return to the residuum B, in which may be expected lime, magnesia, and some of the metallic oxides. But if it be suspected that this residuum contains any yttria, it is to be treated with carbonate of ammonia, which dissolves the yttria, and leaves the other bodies untouched. The yttria being separated, the residuum B is to be dissolved in weak sulphuric acid, and the solution evaporated to dryness. Add a small quantity of water, which will dissolve the sulphate of magnesia, as well as the metallic sulphates; but the sulphate of lime remains undissolved, or if any part of it should Preliminary dissolve, it may be thrown down by adding a small portion of weak alcohol. After being made red hot in a crucible, it is to be weighed, and the lime will amount to \( \frac{1}{3} \) of the weight. The solution containing the remaining sulphates being diluted with a large portion of water, a small excess of acid is to be added, and then a saturated carbonate of potash. The magnesia and oxide of manganese remain dissolved, and the oxides of chromium, iron, and nickel, are precipitated. This precipitate may be denominated C.

Add to the solution a solution of hydrosulphuret of potash, and the manganese in the state of a hydrosulphuret will be precipitated. Calcine the precipitate in contact with air, and weigh it. The addition of pure potash to the solution will precipitate the magnesia, which being washed, and subjected to a red heat, is also to be weighed.

The residuum C is to be repeatedly boiled with nitric acid, and then mixed with pure potash; and, being heated, the liquid is to be decanted off. The precipitate thus obtained, consisting of the oxides of iron and nickel, is to be washed with pure water, and this water is to be added to the solution of the nitric acid and potash. The chromium, if any be present, is contained in that solution, and is in the form of an acid. Add to the solution muriatic acid in excess, and let the evaporation be continued till the liquor become of a green colour; then add a pure alkali, by which the chromium is precipitated in the state of oxide, which is to be dried in the usual way, and weighed.

The precipitate containing the oxides of iron and nickel is to be dissolved in muriatic acid; ammonia is to be added in excess, when the oxide of iron precipitates, and being collected, washed, and dried, is to be weighed. By evaporating the solution, the oxide of nickel will be also precipitated, or the whole may be precipitated by the addition of hydrosulphuret of ammonia. This being treated in the same manner as the other substances, is also to be weighed.

The weight of the whole substances thus obtained being added together, and being compared with the weight of the matter originally operated upon, if the two be equal, or if the difference do not exceed three or four parts in 100, it may be inferred that the analysis is nearly correct; but a considerable loss of weight indicates some error, and requires the analysis to be carefully repeated. If the same loss of weight appear, it may be concluded that the stone contained some substance which is soluble in water, or has been driven off by the heat. To ascertain the last point, a portion of the stone is to be broken into small pieces, and exposed to a strong heat, in a porcelain retort. If it contain water, or any volatile substance, it will come over into the receiver, and by this means the nature and weight of the ingredients separated may be ascertained. If nothing come over into the receiver, or if what is obtained be not equal to the deficient weight, it may be inferred that the stone contains some matter which is soluble in water.

A fixed alkali has been not unfrequently found in simple stones; and to ascertain whether the mineral subjected to analysis contains any alkaline matter, different methods have been pursued. These methods we shall now describe. The stone being reduced to an impalpable powder, is cautiously heated repeatedly with sulphuric acid, and the mass is to be digested in water; and this solution being properly concentrated, is set aside for some days. The appearance of crystals of alum is a certain indication that the mineral contained potash; and the quantity of potash may be estimated at \( \frac{1}{3} \) of the weight of those crystals; but if no crystals be obtained, the solution is to be evaporated to dryness, and the residuum exposed to a moderate red heat. Digest it afterwards in water, and add carbonate of ammonia, and filter; evaporate again to dryness, expose the residue to a heat of 700°, and redissolve it. The solution being properly concentrated, will give crystals of sulphate of soda or of potash, as the one or the other alkali is present. Potash may be discovered by adding to the solution of the salt, a solution of nitro-muriate of platinum somewhat concentrated. A yellow precipitate, which is muriate of platinum and potash, is thus obtained.

Klaproth's method for discovering fixed alkalies in minerals is the following. He takes four parts of nitrate of barytes to one of the mineral to be examined, and fuses them together in a porcelain crucible. A spongy mass of a light-blue colour was thus obtained, and with the addition of diluted muriatic acid, was completely dissolved. The solution, which was of a yellow colour, was then mixed with a sufficient quantity of sulphuric acid, by which the barytes is precipitated, and the muriatic acid expelled. The liquid is next evaporated to dryness, and the mass being digested in water, is filtered, and the sulphate of barytes and silica remain on the filter. The clear solution is saturated with carbonate of ammonia, and filtered a second time; and all the earthy and metallic bodies being separated, the sulphates of fixed alkali and ammonia only remain in the solution, which being evaporated to dryness, the dry saline mass is introduced into a porcelain crucible, and subjected to such a degree of heat as is sufficient to drive off the sulphate of ammonia. The residuum is then dissolved in water, and crystallized; and thus a pure, fixed alkaline sulphate is obtained, which is again dissolved in water, and decomposed, by adding acetate of barytes. The solution is then filtered, and the liquid is evaporated to dryness. The saline mass obtained is the acetate of a fixed alkali, which being exposed to heat in a crucible, became of a reddish colour. The carbonaceous residuum is then to be dissolved in water, filtered, and crystallized, and the salt thus procured is a carbonate of a fixed alkali, the nature of which may be easily recognised by the means stated above.

Mr Davy's method of detecting a fixed alkali in minerals, is different*. One hundred grains of the stone, in very fine powder are to be fused for half an hour at a very strong red heat, in a crucible of platina or silver, with \( \frac{200}{\text{grains}} \) of boracic acid. An ounce and a half of nitric acid diluted with seven or eight times its quantity of water, is then digested upon the fused mass, till the decomposition of the whole is completed. Evaporate the fluid to about two ounces, or one ounce and a half; by this means the siliceous earth is separated, which being collected on a filter, is to be washed with distilled water, till the boracic acid and the whole of the saline matter are separated. The fluid is then mixed with water that has passed through the filter, and evaporated to the quantity of half a pint, after which it is saturated with carbonate of ammonia, and boiled with an excess of this salt, till the whole of the substances capable of being precipitated, have been thrown down. The solution being filtered, the earths and metallic oxides remain on the filter. Add nitric acid to the liquid till it acquire a strong sour taste, and evaporate till the boric acid appear free.

The fluid is then to be filtered, and evaporated to dryness, and the dry mass being exposed to a heat of about 450° Fahrenheit, the nitrate of ammonia is decomposed, and the nitrate of potash or soda remains behind.

To detect fluoric acid, which has been sometimes met with as a component part of stones, Klaproth heats the mineral with sulphuric acid in a glass retort, the corrosion of which, and the deposition of silica in the water of the receiver, are certain tests of fluoric acid.

After the general observations which have now been offered, we proceed to give examples of the analysis of minerals belonging to the different genera of earths and stones; and we shall follow the same order in which those genera are described in the article Mineralogy.

1. Zircon Genus.

The mineral affording the earth which characterises this genus, was analysed by Klaproth in the following manner*. We select that species which is called hyacinth.

A. 100 grains of hyacinth being levigated in the flint mortar, received an increase of weight of half a grain.

B. This pulverized hyacinth, digested with two ounces of nitro-muriatic acid, yielded, upon saturating the solution with potash, a light-brown precipitate, of three grains and a half, when dried. Ammonia, added to it, dissolved nothing; and it remained colourless. After the precipitate had been again separated from the volatile alkali, muriatic acid was added, which dissolved its ferruginous contents, leaving a white earth behind, which, when ignited, weighed 1½ grain. The portion of iron, precipitated by caustic ammonia from the muriatic solution, weighed half a grain, when ignited, and became black, and resplendent. It was fused with a neutral phosphate, upon charcoal, to find whether it contained manganese; no trace was perceptible.

C. The above 1½ grain of earth B was now added again to the hyacinth, after treatment with acids. The stone was then subjected to red heat, with six times its quantity of caustic alkali, in the manner explained in the essay on the jargon of Ceylon; the ignited mass was again liquefied with water; and the earth remaining after this process weighed 123 grains, when collected, edulcorated, and dried.

D. The alkaline lixivium was then saturated with muriatic acid, and evaporated. At first it continued clear; but towards the end siliceous earth separated, the quantity of which, after ignition, amounted to six grains.

E. To the 123 grains, previously well washed with water, a sufficient quantity of muriatic acid was added; which, with the assistance of heat, dissolved nearly the whole, a trifling residue excepted. This muriatic solution, evaporated in a moderate heat to a sixth or eighth part, lost its fluidity, and formed a limpid gelatinous coagulum. It was then covered with water, and exposed, with repeated agitation, to a digesting heat.

By this management, the siliceous earth separated in slimy, intumesced grains, and weighed, after ignition, 23½ grains.

F. The solution, thus freed from its silica, was now saturated with a boiling ley of mild alkali; and the precipitate was washed and dried in the air. This last weighed 114 grains, proving, upon every trial, to be jargonic earth. A fourth part of it, heated to redness, weighed 16½ grains; which make the whole amount to 66 grains.

G. The above six grains D, with the 23½ grains E, in the whole 29½ grains of siliceous earth, were ignited with a quadruple weight of vegetable alkali. When this mass had been again softened with water, it left a residue, which was extracted by muriatic acid. From this muriatic solution, also, when saturated with potash, jargonic earth fell down, weighing four grains after ignition. Hence, subtracting these, the quantity of siliceous earth is reduced to 25½ grains.

One hundred parts of hyacinth, therefore, have given

| Jargonia | F | 66 | |----------|---|----| | Silica | G | 25½ | | Subtract | A | |

Oxide of iron, B - 0.59

Loss, 4.50

100

2. Of the Siliceous Genus.

A great proportion of the stones belonging to this genus are transparent, and have a vitreous appearance. They are so hard as to scratch glass; and, excepting the fluoric acid, they are not acted upon by acids. By fusion with alkalies they form glass; they also enter into fusion with boric acid, and the acid of phosphorus. Stones composed chiefly of pure silica, are transparent and colourless. When a mineral is presented for examination, even if it possess most of the properties which characterize stones belonging to this genus, some preliminary processes may be pursued to ascertain farther its nature and component parts.

A. It is sometimes difficult to reduce siliceous stones to a fine powder. To facilitate this operation, a portion of the stone may be heated to redness, and in this state suddenly plunged into cold water. If by the first heating it is not sufficiently brittle, the operation may be repeated until the mineral can be reduced to a fine powder, as already directed.

B. One part of the stone in fine powder is now to be mixed with four or five parts of potash, dissolved in the same quantity of water. The mixture is introduced into a silver crucible, and evaporated to dryness, stirring it constantly with a silver rod, according to the directions given above. The mass being evaporated to dryness, the heat is to be gradually increased, till the crucible appears of a dull red heat, or till the mass enter into quiet fusion. In this state it is kept for an hour.

C. Remove the crucible from the fire before it is completely cold; soften the mass with water, by adding fresh... Siliceous fresh portions from time to time, till the whole is detached from the crucible, and then add 12 times its bulk of water to effect a solution. If the stone consisted chiefly of siliceous earth, the greater part of the mass will be dissolved.

D. Add muriatic acid till no farther precipitate is effected, and without separating the precipitate, evaporate the whole to dryness.

E. Pour six times its bulk of muriatic acid, previously diluted with four parts of water, on the dry mass; boil the mixture for half an hour; let the insoluble part subside, and then collect it on a filter, and after being dried, subject it in a crucible to a red heat. This powder is the siliceous earth contained in the mineral.

But stones included under this genus contain very different proportions, not only of siliceous earth, but also of the other earths; and some of them even contain a far greater proportion of other earths than that which characterizes the genus under which they are arranged.

Analysis of Leucite.

The analysis of this mineral is particularly interesting, not only as Klapproth first detected in it potash, which was supposed to belong exclusively to the vegetable kingdom, and hence called vegetable alkali, but also as it places the skill and address of that eminent chemist in its examination in a very conspicuous light. The process was conducted in the following manner:

Ignited alone upon charcoal, the leucite is completely infusible. It undergoes no manner of alteration, and its splinters lose nothing of their lustre.

A small fragment, put into fused borax, is for a long time moved about in it before it dissolves, which it does by degrees; and the glass globule obtained is clear and light-brown.

By fusion with a neutral phosphate, the solution is still slower, and a colourless risty glass pearl is produced.

One hundred grains of coarsely pounded leucite, exposed for an hour to a strong red heat, in a small porcelain pot, lost of weight only one-eighth of a grain, and even the violent heat of the porcelain furnace produced in the leucite only an inconsiderable change.

A. One hundred grains of leucite, reduced to an impalpable powder, being several times digested in muriatic acid, dissolved a considerable part. A siliceous residue of 54 grains remained after ignition.

B. The siliceous earth ignited with twice its weight of caustic alkali, softened again with water, covered with muriatic acid, added to excess of saturation, and, after sufficient digestion with this last, being collected on the filter, and heated to redness, was found to have lost little of its weight.

C. Prussiate of potash added to the muriatic solution produced a precipitate which indicated one-eighth of a grain of oxide of iron.

D. The solution by caustic ammonia being decomposed, and the precipitate being separated, the remaining liquor was tried with carbonate of soda, but no further change was effected.

E. The precipitate produced by means of pure ammonia D was first dried. It was next purified by digesting it with distilled vinegar, and afterwards neutralizing this acid by ammonia. It weighed 24 grains and a half, when edulcorated and ignited. Diluted sulphuric acid completely dissolved it to a limpid liquor, and when properly treated, the solution yielded only alum.

F. To obtain the earth, which possibly might have remained latent in the several washings, the whole were evaporated to dryness. After having re-dissolved the saline mass in water, the remaining portion of earth was collected, it amounted only to half a grain, and was siliceous earth.

There were therefore obtained,

| Substance | (A) | (F) | |-----------|-----|-----| | Silica | 54 | | | Alumina | 54½ | 24·50 | | Loss | 79 | |

The remarkable loss of more than one-fifth of the whole weight of the mineral under examination, excited suspicion that some error had crept into the analysis, and led to a repetition of the experiments, by varying the processes as follows.

A. One hundred grains of leucite in fine powder were ignited for half an hour, with double their weight of caustic potash. To the mass softened with water muriatic acid was added, just to the point of saturation, and the mixture being filtered, the remaining undissolved residuum was washed and dried.

B. The mineral thus prepared for decomposition, was then treated with muriatic acid, and kept for some time at a boiling heat. By this process a quantity of silica separated, which after being heated to redness weighed 54 grains and a half.

C. Oxalate of potash being added to the muriatic solution, concentrated by evaporation, produced no turbidity. The alumina was separated by the same means as in the former experiments, and its weight amounted to nearly the same. By other trials it did not appear to have any mixture of other earths, and no other earth could be obtained by evaporating the waters with which the powders had been washed.

Thus, after varying the experiments the same results were obtained, and the same loss still appeared. In the farther prosecution of this investigation, the following experiments were had recourse to.

A. Two hundred grains of leucite in fine powder were repeatedly digested with muriatic acid, and the siliceous earth collected on the filter, washed, and weighed after being red hot, amounted to 100 grains.

B. The muriatic solution was of a yellowish colour, and being reduced by evaporation in a sand heat to the consistence of honey, the surface appeared covered with a saline crust; and when completely cooled, the mass appeared like a thick clear oil, of a golden yellow colour, and full of crystals, some of which were of a cubic, and some of a tabular form. The yellow fluid was gently poured off, and the salt rinsed with small portions of alcohol. The solution diluted with alcohol was again evaporated, and the small portion of salt thus obtained...

&c. ANALYSIS OF.

The whole of the salt being dried, weighed 70 grains. This was dissolved in water, and some drops of a solution of ammonia being added, threw down some particles of alumina. The solution being crystallized in a warm place, yielded only cubical crystals, some of which were elongated to four-sided columns.

C. That part of the muriatic solution which shot into crystals being diluted with water, and decomposed in a boiling heat, by carbonate of soda, yielded a precipitate, which, after washing, drying, and ignition, amounted to 47½ grains of aluminous earth. Three times its weight of concentrated sulphuric acid was added, and the mixture was evaporated nearly to dryness. The mass was again dissolved in water, and combined with solution of acetate of potash, which being crystallized, produced only alum.

D. The siliceous earth A was mixed with double its weight of potash, and subjected to a strong red heat for an hour. The mass was reduced to powder, and diluted with water. Muriatic acid was added in excess, and digested with it. The filtered muriatic solution being saturated with soda yielded 1½ grain of aluminous earth, after which there remained of silica 107½ grains.

The 200 grains of leucite have thus afforded of

| Silica D | 107.50 | | Alumina C | 47.75 | | D | 1.55 |

Here there was still a deficiency of 43.25 grains, to account for which the 70 grains of salt B must be examined. This examination was conducted in the following manner:

1. The taste and figure of the crystals were found to be the same with those of muriate of potash. 2. The solution produced no change in vegetable blues, or in reddened litmus paper. 3. When heated to redness, the salt made a crackling noise, and remained fixed in the fire. 4. Neither carbonate of soda nor caustic ammonia produced any turbidity in the solution. 5. Two parts of strong sulphuric acid were added to three of the salt, and the muriatic acid being driven off by heat, the mass was again dissolved in water, which afforded crystals of sulphate of potash. 6. The remaining portion of salt was dissolved in a small quantity of water, and to this was added a concentrated solution of crystallized acid of tartar. The acidulous tartrate of potash (cream of tartar) was thus immediately produced and precipitated in the form of sand. This was washed, dried, burnt in a silver crucible, and the coal obtained repeatedly washed with water. The solution being evaporated to dryness, after being examined by the proper tests, appeared to be a carbonate of potash, which being saturated with nitric acid, afforded nitrate of potash.

Thus it appears that the base of the 70 grains of salt consisted entirely of pure potash, which was neutralized by part of the muriatic acid employed in decomposing the mineral; and according to the proportion of base in muriate of potash, the 70 grains A contain 42.7 grains of alkali; and in this way the deficiency in the examination of the leucite is accounted for.

The result of the analysis is as follows.

| Silica | 53.75 | | Alumina | 24.62 | | Potash | 21.35 |

Analysis of Pitchstone.

The pitchstone which is the subject of the following analysis, also conducted by Klaproth, is the transparent yellowish or olive green variety of that mineral from Meissen. It forms an example of soda, the other fixed alkali, forming a component part of stones.

A. 100 grains in coarse fragments were introduced into a covered crucible, and were subjected to a red heat for half an hour. When taken from the fire they appeared of a white gray mixed with a yellowish colour, and having a rough feel, with something of the appearance of glazing. They lost 8½ grains of weight.

B. In the heat of a porcelain furnace, the pitchstone was fused both in the clay and charcoal crucible, and was converted into a clear glass, full of small froth holes.

C. 100 grains of pitchstone in fine powder were treated with a solution of 200 grains of caustic soda, and being put into a silver crucible, were kept for half an hour in a pretty strong red heat. The mass was then softened with water; muriatic acid was added in excess; the solution was evaporated in a sand heat, nearly to dryness; water was again poured upon it, after which it was filtered, and 73 grains of siliceous earth were obtained.

D. Caustic soda was mixed in excess with the muriatic solution, and the whole was digested in a boiling heat, by which the precipitate formed at the beginning of the process was again dissolved; a brown residuum still remained, which being separated, the alkaline solution was neutralized, and precipitated with carbonate of soda. The precipitate, which was alumina, after being washed, dried, and heated to redness, amounted to 14½ grains. The whole of it yielded crystals of alum, with sulphuric acid and potash.

E. The residuum which remained undissolved by the caustic soda, D, was first dissolved in muriatic, and then united with sulphuric acid. Sulphate of lime was obtained, which was collected, and washed with diluted alcohol. By reducing the filtered fluid by evaporation to a smaller quantity, and combining it with sulphuric acid, another portion of sulphate of lime, which, added to the first, amounted to three grains, indicating 18 grains of pure lime.

F. The fluid was now freed from the calcareous earth; the iron which it contained was precipitated by carbonate of ammonia, which amounted to one grain. The remaining fluid was evaporated to dryness, and water being added to the saline residuum, fine minute flocks of oxide of manganese separated, but in no greater quantity than one-tenth of a grain.

G. 100 grains of pitchstone in powder were mixed with 300 grains of crystallized nitrate of barytes, and heated to redness in a porcelain vessel, till the salt was entirely. entirely decomposed. The cold mass was softened with water, neutralized with muriatic acid, and combined in such proportion with sulphuric acid, that the latter, after the evaporation of the mixture, and separation of the muriatic acid by heat, was still in excess. The mass was washed with hot water; the residuum separated by filtration; and the clear fluid was mixed with carbonate of ammonia in excess. The precipitate thus obtained was collected on a filter, and the remaining fluid was evaporated to dryness, and the portion of sulphate of ammonia subjected to a moderate heat in a porcelain vessel, was driven off. A fixed salt remained, which appeared to be sulphate of soda. This was redissolved, and decomposed by acetate of barytes; the filtered solution was evaporated to dryness; the dry salt was heated to redness in a crucible of platina. The saline residuum being redissolved, filtered, and again evaporated to dryness, yielded three grains of dry carbonate of soda, indicating 1½ grain of pure soda. This being neutralized with nitric acid, gave crystals of nitrate of soda.

The 100 grains of the mineral thus examined consist of

| Component | Grams | |---------------|-------| | Silica C | 73 | | Alumina D | 14.5 | | Lime E | 1 | | Oxide of iron D | 1 | | Manganese D | 1.10 | | Soda G | 1.75 | | Water A | 8.50 |

99.85

3. Argillaceous Genus.

As many of the stones included under this genus are composed of similar substances with those arranged in the former genus, it is obvious that the examination is to be conducted in the same way. We shall therefore give one example of the analysis of a stone belonging to this genus, and the example is that of basalt by Klapproth*.

Analysis of Basalt.

A. Small fragments of this stone were subjected to a strong red heat for 30 minutes; the loss of weight was two per cent, and the mass became of a lighter colour, and more readily yielded to the pestle.

B. Basalt exposed to the heat of a porcelain furnace in a common clay crucible, fused into a compact black brown glass, which in thin splinters was transparent. It also entered into thin fusion in a crucible of semi-indurated steatites; part of it ran into the clefts produced in the steatites, and the rest was found crystallized in brown shining lamellae, which on the surface were striated, and cellularly concreted. In a charcoal crucible it was converted into a dull gray and finely porous mass, in which were inserted numerous grains of iron.

C. To ascertain whether this stone contained soda, 100 grains of basalt in fine powder were mixed with 400 grains of nitrate of barytes, and were at first exposed in a large porcelain vessel to a moderate heat, and afterwards to a heat gradually raised to ignition. The mixture swelled up, and when the heat was increased, white fumes arose on uncovering the vessel, which led to a supposition that the soda was beginning to volatilize. The fire was then removed.

D. The porous mass, after cooling and being reduced to powder, was drenched with water, and treated with muriatic acid. The whole entered into solution, and produced a clear yellow fluid. The solution was evaporated, and sulphuric acid was added gradually, till it was in excess. The sulphate of barytes was precipitated.

E. The saline mass by filtration was reduced to dryness, and water was added, the sediment separated, and appeared to consist of the sulphate of barytes, and the siliceous earth of the stone. The clear fluid was saturated with ammonia, and the precipitate, which was obtained being filtered off, the neutralized liquor was evaporated to dryness, and then exposed in a porcelain vessel to a moderately intense heat, till the whole sulphate of ammonia was driven off. The fixed portion remaining dissolved in water, and crystallized, appeared to be pure sulphate of soda. This was dissolved, decomposed by acetate of barytes; the precipitate, which was sulphate of barytes, was separated by the filter, and the clear fluid being evaporated to dryness, the dry acetate of soda was heated to redness in a crucible of platina; and in this way 45 grams of dry carbonate of soda was obtained, which is equal to 2.6 grams of pure soda.

F. To separate the other ingredients, 100 grams of powdered basalt were ignited for two hours with 400 grams of carbonate of soda, in a crucible of porcelain; but with a degree of heat which did not produce fusion. It united into a yellowish, somewhat hard mass, which being reduced to powder, and softened with water, was neutralized with muriatic acid. It was then a little supersaturated with nitric acid, and evaporated to dryness. The colour of the dry mass was saffron yellow. It was diffused in water, slightly acidulated with muriatic acid, and after being digested for a short time it was filtered. The siliceous earth collected on the filter was exposed to a red heat, and being weighed, amounted to 44½ grams.

G. The muriatic solution being sufficiently diluted with water, was precipitated at the temperature of boiling water, by means of carbonate of soda. The precipitate being separated, was digested with a solution of caustic soda, and a dark brown residuum was separated by filtration. Muriatic acid was added in a small excess to the alkaline fluid, and this was precipitated with carbonate of ammonia. The precipitate obtained after being washed and ignited, amounted to 16½ grams. It yielded alum, when treated with sulphuric acid and potash, and was therefore aluminous earth.

H. The brown residuum G was dissolved in muriatic acid with particular attention to the precise point of saturation. Succinate of ammonia was added to the solution, to precipitate the iron; and the succinate of iron obtained, when perfectly washed and strongly heated in a covered crucible, afforded 20 grams of oxide of iron, which were attracted by the magnet.

I. The iron being separated, the fluid was treated at the temperature of boiling with carbonate of soda; a white precipitate was obtained, which was dissolved in nitric acid; and sulphuric acid being combined with the solution, threw down sulphate of lime. This was separated, and the remaining liquor being evaporated nearly

&c. ANALYSIS OF.

nearly to dryness, was again diluted with a mixture of water and alcohol. Another portion of sulphate of lime fell down, which being separated, was added to the former. The whole of the sulphate of lime was decomposed by boiling it with carbonate of soda in solution, and the carbonate of lime thus obtained, after being washed and dried, weighed 17 grains, indicating nine grains and a half of pure lime.

K. Upon the fluid left from the last process, caustic soda was affused; a slimy precipitate was formed, which rapidly dissolved in sulphuric acid, and communicated a brown colour to the solution. It was evaporated in a sand bath; loose brown flakes fell down at the commencement of the process, and these being separated by the filter, appeared to be oxide of manganese; the quantity estimated did not exceed one-eighth of a grain.

L. The remaining portion of the fluid was evaporated to dryness, and the residuum was exposed in a small crucible to a strong red heat. It was again dissolved in water, and yielded a small portion of alumina coloured with iron, and contaminated with manganese. After ignition it did not weigh more than half a grain; but the clear solution was entirely crystallized, and afforded sulphate of magnesia. Carbonate of soda was added to the magnesian salt in solution, by which the earthy base was precipitated in the state of carbonate. It weighed six grains, which is equal to 25 grains of pure magnesia.

The following is the result of the preceding analysis:

| Substance | Weight | |-----------------|--------| | Silica F | 44.5 | | Alumina G | 16.25 | | I | .5 | | Oxide of iron H | 20. | | Lime I | 9.5 | | Magnesia L | 2.25 | | Oxide of manganese K | .12 | | Soda E | 2.60 | | Water A | 2. |

97.72

4. MAGNESIAN Genus.

Besides several of the earths detected in minerals belonging to the former genera, the stones arranged under this genus are distinguished by being combined with magnesia. We shall only give one example of the analysis of a magnesian stone.

Analysis of Steatites.

This mineral, which was found in Cornwall, was analyzed by Klaproth in the following manner.

A. One ounce of the stone in small pieces was subjected to a strong red heat, by placing the glass retort which contained it in an open fire. A small portion of water distilled over, which was pure and tasteless. The mineral lost 75 grains of its weight, and became darker in the colour, and considerably harder.

B. After being reduced to powder, it was carefully mixed, and heated red hot, with two ounces of carbonate of potash in a porcelain pot. The concreted mass was levigated with water, and digested with muriatic acid in excess. A white loose slimy earth was precipitated, which after being washed, dried, and subjected to a red heat, weighed 204 grains. It was pure silica.

C. Prussiate of potash was added to the filtered solution and produced a blue precipitate, which being collected, washed, dried, and ignited with a little wax, was found, after cooling, to weigh seven grains. The whole of it was attracted by the magnet. The portion of iron belonging to the prussiate of potash being subtracted, left 3½ grains of oxide of iron as a constituent of the mineral under examination.

D. Carbonate of potash being added to the solution freed from the iron, precipitated its earthy ingredient. This, after washing, and gentle ignition, weighed 192 grains. These were covered with a proportionate quantity of concentrated distilled vinegar, and being digested in a low heat, were thrown upon the filter. The earth remaining on the paper, which, after being dried and heated red hot, weighed 93 grains, was mixed with three times its weight of strong sulphuric acid, and the mixture being evaporated in a sand heat nearly to dryness, the dry mass was dissolved in water and filtered; 26 grains of siliceous earth were thus obtained.

E. In the sulphuric solution D, there still remained 67 grains of earth, which being precipitated by an alkali, appeared to consist entirely of aluminous earth.

F. Ninety-nine grains of the first, 192 grains of the earthy precipitate D, were taken up by the acetic acid, which being precipitated by carbonate of potash, and the earth obtained being tried by sulphuric acid, was found to be pure magnesia.

This analysis shows that the 480 grains of steatites, thus examined, afforded:

| Substance | Weight | |-----------------|--------| | Silica B | 224 | | D | 26 | | Magnesia F | 99 | | Alumina E | 67 | | Oxide of iron C | 3.75 | | Water A | 75 | | Loss | 474.75 | | | 5.25 | | | 480.00 |

or 100 parts of the mineral contain:

| Substance | Parts | |-----------------|-------| | Silica | 48 | | Magnesia | 20.5 | | Alumina | 14 | | Oxide of iron | 1 | | Water | 15.5 |

99.0

5. CALCAREOUS Genus.

The analysis of stones belonging to this genus must be varied according to the nature of the combination into which the lime has entered. With regard to the processes to be followed in the examination of calcareous stones, they are susceptible of a natural division into such as are soluble in muriatic or nitric acid with effervescence, and such as are scarce soluble in those acids, and do not effervesce. To the first belong all the stones called limestones, or carbonates of lime; and to the second belongs sulphate of lime, or gypsum.

Analysis of Carbonate of Lime.

Carbonate of lime, whether in the form of lime spar, or in a less pure state, in the form of limestone, is soluble Calcaceous stones with effervescence in nitric or muriatic acid. When exposed to heat, it yields carbonic acid gas, and is converted into quicklime; and when fused with an alkali, does not form a uniform mass. But we shall give a short view of the processes to be followed in a more particular examination.

A. Let a determinate quantity of the stone be reduced to a fine powder. Digest it repeatedly with muriatic acid till no further action is produced upon it. Dilute the solution, throw it upon a filter, and, after drying, weigh the insoluble residuum.

B. Let the remaining solution be diluted with 24 times its bulk of water; add sulphuric acid diluted; a precipitate takes place if the stone contained any barytes, the amount of which, after being collected and dried, may be ascertained by weighing.

C. Add to the filtered solution, after the barytes has been separated, a solution of carbonate of soda, as long as any precipitate is formed. Collect this precipitate, and let it be so much dried that it may be easily removed from the filter.

D. Affuse the precipitate with sulphuric acid till all effervescence ceases.

E. Introduce the whole into a mixture of three parts of distilled water, and one of alcohol, in the proportion of eight parts of the mixture to the quantity of the substance previously dissolved in nitric acid. Let the whole be digested for some hours in the cold, filter the fluid, and dry the insoluble residuum and weigh it.

F. The remaining solution is next to be decomposed by a solution of carbonate of potash, and the precipitate being collected, is to be washed, dried, and weighed.

By this examination, if the stone is to be ranked with carbonate of lime, the weight of the insoluble part E, after subtracting from it one-third, must exceed the weight of the insoluble parts A and B.

Analysis of Sulphate of Lime.

As this is insoluble in nitric or muriatic acids, its analysis must be conducted in a different manner.

A. Let one part of the mineral, reduced to fine powder, be boiled with four times its weight of carbonate of potash, in a sufficient quantity of water for two or three hours; as the fluid evaporates, water is to be added.

B. Introduce the insoluble mass obtained by the last process into a flask containing diluted nitric acid, and the whole being dissolved, let it be evaporated to dryness, and weighed.

C. Add to the dried mass more than its own weight of strong sulphuric acid; apply heat, and let it be gradually increased till fumes cease to rise, and let it be again weighed.

D. Let the insoluble part be digested in twice its weight of cold water; filter the fluid, collect the insoluble residuum, and dry it in a dull red heat. To ascertain the quantity of lime, subtract from the weight of the insoluble mass left (in C) 59 parts; what remains is equal to the quantity of lime.

E. The quantity of lime also may be ascertained, by subjecting for some hours to a red heat, the insoluble mass B; for by this process it will be converted into quicklime.

Analysis of Fluate of Lime.

In the examination of this mineral, a quantity of it may be reduced to powder, and moistened with sulphuric acid, in a leaden or pewter vessel. The mixture being heated, fumes arise, to which a plate of glass being exposed, is soon corroded. In this way the fluoric acid may be detected, and the quantity of base may be ascertained by decomposing the mineral by means of sulphuric acid, and afterwards analysing the sulphate of lime, as already directed.

Analysis of Phosphate of Lime.

The analysis of this mineral may be conducted in the following manner.

A. Let a determinate portion be digested in five times its quantity of muriatic acid, and let the operation be repeated till the acid has no farther action upon the residuum; decant the fluid, and then let it be diluted with water and filtered.

B. Add to the mucic acid solution, liquid ammonia; collect the precipitate which is formed, and after being washed and dried, expose it to heat.

C. Add nitric acid to the precipitate till the whole is dissolved. Precipitate again by means of sulphuric acid; let the whole then be filtered, and let the insoluble residuum be washed with as little water as possible.

D. Evaporate the filtered fluid to the consistence of syrup; the fluid thus obtained is phosphoric acid, if the stone examined have been phosphate of lime. The test of phosphoric acid is, that it precipitates lime water, and also forms precipitates with the solutions of sulphate of iron, and nitrate of mercury; but it does not precipitate the muriate or nitrate of barytes.

6. BARYTIC GENUS.

Analysis of Carbonate of Barytes.

A. Take a determinate quantity of the mineral, and dissolve it in diluted nitric acid; take a portion of the solution, and add to it a solution of sulphate of soda. If a precipitate take place, by adding a small quantity of the salt to the solution of the earth, diluted with 24 times its bulk of water, it may be inferred that the base of the mineral is barytes.

B. Let the nitric solution be evaporated to dryness, and exposed in a silver crucible to a white heat; the earth obtained is barytes, which is soluble in 20 times its weight of water; and after evaporation, crystallizes into long four-sided prisms.

Analysis of Sulphate of Barytes.

This mineral was analyzed by Klaproth in the following manner.

A. 200 grains were mixed with 300 grains of carbonate of potash, and were exposed for two hours to a red heat; the mass was reduced to powder, boiled with water, and the undissolved earth was collected on the filter.

B. To separate the siliceous earth, the fluid was neutralized by muriatic acid, and evaporated to dryness. The saline mass was redissolved in water, and the silica remaining after being ignited, weighed 18 grains.

C. The barytic earth, freed from the sulphuric acid B, was covered with water; muriatic acid was added; the whole was dissolved by digestion, except two grains of silica. The filtered solution was crystallized, and afforded muriate of barytes.

D. The crystals were redissolved in water, and sulphuric acid was added to the solution, while any precipitate appeared, and the regenerated sulphate of barytes being...

&c.

ANALYSIS OF.

Barytic Genus being washed and dried, weighed 185 grains, but after ignition, only 180 grains.

One hundred parts of this mineral are therefore composed of:

- Sulphate of barytes D, 90 - Silica B, 9 - C, 1

100

7. STRONTIAN GENUS.

Analysis of Carbonate of Strontites.

This mineral was analyzed by Klaproth, in the following manner.

A. 100 parts were dissolved in muriatic acid, diluted with half its quantity of water. Thirty parts of carbonic acid were driven off during the solution, which being evaporated, afforded crystals in the shape of needles; and these crystals being dissolved in alcohol, communicated to it the property of burning with a carmine red flame. This is the test of strontite earth.

B. To ascertain whether the mineral examined contained any barytes, three drops of a solution of one grain of sulphate of potash in six ounces of water were added to the muriatic solution; no appearance of precipitate was observed till next day, and therefore it contained no barytes, as in that case an immediate precipitate would have taken place.

C. Carbonate of potash was then added to the muriatic solution; a decomposition took place; and the carbonate of strontites was precipitated. This being subjected to a strong heat, the carbonic acid was driven off, and the whole of the remaining earth being dissolved in water, crystallized. After being dried, it weighed 69.5.

One hundred parts of this mineral therefore contain:

- Pure earth, 69.5 - Carbonic acid, 30 - Water, .5

100.0

II. SALTS.

The analysis of minerals arranged under this class, is in general less difficult, in consequence of their easy solubility, than those already examined. We shall therefore give only one example.

Analysis of Native Saltpetre.

This native salt was examined by Klaproth, according to the following method.

A. 1000 grains of the native salt, with limestone and gypsum to which it adhered, were covered with boiling water. The colourless solution was gently evaporated; during the crystallization, tender needle-shaped crystals of selenite appeared, and the whole of the solution crystallized to a perfect prismatic nitre. The selenite weighed 40 grains, and the salt amounted to 446 grains.

B. To ascertain whether any common salt could be detected in the mineral, the crystals were redissolved in water, and acetate of barytes was dropped into the solution. A precipitate was obtained, amounting to 26 grains of sulphate of barytes, shewing that 18½ grains of selenite were still combined with the neutral salt. A solution of nitrate of silver was added to the nitric solution, which produced a precipitate of 4½ grains of muriate of silver, so that the quantity of common salt can only be estimated at two grains. The pure nitre is thus reduced to 425½ grains. Klaproth suspects that the neutral muriate mixed with the native nitre, is rather a muriate of potash, than the muriate of soda.

C. The stony matters remaining amounted to 500 grains; muriatic acid was poured upon them, and produced great effervescence with pieces of limestone. One hundred and eighty-six grains of white gypsum remained; and the sulphuric acid being separated from it, by boiling with carbonate of potash, the carbonate of lime remaining behind dissolved without residuum in nitric acid.

D. The limestone taken up by the muriatic acid, weighed 304 grains. Being farther examined, it appeared to be calcareous earth, slightly contaminated with iron.

One hundred parts, therefore, of this salt contain:

- Pure prismatic nitre B, 42.55 - Muriate of a neutral salt B, .20 - Sulphate of lime A B C, 25.45 - Carbonate of lime D, 30.4 - Loss, 1.4

100.0

III. COMBUSTIBLES.

Analysis of Coal.

The constituent parts of coal are carbone and bitumen, with some earthy matters, and sometimes a small quantity of metallic matter. The proportion of earthy matters contained in coal may be ascertained by weighing a determinate quantity, and burning it. The nature of the earths contained in the residuum may be discovered by the processes already given.

To ascertain the proportion of charcoal and bitumen contained in coal, we shall describe the method followed by Mr Kirwan.

It has been found that a certain proportion of carbone or pure charcoal, detonated with nitre in the state of ignition, decomposes a given proportion of that salt; and it appears from the experiments of Lavoisier, that 13.21 parts of charcoal decompose 100 parts of nitre, while the detonation is performed in close vessels; but in an open crucible, a smaller proportion of charcoal is required, in consequence of part of the nitre being decomposed by the action of the air of the atmosphere. According to Kirwan, about 10 parts of charcoal are sufficient to decompose 66 parts of nitre. Mr Kirwan also found that vegetable pitch and maltha did not produce any detonation with nitre, but merely burnt on its surface; and that the same quantity of charcoal was required for the decomposition of the nitre, as if no bituminous substance had been employed. Since, therefore, bitumen produces no effect in decomposing nitre, Kirwan thought that the proportion of charcoal, in any coal, might be ascertained by detonation with nitre. In this way the proportion of carbonaceous and earthy matter in any coal being discovered, the proportion of bitumen which it contains may be estimated by calculation.

In the experiments on the analysis of coal, Mr Kirwan employed a large crucible placed in a wind furnace, and exposed to an equable heat. The coal was reduced to small pieces of the size of a pin head, and was projected in portions of one or two grains at a time, into the nitre, the moment it became red hot. This was continued till the detonation ceased.

By this process it appeared that 50 grains of Kilkenney coal were necessary to decompose 480 grains of nitre. According to the same proportion, 96 grains of nitre would have required for its decomposition 10 grains of coal, which is exactly equal to the quantity of charcoal that would have been required to produce the same effect; and thus it appeared that Kilkenney coal is almost entirely composed of carbonaceous matter.

In the examination of cannel coal, Mr Kirwan burnt 240 grains, till the whole of the carbonaceous matter was consumed; a residuum of seven grains and a half of reddish brown ashes, which appeared to be chiefly alumino-ous earth, was left, or about 3.12 per cent. Sixty-six grains and a half of this coal were found necessary to decompose 480 grains of nitre. Fifty grains of charcoal would have produced the same effect; and hence 66½ grains of coal contain 50 of charcoal, and 2.08 parts of ashes, which being subtracted from 66½ grains, leaves 14.42 for the quantity of bitumen contained in the coal. Hence the constituent parts of this coal are,

| Charcoal | 75.2 | | Bitumen | 21.68 | | Ashes | 3.1 |

For a more particular analysis of combustible minerals, see Mr Hatchett's experiments, detailed in the Philosophical Transactions for 1824.

IV. Analysis of Soils.

The examination of soils is by no means the least important, because on a knowledge of the nature and proportions of the ingredients which enter into the composition of soils, depends the opinion to be formed of their fertility. Soils consist of different combinations of the earths, mixed with a certain proportion of animal and vegetable matter. The investigation of the nature of soils has been particularly prosecuted by Mr Kirwan* and Mr Davy. From the observations of the latter, the following account of the analysis of soils is extracted.

1. The really important instruments required for the analysis of soils are few, and but little expensive. They are, a balance capable of containing a quarter of a pound of common soil, and capable of turning when loaded with a grain; and a series of weights from a quarter of a pound troy to a grain; a wire sieve, sufficiently coarse to admit a pepper-corn through its apertures; an Argand lamp and stand; some glass bottles; Hessian crucibles; porcelain or queen's ware evaporating basins; a Wedgewood pestle and mortar; some filters made of half a sheet of blotting paper, folded so as to contain a pint of liquid, and greased at the edges; a bone knife, and an apparatus for collecting and measuring aeriform fluids.

The chemical substances or reagents required for separating the constituent parts of the soil, are muriatic acid (spirit of salt), sulphuric acid, and pure volatile alkali dissolved in water, solution of prussiate of potash, soap lye, solution of carbonate of ammonia, of muriate of ammonia, solution of neutral carbonate of potash, and nitrate of ammonia.

2. In cases when the general nature of the soil of a field is to be ascertained, specimens of it should be taken from different places, two or three inches below the surface, and examined as to the similarity of their properties. It sometimes happens, that upon plains the whole collecting of the upper stratum of the land is of the same kind, and in this case one analysis will be sufficient; but in valleys, and near the beds of rivers, there are very great differences, and it now and then occurs, that one part of a field is calcareous, and another part siliceous; and in this case, and in analogous cases, the portions different from each other should be separately submitted to experiment.

Soils, when collected, if they cannot be immediately examined, should be preserved in phials quite filled with them, and closed with ground glass stoppers.

The quantity of soil most convenient for a perfect analysis is from two to four hundred grains. It should be collected in dry weather, and exposed to the atmosphere till it becomes dry to the touch.

The specific gravity of a soil, or the relation of its weight to that of water, may be ascertained by introducing into a phial, which will contain a known quantity of water, equal volumes of water and of soil; and this may be easily done by pouring in water till it is half full, and then adding the soil till the fluid rises to the mouth; the difference between the weight of the soil and that of the water will give the result. Thus, if the bottle contain 400 grains of water, and gains 200 grains when half filled with water and half with soil, the specific gravity of the soil will be two, that is, it will be twice as heavy as water; and if it gained 165 grains, its specific gravity would be 1.825, water being 1000.

It is of importance that the specific gravity of a soil should be known, as it affords an indication of the quantity of animal and vegetable matter it contains; these substances being always most abundant in the lighter soils.

The other physical properties of soils should likewise be examined before the analysis is made, as they denote, to a certain extent, their composition, and serve as guides in directing the experiments. Thus siliceous soils are generally rough to the touch, and scratch glass when rubbed upon it; aluminoous soils adhere strongly to the tongue, and emit a strong earthy smell when breathed on; and calcareous soils are soft, and much less adhesive than aluminoous soils.

3. Soils, though as dry as they can be made by continued exposure to air, in all cases still contain a considerable quantity of water, which adheres with great tenacity to the earths and animal and vegetable matter, and can only be driven off from them by a considerable degree of heat. The first process of analysis is, to free the given weight of the soil from as much of this water as possible, without, in other respects, affecting its composition; and this may be done by heating it for ten or twelve minutes over an Argand's lamp, in a basin of porcelain, to a temperature equal to 300 Fahrenheit; and in case a thermometer is not used, the proper degree may be easily ascertained, by keeping a piece of wood in contact with the bottom of the dish: as long as the colour of the wood remains unaltered, the heat is not too high; but when the wood begins to be charred, the process must be stopped. A small quantity of water will perhaps remain in the soil even after this operation, but but it always affords useful comparative results; and if a higher temperature were employed, the vegetable or animal matter would undergo decomposition, and in consequence the experiment be wholly unsatisfactory.

The loss of weight in the process should be carefully noted; and when in 400 grains of soil it reaches as high as 50, the soil may be considered as in the greatest degree absorbent, and retentive of water, and will generally be found to contain a large proportion of aluminous earth. When the loss is only from 20 to 10, the land may be considered as only slightly absorbent and retentive, and the siliceous earth as most abundant.

4. None of the loose stones, gravel, or large vegetable fibres should be divided from the pure soil till after the water is drawn off; for these bodies are themselves often highly absorbent and retentive, and in consequence influence the fertility of the land. The next process, however, after that of heating, should be their separation, which may be easily accomplished by the sieve, after the soil has been gently bruised in a mortar. The weights of the vegetable fibres or wood, and of the gravel and stones, should be separately noted down, and the nature of the last ascertained: if calcareous, they will effervesce with acids; if siliceous, they will be sufficiently hard to scratch glass; and if of the common alumino class of stones, they will be soft, easily scratched with a knife, and incapable of effervescing with acids.

5. The greater number of soils, besides gravel and stones, contain larger or smaller proportions of sand of different degrees of fineness; and it is a necessary operation, the next in the process of analysis, to detach them from the parts in a state of more minute division, such as clay, loam, marle, and vegetable and animal matter. This may be effected in a way sufficiently accurate, by agitation of the soil in water. In this case, the coarse sand will generally separate in a minute, and the finer in two or three minutes; whilst the minutely divided animal or vegetable matter will remain in a state of mechanical suspension for a much longer time; so that, by pouring the water from the bottom of the vessel, after one, two, or three minutes, the sand will be principally separated from the other substances, which, with the water containing them, must be poured into a filter, and after the water has passed through, collected, dried, and weighed. The sand must likewise be weighed, and their respective quantities noted down. The water of lixiviation must be preserved, as it will be found to contain the saline matter, and the soluble animal or vegetable matters, if any exist in the soil.

6. By the process of washing and filtration, the soil is separated into two portions, the most important of which is generally the finely divided matter. A minute analysis of the sand is seldom or never necessary, and its nature may be detected in the same manner as that of the stones or gravel. It is always either siliceous sand, or calcareous sand, or a mixture of both. If it consist wholly of carbonate of lime, it will be rapidly soluble in muriatic acid, with effervescence; but if it consist partly of this substance, and partly of siliceous matter, the respective quantities may be ascertained by weighing the residuum after the action of the acid, which must be applied till the mixture has acquired a sour taste, and has ceased to effervesc. This residuum is the siliceous part; it must be washed, dried, and heated strongly in a crucible: the difference between the weight of the whole, indicates the proportion of calcareous sand.

7. The finely divided matter of the soil is usually very compound in its nature; it sometimes contains all the four primitive earths of soils, as well as animal and vegetable matter; and to ascertain the proportions of these with tolerable accuracy, is the most difficult part of soils, and mode of detection.

The first process to be performed, in this part of the analysis, is the exposure of the fine matter of the soil to lime and the action of the muriatic acid. This substance should be poured upon the earthy matter in an evaporating basin, in a quantity equal to twice the weight of the earthy matter; but diluted with double its volume of water. The mixture should be often stirred, and suffered to remain for an hour or an hour and a half before it is examined.

If any carbonate of lime or of magnesia exist in the soil, they will have been dissolved in this time by the acid, which sometimes takes up likewise a little oxide of iron; but very seldom any alumina.

The fluid should be passed through a filter; the solid matter collected, washed with rain water, dried at a moderate heat, and weighed. Its loss will denote the quantity of solid matter taken up. The washings must be added to the solution; which, if not sour to the taste, must be made so by the addition of fresh acid, when a little solution of common prussiate of potash must be mixed with the whole. If a blue precipitate occur, it denotes the presence of oxide of iron, and the solution of the prussiate must be dropped in till no further effect is produced. To ascertain its quantity, it must be collected in the same manner as other solid precipitates, and heated: the result is oxide of iron.

Into the fluid freed from oxide of iron, a solution of neutralized carbonate of potash must be poured till all effervescence ceases in it, and till its taste and smell indicate a considerable excess of alkaline salt.

The precipitate that falls down is carbonate of lime; it must be collected on the filter, and dried at a heat below that of redness.

The remaining fluid must be boiled for a quarter of an hour, when the magnesia, if any exist, will be precipitated from it, combined with carbonic acid, and its quantity is to be ascertained in the same manner as that of the carbonate of lime.

If any minute portion of alumina should, from peculiar circumstances, be dissolved by the acid, it will be found in the precipitate with the carbonate of lime, and it may be separated from it by boiling for a few minutes with soap lye, sufficient to cover the solid matter. This substance dissolves alumina, without acting upon carbonate of lime.

Should the finely divided soil be sufficiently calcareous to effervesce very strongly with acids, a very simple method may be adopted for ascertaining the quantity of carbonate of lime, and one sufficiently accurate in all common cases.

Carbonate of lime, in all its states, contains a determinate proportion of carbonic acid, i.e., about 45 per cent.; so that when the quantity of this elastic fluid, given out by any soil during the solution of its calcareous matter in an acid, is known, either in weight or measure, the quantity of carbonate of lime may be easily discovered. When the process by diminution of weight is employed, two parts of the acid and one part of the matter of the soil must be weighed in two separate bottles, and very slowly mixed together till the effervescence ceases; the difference between their weight before and after the experiment denotes the quantity of carbonic acid lost; for every four grains and a half of which, ten grains of carbonate of lime must be estimated.

The best method of collecting the carbonic acid, so as to discover its volume, is by the pneumatic apparatus, the construction and application of which are described at the end of this article. The estimation is, for every ounce measure of carbonic acid, two grains of carbonate of lime.

8. After the fine matter of the soil has been acted upon by muriatic acid, the next process is to ascertain the quantity of finely divided insoluble animal and vegetable matter that it contains.

This may be done with sufficient precision, by heating it to strong ignition in a crucible over a common fire till no blackness remains in the mass. It should be often stirred with a metallic wire, so as to expose new surfaces continually to the air; the loss of weight that it undergoes denotes the quantity of the substance that it contains destructible by fire and air.

It is not possible to ascertain whether this substance is wholly animal or vegetable matter, or a mixture of both. When the smell emitted during the incineration is similar to that of burnt feathers, it is a certain indication of some animal matter; and a copious blue flame at the time of ignition almost always denotes a considerable proportion of vegetable matter. In cases when the experiment is needed to be very quickly performed, the destruction of the decomposable substances may be assisted by the agency of nitrate of ammonia, which, at the time of ignition, may be thrown gradually upon the heated mass, in the quantity of twenty grains for every hundred of residual oil. It affords the principle necessary to the combustion of the animal and vegetable matter, which it causes to be converted into elastic fluids; and it is itself at the same time decomposed and lost.

9. The substances remaining after the decomposition of the vegetable and animal matter, are generally minute particles of earthy matter containing usually alumina and silica with combined oxide of iron.

To separate these from each other, the solid matter should be boiled for two or three hours with sulphuric acid, diluted with four times its weight of water; the quantity of the acid should be regulated by the quantity of solid residuum to be acted on, allowing for every hundred grains two drachms or one hundred and twenty grains of acid.

The substance remaining after the action of the acid may be considered as siliceous; and it must be separated and its weight ascertained, after washing and drying in the usual manner.

The alumina and the oxide of iron, if they exist, are both dissolved by the sulphuric acid; they may be separated by carbonate of ammonia, added to excess; it throws down the alumina, and leaves the oxide of iron in solution; and this substance may be separated from the liquid by boiling.

Should any magnesia and lime have escaped solution in the muriatic acid, they will be found in the sulphuric acid; this, however, is scarcely ever the case; but the process for detecting them, and ascertaining their quantities, is the same in both instances.

The method of analysis by sulphuric acid is sufficiently precise for all usual experiments; but if very great accuracy be an object, dry carbonate of potash must be soluble and employed as the agent, and the residuum of the incineration must be heated red for half an hour, with four vegetable times its weight of this substance, in a crucible of silver, matter, or of well baked porcelain. The mass obtained must be dissolved in muriatic acid, and the solution evaporated till it is nearly solid; distilled water must then be added, by which the oxide of iron and all the earths, except silica, will be dissolved in combination as muriates. The silex, after the usual process of lixiviation, must be heated red; the other substances may be separated in the same manner as from the muriatic and sulphuric solutions.

10. If any saline matter, or soluble vegetable or animal matter, be suspected in the soil, it will be found in the water of lixiviation used for separating the sand.

This water must be evaporated to dryness in an appropriate dish, at a heat below its boiling point.

If the solid matter obtained is of a brown colour and inflammable, it may be considered as partly vegetable extract. If its smell, when exposed to heat, be strong and fetid, it contains animal mucilaginous or gelatinous substance; if it be white and transparent, it may be considered as principally saline matter. Nitrate of potash (nitre), or nitrate of lime, is indicated in this saline matter, by its detonating with a burning coal. Sulphate of magnesia may be detected by its bitter taste; and sulphate of potash produces no alteration in solution of carbonate of ammonia, but precipitates solution of muriate of barytes.

11. Should sulphate or phosphate of lime be suspected in the entire soil, the detection of them requires a particular process upon it. A given weight of it, for instance four hundred grains, must be heated red for half an hour (gypsum) and phosphate of lime in a crucible, mixed with one-third of powdered charcoal. The mixture must be boiled for a quarter of an hour, in a half-pint of water, and the fluid collected through the filter, and exposed for some days to the atmosphere in an open vessel. If any soluble quantity of sulphate of lime (gypsum) existed in the soil, a white precipitate will gradually form in the fluid, and the weight of it will indicate the proportion.

Phosphate of lime, if any exist, may be separated from the soil after the process for gypsum. Muriatic acid must be digested upon the soil, in quantity more than sufficient to saturate the soluble earths; the solution must be evaporated, and water poured upon the solid matter. This fluid will dissolve the compounds of earths with the muriatic acid, and leave the phosphate of lime untouched.

12. When the examination of a soil is completed, the products should be classed, and their quantities added together; and if they nearly equal the original quantity of soil, the analysis may be considered as accurate. It must however be noticed, that when phosphate or sulphate of lime is discovered by the independent process, a correction must be made for the general process, by subtracting a sum equal to their weight from the quantity of carbonate of lime obtained by precipitation from the muriatic acid.

In arranging the products, the form should be in the order Thus, 400 grains of a good siliceous sandy soil may be supposed to contain

| Component | Amount | |------------------------------------|--------| | Of water of absorption | 18 | | Of loose stones and gravel, principally siliceous | 42 | | Of undecomposed vegetable fibres | 10 | | Of fine siliceous sand | 200 | | Of minutely divided matter separated by filtration, and consisting of | | | Carbonate of lime | 25 | | Carbonate of magnesia | 4 | | Matter destructible by heat, principally vegetable | 10 | | Silica | 40 | | Alumina | 32 | | Oxide of iron | 4 | | Soluble matter, principally sulphate of potash and vegetable extract | 5 | | Gypsum | 3 | | Phosphate of lime | 2 |

Amount of all the products, 395

Loss, 5

In this instance the loss is supposed small; but in general, in actual experiments, it will be found much greater, in consequence of the difficulty of collecting the whole quantities of the different precipitates; and when it is within thirty or four hundred grains, there is no reason to suspect any want of due precision in the processes.

13. A very fertile corn soil from Ormiston in East Lothian afforded, in 100 parts, only 11 parts of mild calcareous earth; it contained 25 parts of siliceous sand; the finely divided clay amounted to 45 parts. It lost nine in decomposed animal and vegetable matter, and four in water, and afforded indications of a small quantity of phosphate of lime.

This soil was of a very fine texture, and contained very few stones or vegetable fibres. It is not unlikely that its fertility was in some measure connected with the phosphate; for this substance is found in wheat, oats, and barley, and may be a part of their food.

A soil from the low lands of Somersetshire, celebrated for producing excellent crops of wheat and beans without manure, was found to consist of one-ninth of sand, chiefly siliceous, and eight-ninths of calcareous marl tinged with iron, and containing about five parts in 100 of vegetable matter. No phosphate or sulphate of lime could be detected in it; so that its fertility must have depended principally upon its power of attracting principles of vegetable nourishment from water and the atmosphere.

Mr Tillet, in some experiments made on the composition of soils at Paris, found that a soil composed of three-eighths of clay, two-eighths of river sand, and three-eighths of the parings of limestone, was very proper for wheat.

14. In general, bulbous roots require a soil much more sandy and less absorbent than the grasses. A very good potato soil, from Varsel in Cornwall, afforded seven-eighths of siliceous sand; and its absorbent power was so small, that 100 parts lost only two by drying at 400 Fahrenheit.

Plants and trees, the roots of which are fibrous and hard, and capable of penetrating deep into the earth, will vegetate to advantage in almost all common soils which are moderately dry, and which do not contain a very great excess of vegetable matter.

The soil taken from a field at Sheffield-place in Sussex, remarkable for producing flourishing oaks, was found to consist of six parts of sand, and one part of clay and finely divided matter. And 100 parts of the entire soil, submitted to analysis, produced

| Component | Amount | |------------------------------------|--------| | Water | 3 | | Silica | 54 | | Alumina | 28 | | Carbonate of lime | 3 | | Oxide of iron | 5 | | Decomposing vegetable matter | 4 | | Loss | 3 |

15. From the great difference of the causes that influence the productivity of lands, it is obvious that, in the present state of science, no certain system can be devised for their improvement, independent of experiment; but there are few cases in which the labour of analytical trials will not be amply repaid by the certainty with which they denote the best methods of amelioration; and this will particularly happen when the defect of composition is found in the proportions of the primitive earths.

In supplying animal or vegetable manure, a temporary food only is provided for plants, which is in all cases exhausted by means of a certain number of crops; but when a soil is rendered of the best possible constitution and texture, with regard to its earthly parts, its fertility may be considered as permanently established. It becomes capable of attracting a very large portion of vegetable nourishment from the atmosphere, and of producing its crops with comparatively little labour and expense.

Description of the Apparatus for the Analysis of Soils.

A, Retort. B, B, Funnels for the purpose of filtrating. D, Balance. E, Argand's lamp. F, G, H, K, The different parts of the apparatus required for measuring the quantity of elastic fluid given out during the action of an acid on calcareous soils. F, Represents the bottle for containing the soil. K, The bottle containing the acid furnished with a stopcock. G, The tube connected with a flaccid bladder. I, The graduated measure. H, The bottle for containing the bladder. When this instrument is used, a given quantity of soil is introduced into F; K is filled with muriatic acid diluted with an equal quantity of water; and the stopcock being closed is connected with the upper orifice of F, which is ground to receive it. The tube G is introduced into the lower orifice of F, and the bladder connected with it placed in its flaccid state into H, which is filled with water. The graduated measure is placed under the tube of H. When the stopcock of K is turn- ed, the acid flows into F, and acts upon the soil; the elastic fluid generated passes through G into the bladder, and displaces a quantity of water in H equal to it in bulk, and this water flows through the tube into the graduated measure; the water in which gives by its volume the proportion of carbonic acid disengaged from the soil; for every ounce measure of which two grains of carbonate of lime may be estimated.

L. Represents the stand for the lamp.

M, N, O, P, Q, R, S. Represent the bottles containing the different reagents*. See Chemistry, and De-

Composition Chemical, Supplement.

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**Artificial Stone.** See Stucco.

**Elastic Stone.** Some marbles possess the property of elasticity, and hence come under the denomination of elastic stones. But the most remarkable stone of this nature is the elastic sandstone from Brazil. It is a micaceous sandstone in laminae not exceeding half an inch in thickness. Some siliceous stones also have the same property, or acquire it by being exposed to a certain degree of heat.

**Philosopher's Stone.** See Philosopher's Stone.

**Precious Stones.** See Gem.

**Rocking-Stone,** or Logan, a stone of a prodigious size, so exactly poised, that it would rock or shake with the smallest force. Of these stones the ancients give us some account. Pliny says, that at Harpasa, a town of Asia, there was a rock of such a wonderful nature, that if touched with the finger it would shake, but could not be moved from its place with the whole force of the body*. Ptolemy Hephestion mentions† a gygonian stone near the ocean, which was agitated when struck by the stalk of an asphodel, but could not be removed by a great exertion of force. The word *gygonius* seems to be Celtic; for *gygonos* signifies *motitans*, the rocking-stone.

Many rocking stones are to be found in different parts of this island; some natural, others artificial, or placed in their position by human art. In the parish of St Leven, Cornwall, there is promontory called Castle Tryryn. On the western side of the middle group, near the top, lies a very large stone, so evenly poised that any hand may move it from one side to another; yet it is so fixed on its base, that no lever nor any mechanical force can remove it from its present situation. It is called the Logan-stone, and is at such a height from the ground that no person can believe that it was raised to its present position by art. But there are other rocking-stones, which are so shaped and so situated, that there can be no doubt but they were erected by human strength. Of this kind Borlase thinks the great Quoit or Karn-lehou, in the parish of Tywidnek, to be. It is 39 feet in circumference, and four feet thick at a medium, and stands on a single pedestal. There is also a remarkable stone of the same kind in the island of St Agnes in Scilly. The under rock is 10 feet six inches high, 47 feet round the middle, and touches the ground with no more than half its base. The upper rock rests on one point only, and is so nicely balanced, that two or three men with a pole can move it. It is eight feet six inches high, and 47 in circumference. On the top there is a bason hollowed out, three feet eleven inches in diameter at a medium, but wider at the brim, and three feet deep. From the globular shape of this upper stone, it is highly probable that it was rounded by human art, and perhaps even placed on its pedestal by human strength. In Sithney parish, near Helston, in Cornwall, stood the famous logan, or rocking stone, commonly Borlase, called Men Amber, q. d. Men on Bar, or the top stone, chap. iv. It was eleven feet by six, and four high, and so nicely poised on another stone that a little child could move it, and all travellers who came this way desired to see it. But Shrubshall, Cromwell's governor of Pendennis, with much ado caused it to be undermined, to the great grief of the country. There are some marks of the tool on it, and, by its quadrangular shape, it was probably dedicated to Mercury.

That the rocking stones are monuments erected by the Druids cannot be doubted; but tradition has not informed us for what purpose they were intended. Mr Toland thinks that the Druids made the people believe that they alone could move them, and that by a miracle; and that by this pretended miracle they condemned or acquitted the accused, and brought criminals to confess what could not otherwise be extorted from them. How far this conjecture is right we shall leave to those who are deeply versed in the knowledge of antiquities to determine.

**Sonorous Stone,** a kind of stone remarkable for emitting an agreeable sound when struck, and much used in China for making musical instruments which they call king.

The various kinds of sonorous stones known in China differ considerably from one another in beauty, and in the strength and duration of their tone; and what is very surprising, is that this difference cannot be discovered either by the different degrees of their hardness, weight, or fineness of grain, or by any other qualities which might be supposed to determine it. Some stones are found remarkably hard, which are very sonorous; and others exceedingly soft, which have an excellent tone; some extremely heavy emit a very sweet sound; and there are others as light as pumice stone which have also an agreeable sound.

The chemists and naturalists of Europe have never yet attempted to discover, whether some of our stones may not have the same properties as the sonorous stones of the extremities of Asia. It however appears, that the Romans were formerly acquainted with a sonorous stone of the class of *hanging-cher.* Pliny (says the Abbé du Bos, in his Reflections on Poetry and Painting, when speaking of curious stones) observes that the stone called *cophonaz,* or *brazen sound,* is black; and that, according to the etymology of its name, it sends forth a sound much resembling that of brass when it is struck. The passage of Pliny is as follows: *Chalcophonaz nigra est; sed clara avis tinnitum reddit.*

Some sonorous stones were at length sent into France, and the late Duke de Chaunnes examined them with particular attention. The following are some of his observations: "The Academy of Sciences, Mr Romé de Lisle, and several other learned mineralogists, when asked if they were acquainted with the black stone of which the Chinese king was made, for answer cited the passage of Pliny mentioned by Boetius de Bont, Linnæus, and in the Dictionary of Bomare, and added what Mr Anderson says in his Natural History of Iceland respecting a bluish kind of stone which is very sonorous. As the black stone of the Chinese becomes of a bluish colour when filed, it is probably of the same species. None of the rest who were consulted had ever seen it. The Chinese stone has a great resemblance at first sight to black marble, and like it is calcareous; but marble generally is not sonorous. It also externally resembles touchstone, which is a kind of basalt, and the basalts found near volcanoes; but these two stones are vitrifications."

The duke next endeavoured to procure some information from the stone-cutters. They all replied, that blue-coloured marble was very sonorous, and that they had seen large blocks of it which emitted a very strong sound; but the duke having ordered a king to be constructed of this kind of stone, it was found that it did not possess that property. By trying the black marble of Flanders, a piece was at length found which emitted an agreeable sound: it was cut into a king, which is almost as sonorous as those of China. All these observations give us reason to believe that the stones of which the kings are formed are nothing else but a black kind of marble, the constituent parts of which are the same as those of the marble of Europe, but that some difference in their organization renders them more or less sonorous.

**Stone-Stone (lapis sylvis), or fetid stone, so called from its excessively fetid smell, is a calcareous stone impregnated with petroleum. See Mineralogy Index.**

**Stone-Marrow, a variety of clay so called from its having the appearance of marrow.**

**Stone-Ware, a species of pottery so called from its hardness. See Delft Ware and Porcelain.**

**Stone in the Bladder. See Medicine, No. 400, and Surgery Index.**

**Stone, in merchandise, denotes a certain weight for weighing commodities. A stone of beef at London is the quantity of eight pounds: in Herefordshire 12 pounds: in the North 16 pounds. A stone of glass is five pounds; of wax eight pounds. A stone of wool (according to the statute of 11 Hen. VII.) is to weigh 14 pounds; yet in some places it is more, in others less; as in Gloucestershire 15 pounds; in Herefordshire 12 pounds. Among horse-coursers a stone is the weight of 14 pounds.**

The reason of the name is evident. Weights at first were generally made of stone. See Deut. xxv. 13, where the word translated weight, properly signifies a stone.

**Stone-Chatter. See Motacilla, Ornithology Index.**

**Stonehenge, a celebrated monument of antiquity, stands in the middle of a flat area near the summit of a hill six miles distant from Salisbury. It is inclosed by a circular double bank and ditch near 30 feet broad, after crossing which we ascend 30 yards before we reach the work. The whole fabric consisted of two circles and two ovals. The outer circle is about 108 feet diameter, consisting when entire of 62 stones, 32 uprights and 30 imposts, of which remain only 24 uprights, 17 standing and 7 down, 3½ feet asunder, and 8 imposts. Eleven uprights have their 5 imposts on them by the grand entrance. These stones are from 13 to 22 feet high. The lesser circle is somewhat more than 8 feet from the inside of the outer one, and consisted of 40 lesser stones (the highest 6 feet), of which only 19 remain, and only 11 standing: the walk between these two circles is 300 feet in circumference. The adytum or cell is an oval formed of 10 stones (from 16 to 22 feet high), in pairs, with imposts, which Dr Stukeley calls trilithons, and above 30 feet high, rising in height as they go round, and each pair separate, and not connected as the outer pair; the highest 8 feet. Within these are 19 more smaller single stones, of which only 6 are standing. At the upper end of the adytum is the altar, a large slab of blue coarse marble, 20 inches thick, 16 feet long, and 4 broad; pressed down by the weight of the vast stones that have fallen upon it. The whole number of stones, uprights, imposts, and altar, is exactly 140. The stones are far from being artificial, but were most probably brought from those called the Grey Weathers on Marlborough Downs, 15 or 16 miles off; and if tried with a tool they appear of the same hardness, grain, and colour, generally reddish. The heads of oxen, deer, and other beasts, have been found on digging in and about Stonehenge; and human bones in the circumjacent barrows. There are three entrances from the plain to this structure, the most considerable of which is from the north-east, and at each of them were raised on the outside of the trench two huge stones with two smaller within parallel to them.

It has been long a dispute among the learned, by what nation, and for what purpose, these enormous stones were collected and arranged. The first account of this structure we meet with is in Geoffrey of Monmouth, who, in the reign of King Stephen, wrote the history of the Britons in Latin. He tells us, that it was erected by the counsel of Merlin the British enchanter, at the command of Aurelius Ambrosius the last British king, in memory of 460 Britons who were murdered by Hengist the Saxon. The next account is that of Polydore Virgil, who says that the Britons erected this as a sepulchral monument of Aurelius Ambrosius. Others suppose it to have been a sepulchral monument of Boadicea the famous British queen. Inigo Jones is of opinion, that it was a Roman temple; from a stone 16 feet long, and four broad, placed in an exact position to the eastward altar-fashion, Mr Charlton attributed it to the Danes, who were two years masters of Wiltshire. A tin tablet, on which were some unknown characters, supposed to be Punic, was dugged up near it in the reign of Henry VIII., but is lost; probably that might have given some information respecting its founders. Its common name, Stonehenge, is Saxon, and signifies a "stone gallows," to which these stones, having transverse imposts, bear some resemblance. It is also called in Welch choir gwr, or "the giants dance."

Mr Grese thinks that Dr Stukeley has completely proved this structure to have been a British temple in which the Druids officiated. He supposes it to have been the metropolitan temple of Great Britain, and translates the words *choir* your "the great choir or temple." The learned Mr Bryant is of opinion that it was erected by a colony of Cathites probably before the time of the Druids; because it was usual with them to place one vast stone upon another for a religious memorial; and these they often placed so equably, that even a breath of wind would sometimes make them vibrate. Of such stones one remains at this day in the pile of Stonehenge. The ancients distinguished stones erected with a religious view, by the name of *amber*; by which was signified anything solar and divine. The Grecians called them *amphora ambrosia*, *petra ambrosia*. Stonehenge, according to Mr Bryant, is composed of these amber stones; hence the next town is denominated *Ambrosbury*; not from a Roman Ambrosius, for no such person ever existed, but from the *ambrosiac petra*, in whose vicinity it stood. Some of these were rocking stones; and there was a wonderful monument of this sort near Penzance in Cornwall, which still retains the name of *main-amber*, or the sacred stones. Such a one is mentioned by Apollonius Rhodius, supposed to have been raised in the time of the Argonautic, in the island Teinos, as the monument of the two winged sons of Boreas, slain by Hercules; and there are others in China and other countries.