neral, actually succeeded in reducing it by the following process: he lined a crucible with charcoal powder moistened with water, put into it some of the mineral formed into a ball by means of oil, then filled up the crucible with charcoal-powder, luted another crucible over it, and exposed the whole for about an hour to a very intense heat. At the bottom of the crucible was found a metallic button, or rather a number of small metallic globules, equal in weight to one-third of the mineral employed. It is easy to see by what means this reduction was accomplished. The charcoal attracted the oxygen from the oxyd, and the metal remained behind. The inetal obtained, which is called manganese, was farther examined by Ilseman in 1782, Hielm in 1785, and Bindheim in 1789.

1. Manganese, when pure, is of a greyishwhite colour, and has a good deal of bril liancy. Its texture is granular. It has neither taste nor smell. Its hardness is equal to that of iron. Its specific gravity is 7,000. It is very brittle; of course it can neither be hammered, nor drawn out into wire. Its tenacity is unknown. It requires, according to Morveau, the temperature of 160 Wedgewood to melt it; so that, platinum excepted, it is the most infusible of all the metals. When reduced to powder, it is attracted by the magnet, owing probably to a small portion of iron from which it can with difficulty be parted.

II. Manganese, when exposed to the air, attracts oxygen more rapidly than any other body, phosphorus excepted. It loses its lastre almost instantly, becomes grey, violet, brown, and at last black. These changes take place still more rapidly if the metal is heated in an open vessel.

This metal seems capable of combining with three different proportions of oxygen, and of forming three different oxyds, the white, the red, and the black.

The protoxyd or white oxyd, may be obtained by dissolving the black oxyd of manganese in nitric acid, by adding a little sugar. The sugar attracts oxygen from the black oxyd, and converts it into the white, which is dissolved by the acid. Into the solution pour a quantity of potass; the protoxyd precipitates in the form of a white powder. It is composed, according to Bergman, of 80 parts of manganese, and 20 of oxygen. When exposed to the air, it Soon attracts oxygen, and is converted into the black oxyd.

The deutoxyd or red oxyd, may be obtained by disolving the black oxyd in sulphuric acid, without the addition of any combustible substance. When black oxyd of manganese, made into a paste with sulphuric acid, is heated in a retort, a great quantity of oxygen gas comes over, while the oxyd, thus deprived of part of its oxygen, dissolves in the acid. Distil to dry ness, and pour water upon the residuum, and pass it through a filtre. A red-coloured

solution is obtained, consisting of the sul phat of manganese dissolved in water. On the addition of an alkali, a red substance precipitates, which is the red oxyd of man. ganese. According to Bergman, it is composed of 74 parts of manganese, and 26 of oxygen. This oxyd likewise attracts oxygen, when exposed to the atmosphere, and is converted into the black oxyd.

The peroxyd of black oxyd of manganese exists abundantly in nature; indeed it is almost always in this state that manganese is found. It was to the black oxyd that the appellation manganese itself was originally applied. It may be formed very soon by exposing the metal to the air. This oxyd according to Fourcroy, is composed of 60 parts of manganese, and 40 of oxygen. When heated to redness in an earthen retort, it gives out abundance of oxygen gas, which may be collected in proper vessels. By this operation it is reduced nearly to the state of red oxyd. It is exposed to the air, and moistened occasionally; it absorbs a new dose of oxygen; and thus the same process may again be repeated. No oxygen gas can be obtained from the white oxyd: a proof that its oxygen is retained by a stronger affinity than the additional dose of oxygen which constitutes the black oxyd. Seguin has observed, that in some cases the black oxyd of manganese emits, before it becomes red, a quantity of azotic gas. When long exposed to a strong heat, it assumes a green colour. In that state it is whitened by sul phuric acid, but not dissolved. A very vio lent heat fuses this oxyd, and converts it into a green-coloured glass.

III. Manganese does not combine with hydrogen. When dissolved in sulphuric acid, a black spongy mass of carburet of iron is left behind. Hence it has been supposed capable of combining with carbon; but it is more probable that the carbon is combined with the iron, which is almost It seems always present in manganese. pretty clear, however, that carburet of iron is capable of combining with this metal, and that it always forms a part of steel.

Bergman did not succeed in his attempt to combine manganese with sulphur; but he formed a sulphureted oxyd of manganese by combining eight parts of the black oxyd with three parts of sulphur. It is of a green colour, and gives out sulphureted hydrogen gas, when acted upon by acids. It cannot be doubted, however, that sulphur is capable of combining with manganese; for Proust has found native sulphuret of manganese in that ore of tellurium which is known by the name of gold ore of Nagyag.

Phosphorus may be combined with manganese by melting together equal parts of the metal and of phosphoric glass; or by dropping phosphorus upon red-hot manganese. The phosphuret of manganese is of a white colour, brittle, granulated, disposed

to crystallize, not altered by exposure to the air, and more fusible than manganese. When heated the phosphorus burns, and the metal is oxydyzed.

IV. Manganese does not combine with either of the simple combustibles.

V. Manganese combines with many of the metals, and forms with them alloys which have been but very imperfectly examined.

It unites readily with copper. The compound, according to Bergman, is very malleable; its colour is red, and it sometimes becomes green by age. Gmelin made a number of experiments to see whether this alloy could be formed by fusing the black oxyd of manganese along with copper. He partly succeeded, and proposed to substitute this alloy, instead of the alloy of copper and arsenic, which is used in the

arts.

It combines readily with iron; indeed it has scarcely ever been found quite free from some mixture of that metal. Manganese gives iron a white colour, and renders it brittle. It combines also with tin, but scarcely with zinc.

It does not combine with mercury nor with bismuth. Gmelin found that manganese cannot be alloyed with bismuth without great difficulty, and that it unites to antimony very imperfectly. Chemists have not at tempted to combine it with gold, platinum, silver, nickel, nor cobalt.

VI. The affinities of manganese and of its white and red oxyds, are, according to Bergman, as follows:

:

Prussic, Carbonic.

Reduction of Ores. As manganese is applied to no use in its metallic state, there are no establishments for the reduction of its ores in the great way and even in the laboratory the process is seldom performed, chiefly on account of the intense heat which is requisite, and which cannot be obtained in small furnaces, unless they are peculiarly well constructed. The use of all alkaline and vitreous fluxes must be carefully avoided: for the affinity of these with the oxyd of manganese is so considerable, as entirely to prevent its reduction when they are pre

sent. The only method that has been attended with any tolerable success, is the following, invented by Berginan. Select a sound and very refractory crucible, and line it with charcoal, or still better, with a mixture of linseed meal and water, beaten up with as much finely sifted charcoal as it will take without losing its tenacity: dry the crucible tho roughly, gradually increasing the heat till the meal begins to be scorched: then take some oxyd of manganese purified from all extraneous substances, and make it up into a ball with any kind of oil; put this into the cavity of the crucible and cover it with powdered charcoal: then lute in a pierced cover or an inverted crucible, and place it in a blast furnace: keep it a moderate red heat till the jet of blue flame through the hole in the cover has ceased: then bring the furnace rapidly to its highest heat, and keep it so for about three quarters of an hour: then let the fire go out, and when the crucible is quite cold, break it up carefully, and the manganese will be found in globules of various sizes, covered for the most part with a thin vitreous crust. MAGNET, or Loadstone, in mineralogy. See FERRUM magnes. MAGNETICAL. a. (from magnet.) 1. MAGNETIC.

} Relating magnet mag:

net (Newton). 2. Having powers corre spondent to those of the magnet (Newton). 3. Attractive; having the power to draw things distant (Donne).

MAGNETIC Iron-stone. See FERRUM. MAGNETIC Sand. See FERRUM. MAGNETIC Needle. See NEEDLE and COMPASS.

MAGNETISM, the power by which the loadstone is influenced, and manifesting itself by cer tain phenomena of attraction and repulsion. Or, it is the science in which phenomena of this kind are classified and reduced to laws.

The loadstone was long regarded as a simple stone, possessing the property of attracting iron, as the name given, in the common language every country, to the ferruginous mineral endowed such with this quality, will show ; as pierre d'aimant, for example, in French; and the loadstone in English. Men judged of its substance by the stony particles that are often mixed with it, but which are purely accidental.

1. The attractive virtue of the loadstone was known to the ancients, and they had even remarked, that it communicated to one piece of iron the power of attracting another piece. But though, from the sympathy it seemed to evince for iron, the loadstone became one of those sports in which curiosity delights, and which it repaid in various ways, the best and most important property of this mineral, which occasions one of its extremities to have a northern and the other discovery was made about the twelfth century, and se a southern direction, long escaped observation. This

veral nations claim the honour of it.

the

2. The earliest theories of magnetism partook of the systematic ideas that prevailed among philosophers of the day. The vortices of Des cartes captivated the mind to such a degree, that

attempts were made to introduce them every where. They were given to electric bodies, and the magnet also must have its share. Afterwards the idea suggested itself of simple effluvia of magnetic matter, the molecule of which advanced towards each other, or took a retrograde motion, according to the manner in which the respective effluvia of two magnets met. There were supposed to be in the iron a kind of small hairs that performed the office of valves, to aid the passage of the fluid in one way, and to oprose its passage when it presented itself in a centrary direction. Such was, among others, the opinion of Dufay: and this philosopher, who had seen so clearly the principle of electric motion, when he came to apply it to magnetism, presented a machine of his own invention, instead of the mechanism of

nature.

3. pinus was the first, who, to explain the phenomena of magnetism, made use of simple powers subjected to calculation. The idea which served as the basis of his theory was suggested to him while holding a tourmalin in his hand. He Lad discovered, that the effects of this stone were the result of electricity, and had remarked, that it repelled on one side, and attracted on the other, a small electrised body. To these two sides he gave the name of poles, and this appellation, which might have passed for a convenient mode of expression only, became the word really expressive of the thing. He saw in the tourmalin a kind of small electric magnet, and comparing the prenomena of real magnets with those of idio-electric bodies, he found, that the action of the two fluids might be reduced to the same laws; and thus added to the merit of having improved the theory of electricity, and created, as it were, the theory of magnetism, that of combining in the same link these two grand portions of the chain of human science.

Coulomb, receiving from the hands of Æpinus the first of these theories, to give it a new modification, thereby contracted a sort of engagement to improve the second also; and it will presently be seen, from the sketch we shall give of his results, with what fidelity be has acquitted himself.

fluid; and Coulomb has proved, as we shall presently see, that these different actions follow the inverse ratio of the square of the distance.

6. All the natural fluid of the magnetic body, even after its decomposition, remains in the interior of that body; and, in this view, magnets may be assimilated to idio-electric bodies. The two fluids disengaged from the state of combination, take contrary movements towards the extremities of the magnet, and thus exhibit actions analogous to those of vitreous and resinous electricity.

But, before we proceed further, let us take a general view of magnetism as it presents itself in all its extent; for to understand well the developement of the theory, it is necessary to have at least an idea of it as a whole.

It con

7. All the phenomena that magnets which have been subjected to experiment, have furnished, are only so many different aspects, as it were, of a fundamental fact, that has long been remarked. sists in this, that if we take at pleasure one of the extremities of a magnet, and apply it to the two extremities of another magnet, there will be attraction on one part and repulsion on the other between the two magnets. The opposed extremity of the first magnet will produce on those of the other magnet inverse effects. In general there is in every magnet two opposite points, that exhibit contrary actions and to which the name of poles had been given. We may judge of the energy of these contrary influences by making a magnet act in presence of a magnetised needle freely suspended; the extremities of this needle will make different circuits, and sometimes a complete revolution, to find the position required by the equilibrium.

8. Now, we have a phenomenon, extremely remarkable by its continuity, and the immense distances to which it extends itself, in the terrestrial globe, which performs, relatively to a magnetised needle, the same function as the magnet in the instance we have just mentioned; so that the needle, left to the influence of this vast magnetic body, takes a direction from north to south, and which we see to be that which accords with the manner of acting of this same governing influence. For if, when the needle is at

ism.

4. Though the magnetic fluid is governed by the same laws as the electric fluid, there are several things, in the present state of our knowledge, that indicate a difference between them. Iron, and one or two other metallic substances, are the only bodies that have hitherto exhibited unequivocal signs of magnetism, whereas all bodies are susceptible of the electric virtue. If an electrised tourmalin be preseated to a magnetised needle freely suspended, whatever may be the direction of the two bodies as to the poles, the tourmalin exercises on the needle, to alter its position, the same attractive force only that it would exercise on any other body; which implies, that its presence gives rise in the needle itself to an electric virtue, independent of the magnetic virtue.

5. The correspondence between the two theories leads us further to consider the magnetic fluid as composed of two distinct fluids, combined together in iron that exhibits no sign of magnetism, and existing apart in that which has undergone a state of magnetism. The molecule of each fluid also repel one another, and attract those of the other VOL. VII.

oscillations, to return to it again. What would have been the sentiments of the ancient philosophers, who already ascribed a soul to magnets, though they knew nothing of their powers of action, bat in circumstances of contact, had the idea occurred to them of suspending one of these bodies to a thread?

9. What we have remarked in the preceding paragraph, leads to an observation that we conceive to be interesting, relative to the manner of denominating the two fluids which compose the magnetic fluid, as well as the poles in which their powers of action reside. The mere mention of the hypothesis relative to the existence of these fluids, is sufficient to enable us to understand that the magnetic repulsions, similar in this respect to electric repulsions, are ascribable to those which exist between homogeneous fluids, and the attractions to those which heteroge neous fluids exert on one another. It follows from this, that when a magnetised needle is in its natural direction, the pole of that needle, which is turned to the north, is in the opposite state to that of the pole of our globe, which is in the same quarter; and as this last mentioned pole ought to be the true north pole relative to magnetisin S

answers to the north pole of the globe, if the experiment be made in a northern country, or, in a a contrary case, to the south pole. Now, assuming as a fact that the directing forces are in proportion to the sines of the angles of deviation, it appears that the resulting force we have mentioned is a constant quantity, passing always by one and the same point of the needle.

But it was not sufficient to have established, by means of the results we have stated, a theory of magnetic phenomena: it was necessary to determine the law by which the forces that act in these phenomena are governed at different distances. Many philosophers, who devoted their attention to this subject, had recourse to means so very imperfect, that we must not be surprised to see their results accord so httle with one another, and be so remote from the true principle.

16. The precision of the methods employed by Coulomb, to ascertain this law, leaves no doubt that it follows the inverse ratio of the square of the distance, like that which governs electrical actions. But here, the manner in which the fluid is distributed in the bodies that were subjected to experiment, required distinct consideration; from the circumstance of these bodies having two centres of action that are in two opposite states, while the electrical bodies that were employed in researches directed to a similar end, were solicited only by a single electricity, which enabled the observer to consider all the forces as united in a single centre of action. For the present, we shall content ourselves with remarking, that in the magnet the two centres of action are at a very trifling distance from the extremities.

Coulomb has obtained the end he had in view by two different methods. The first consisted in placing in a state of oscillation a small needle, 27 millimetres, or an inch, in length, directly opposite to the inferior centre of action of a magnetic steel wire, about 6-8 decimetres, or 25 inches, in length, situated vertically in the plane of the magnetic

meridian.

Leaving for an instant the superior centre of action out of the question, we must conceive that the needle, while it makes its oscillations, is at the same time solicited by two forces, of which one resides in the inferior centre of action of the steel wire, and the other is the directing force of the needle. The effect of this last force also, when it acts alone on a needle in a deranged state as to its magnetic meridian, is to give to the needle an oscillatory motion. Now Coulomb had ascertained, prior to the experiment, that the needle, left to its own directing force, made 15 oscillations in 60 seconds. But it is with the needle here, as with the pendulum oscillating by virtue of its weight: and it is proved that the action of this force, to make the pendulum oscillate, is proportional to the square of the num. ber of oscillations made in a given time, assumed for the unit of time. Accordingly, in the present bypothesis, which supposes the needle to be solicited at once by its own directing force and by that of the steel wire, the value of the last is obtained by subtracting the square of 15 from the number of oscillations made by the needle in 60 seconds.

To give precision to the experiments, it was further necessary to determine the distance at which the steel wire was supposed to act on the Beedle. Now we shall presently see, that this action depends upon two forces, each exerting itself on one of the poles of the needle, and con

spiring, as it were, to impress upon it the same motion; and as the needle was very short, so that the distances of its poles at the centre of action of the steel wire differed but little from one another, the middle of this needle might, without striking error, be considered as the mean distance between those at which the two actions exerted themselves; and it was relatively to this point, that the question of estimating the force of the wire in presence of which the needle oscillates, was undertaken.

An example will serve to throw light on all that has been said. The needle, being so placed that its centre of action was at the distance of 108 millimetres, or 4 inches, from the steel wire, made 41 oscillations in a minute: placed afterwards at double that distance, it made but 24 oscillations in a minute. The total forces, then, which solicited the needle in its two positions, were respectively as the square of 41 is to that of 24, or as 1681 to 576. If from each of these numbers we take the square of 15, or 225, we shall have for the ratio between the forces of the steel wire, that of 1456 to 351, which differs but little from the proportion of 4 to 1. And as the corresponding distances are to each other as 1 is to 2, we may infer, that the forces are in the inverse ratio of the square of the distances.

But

The number of oscillations that took place in 60 seconds, did not however always give exactly the quantity of action exerted by the steel wire. That exactness only obtained, as to sense, so long as the needle was at distances from the steel wire small enough to permit the neglecting the force of the superior pole of that wire, which was then directed according to a line deviating but little from the vertical, and which, besides, acted much farther off than the inferior pole. when the needle was placed at a greater distance from the steel wire, then the part of the decomposition or resolution of that force which was in the horizontal direction, as well as that according to which the inferior pole acted, would become more appreciable with respect to the force of that same pole; and hence it was only by making the little requisite correction, that one could be able to represent the law sought, with the suitable precision.

17. The other method was analogous to that which Coulomb had employed in electricity. He converted the electrical balance into a magnetic balance, supplying, by means of a long magnetic needle, the lever suspended to the wire, and substituting for the copper ball a similar needle placed vertically on the magnetic meridian. Such was the respective disposition of the two needles, that when that which was moveable was on the point of touching the other, by preserving its nearly horizontal position, the contact took place at one of the centres of action of the first, and the inferior centre of the second.

The natural tendency of the needle to return to its magnetic meridian, was here also a particular action that combined itself with the reci procal actions of the two needles; and the object was to discover the relation between these actions, by disengaging them from their combination. To succeed in this, Coulomb began with comparing the first force alone with the force of torsion; and he found, that if a torsion making an angle of 35 degrees was given to the wire that sustained the moveable needle, the needle deviated a degree from its magnetic meridian: and if the torsions were increased so as to form angles