CHAP. XXV.

Exaltation of the power of the Magnet.

One loadstone far surpasses another in power, since one draws iron of almost its own weight, another can hardly stir some shreds. Whatever things, whether animals or plants, are endowed with life need some sort of nourishment, by which their strength not only persists but grows firmer and more vigorous. But iron is not, as it seemed to Cardan and to Alexander Aphrodiseus, attracted by the loadstone in order that it may feed on shreds of it, nor does the loadstone take up vigour from iron filings as if by a repast on victuals. Since Porta had doubts on this and resolved to test it, he took a loadstone of ascertained weight, and buried it in iron filings of not unknown weight; and when he had left it there for many months, he found the stone of greater weight, the filings of less. But the difference was so slender that he was even then doubtful as to the truth. What was done by him does not convict the stone of voracity, nor does it show any nutrition; for minute portions of the filings are easily scattered in handling. So also a very fine dust is insensibly born on a loadstone in some very slight quantity, by which something might have been added to the weight of the loadstone but which is only a surface accretion and might even be wiped off with no great difficulty. Some think that a weak and sluggish stone can bring itself back into better condition, and that a very powerful one also might present it with the highest powers. Do they acquire strength like animals when {93} they eat and are sated? Is the medicine prepared by addition or subtraction? Is there anything which can re-create this primary form or bestow it anew? And, certes, nothing can do this which is not magnetical. Magneticks can restore a certain soundness to magneticks (when not incurable); some can even exalt them beyond their proper strength; but when a body is at the height of perfection in its own nature, it is not capable of being strengthened further. So that that imposture of Paracelsus, who affirms that the force and virtue can be increased and transmuted tenfold, turns out to be the more infamous. The method of effecting this is as follows, viz., you make it semi-incandescent in a fire of charcoal (that is, you heat it very hot), so that it does not become red-hot, however, and immediately slake it, as much indeed as it can imbibe, in oil of saffron of Mars, made from the best Carynthian steel. "In this way you will be able so to strengthen a loadstone that it can draw a nail out of a wall and accomplish many other like wonderful things, which are not possible for a common loadstone." But a loadstone thus slaked in oil not only does not gain power, but suffers also a certain loss of its inborn strength. A loadstone is improved if polished and rubbed with steel.

Buried in filings of the best iron or of pure steel, not rusty, it preserves its strength. Sometimes also a somewhat good and strong one gains [Illustration] some strength when it is rubbed on the pole of another, on the opposite part, and receives virtue. In all these experiments it is an advantage to observe the pole of the earth, and to adjust according to magnetick laws the stone which we wish to strengthen; which we shall set forth below. A somewhat powerful and fairly large loadstone increases the strength of a loadstone as it does of iron. A loadstone being placed over the boreal pole of a loadstone, * {94} the boreal pole becomes stronger, and an iron rod (like an arrow) sticks to the boreal pole A, but not at all to the pole B. The pole A also, when it is at the top in a right line with the axis of both loadstones joined in accordance with magnetick laws, raises the rod to the perpendicular, which it cannot do if the large loadstone be removed, on account of its own weaker strength. But as a small iron globe, when placed above the pole of a terrella, raises the rod to the * perpendicular, so, when placed at the side, the rod is not directed towards the centre of the globe, but is raised obliquely and cleaves anywhere, because the pole in a round piece of iron is always the point which is joined most closely to the pole of the terrella and is not constant as in a smaller terrella. The parts of the earth, as of all magneticks, are in agreement and take delight in their mutual proximity; if placed in the highest power, they do not harm their inferiors, nor slight them; there is a mutual love among them all, a perennial good feeling. The weaker loadstones are re-created by the more powerful, and the less powerful cause no harm to the stronger. But a powerful one attracts and turns a somewhat strong one more than it does an impotent one. Because a strenuous one confers a stronger activity, and itself hastens, flies up to the other, and solicits it more keenly; therefore there is a more certain and a stronger co-action and cohaerency.

CHAP. XXVI.

Why there should appear to be a greater love between _iron and loadstone, than between loadstone and loadstone, or_ between iron and iron, when close to the loadstone, _within its orbe of virtue._

Magnet attracts magnet, not in every part and on every side with equal conditions, as iron, but at one and a fixed point; therefore the poles of both must be exactly disposed, otherwise they do not cleave together duly and strongly. But this disposition is not easy and expeditious; wherefore a loadstone seems not to conform to a loadstone, when nevertheless they agree very well together. A piece of iron by the sudden impression of a loadstone is not only allured by the stone, but is renewed, its forces being drawn forth; by which it follows and solicits the loadstone with no less impulse, and even leads another piece of iron captive. Let there be a small iron spike above a loadstone clinging firmly to it; if you apply an unmagnetized rod of iron to the spike, not, however, {95} so that it touches the stone, you will see the spike when it has touched the iron, leaving the loadstone, follow the rod, try to grasp it by leaning toward it, and (if it should touch it) cleave firmly to it: for a piece of iron, when united and joined to another piece of iron placed within the orbe of virtue of the loadstone, draws it more strongly than does the loadstone itself. The natural magnetick virtue, confused and dormant in the iron, is aroused by the loadstone, is linked to the loadstone, and rejoices with it in its primary form; then smelted iron becomes a perfect magnetick, as robust as the loadstone itself. For as the one imparts and stirs, so the other conceives, and being stirred remains in virtue, and pours back the forces also by its own activity. But since iron is more like iron than loadstone, and the virtue in both pieces of iron is exalted by the proximity of the loadstone, so in the loadstone itself, in case of equal strength, likeness of substance prevails, and iron gives itself up rather to iron, and they are united by their very similar homogenic powers. Which thing happens not so much from a coition, as from a firmer unition; and a knob or snout of steel, fixed skilfully on the pole of the stone, raises greater weights of iron than the stone of itself could. When steel or iron is smelted from loadstone or iron ore, the slag and corrupt substances are separated from the better by the fusion of the material; whence (in very large measure) that iron contains the nature of the earth, purified from alien flaw and blemish, and more homogenic and perfect, though deformed by the fusion. And when that material indeed is provoked by a loadstone, it conceives the magnetick virtues, and within their orbe is raised in strength more than the weaker loadstone, which with us is often not free from some admixture of impurities.

CHAP. XXVII.

The Centre of the Magnetick Virtues in the earth is the centre of the earth; and in a terrella _is the centre of the stone_.

Rays of magnetick virtue spread out in every direction in an orbe; the centre of this orbe is not at the pole (as Baptista Porta reckons, Chap.

22), but in the centre of the stone and of the terrella. So also the centre of the earth is the centre of the magnetick motions of the earth; though magneticks are not borne directly toward the centre by magnetical motion, except when they are attracted by the true pole. For since the formal {96} power of the stone and of the earth does not promote anything but the unity and conformity of disjoined bodies, it comes about that everywhere at an equal distance from the centre or from the circumference, just as it seems to attract perpendicularly at one place, so at another it is able even to dispose and to turn, provided the stone is not uneven in virtue. For if at the distance C from the pole D the stone is able to allure a versorium, *

at an equally long interval above the aequator at A that stone can also direct and turn the versorium. So the very centre and middle of the terrella is the centre of its virtue, and from this to the circumference of the orbe (at equal intervals on every side) its magnetick virtues are emitted.

[Illustration]

CHAP. XXVIII.

A Loadstone attracts magneticks not only to a fixed point or pole, but to every part of a _terrella save the aequinoctial zone_.

Coitions are always more powerful when poles are near poles, since in them by the concordancy of the whole there exists a stronger force; wherefore the one embraces the other more strongly. Places declining from the poles have attractive forces, but a little weaker and languid in the ratio of their distance; so that at length on the aequinoctial circle they are utterly enervated and evanescent. Neither do even the poles attract as mathematical points; nor do magneticks come into conjunction by their own poles, only on the poles of a loadstone. But coition {97} is made on every part of the periphery, both Northern and Southern, by virtue emanating from the whole body; magneticks nevertheless incline languidly towards magneticks in the parts bordering on the aequator, but quickly in places nearer the pole. Wherefore not the poles, not the parts alone nearest to the pole allure and invite magneticks, but magneticks are disposed and turned round and combine with magneticks in proportion as the parts facing and adjoined unite their forces together, which are always of the same potency in the same parallel, unless they are distributed otherwise from causes of variation.

CHAP. XXIX.

On Variety of Strength due to Quantity _or Mass_.

Quite similar in potency are those stones which are of the same mine, and not corrupted by adjacent ores or veins. Nevertheless that which excels in size shows greater powers, since it seizes greater weights and has a wider orbe of virtue. For a loadstone weighing one ounce does not lift a large nail as does one weighing a pound, nor does it rule so widely, nor extend its forces; and if from a loadstone of a pound weight a portion is taken away, something of its power will be seen to go also; for when a portion is abstracted the virtue is lessened. But if that part is properly applied and united to it, though it is not fastened * to nor grown into it, yet by the application it obtains its pristine power and its vigour returns.

Sometimes, however, when a part is taken away, the virtue turns out to be stronger on account of the * bad shape of the stone, namely, when the vigour is scattered through inconvenient angles. In various species the ratio is various, for one stone of a drachm weight draws more than another of twenty pounds. Since in very many the influence is so effete that it can hardly be perceived, those weak stones are surpassed by prepared pieces of clay. But, it may be asked[179], if a stone of the same species and goodness weighing a drachm would seize upon a drachm of iron, would a stone of an ounce weight seize on an ounce, a pound on a pound, and so on? And this is indeed true; for it both strains and remits its strength proportionately, so that if a loadstone, one drachm of which would attract one drachm of iron, were in equal proportion applied either to a suitably large obelisk or to an immense pyramid of iron, it would lift it directly in such {98} proportion and would draw it towards itself with no greater effort of its nature or trouble than a loadstone of a drachm weight embraces a drachm. But in all such experiments as this let the vigour of the magnets be equal; let there be also a just proportion in all of the shapes of the stones, and let the shape of the iron to be attracted be the same, and the goodness of the metal, and let the position of the poles of the loadstones be most exact. This is also no less true in the case of an armed loadstone than of an unarmed one. For the sake of experiment, let there be given a loadstone of eight ounces weight, which when armed lifts twelve ounces of iron; if you cut off from that loadstone a certain portion, which when it has been * reduced to the shape of the former whole one is then only of two ounces, such a loadstone armed lifts a piece of iron applied to it of three ounces, in proportion to the mass. In this experiment also the piece of iron of three ounces ought to have the same shape as the former one of twelve ounces; if that rose up into a cone, it is necessary that this also in the ratio of its mass should be given a pyramidal shape proportioned to the former.

CHAP. XXX.

The Shape and Mass of the Iron are of most _importance in coition_.

Observation has shown above that the shape and mass of the loadstone have great influence in magnetick coitions; likewise also the shape and mass of the iron bodies give back more powerful and steady forces. Oblong iron rods are both drawn more quickly to a loadstone and cleave to it with greater obstinacy than round or square pieces, for the same reasons which we have proven in the case of the loadstone. But, moreover, this is also worthy of observation, that a smaller piece of iron, to which is hung a weight of another material, so that it is altogether in weight equal to another large whole piece of iron of a right weight * (as regards the strength of the loadstone), is not lifted by the loadstone as the larger piece of iron would be. For a smaller piece of iron does not join with a loadstone so firmly, because it sends back less strength, and only that which is magnetick conceives strength; the foreign material hung on cannot acquire magnetick forces.

{99} CHAP. XXXI.

On Long and Round Stones.

Pieces of iron join more firmly with a long stone than with a round one, provided that the pole of the stone is at the extremity and end of its length; because, forsooth, in the case of a long stone, a magnetick is directed at the end straight towards the body in which the virtue proceeds in straighter lines and through the longer diameter. But a somewhat long stone has but little power on the side, much less indeed than a round one.

It is demonstrable[180], indeed, that at A and B the coition is * stronger in a round stone than at C and D, at like distances from the pole.

[Illustration]

CHAP. XXXII.

Certain Problems and Magnetick Experiments about the Coition, and Separation, and regular Motion _of bodies magnetical_.

Equal loadstones come together with equal incitation. *

Also magnetick bodies of iron, if alike in all respects, * come together when excited with similar incitation.

Furthermore, bodies of iron not excited by a * loadstone, if they are alike and not weighed down by their bulk, move towards one another with equal motion.

Two loadstones, disposed on the surface of some water in {100} suitable skiffs, if they are drawn up suitably within their orbes of virtue, incite one another mutually to an embrace. So a proportionate * piece of iron in one skiff hurries with the same speed towards the loadstone as the loadstone itself in its boat strives towards the iron. From their own positions, indeed, they are so borne together, that they are joined and come to rest at length in the middle of the space. Two iron wires magnetically excited, floating in water by means of * suitable pieces of cork, strive to touch and mutually strike one another with their corresponding ends, and are conjoined.

Coition is firmer and swifter than repulsion and separation in * equal magnetick substances. That magnetick substances are more sluggishly repelled than they are attracted is manifest in all magnetical experiments in the case of stones floating on water in suitable skiffs; also in the case of iron wires or rods swimming (transfixed through corks) and well excited by a loadstone, and in the case of versoria. This comes about because, though there is one faculty of coition, another of conformation or disposition, repulsion and aversion is caused merely by something disposing; on the other hand, the coming together is by a mutual alluring to contact and a disposing, that is, by a double vigour.

A disponent vigour is often only the precursor of coition, in order that the bodies may stand conveniently for one another before conjunction; wherefore also they are turned round to the corresponding ends, if they can [not][181] reach them through the hindrances.

[Illustration]

If a loadstone be divided through a meridian into two equal parts, the separate parts mutually repel one another, the poles being * placed directly opposite one another at a convenient and equal distance. They repel one another also with a greater velocity than when pole is put opposite pole incongruously. Just as the part B of the loadstone, placed almost opposite the part A, repels it floating in its skiff, because D turns away from F, and E from C; but if B is exactly joined with A again, they agree and become one body {101} magnetical; but in proximity they raise enmities. But if one part of the stone is turned round, so that C faces D and F faces E, then A pursues B within its orbe until they are united.

The Southern parts of the stone avoid the Southern parts, and the Northern parts the Northern. Nevertheless, if by force you move up the Southern cusp of a piece of iron too near the Southern part of the stone, the cusp is seized and both are linked together in friendly embraces: because it immediately reverses the implanted verticity of the iron, and it is changed by the presence of the more powerful stone, which is more constant in its forces than the iron. For they come together according to their nature, if by reversal and mutation true conformity is produced, and just coition, as also regular direction. Loadstones of the same shape, size, and vigour, attract one another mutually with like efficacy, and in the opposite position repel one another mutually with a like vigour.