CHAP. VI.

What seems an Opposing Motion in Magneticks _is a proper motion toward unity_.

[Illustration]

In things magnetical nature always tends to unity, not merely to confluence and agglomeration, but to harmony; in such a way that the rotational and disponent faculty should not be disturbed, as is variously shown in the following example. Let C D be an entire body of some magnetick substance, in which C tends to B, the north of the earth, and D to the south, A.

Then[205] divide it in the middle in its aequator, and it will be E that is tending toward A, and F tending toward B. For just as in the undivided body, so in the divided, nature aims at these bodies being united; the end E again joins with F harmoniously and * eagerly and they stick together, but E is never joined to D, nor F to C; for then C must be turned contrary to nature toward A, the south, or D toward B, the north, which is foreign to them and incongruous. Separate the stone in the place where it is cut and turn D round to C; they harmonize and combine excellently. For D is tending to the south, as before, and C to the north; E and F, parts which were cognate in the ore, are now widely separated, for they do not move together on account of material affinity, but they take their motion and inclination from their form. So the ends, whether joined or divided, tend magnetically in the same way to the earth's poles in the first figure where there is one whole, or divided as in the second figure; and F E in the second figure is a perfect magnetick joined together into one body and C D, just as it was primarily produced in its ore, and F E in its boat, turn in {131} this way to the poles of the earth and are conformed to them. * This harmony of the magnetick form is shown also in the forms of vegetables. Let A B be a twig from a branch of osier or other * tree which sprouts easily.

Let A be the upper part, B the lower part toward the root; divide it at C D; I say that the end D, if grafted again to C by the primer's art, grows to it; just as also if B is grafted to A, they grow together and germinate.

But D being grafted on A, or C on B, they are at variance, and never grow into one another, but one of them dies on account of the inverted and inharmonious arrangement, since the vegetative force, which moves in one way, is now impelled in opposite directions.

[Illustration]

CHAP. VII.

A determined Verticity and a disponent Faculty are what arrange magneticks, not a force, attracting or pulling them _together, nor merely strongish coition or unition_.

[Illustration] {132}

In the neighbourhood of the aequinoctial A there is no coition of the ends of a piece of iron with the terrella; at the poles there is the strongest.

The greater the distance from the aequinoctial, the stronger is the coition with the stone itself, and with any part of it, not with its pole alone.

Yet pieces of iron are not raised up on account of some peculiar attracting force or a stronger combined force, but on account of that common directing or conforming and rotating force; nor indeed is a spike in the part about B, even one that is very small and of no * weight[206], raised up to the perpendicular by the strongest terrella, but cleaves to it obliquely. Also just as a terrella attracts magnetick bodies variously with dissimilar forces, so also an iron snout placed on the stone obtains a different potency in proportion to the latitude, * just as a snout at L by its firmer connection resists a greater weight more stoutly than one at M, and at M than at N. But neither does the snout raise the spike to the perpendicular except at the poles, as is shown in the figure. A snout at L may hold and lift from the earth two ounces of iron in one piece; yet it is not strong enough to raise an iron wire of two grains weight to the perpendicular, which would happen if the verticity arose on account of a * stronger attraction, or rather coition or unition.

CHAP. VIII.

Of Discords between pieces of Iron upon the same pole of a loadstone, and how they can agree and _stand joined together_.

Suppose two iron wires or a pair of needles stuck on the pole of a terrella; though they ought to stand perpendicularly, they mutually repel one another at the upper * end, and produce the appearance of a fork; and if one end be forcibly impelled toward the other, the other declines and bends away from association with it, as in the following figure.

[Illustration] {133} A and B, iron spikes, adhaere obliquely[207] upon the pole on account of their nearness to one another; either alone would otherwise stand erect and perpendicular. For the extremities A B, being of the same verticity, mutually abhor and fly one another. For if C be the northern pole of the terrella, A and B are also northern ends; but the ends which are joined to and held at the pole C are both * southern. But if those spikes be a little longer (as, for example, of two digits length) and be joined by force, they adhaere together and unite in a friendly style, and are not separated without force. For they are magnetically welded, and there are now no longer two distinct ends, but one end and one body; no less than a wire which is doubled and set up perpendicularly. But here is seen also another subtile point, that if those spikes were shorter, not as much as the * breadth of one digit, or even the length of a barleycorn, they are in no way willing to harmonize or to stand straight up at the same time, because naturally in shorter wires the verticity is stronger in the ends which are distant from the terrella and the magnetick discord more vehement than in long ones. Wherefore they in no way admit of an intimate association and connection.

[Illustration]

Likewise if those lighter pieces of iron or iron wires be suspended, hanging, as A and B, from a very fine silk thread, not twisted * but braided, distant from the stone the length of a single barleycorn, then the opposing ends, A and B, being situated within the orbe of virtue above the pole, keep a little away from one another for the same reason; except when they are very near the pole of the stone C, the stone then attracting them more strongly toward one end.

{134} CHAP. IX.

Figures illustrating direction and showing varieties _of rotations_.

[Illustration]

Passing from the probable cause of motion toward fixed points (according to magnetick laws and principles), it remains for us to indicate those motions. Above a round loadstone (whose poles are A, B) let a versatory needle be placed whose cusp has been excited by the pole A; that cusp is certainly directed toward A, and is strongly attracted by A; because, having been touched by A, it is in true harmony with A, and combines with it; and yet it is called contrary, because when the versorium is separated from the stone, it is seen to be moved toward the opposite part of the earth to that toward which the pole A of the loadstone is moved. For if A be the northern pole of the terrella, the cusp is the southern end of the needle, of which the other end (namely, the cross) is pointed to B; so B is the southern pole of the loadstone, but the cross is the northern end of the versorium. So also the cusp is attracted by E, F, G, H, and by every *

part of a meridian, from the aequator toward the pole, by the faculty disponent; and when the versorium is on the same parts of the meridian, the cusp is directed toward A. For it is not the point A that turns the versorium toward it, but the whole loadstone; as also the whole earth does, in the turning of loadstones to the earth.

[Illustration]

_Figures illustrating magnetick directions in a right sphere[208] of stone, and in the right sphere of the earth, as well as the polar directions to the perpendicular of the poles._ All these cusps have been touched by the pole A; all the cusps are turned toward A, excepting that one which is repelled by B.

{135}

[Illustration] _Figures illustrating horizontal directions above the body of a loadstone._ All the cusps that have been made southern by rubbing on the boreal pole, or some place round the northern pole A, turn toward the pole A, and turn away from the southern pole B, toward which all the crosses look. I call the direction horizontal, because it is arranged along the plane of the horizon; for nautical and * horological instruments are so constructed that the iron hangs or is supported in aequilibrium on the point of a sharp pin, which prevents the dipping of the versorium, about which we intend to speak later. And in this way it is of the greatest use to man, indicating and distinguishing all the points of the horizon and the winds.

Otherwise on every oblique sphere (whether of stone or the earth) versoria and all magnetick substances would have a dip by their own nature below the horizon; and at the poles the directions would be perpendicular, which appears in our discussion _On Declination_.

[Illustration]

_A round stone (or terrella) cut in two at the aequator;_ and all the cusps have been touched by the pole A. The points at the centre of the earth, and between the two parts of the terrella which has been cut in two through the plane of the aequator, {136} are directed as in the present[209] diagram.

This would also happen in the same way if the division of the stone were through the plane of a tropick, and the mutual separation of the divided parts and the interval between them were the same as before, when the loadstone was divided through the plane of the aequator, and the parts separated. For the cusps are repelled by C, are attracted by D; and the versoria are parallel, the poles or the verticity in both ends mutually requiring it.

[Illustration]

_Half a terrella by itself and its directions, unlike the directions * of the two parts close to one another as shown in the figure above_. All the cusps have been touched by A; all the crosses below except the middle one tend toward the loadstone, not straight, but obliquely; because the pole is in the middle of the plane which before was the plane of the aequator. All cusps touched by places distant from the pole move toward the pole (exactly the same as if they had been rubbed upon the pole itself), not toward the place where they were rubbed, wherever that may have been in the undivided stone in some latitude between the pole and the aequator. And for this reason there are only two distinctions of regions, northern and southern, in the terrella, just {137} as in the general terrestrial globe, and there is no eastern nor western place; nor are there any eastern or western regions, rightly speaking; but they are names used in respect of one another toward the eastern or western part of the sky. Wherefore it does not appear that Ptolemy did rightly in his _Quadripartitum_, making eastern and western districts and provinces, with which he improperly connects the planets, whom the common crowd of philosophizers and the superstitious soothsayers follow.

CHAP. X.

On Mutation of Verticity and of Magnetick Properties, or on alteration in the power _excited by a loadstone_.

Friction with a loadstone gives to a piece of iron a verticity strong enough; not, however, so stable that the iron may not by being rubbed on the opposite part (not only with a more powerful loadstone, but with the same) be changed and deprived of all its former verticity, and indued with a new and opposite one. Take a piece of iron wire and rub each end of the wire equally with one and the same pole of a loadstone, and let it be passed through a suitable cork and place it on water. Then truly one end of the wire will be directed toward that pole of the earth toward which that end of the stone will not turn. But which end of the iron wire will it be?

That certainly which was rubbed last. Rub the other end of this again with the same pole, and immediately * that end will turn itself in the opposite direction. Again touch the former end of the iron wire only with the same pole of the loadstone as before; and that[210] end, having gained the command, immediately changes to the contrary side. So you will be able to change the property of the iron frequently, and that end of the wire rules which has been touched the last. Now then merely hold the boreal pole of the stone for some time near the boreal part of the wire which was last touched, so that it does not touch, but so that it is removed from it by one, two, or even three digits, if the stone have been pretty * strong; and again it will change its property and will turn round to the contrary side; which will also happen (albeit rather more feebly) even if the loadstone be removed to a distance of four digits. You will be able to do the same thing, moreover, with both the austral and the boreal part of the stone in all these experiments. Verticity may likewise be acquired and changed when thin plates of gold, * silver, and glass are interposed between the stone and the end of the iron or iron wire, if the stone were rather strong, even if the {138} intermediate lamina is not touched either by the iron or the stone. And these changes of verticity take place in smelted iron. Indeed what the one pole of the stone implants and excites, the other disturbs and extinguishes, and confers a new force. For it does not require a stronger loadstone to take away the weaker and sluggish virtue and to implant the new one; nor is iron inebriated by the equal strength of loadstones, and made utterly uncertain and neutral, as Baptista Porta teaches; but by one and the same loadstone, or by loadstones endowed with equal power and might, its strength is, in accordance with magnetick rules, turned round and changed, excited, repaired, or disturbed. But a loadstone itself, by being rubbed on another, whether a larger or a more powerful stone, is not disturbed from its own property and verticity, nor does it turn round toward the opposite direction in its boat, or to the other pole opposite to that to which it inclines by its own nature and implanted verticity. For strength which is innate and has been implanted for a very long time abides more firmly, nor does it easily yield from its ancient holding; and that which has grown for a long time is not all of a sudden brought to nothing, without the destruction of the substance containing it. Nevertheless in a long interval of time a change * does take place; in one year, that is to say, or two, or sometimes in a few months; doubtless when a weaker loadstone remains lying by a stronger one contrary to the order of nature, namely, with the northern pole of one loadstone adjoined to the northern pole of another, or the southern to the southern. For so the weaker strength gradually declines with the lapse of time.

CHAP. XI.

On the Rubbing of a piece of Iron on a Loadstone in places midway between the poles, and upon _the aequinoctial of a terrella_.

Select a piece of iron wire of three digits length, not touched by a loadstone (but it will be better if its acquired verticity be rather weak or have been damaged in some way); touch it and rub it on the aequator of a terrella, exactly on the aequinoctial line in the direction of its length, on the one end, or the ends only, or in all its parts; place the wire touched in this * way on water in a cork fitted for it; it will swim about doubtfully on the waves without any acquired verticity, and the verticity previously implanted will be disturbed. If, however, it float by chance toward the poles, it will be checked a little by the poles of the earth, and will at length by the influence of the earth be indued with verticity.

{139} CHAP. XII.

In what way Verticity exists in any Iron that has _been smelted though not excited by a lodestone_.