An entire body of philosophy according to the principles of the famous Renate Des Cartes in three books, (I) the institution ... (II) the history of nature ... (III) a dissertation of the want of sense and knowledge in brute animals ... / written originally in Latin by the learned Anthony Le Grand ; now carefully translated from the last corrections, alterations, and large additions of the author, never yet published ... by Richard Blome.

CHAP. X. Of the Magnet or Loadstone.

I. Why a Loadstone points to∣wards the North Pole. IF a Loadstone be hung up in the Air, or be suffered to swim on the top of Quicksilver, it will wave this way and that way, till one of its Poles look towards the North, and the other towards the South: Yet not altogether in an even Horizontal Situation, but so as that that part which points to the North, will be deprest beneath the Level of the Horizon, to the end it may the better be directed towards the Northern Pole of the Earth.

The Reason of this Conversion must be fetch'd from the striate matter, whence the Magnet receives all its virtue; the particles whereof are so twist∣ed, that those which proceed from the South Pole, cannot enter in at the opposite Northern Pole; and therefore rushing obliquely into the pores of the Loadstone, swimming in the Quicksilver, they do by the force they have, drive them to continue their motion according to Right Lines. And by this means it comes to pass, that the Magnet, af∣ter some motions this and that way, returns to its natural state. So that being left to its liberty, the South Pole of the Magnet tends to the North Pole of the Earth, and the North to the South; be∣cause the striate matter, which passeth from the North Pole of the Earth, and takes its course through the Air, towards the South, comes first from the South part of Heaven, through the midst of the Earth; as that comes from the Northern part of the Earth, which returns to the North. Furthermore the reason why the Loadstone doth not keep it self in an Horizontal Situation, but de∣clines towards the North Pole is, because we live in the North part of the World, and consequently have the North Pole nearer our Horizon, than the South.

II. Why one Loadstone approach∣eth to ano∣ther, or withdraws from it. Wherefore if you apply the North Pole of a Loadstone▪ you hold in your hand, to the North Pole of another swimming on Quicksilver; or wa∣ter with the help of a Cork; this latter will with∣draw from the Loadstone you hold in your hand, because the striate matter that proceeds from it, in taking its compass, doth hinder the other. But when this latter Loadstone turns its South Pole to that which is immoveable in your hand, then it will approach to it; because the interposing Air being driven away by the striate matter, the Loadstone, by how much the less resistance it finds, is the more forcibly driven on by the Air that doth surround it.

III. Arguments proving that there is a Vortex of the Mag∣netick Mat∣ter. Now that the Magnetick matter doth make a kind of Vortex about every Loadstone, may be evinced by several Arguments. We find that the Needle of a Compass, is put into various situations, according as it is differently posited about the Loadstone: being placed even with the Poles of the Loadstone, it lies in a straight line, and makes one Line with the Axis of the Loadstone; but is variously inclined when it is otherwise placed. Another experiment that makes out this, is, that if you pour out the filings of Steel upon Paper, having a Loadstone fitly placed in the midst of it, we shall find in the said filings the plain draught and appearance of a Vortex. For upon the shaking of the Paper, we shall with pleasure behold the filings of Steel ranging themselves, as it were, in∣to certain Rings, whereof those are the largest which shall return to those parts that are nearer to the Poles. And if afterwards another Magnet be laid near to the former, then those Rings of the Vortex will appear under another Figure, to the end they may pass now through the Poles of this last placed Loadstone, in case that care be taken, that the South Pole of the one of these Magnets, be turned towards the North Pole of the other. Which Experiments demonstrate to the Eye, the various Rings and turnings the magnetical matter makes about every Loadstone.

IV. When a Loadstone is divided, its Poles are changed. When a Loadstone is divided in length, its Poles by this means are changed, and those parts of the Fragments or Pieces, which before this Divi∣sion were join'd together, and pointed to the same Poles, do now withdraw and flee from one ano∣ther. For if the Parts A and a were before join'd together, and so likewise B and b at the other end; as soon as this division is made, a will turn to B, * 1.1and b towards A; so that the North Pole of the one doth no longer agree with the North Pole of the other; nor the South with the South Pole.

The Reason is, because the Southern striate Par∣ticles, which come forth through the Northern Part of one Section, must enter into the other through the Southern Part, and come forth through the North. Forasmuch therefore as the striate Par∣ticles, which come forth from the greater Frag∣ment AB, are Southern, they must turn about the upper piece a b, and so fit and dispose the same, as that they may freely enter through a, and go out again through B. For A is supposed to be the South Pole, by which the Southern Particles do enter, that come forth from the other part of the Segment or Division through b, and which there∣fore

cannot enter through b into the upper part of the Loadstone, because it is Northern, and therefore unfit to admit the Northern striate mat∣ter.

V. How a Knife that hath ac∣quired a Magnetick Virtue, by being rub∣bed on a Loadstone, comes to be deprived of its Virtue. A Knife that hath been rubb'd with a Loadstone, attracts Iron after the same manner as the Magnet it self doth; but if we pass it over the Pole of the Loadstone, a quite contrary way, than we passed it at first, it will lose the virtue of drawing Iron, which by the former rubbing or passing of it over the Loadstone it had acquired.

The Reason hereof is, because the Knife by be∣ing passed over the Loadstone, or rubb'd against it, was become a perfect Loadstone, for this rea∣son only, because the magnetical matter had open∣ed its Pores, and had smoothed those prominent little Branches of the metallick particles in the said pores that before hindred their free and ready pas∣sage through them. And so in like manner it lo∣seth the quality of a Perfect Loadstone, by being passed in a quite contrary way over the same Pole of the Loadstone; because the magnetical matter, exerts now a contrary effect upon the Knife to what it did before, that is, it now raiseth again the prominent extremities of the Branchy Particles in the Pores of the Knife, which it had before couched, and smoothed.

Now that this is so, appears evidently from this Experiment, that if we lay some filings of Steel upon a Paper, as was before-mentioned, and draw or pass a Loadstone over them, we shall see that the parts of the said filings will range themselves one upon the top of another, and constitute, as it were, so many Hairs, which all of them lie one way; and if then we pass the Loadstone over them the contrary way, we shall find the said Hairs to turn themselves, and to lay themselves a quite contrary way to what they were before.

VI. What is the Cause of the Declinati∣on that is found in the Magnet. The Poles of the Loadstone do not always point directly to the Poles of the World, but variously decline from the same, as may be seen in Dr. GIL∣BERTS Treatise of the Loadstone, who gives us an account of the observation of one Mr. BOR∣ROUGHS, who in the year 1580 at Limehouse near London, observed that the Declination of the Loadstone was 13 degrees and 35 minutes: And of Mr. GUNTER, who in the year 1622 found the said Declination to be only of 6 degrees, and 13 minutes: And last of all his own observa∣tion, who in the year 1634, found it to be only of 4 degrees and 2 minutes.

The decrease of these Declinations, proceeds from the Earths inequalities. For it is certain that some places abound with Iron Mines more than others, and that the Loadstone is not equally dis∣perst in all places; but is found much more plentiful in one than another. And therefore it is that the striate particles, which find a more free passage through the Magnetical Bodies than through any other, breaking forth from the in∣ward part of the Earth, do flow in more abun∣dance towards some places, than towards others: And by this means do frequently deviate from their course, and turn aside towards other Bodies, through which they pass more easily and readily. And forasmuch as the turning of the Poles of the Magnet, or of the Points of the Needle, doth only depend on the course of those Particles, it must needs point that way where there is a greater quantity of matter, that is proper to draw it. This is evident in any Loadstone that is not of a Round or Spherical Figure: For if a small Needle be applied to the different parts of it, it will not always turn it self to the Poles of it in one and the same manner, but will frequently decline a little from them. And therefore it cannot seem strange to us, if the Declination of the Loadstone be changed in one and the same place; and that in process of time its Poles do not exactly point to the Poles of the Earth; Because this matter may shift its place; as for instance, in the bot∣tom of the Sea, or in the cavities of the Earth; or the Iron may be dug out of the Earth in some parts, or be corrupted, and degenerate into ano∣ther Body.

VII. Magnetical Bodies are not always turned from South to North. Hence it appears, with how little reason some Philosophers do endeavour to explain the Declina∣tion of the Magnet, by the Deviation of the Lit∣tle Bear, or of the Poles of the Ecliptick, from the Pole of the World: Seeing that there be many places found, where this Declination is towards the West, as it is generally on the Eastern side of the North part of America; on the Western Coast of Nova Zembla; on the Eastern Shoar of Africa, and the Western of Goa. Yea, in the Azores Islands, which lie betwixt Europe to the East, and America to the West, it declines neither way: As in Trinity Isle, at the Promontory of Needles, near to the Promontory or Cape of Good Hope, at Vi∣enna in Austria, and other places.

VIII. VVhat ••s the Reason that a less Declinati∣on is found in a Load∣stone that is placed upright on one of its Poles. Some tell us that a Spherical Loadstone being placed upright on one of its Poles, hath less decli∣nation, than when its Poles are at an equal distance from the Earth.

The Reason of this may be, because the striate particles that are in the upper part of this our Earth, do not only turn from one Pole to the other, by Lines that are at an equal distance from its center; but also because every where (the Equator only excepted) some of the said particles do ascend from its inward parts, the turning of the Magnet set upright on its Poles, depending on these latter particles, but its declination chiefly on the former.

IX. Iron, being touched by a Loadstone, acquires a Magnetick Virtue. The Loadstone communicates its virtue to Iron, and doth so change it with a Touch, as to make it point towards the Poles of the World, in the same manner as it self doth. The famous GAS∣SENDUS observes, that the Iron Cross, which had been fixt a long time on the top of the Great Church of Aix, being cast down by a Storm, did acquire a Magnetick Virtue from the Earth, so as that the parts of it did attract Iron Nails, and turn themselves towards the Poles of the World. So likewise it is observed, that when a Rod of Iron has toucht the Earth, the lower part of the Rod draws the point of the Needle of a Compass that points to the South, to it self.

This happens because of the great affinity there is between the Loadstone and Iron: for they are so much alike, that the Loadstone may be called Raw and Undigested Iron; and Iron the Riper and more Pure part of the Loadstone. For Iron is melted out of the Loadstone, as out of its proper Vein. Hence it is, that in England, Germany, Ita∣ly, and other places where Iron is found, the Load∣stone is found also, as proceeding both of them from the same Matrix. But as for the manner how

Iron is made partaker of the Virtue of the Magnet, and by touching it, doth acquire the same Inclina∣tion: This we shall understand if we suppose that Iron is endued with fit pores to receive the striate matter, and that it wants nothing towards the obtaining of this Magnetick Virtue; but only that some little branchy particles sticking out in the pores of it, which do make them somewhat rough and uneven, must be bended one way for the easie passage thereof. Now upon the ap∣plication of a Loadstone to Iron, the striate matter which continually takes a round from one Pole of the Earth to another, with vehement force and in great quantity, rushing like a Torrent into the Pores of the Iron, doth bend these prominent ex∣tremities of the branchy particles all one way; and therefore effects whatsoever is necessary to the making of it fit partaker of this Magnetical Virtue.

X. Why Steel is more pro∣per and fit to admit this Mag∣netick Vir∣tue than Iron. Hence it is that Steel is more proper to receive this Magnetick Force than Iron, because it hath more, and more accurately framed Pores for the reception of these striate particles. And doth also preserve the said Virtue longer, because the promi∣nences of the extremities of these branchy particles that are in the Pores of the Earth, are less flexible, and therefore cannot so easily be bent the contrary way.

XI. How Steel Scissars may be made par∣takers of Magnetick Virtue. The Famous Mathematician Mr. BUOT hath found by experience, that Steel Scissars or Penknives having been heated in a Forge till they be of a Red Colour, and then suddainly extinguisht in cold water, and afterwards neal'd in the fire again, till they be of a Blue or Purple Colour, and then whetted and made bright on a Whetstone, if presently after they be made to cut, or pierce through Plates of Iron or Steel, by this means a Magnetick Virtue will be communicated to them, so as to attract Iron Nails. Of which no other reason can be assigned, but this, because the Pores are so disposed in Steel prepared after this manner, that the Heavenly matter can with more ease have Egress and Regress through them: So as that no out flowing particles from the Magnet do remain, but doth only afford a free passage to the External matter.

XII. Why an Armed Leadstone doth at∣tract stron∣ger than one that is Unarmed. The Armed Loadstone A, doth bear up more Iron B and C, than another that is not: For GA∣LILAEUS hath observed, that a piece of Load∣stone weighing 6 ounces, will scarcely bear 2 ounces unarmed; whereas the same Loadstone armed will bear up 160 ounces; so as that it attracts 8 times more than when it is unarmed, and a weight 25 times greater than its own weight.

The cause of this encrease of the attractive Vir∣tue * 1.2is, because the Iron DE, wherewith the Mag∣net A is armed, is endued with Magnetical Parts, that are purged from Terrestrial Filth, and Hete∣rogeneous Impurities; for which reason its Pores do most fitly correspond and agree with the Pores of the Iron that hangs at it B and C, and by this means the striate particles that pass through these Pores from the one Iron into the others, do drive away all the intermediate air, and makes their surfaces to touch one another immediately; by which means they cannot, without great difficul∣ty, be separated; and therefore the weight B, or C, doth stick more strongly to the Iron DE For nothing can be more proper to join 2 Bodies together, than immediate contact.

XIII. A Loadstone throughly heated lo∣seth its force to draw Iron. A Loadstone, being throughly heated, loseth its force of drawing of Iron, and doth no longer turn towards the Poles of the World. For if you heap live Coals about a Loadstone, you will see a Blue Sulphurous Flame to break forth from it; upon the dissipation of which you will judge it to have lost its attractive Virtue.

The Cause of this Loss of the Magnetical Vir∣tue is, for that the Fire entring into the Pores of the Magnet, many of its thin and slippery parts are driven away; upon the removal whereof, a new texture of Parts is produced in the Magnet. As we see that a Stick being put into the Fire, becomes crooked by degrees; because the force of Heat brings some of its parts closer together, and at the same time separates others of them. The Fire therefore having thus changed and confound∣ed the former situation of the particles of the Loadstone, the striate matter which was used to pass through them, finding the Pores much wider than they were before, doth exert but a very small force, or rather none at all upon them.

XIV. A Magnet that hath been heat∣ed, may re∣cover its lost Virtue again. Tho' there be many great Philosophers, who deny that a heated Magnet can ever recover its lost Virtue again; yet the contrary hath been found by experience. Some indeed have observed, that a Magnet that hath been made red hot, is by this means robb'd of the gre••test part of its Virtue, and changeth its Poles in ••ase it be p••ace•• to cool in an inverted situation towards the North. Or if when it is a cooling, the situation of it be frequent∣ly changed from one position to another that is opposit, it will wholly change its Poles▪ so 〈◊〉〈◊〉 that that which was before the North Pole, will become the South, notwithstanding that the Load∣stone be then placed perpendicularly upon the Ho∣rizon.

XV. Glass drops when put to the Fire, lose their Elastick Virtue. Thus those Glass-Drops, which upon the break∣ing off of their Points become shattered into the smallest Dust, being by degrees pu•• to the fire, do lose their Elastick virtue.

The Reason is, because the Parts which before were stretched, are made wider by the admission of Heat, and by degrees sit looser from one ano∣ther; and thus the Texture of the parts being changed, they are now no longer like Sticks, with Wreaths twisted hard about them, and there∣fore do not so strongly resist the force of the Hammer, and become wholly deprived of their Elastick virtue.

XVI. A Loadstone upon the changing of its Poles, doth lose its Virtue also. But if a Piece of Iron be applied to the Pole of a Magnet from the Right to the Left, it pre∣sently loseth the virtue it had before acquired; because the parts of the Magnet are changed, by this contrary passage of the subtil matter through them, and the pores differently ranged and forme▪ from what they were before. And on the con∣trary, it hath been frequently found by Experi∣ence, that the Iron-bars of Windows looking to∣wards the North or South, do retain a perpetual Magnetick virtue: Because the striate Matter that proceeds from the said Poles, by process of time, do hollow pores for themselves through the said Iron-bars.

XVII. How a Magnet may be some time hindred from draw∣ing the Needle to it. A Plate of Iron, which we have said before, being joyned to the Pole of the Loadstone, doth increase its force to bear Iron, doth hinder the virtue it hath of turning Iron towards it. For the Iron-Plate DCD, doth hinder the Loadstone

* 1.3 AB, to whose Pole it is joyned, from drawing the Needle EF towards it.

The Reason is, because the striate Particles that proceed from the Loadstone, do rather pass through Iron, than any other Body; and therefore the said particles are diverted by the Iron-Plate, from passing through the Air to EF. And certainly, besides the Iron or Magnet, no other Body can be substituted in place of the Iron-plate CD, by which the Loadstone AB is hindred from exerting its force upon the Needle EF; as hath been said in the Institution of Philosophy.

XVIII. Whether there be any thing of Truth in the story of Maho∣mets Tomb. There is a Common Story goes of MAHO∣MET's Tomb, that it is pois'd in the midst of the Air, between 2 Loadstones, without touching either the top or the bottom of the Temple at Mecha.

I take this to be a meer Fable: For it is be∣yond the power or wit of Man, to get 2 or more Magnets that are altogether of the very same force and virtue; and if these could be got, yet would it still be as impracticable, or rather impossible to place them so, as that the Iron placed between them, should not be drawn in one part of it more than in the other: Seeing that a very small and inconsiderable difference in the Loadstone, Iron, or in the place it self, would be sufficient to over∣throw that Equality. Neither are we to ascribe any greater Authority to the Stories that some Authors tell us of the Horse of Bellerophon, and of the Statue that was in the Temple of Serapis. These being nothing else but pure invented Stories, which have gained Authority by the Credulity of the Vulgar.

Notes

• * 1.1

  Figure 21.
• * 1.2

  Figure 22.
• * 1.3

  Figure 45. in the In∣stitution.