The Works of Sir Thomas Browne, Volume 1

Nor is this onely true in Irons, but in the Loadstone it self. For if a Loadstone be made red hot, it loseth the magnetical vigour it had before in it self, and acquires another from the Earth in its refrigeration; for that part which cooleth toward the Earth will acquire the respect of the North, and attract the Southern point or cuspis of the Needle. The experiment hereof we made in a Loadstone of a parallelogram or long square figure; wherein onely inverting the extreams, as it came out of the fire, we altered the poles or faces thereof at pleasure.

It is also true what is delivered of the Direction and coition of Irons, that they contract a verticity by long and continued position: that is, not onely being placed from North to South, and lying in the Meridian, but respecting the Zenith and perpendicular unto the Center of the Earth; as is manifest in bars of windows, casements, hinges and the like. For if we present the Needle unto their lower extreams, it wheels about and turns its Southern point unto them. The same condition in long time do Bricks contract which are placed in walls, and therefore it may be a fallible way to find out the Meridian by placing the Needle on a wall; for some Bricks therein by a long and continued position, are often magnetically enabled to distract the polarity of the Needle. And therefore those Irons which are said to have been converted into Loadstones; whether they were real conversions, or onely attractive augmentations, might be much promoted by this position: as the Iron cross of an hundred weight upon the Church of St. John in Ariminum,De miner. l. 1. or that Loadston'd Iron of Cæsar Moderatus, set down by Aldrovandus.

Lastly, Irons do manifest a verticity not only upon refrigeration and constant situation, but (what is wonderful and advanceth the magnetical Hypothesis) they evidence the same by meer position according as they are inverted, and their extreams disposed respectively unto the Earth. For if an Iron or Steel not firmly excited, be held perpendicularly or inclinatorily unto the Needle, the lower end thereof will attract the cuspis or Southern point; but if the same extream be inverted and held under the Needle, it will then attract the lilly or Northern point; for by inversion it changeth its direction acquired before, and receiveth a new and Southern polarity from the Earth, as being the upper extream. Now if an Iron be touched before, it varieth not in this manner; for then it admits not this magnetical impression, as being already informed by the Loadstone, and polarily determined by its preaction.

And from these grounds may we best determine why the Northern Pole of the Loadstone attracteth a greater weight than the Southern on this side the Æquator; why the stone is best preserved in a natural and polary situation; and why as Gilbertus observeth, it respecteth that Pole out of the Earth, which it regarded in its Mineral bed and subterraneous position.

It is likewise true and wonderful what is delivered of the Inclination or Declination of the Loadstone; that is, the descent of the Needle below the plain of the Horizon. For long Needles which stood before upon their axis, parallel unto the Horizon, being vigorously excited, incline and bend downward, depressing the North extream below the Horizon. That is the North on this, the South on the other side of the Equator; and at the very Line or middle circle stand without deflexion. And this is evidenced not onely from observations of the Needle in several parts of the earth, but sundry experiments in any part thereof, as in a long Steel wire, equilibrated or evenly ballanced in the air; for excited by a vigorous Loadstone it will somewhat depress its animated extream, and intersect the horizontal circumference. It is also manifest in a Needle pierced through a Globe of Cork so cut away and pared by degrees, that it will swim under water, yet sink not unto the bottom, which may be well effected; for if the Cork be a thought too light to sink under the surface, the body of the water may be attenuated with spirits of wine; if too heavy, it may be incrassated with salt; and if by chance too much be added, it may again be thinned by a proportionable addition of fresh water. If then the Needle be taken out, actively touched and put in again, it will depress and bow down its Northern head toward the bottom, and advance its Southern extremity toward the brim. This way invented by Gilbertus may seem of difficulty; the same with less labour may be observed in a needled sphere of Cork equally contiguous unto the surface of the water; for if the Needle be not exactly equiponderant, that end which is a thought too light, if touched becometh even; that Needle also which will but just swim under the water, if forcibly touched will sink deeper, and sometime unto the bottom. If likewise that inclinatory vertue be destroyed by a touch from the contrary Pole, that end which before was elevated will then decline, and this perhaps might be observed in some scales exactly ballanced, and in such Needles which for their bulk can hardly be supported by the water. For if they be powerfully excited and equally let fall, they commonly sink down and break the water at that extream whereat they were septentrionally excited: and by this way it is conceived there may be some fraud in the weighing of precious commodities, and such as carry a value in quarter-grains; by placing a powerful Loadstone above or below, according as we intend to depress or elevate one extream.

Now if these Magnetical emissions be onely qualities, and the gravity of bodies incline them onely unto the earth; surely that which alone moveth other bodies to descent, carrieth not the stroak in this, but rather the Magnetical alliciency of the Earth; unto which with alacrity it applieth it self, and in the very same way unto the whole Earth, as it doth unto a single Loadstone. For if an untouched Needle be at a distance suspended over a Loadstone, it will not hang parallel, but decline at the North extream, and at that part will first salute its Director. Again, what is also wonderful, this inclination is not invariable; for just under the line the Needle lieth parallel with the Horizon, but sailing North or South it beginneth to incline, and encreaseth according as it approacheth unto either Pole; and would at last endeavour to erect it self. And this is no more then what it doth upon the Loadstone, and that more plainly upon the Terrella or spherical magnet Cosmographically set out with circles of the Globe. For at the Equator thereof, the Needle will stand rectangularly; but approaching Northward toward the Tropick it will regard the stone obliquely, and when it attaineth the Pole, directly; and if its bulk be no impediment, erect it self and stand perpendicularly thereon. And therefore upon strict observation of this inclination in several latitudes and due records preserved, instruments are made whereby without the help of Sun or Star, the latitude of the place may be discovered; and yet it appears the observations of men have not as yet been so just and equal as is desirable; for of those Tables of declination which I have perused, there are not any two that punctually agree; though some have been thought exactly calculated, especially that which Ridley received from Mr. Brigs, in our time Geometry Professor in Oxford.

What the variation of the Compass is.

It is also probable what is delivered concerning the variation of the Compass that is the cause and ground thereof, for the manner as being confirmed by observation we shall not at all dispute. The variation of the Compass is an Arch of the Horizon intercepted between the true and Magnetical Meridian; or more plainly, a deflexion and siding East and West from the true Meridian. The true Meridian is a major Circle passing through the Poles of the World, and the Zenith or Vertex of any place, exactly dividing the East from the West. Now on this line the Needle exactly lieth not, but diverts and varieth its point, that is, the North point on this side the Equator, the South on the other; sometimes on the East, sometime toward the West, and in some few places varieth not at all. First, therefore it is observed that betwixt the Shore of Ireland, France, Spain, Guiny, and the Azores, the North point varieth toward the East, and that in some variety; at London it varieth eleven degrees, at Antwerp nine, at Rome but five: at some parts of the Azores it deflecteth not, but lieth in the true Meridian; on the other side of the Azores, and this side of the Equator, the North point of the Needle wheeleth to the West; so that in the latitude of 36 near the shore, the variation is about eleven degrees; but on the other side the Equator, it is quite otherwise: for about Capio Frio in Brasilia, the South point varieth twelve degrees unto the West, and about the mouth of the Straits of Magellan five or six; but elongating from the coast of Brasilia toward the shore of Africa it varieth Eastward, and arriving at Capo de las Agullas, it resteth in the Meridian, and looketh neither way.

The cause of the variation of the Compass.

Now the cause of this variation was thought by Gilbertus to be the inequality of the Earth, variously disposed, and indifferently intermixed with the Sea: withal the different disposure of its Magnetical vigor in the eminencies and stronger parts thereof. For the Needle naturally endeavours to conform unto the Meridian, but being distracted, driveth that way where the greater and powerfuller part of the Earth is placed. Which may be illustrated from what hath been delivered and may be conceived by any that understands the generalities of Geography. For whereas on this side the Meridian, or the Isles of Azores, where the first Meridian is placed, the Needle varieth Eastward; it may be occasioned by that vast Tract of Earth, that is, of Europe, Asia, and Africa, seated toward the East, and disposing the Needle that way. For arriving at some part of the Azores, or Islands of Saint Michael, which have a middle situation between these Continents, and that vast and almost answerable Tract of America, it seemeth equally distracted by both; and diverting unto neither, doth parallel and place it self upon the true Meridian. But sailing farther, it veers its Lilly to the West, and regardeth that quarter wherein the Land is nearer or greater; and in the same latitude as it approacheth the shore augmenteth its variation. And therefore as some observe, if Columbus or whosoever first discovered America, had apprehended the cause of this variation, having passed more then half the way, he might have been confirmed in the discovery, and assuredly foretold there lay a vast and mighty continent toward the West. The reason I confess and inference is good, but the instance perhaps not so. For Columbus knew not the variation of the compass, whereof Sebastian Cabot first took notice, who after made discovery in the Northern part of that continent. And it happened indeed that part of America was first discovered, which was on this side farthest distant, that is, Jamaica, Cuba, and the Isles in the Bay of Mexico. And from this variation do some new discoverers deduce a probability in the attempts of the Northern passage toward the Indies.

Now because where the greater continents are joyned, the action and effluence is also greater; therefore those Needles do suffer the greatest variation which are in Countries which most do feel that action. And therefore hath Rome far less variation then London; for on the West side of Rome are seated the great continents of France, Spain, Germany, which take off the exuperance, and in some way ballance the vigor of the Eastern parts. But unto England there is almost no Earth West, but the whole extent of Europe and Asia lieth Eastward; and therefore at London it varieth eleven degrees, that is almost one Rhomb. Thus also by reason of the great continent of Brasilia, Peru, and Chili, the Needle deflecteth toward the Land twelve degrees; but at the straits of Magellan where the Land is narrowed, and the Sea on the other side, it varieth but five or six. And so likewise, because the Cape de las Agullas hath Sea on both sides near it, and other Land remote, and as it were æquidistant from it, therefore at that point the Needle conforms unto the true Meridian, and is not distracted by the vicinity of Adjacencies. This is the general and great cause of variation. But if in certain Creeks and Vallies the Needle prove irregular, and vary beyond expectation, it may be imputed unto some vigorous part of the Earth, or Magnetical eminence not far distant. And this was the invention of D. Gilbert, not many years past, a Physician in London. And therefore although some assume the invention of its direction, and other have had the glory of the Card; yet in the experiments, grounds, and causes thereof, England produced the Father Philosopher, and discovered more in it then Columbus or Americus did ever by it.

Unto this in great part true the reason of Kircherus may be added: That this variation proceedeth not only from terrestrious eminencies, and magnetical veins of the Earth, laterally respecting the Needle, but the different coagmentation of the Earth disposed unto the Poles, lying under the Sea and Waters, which affect the Needle with great or lesser variation, according to the vigour or imbecility of these subterraneous lines, or the entire or broken compagination of the magnetical fabrick under it. As is observable from several Loadstones placed at the bottom of any water, for a Loadstone or Needle upon the surface, will variously conform it self, according to the vigour or faintness of the Loadstones under it.

Thus also a reason may be alledged for the variation of the variation, and why, according to observation, the variation of the Needle hath after some years been found to vary in some places. For this may proceed from mutations of the earth, by subterraneous fires, fumes, mineral spirits, or otherwise; which altering the constitution of the magnetical parts, in process of time, doth vary the variation over the place.

It is also probable what is conceived of its Antiquity, that the knowledge of its polary power and direction unto the North was unknown unto the Ancients; and though Levinus Lemnius, and Cælius Colcagninus, are of another belief, is justly placed with new inventions by Pancirollus. For their Achilles and strongest argument is an expression in Plautus, a very Ancient author, and contemporary unto Ennius. Hic ventus jam secundus est, cape modo versoriam. Now this versoriam they construe to be the compass, which notwithstanding according unto Pineda, who hath discussed the point, Turnebus, Cabeus, and divers others, is better interpreted the rope that helps to turn the Ship, or as we say, doth make it tack about; the Compass declaring rather the Ship is turned, then conferring unto its conversion. As for the long expeditions and sundry voyages of elder times, which might confirm the Antiquity of this invention, it is not improbable they were performed by the help of Stars; and so might the Phœnicean navigators, and also Ulisses sail about the Mediterranean, by the flight of Birds, or keeping near the shore; and so might Hanno coast about Africa; or by the help of Oars, as is expressed in the voyage of Jonah. And whereas it is contended that this verticity was not unknown unto Solomon, in whom is presumed an universality of knowledge; it will as forcibly follow, he knew the Art of Typography, Powder and Guns, or had the Philosophers Stone, yet sent unto Ophir for Gold. It is not to be denied, that beside his Political wisdom, his knowledge in Philosophy was very large; and perhaps from his works therein, the ancient Philosophers, especially Aristotle, who had the assistance of Alexanders acquirements, collected great observables. Yet if he knew the use of the Compass, his Ships were surely very slow, that made a three years voyage from Eziongeber in the red Sea unto Ophir; which is supposed to be Taprobana or Malaca in the Indies, not many moneths sail; and since in the same or lesser time, Drake and Candish performed their voyage about the Earth.

And as the knowledge of its verticity is not so old as some conceive, so it is more ancient then most believe; nor had its discovery with Guns, Printing, or as many think, some years before the discovery of America. For it was not unknown unto Petrus Peregrinus a Frenchman, who two hundred years since left a Tract of the Magnet, and a perpetual motion to be made thereby, preserved by Gasserus. Paulus Venetus, and about five hundred years past Albertus Magnus make mention hereof, and quote for it a Book of Aristotle, De Lapide; which Book although we find in the Catalogue of Laertius, yet with Cabeus we may rather judge it to be the work of some Arabick Writer, not many years before the days of Albertus.

Lastly, It is likewise true what some have delivered of Crocus Martis, that is, Steel corroded with Vinegar, Sulphur, or otherwise, and after reverberated by fire. For the Loadstone will not at all attract it, nor will it adhere, but lye therein like Sand. This to be understood of Crocus Martis well reverberated, and into a violet colour: for common chalybs præparatus, or corroded and powdered Steel, the Loadstone attracts like ordinary filings of Iron; and many times most of that which passeth for Crocus Martis. So that this way may serve as a test of its preparation; after which it becometh a very good medicine in fluxes. The like may be affirmed of flakes of Iron that are rusty and begin to tend unto Earth; for their cognation then expireth, and the Loadstone will not regard them.

And therefore this may serve as a trial of good Steel. The Loadstone taking up a greater mass of that which is most pure, it may also decide the conversion of Wood into Iron, as is pretended from some Waters: and the common conversion of Iron into Copper by the mediation of blew Coperose, for the Loadstone will not attract it. Although it may be questioned, whether in this operation, the Iron or Coperose be transmuted, as may be doubted from the cognation of Coperose with Copper; and the quantity of Iron remaining after the conversion. And the same may be useful to some discovery concerning Vitriol or Coperose of Mars, by some called Salt of Steel, made by the spirits of Vitriol or Sulphur. For the corroded powder of Steel will after ablution be actively attracted by the Loadstone, and also remaineth in little diminished quantity. And therefore whether those shooting Salts partake but little of Steel, and be not rather the vitriolous spirits fixed into Salt by the effluvium or odor of Steel, is not without good question.

CHAPTER III

Concerning the Loadstone, therein of sundry common Opinions, and received several relations: Natural, Historical, Medical, Magical.

And first not only a simple Heterodox, but a very hard Paradox, it will seem, and of great absurdity unto obstinate ears, if we say, attraction is unjustly appropriated unto the Loadstone, and that perhaps we speak not properly, when we say vulgarly and appropriately the Loadstone draweth Iron; and yet herein we should not want experiment and great authority. The words of Renatus des Cartes in his Principles of Philosophy are very plain. Præterea magnes trahet ferrum, sive potius magnes & ferrum ad invicem accedunt, neque enim ulla ibi tractio est. The same is solemnly determined by Cabeus. Nec magnes trahit proprie ferrum, nec ferrum ad se magnetem provocat, sed ambo pari conatu ad invicem confluunt. Concordant hereto is the assertion of Doctor Ridley, Physitian unto the Emperour of Russia, in his Tract of Magnetical Bodies, defining Magnetical attraction to be a natural incitation and disposition conforming unto contiguity, an union of one Magnetical Body with another, and no violent haling of the weak unto the stronger. And this is also the doctrine of Gilbertus, by whom this motion is termed Coition, and that not made by any faculty attractive of one, but a Syndrome and concourse of each; a Coition alway of their vigours, and also of their bodies, if bulk or impediment prevent not. And therefore those contrary actions which flow from opposite Poles or Faces, are not so properly expulsion and attraction, as Sequela and Fuga, a mutual flight and following. Consonant whereto are also the determination of Helmontius, Kircherus, and Licetus.

Attraction reciprocal betwixt the Loadstone and Iron.

The same is also confirmed by experiment; for if a piece of Iron be fastened in the side of a bowl or bason water, a Loadstone swimming freely in a Boot of Cork, will presently make unto it. So if a Steel or Knife untouched, be offered toward the Needle that is touched, the Needle nimbly moveth toward it, and conformeth unto union with the Steel that moveth not. Again, If a Loadstone be finely filed, the Atoms or dust thereof will adhere unto Iron that was never touched, even as the powder of Iron doth also unto the Loadstone. And lastly, if in two Skiffs of Cork, a Loadstone and Steel be placed within the Orb of their activities, the one doth not move the other standing still, but both hoise sail and steer unto each other. So that if the Loadstone attract, the Steel hath also its attraction; for in this action the Alliciency is reciprocal, which joyntly felt, they mutually approach and run into each others arms.

And therefore surely more moderate expressions become this action, then what the Ancients have used, which some have delivered in the most violent terms of their language; so Austin calls it, Mirabilem ferri raptorem: Hippocrates λίθος τὸν σίδηρον ἁρπάζει, Lapis qui ferrum rapit. Galen disputing against Epicurus useth the term ἕλκειν, but this also is too violent: among the Ancients Aristotle spake most warily, ὅστις τὸν σίδηρον κινεῖ, Lapis qui ferrum movet: and in some tolerable acception do run the expressions of Aquinas, Scaliger and Cusanus.

Many relations are made, and great expectations are raised from the Magnes Carneus, or a Loadstone, that hath a faculty to attract not only iron but flesh; but this upon enquiry, and as Cabeus also observed, is nothing else but a weak and inanimate kind of Loadstone, veined here and there with a few magnetical and ferreous lines; but consisting of a bolary and clammy substance, whereby it adheres like Hæmatites, or Terra Lemnia, unto the Lips. And this is that stone which is to be understood, when Physitians joyn it with Ætites, or the Eagle stone, and promise therein a vertue against abortion.

There is sometime a mistake concerning the variation of the Compass, and therein one point is taken for another. For beyond that Equator some men account its variation by the diversion of the Northern point, whereas beyond that Circle the Southern point is Soveraign, and the North submits his preheminency. For in the Southern coast either of America or Africa, the Southern point deflects and varieth toward the Land, as being disposed and spirited that way by the Meridional and proper Hemisphere. And therefore on that side of the Earth the varying point is best accounted by the South. And therefore also the writings of some, and Maps of others, are to be enquired, that make the Needle decline unto the East twelve degrees at Capo Frio, and six at the straits of Magellan; accounting hereby one point for another, and preferring the North in the Liberties and Province of the South.