On the magnet, magnetick bodies also, and on the great magnet the earth.

by William Gilbert of Colchester.

PREFACE TO THE CANDID READER, STUDIOUS OF THE MAGNETICK PHILOSOPHY.

Clearer proofs, in the discovery of secrets, and in the investigation of the hidden causes of things, being afforded by trustworthy experiments and by demonstrated arguments, than by the probable guesses and opinions of the ordinary professors of philosophy: so, therefore, that the noble substance of that great magnet, our common mother (the earth), hitherto quite unknown, and the conspicuous and exalted powers of this our globe, may be the better understood, we have proposed to begin with the common magnetick, stony, and iron material, and with magnetical bodies, and with the nearer parts of the earth which we can reach with our hands and perceive with our senses; then to proceed with demonstrable magnetick experiments; and so penetrate, for the first time, into the innermost parts of the earth. For after we had, in order finally to learn the true substance of the globe, seen and thoroughly examined many of those things which have been obtained from mountain heights or ocean depths, or from the profoundest caverns and from hidden mines: we applied much prolonged labour on investigating the magnetical forces; so wonderful indeed are they, compared with the forces of all other minerals, surpassing even the virtues of all other bodies about us. Nor have we found this our labour idle or unfruitful; since daily during our experimenting, new and unexpected properties came to light; and our Philosophy hath grown so much from the things diligently observed, that we have attempted to expound the interior parts of the terrene globe, and its native substance, upon magnetick principles; and to reveal to men the earth (our common mother), and to point it out as if with the finger, by real demonstrations and by experiments manifestly apparent to the senses.

And as geometry ascends from sundry very small and very easy principles to the greatest and most difficult; by which the wit of man climbs above the firmament: so our magnetical doctrine and science first sets forth in convenient order the things which are less obscure; from these there come to light others that are more remarkable; and at length in due order there are opened the concealed and most secret things of the globe of the earth, and the causes are made known of those things which, either through the ignorance of the ancients or the neglect of moderns, have remained unrecognized and overlooked. But why should I, in so vast an Ocean of Books by which the minds of studious men are troubled and fatigued, through which very foolish productions the world and unreasoning men are intoxicated, and puffed up, rave and create literary broils, and while professing to be philosophers, physicians, mathematicians and astrologers, neglect and despise men of learning: why should I, I say, add aught further to this so-perturbed republick of letters, and expose this noble philosophy, which seems new and incredible by reason of so many things hitherto unrevealed, to be damned and torn to pieces by the maledictions of those who are either already sworn to the opinions of other men, or are foolish corruptors of good arts, learned idiots, grammatists, sophists, wranglers, and perverse little folk? But to you alone, true philosophizers, honest men, who seek knowledge not from books only but from things themselves, have I addressed these magnetical principles in this new sort of Philosophizing. But if any see not fit to assent to these self-same opinions and paradoxes, let them nevertheless mark the great array of experiments and discoveries (by which notably every philosophy flourisheth), which have been wrought out and demonstrated by us with many pains and vigils and expenses. In these rejoice, and employ them to better uses, if ye shall be able. I know how arduous it is to give freshness to old things, lustre to the antiquated, light to the dark, grace to the despised, credibility to the doubtful; so much the more by far is it difficult to win and establish some authority for things new and unheard-of, in the face of all the opinions of all men.

Nor for that do we care, since philosophizing, as we deemed, is for the few. To our own discoveries and experiments we have affixed asterisks, larger and smaller, according to the importance and subtlety of the matter.

Whoso desireth to make trial of the same experiments, let him handle the substances, not negligently and carelessly, but prudently, deftly, and in the proper way; nor let him (when a thing doth not succeed) ignorantly denounce our discoveries: for nothing hath been set down in these books which hath not been explored and many times performed and repeated amongst us. Many things in our reasonings and hypotheses will, perchance, at first sight, seem rather hard, when they are foreign to the {iij} commonly received opinion; yet I doubt not but that hereafter they will yet obtain authority from the demonstrations themselves. Wherefore in magnetical science, they who have made most progress, trust most in and profit most by the hypotheses; nor will anything readily become certain to any one in a magnetical philosophy in which all or at least most points are not ascertained. This nature-knowledge is almost entirely new and unheard-of, save what few matters a very few writers have handed down concerning certain common magnetical powers. Wherefore we but seldom quote antient Greek authors in our support, because neither by using greek arguments nor greek words can the truth be demonstrated or elucidated either more precisely or more significantly. For our doctrine magnetical is at variance with most of their principles and dogmas. Nor have we brought to this work any pretence of eloquence or adornments of words; but this only have we done, that things difficult and unknown might be so handled by us, in such a form of speech, and in such words as are needed to be clearly understood: Sometimes therefore we use new and unusual words, not that by means of foolish veils of vocabularies we should cover over the facts with shades and mists (as Alchemists are wont to do) but that hidden things which have no name, never having been hitherto perceived, may be plainly and correctly enunciated. After describing our magnetical experiments and our information of the homogenick parts of the earth, we proceed to the general nature of the whole globe; wherein it is permitted us to philosophize freely and with the same liberty which the Egyptians, Greeks, and Latins formerly used in publishing their dogmas: whereof very many errors have been handed down in turn to later authors: and in which smatterers still persist, and wander as though in perpetual darkness. To those early forefathers of philosophy, Aristotle, Theophrastus, Ptolemy, Hippocrates, and Galen, let due honour be ever paid: for by them wisdom hath been diffused to posterity; but our age hath detected and brought to light very many facts which they, were they now alive, would gladly have accepted. Wherefore we also have not hesitated to expound in demonstrable hypotheses those things which we have discovered by long experience. Farewell.

TO THE MOST EMINENT AND LEARNED MAN

DR. WILLIAM GILBERT,

_a distinguished Doctor of Medicine amongst the_

Londoners, and Father of Magnetick Philosophy,

an Encomiastic Preface of Edward Wright

on the subject of these books

_Magnetical_.

_Should there by chance be any one, most eminent Sir, who reckons as of small account these magnetical books and labours of yours, and thinks these studies of yours of too little moment, and by no means worthy enough of the attention of an eminent man devoted to the weightier study of Medicine: truly he must deservedly be judged to be in no common degree void of understanding. For that the use of the magnet is very important and wholly admirable is better known for the most part to men of even the lowest class than to need from me at this time any long address or commendation. Nor truly in my judgment could you have chosen any topick either more noble or more useful to the human race, upon which to exercise the strength of your philosophic intellect; since indeed it has been brought about by the divine agency of this stone, that continents of such vast circuit, such an infinite number of lands, islands, peoples, and tribes, which have remained unknown for so many ages, have now only a short time ago, almost within our own memory, been quite easily discovered and quite frequently explored, and that the circuit of the whole terrestrial globe also has been more than once circumnavigated by our own countrymen, Drake and Cavendish; a fact which I wish to mention to the lasting memory of these men. For by the pointing of the iron touched by a loadstone, the points of South, North, East, and West, and the other quarters of the world are made known to navigators even under an overcast sky and in the darkest night; so that thus they always very easily understand to which point of the world they ought to direct their ship's course; which before the discovery of this wonderful virtue of the magnetick [Greek: boreodeixis] was clearly impossible. Hence in old times (as is established in histories), an incredible anxiety and immense danger was continually threatening sailors; for at the coming on of a tempest and the obscuring of the view of sun and stars, they were left entirely in ignorance whither they were making; nor could they find out this by any reasoning or skill. With what joy then may we suppose them to have been filled, to what feelings of delight must all shipmasters have given utterance, when that index magnetical first offered itself to them as a most sure guide, and as it were a Mercury, for their journey? But neither was this sufficient for this magnetical Mercury; to indicate, namely, the right way, and to point, as it were, a finger in the direction toward which the course must be {iiij} directed; it began also long ago to show distinctly the distance of the place toward which it points. For since the index magnetical does not always in every place look toward the same point of the North, but deviates from it often, either toward the East or toward the West, yet always has the same deviation in the same place, whatever the place is, and steadily preserves it; it has come about that from that deviation, which they call variation, carefully noticed and observed in any maritime places, the same places could afterwards also be found by navigators from the drawing near and approach to the same variation as that of these same places, taken in conjunction with the observation of the latitude. Thus the Portuguese in their voyages to the East Indies had the most certain indications of their approach to the Cape of Good Hope; as appears from the narrations of Hugo van Lynschoten and of the very learned Richard Hakluyt, our countryman. Hence also the experienced skippers of our own country, not a few of them, in making the voyage from the Gulf of Mexico to the islands of the Azores, recognized that they had come as near as possible to these same islands; although from their sea-charts they seemed to be about six hundred British miles from them. And so, by the help of this magnetick index, it would seem as though that geographical problem of finding the longitude, which for so many centuries has exercised the intellects of the most learned Mathematicians, were going to be in some way satisfied; because if the variation for any maritime place whatever were known, the same place could very readily be found afterward, as often as was required, from the same variation, the latitude of the same place being not unknown._

_It seems, however, that there has been some inconvenience and hindrance connected with the observation of this variation; because it cannot be observed excepting when the sun or the stars are shining. Accordingly this magnetick Mercury of the sea goes on still further to bless all shipmasters, being much to be preferred to Neptune himself, and to all the sea-gods and goddesses; not only does it show the direction in a dark night and in thick weather, but it also seems to exhibit the most certain indications of the latitude. For an iron index, suspended on its axis (like a pair of scales), with the most delicate workmanship so as to balance in aequilibrio, and then touched and excited by a loadstone, dips to some fixed and definite point beneath the horizon (in our latitude in London, for example, to about the seventy-second degree), at which it at length comes to rest. But under the aequator itself, from that admirable agreement and congruency which, in almost all and singular magnetical experiments, exists between the earth itself and a terrella (that is, a globular loadstone), it seems exceedingly likely (to say the very least), and indeed more than probable, that the same index (again stroked with a loadstone) will remain in aequilibrio in an horizontal position. Whence it is evident that this also is very probable, that in an exceedingly small progress from the South toward the North (or contrariwise) there will be at least a sufficiently perceptible change in that declination; so that from that declination in any place being once carefully observed along with the latitude, the same place and the same latitude may be very easily recognized afterward, even in the darkest night and in the thickest mist by a declination instrument.

Wherefore to bring our oration at length back to you, most eminent and learned Dr. Gilbert (whom I gladly recognize as my teacher in this magnetick philosophy), if these books of yours on the Magnet had contained nothing else, excepting only this finding of latitude from magnetick declination, by you now first brought to light, our shipmasters, Britains, French, Belgians, and Danes, trying to enter the British Channel or the Straits of Gibraltar from the Atlantick Ocean in dark weather, would still most deservedly judge them to be valued at no small sum of gold. But that discovery of yours about the whole globe of the earth being magnetical, although perchance it will seem to many "most paradoxical," producing even a feeling of astonishment, has yet been so firmly defended by you at all points and confirmed by so many experiments so apposite and appropriate to the matter in hand, in Bk. 2, chap. 34; Bk. 3, chap. 4 and 12; and in almost the whole of the fifth book, that no room is left for doubt or contradiction. I come therefore to the cause of the magnetick variation, which hitherto has distracted the minds of all the learned; for which no mortal has ever adduced a more probable reason than that which has now been set forth by you for the first time in these books of yours on the Magnet.

The [Greek: orthoboreodeixis] of the index magnetical in the middle of the ocean, and in the middle of continents (or at least in the middle of their stronger and more lofty parts), its inclining near the shore toward those same parts, even by sea and by land, agreeing with the experiments Bk. 4, chap. 2, on an actual terrella (made after the likeness of the terrestrial globe, uneven, and rising up in certain parts, either weak or wanting in firmness, or imperfect in some other way),--this inclination having been proved, very certainly demonstrates the probability that that variation is nought else than a certain deviation of the magnetick needle toward those parts of the earth that are more vigorous and more prominent. Whence the reason is readily established of that irregularity which is often perceived in the magnetick variations, arising from the inaequality and irregularity of those eminences and of the terrestrial forces. Nor of a surety have I any doubt, that all those even who have either imagined or admitted points attractive or points respective in the sky or the earth, and those who have imagined magnetick mountains, or rocks, or poles, will immediately begin to waver as soon as they have perused these books of yours on the Magnet, and willingly will march with your opinion. Finally, as to the views which you discuss in regard to the circular motion of the earth and of the terrestrial poles, although to some perhaps they will seem most supposititious, yet I do not see why they should not gain some favour, even among the very men who do not recognize a sphaerical motion of the earth; since not even they can easily clear themselves from many difficulties, which necessarily follow from the daily motion of the {v} whole sky. For in the first place it is against reason that that should be effected by many causes, which can be effected by fewer; and it is against reason that the whole sky and all the sphaeres (if there be any) of the stars, both of the planets and the fixed stars, should be turned round for the sake of a daily motion which can be explained by the mere daily rotation of the earth. Then whether will it seem more probable, that the aequator of the terrestrial globe in a single second (that is, in about the time in which any one walking quickly will be able to advance only a single pace) can accomplish a quarter of a British mile (of which sixty equal one degree of a great circle on the earth), or that the aequator of the _primum mobile_ in the same time should traverse five thousand miles with celerity ineffable; and in the twinkling of an eye should fly through about five hundred British miles, swifter than the wings of lightning, if indeed they maintain the truth who especially assail the motion of the earth). Finally, will it be more likely to allow some motion to this very tiny terrestrial globe; or to build up with mad endeavour above the eighth of the fixed sphaeres those three huge sphaeres, the ninth (I mean), the tenth, and the eleventh, marked by not a single star, especially since it is plain from these books on the magnet, from a comparison of the earth and the terrella, that a circular motion is not so alien to the nature of the earth as is commonly supposed.

Nor do those things which are adduced from the sacred Scriptures seem to be specially adverse to the doctrine of the mobility of the earth; nor does it seem to have been the intention of Moses or of the Prophets to promulgate any mathematical or physical niceties, but to adapt themselves to the understanding of the common people and their manner of speech, just as nurses are accustomed to adapt themselves to infants, and not to go into every unnecessary detail. Thus in Gen. i. v. 16, and Psal. 136, the moon is called a great light, because it appears so to us, though it it is agreed nevertheless by those skilled in astronomy that many of the stars, both of the fixed and wandering stars, are much greater. Therefore neither do I think that any solid conclusion can be drawn against the earth's mobility from Psal. 104, v. 5; although God is said to have laid the foundations of the earth that it should not be removed for ever; for the earth will be able to remain evermore in its own and self-same place, so as not to be moved by any wandering motion, nor carried away from its seat (wherein it was first placed by the Divine artificer). We, therefore, with devout mind acknowledging and adoring the inscrutable wisdom of the triune Divinity (having more diligently investigated and observed his admirable work in the magnetical motions), induced by philosophical experiments and reasonings not a few, do deem it to be probable enough that the earth, though resting on its centre as on an immovable base and foundation, nevertheless is borne around circularly._

_But passing over these matters (concerning which I believe no one has ever demonstrated anything with greater certainty), without any doubt those matters which you have discussed concerning the causes of the variation and of the magnetick dip below the horizon, not to mention many other matters, which it would take too long to speak of here, will gain very great favour amongst all intelligent men, and especially (to speak after the manner of the Chemists) amongst the sons of the magnetick doctrine. Nor indeed do I doubt that when you have published these books of yours on the Magnet, you will excite all the diligent and industrious shipmasters to take no less care in observing the magnetick declination beneath the horizon than the variation. Since (if not certain) it is at least probable, that the latitude itself, or rather the effect of the latitude, can be found (even in very dark weather) much more accurately from that declination alone, than can either the longitude or the effect of the longitude from the variation, though the sun itself is shining brightly or all the stars are visible, with the most skilful employment likewise of all the most exact instruments. Nor is there any doubt but that those most learned men, Peter Plancius (not more deeply versed in Geography than in observations magnetical), and Simon Stevinus, the most distinguished mathematician, will rejoice in no moderate degree, when they first see these magnetical books of yours, and observe their _[Greek: limeneuretike]_, or _Haven-finding Art_, enlarged and enriched by so great and unexpected an addition; and without doubt they will urge all their own shipmasters (as far as they can) to observe also everywhere the magnetick declination below the horizon no less than the variation. May your Magnetical Philosophy, therefore, most learned Dr. Gilbert, come forth into the light under the best auspices, after being kept back not till the ninth year only (as Horace prescribes), but already unto almost a second nine, a philosophy rescued at last by so many toils, studyings, watchings, with so much ingenuity and at no moderate expense maintained continuously through so many years, out of darkness and dense mist of the idle and feeble philosophizers, by means of endless experiments skilfully applied to it; yet without neglecting anything which has been handed down in the writings of any of the ancients or of the moderns, all which you did diligently peruse and perpend. Do not fear the boldness or the prejudice of any supercilious and base philosophaster, who by either enviously calumniating or stealthily arrogating to himself the investigations of others seeks to snatch a most empty glory. Verily_

Envy detracts from great Homer's genius;

_but_

Whoever thou art, Zoilus, thou hast thy name from him.

_May your new physiology of the Magnet, I say (kept back for so many years), come forth now at length into the view of all, and your Philosophy, never to be enough admired, concerning the great Magnet (that is, the earth); for, believe me_

(If there is any truth in the forebodings of seers),

_these books of yours on the Magnet will avail more for perpetuating the memory of your name than the monument of any great Magnate placed upon your tomb._

{vj}

_Interpretation of certain words.[1]_

Terrella, a globular loadstone.

Verticity, polar vigour, not [Greek: peridinesis] but [Greek: peridineisios dunamis]: not a vertex or [Greek: polos] but a turning tendency.

Electricks, things which attract in the same manner as amber.

Excited Magnetick, that which has acquired powers from the loadstone.

Magnetick Versorium, a piece of iron upon a pin, excited by a loadstone.

Non-magnetick Versorium, a versorium of any metal, serving for electrical experiments.

Capped loadstone, which is furnished with an iron cap, or snout.

Meridionally, that is, along the projection of the meridian.

Paralleletically, that is, along the projection of a parallel.

Cusp, tip of a versorium excited by the loadstone.

Cross, sometimes used of the end that has not been touched and excited by a loadstone, though in many instruments both ends are excited by the appropriate termini of the stone.

Cork, that is, bark of the cork-oak.

Radius of the Orbe of the Loadstone, is a straight line drawn from the summit of the orbe of the loadstone, by the shortest way, to the surface of the body, which, continued, will pass through the centre of the loadstone.

Orbe of Virtue, is all that space through which the Virtue of any loadstone extends.

Orbe of Coition, is all that space through which the smallest magnetick is moved by the loadstone.

Proof, for a demonstration shown by means of a body.

Magnetick Coition: since in magnetick bodies, motion does not occur by an attractive faculty, but by a concourse or concordance of both, not as if there were an [Greek: helktike dunamis] of one only, but a [Greek: sundrome] of both; there is always a coition of the vigour: and even of the body if its mass should not obstruct.

Declinatorium, a piece of Iron capable of turning about an axis, excited by a loadstone, in a declination instrument.

INDEX OF CHAPTERS.

_Book 1._