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Digitized by the Internet Archive
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https ://arch i ve . org/detai Is/b28038009
WILLIAM GIL-
t
BERT OF COLCHES- TER, PHYSICIAN OF LONDON.
ON THE MAGNET, MAGNE-
TICK BODIES ALSO, AND ON the great magnet the earth; a new Phyfi- °l°gy, demonflrated by many ar - guments & experiments.
LONDON
IMPRINTED at the Chiswick Press ANNO
MCM.
Lmk, Mr-
Z3.4, a
PREFACE TO THE CANDID
READER, STUDIOUS OF
THE MAGNETICK
PHILOSOPHY.
LEARER proofs, in the difcovery of fecrets, and in the inveftigation of the hidden caufes of things, being afforded by truftworthy experiments and by demonftrated arguments, than by the probable gueffes and opinions of the ordinary profeffors of philofophy : fo, therefore, that the noble fubftance of that great magnet, our common mother (the earth), hitherto quite unknown, and the confpicuous and exalted powers of this our globe, may be the better underflood, we have propofed to begin with the common magnetick, flony, and iron material, and with mag- netical bodies, and with the nearer parts of the earth which we can reach with our hands and perceive with our fenfes ; then to proceed with demonflrable magnetick experiments ; and fo penetrate, for the firft time, into the innermofl parts of the earth. For after we had, in order finally to learn the true fubftance of the globe, feen and thoroughly examined many of thofe things which have been obtained from mountain heights or ocean depths, or from the pro- foundeft caverns and from hidden mines: we applied much prolonged labour on inveftigating the magnetical forces ; fo wonderful indeed are they, compared with the forces of all other minerals, furpafling even the virtues of all other bodies about us. Nor have we found this our labour idle or unfruitful ; fince daily during our experimenting, new and unexpected properties came to light ; and our Philofophy hath grown fo much from the things diligently obferved, that we have attempted to expound the interior parts of the terrene globe, and its native fubftance, upon magnetick prin- ciples; and to reveal to men the earth (our common mother), and to point it out as if with the finger, by real demonftrations and by
* ij experiments
PREFACE
experiments manifeftly apparent to the fenfes. And as geometry afcends from fundry very fmall and very eafy principles to the greateft and moft difficult ; by which the wit of man climbs above the firmament : fo our magnetical doCtrine and fcience firft fets forth in convenient order the things which are lefs obfcure ; from thefe there come to light others that are more remarkable ; and at length in due order there are opened the concealed and moft fecret things of the globe of the earth, and the caufes are made known of thofe things which, either through the ignorance of the ancients or the negleCt of moderns, have remained unrecognized and overlooked. But why fhould I, in fo vaft an Ocean of Books by which the minds of ftudious men are troubled and fatigued, through which very foolifh productions the world and unreafoning men are intoxicated, and puffed up, rave and create literary broils, and while profeffing to be philofophers, phyficians, mathematicians and aftrologers, negleCt and defpife men of learning : why fhould I, I fay, add aught further to this fo-perturbed republick of letters, and expofe this noble philofophy, which feems new and incredible by reafon of fo many things hitherto unrevealed, to be damned and torn to pieces by the maledictions of thofe who are either already fworn to the opinions of other men, or are foolifh corruptors of good arts, learned idiots, grammatifts, fophifts, wranglers, and perverfe little folk ? But to you alone, true philofophizers, honeft men, who feek knowledge not from books only but from things themfelves, have I addreffed thefe magnetical principles in this new fort of Philofophizing. But if any fee not fit to affent to thefe felf-fame opinions and paradoxes, let them neverthelefs mark the great array of experiments and dis- coveries (by which notably every philofophy flourifheth), which have been wrought out and demonftrated by us with many pains and vigils and expenfes. In thefe rejoice, and employ them to better ufes, if ye fhall be able. I know how arduous it is to give frefhnefs to old things, luftre to the antiquated, light to the dark, grace to the defpifed, credibility to the doubtful ; fo much the more by far is it difficult to win and eftablifh fome authority for things new and unheard-of, in the face of all the opinions of all men. Nor for that do we care, fince philofophizing, as we deemed, is for the few. To our own difcoveries and experiments we have affixed afterifks, larger and fmaller, according to the importance and fub- tlety of the matter. Whofo defireth to make trial of the fame experiments, let him handle the fubftances, not negligently and carelefily, but prudently, deftly, and in the proper way ; nor let him (when a thing doth not fucceed) ignorantly denounce our dif- coveries : for nothing hath been fet down in thefe books which hath not been explored and many times performed and repeated amongft us. Many things in our reafonings and hypothefes will, perchance, at firfl: fight, feem rather hard, when they are foreign to the com- monly
TO THE READER
monly received opinion ; yet I doubt not but that hereafter they will yet obtain authority from the demonftrations themfelves. Wherefore in magnetical fcience, they who have made moft pro- grefs, truft moil; in and profit moft by the hypothefes ; nor will anything readily become certain to any one in a magnetical philo- fophy in which all or at leaft moft points are not afcertained. This nature-knowledge is almoft entirely new and unheard-of, fave what few matters a very few writers have handed down concerning cer- tain common magnetical powers. Wherefore we but feldom quote antient Greek authors in our fupport, becaufe neither by ufing greek arguments nor greek words can the truth be demonftrated or elucidated either more precifely or more fignificantly. For our dodtrine magnetical is at variance with moft 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 fo handled by us, in fuch a form of fpeech, and in fuch words as are needed to be clearly underftood: Sometimes therefore we ufe new and unufual words,
not that by means of foolifh veils of vocabularies we fhould cover over the fadts with fhades and mifts (as Alchemifts are wont to do) but that hidden things which have no name, never having been hitherto perceived, may be plainly and corredtly enunciated. After defcribing 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 philofophize freely and with the fame liberty which the Egyptians, Greeks, and Latins formerly ufed in publishing their dogmas : whereof very many errors have been handed down in turn to later authors : and in which fmatterers ftill perfift, and wander as though in perpetual darknefs. To thofe early forefathers of philofophy, Ariftotle, Theophraftus, Ptolemy, Hippocrates, and Galen, let due honour be ever paid : for by them wifdom hath been diffufed to pofterity ; but our age hath detedted and brought to light very many fadts which they, were they now alive, would gladly have accepted. Wherefore we alfo have not heft- tated to expound in demonftrable hypothefes thofe things which we have difcovered by long experience. Farewell.
*
nJ
/
TO
TO THE MOST EMINENT AND LEARNED MAN
Dr. William Gilbert,
a difiinguijhed DoSior of Medicine amongfi the Londoners, and Father of Magnetick Philofophy, an Encomiaftic Preface of Edward Wright on the fubjedt of thefe books Magnetical.
HOTJLD there by chance be any one , mojl eminent Sir , who reckons as of fmall account thefe magnetical books and labours of yours , and thinks thefe fudies of yours of too little moment , and by no means worthy enough of the attention of an eminent man devoted to the weightier fudy of Medicine : truly he mufi defervedly be judged to be in no common degree void of underfanding. For that the ufe of the magnet is very important and wholly admirable is better known for the mojl part to men of even the lowejl clafs than to need from me at this time any long addrefs or commendation. Nor truly in my judgment could you have chofen any topick either more noble or more ufeful to the human race , upon which to exercife the firength of your philoj'ophic intellect ; fnce indeed it has been brought about by the divine agency of this fione, that continents of fuch vafi circuity fuch an infinite number of lands , ijlands , peoples , and tribes, which have remained unknown for fo many ages , have now only a Jhort time ago , almofi within our own memory , been quite eafily difcovered and quite frequently explored , and that the circuit of the whole terrefirial globe alfo has been more than once circumnavigated by our own countrymen , Drake and Cavendifh ; a fa5l which I wifi to mention to the lafiing memory of thefe men. For by the pointing of the iron touched by a loadfione , the points of South , North , Eafi , and Weft , and the other quarters of the world are made known to navigators even under an overcafi fky and in the darkefi night ; fo that thus they always very eafily underfiand to which point of the world they ought to dire 51 their Jhip' s courfe ; which before the difcovery of this wonderful virtue of the magnetick /3opeo$el%is was clearly impofjible. Hence in old times ( as is efiablifhed in hifiories ), an incredible anxiety and immenfe danger was continually threatening failors ; for at the coming on of a tempefi and the obfcuring of the view of fun and fiars, they were left entirely in ignorance whither they were making ; nor could they find out this by any reafoning or fkill. With what joy then may we fuppofi them to have been filled , to what feelings of delight mufi all jhipmafiers have given utterance , when that index magnetical firfi offered it f elf to them as a mojl fare guide , and as it were a Mercury , for their journey ? But neither was this fujficient for this magnetical Mercury ; to indicate , namely , the right way , and to point , as it were , a finger in the dire 51 ion toward which the courfe mufi be
dire Sled;
directed; it began alfo long ago to Jhow difiinClly the diftance of the place toward which it points. For fince the index magnetical does not always in every place look toward the fame point of the North , but deviates from it often , either toward the Eafi or toward the Weft, yet always has the fame deviation in the fame place , whatever the place is, and Jleadily preferves it ; it has come about that from that deviation , which they call variation , carefully noticed and obferved in any maritime places , the fame places could afterwards alfo be found by navigators from the drawing near and approach to the fame variation as that of thefe fame places, taken in conjunction with the obfervation of the latitude. Thus the Portuguefe in their voyages to the Eaf Indies had the mofi certain indications of their approach to the Cape of Good Hope ; as appears from the narrations of Hugo van Lynfchoten and of the very learned Richard Hakluyt, our countryman. Hence alfo the experienced Jkippers of our own country , not a few of them, in making the voyage from the Gulf of Mexico to the i/lands of the Azores , recognized that they had come as near as poffible to thefe fame i/lands; although from their fea-charts they feemed to be about fx hundred Britijh miles from them. And fo, by the help of this magnetick index,
it would feem as though that geographical problem of finding the longitude, which for fo many centuries has exercifed the intellects of the mofi learned Mathematicians, were going to be in fome way fatisfied; becaufe if the variation for any maritime place whatever were known, the fame place could very readily be found afterward, as often as was required, from the fame variation , the latitude of the fame place being not unknown.
It feems, however, that there has been fome inconvenience and hindrance connected with the obfervation of this variation ; becaufe it cannot be obferved excepting when the fun or the fiars are fhining. Accordingly this magnetick Mercury of the fea goes on fill further to blefs all fhipmafiers , being much to be preferred to Neptune himfelf, and to all the fea-gods and goddeffes ; not only does it Jhow the direction in a dark night and in thick weather , but it alfo feems to exhibit the mofi certain indications of the latitude. For an iron index , fufpended on its axis ( like a pair of fettles'), with the mofi delicate workmanfhip fo as to balance in cequilibrio, and then touched and excited by a loadfione, dips to fome fixed and definite point beneath the horizon {in our latitude in London, for example , to about the feventy-fecond degree ), at which it at length comes to refi. But under the cequator itfelfi from that admirable agreement and congruency which, in almofi all and fingular magnetical experiments, exifis between the earth itfelf and a terrella (i that is, a globular loadfione ) , it feems exceedingly likely {to fay the very leaf) , and indeed more than probable, that the fame index {again firoked with a loadfione ) will remain in cequilibrio in an horizontal pofition. Whence it is evident that this alfo is very probable , that in an exceed- ingly fmall progrefs from the South toward the North {or contrari- wife) , there will be at leaf a fujficiently perceptible change in that
* iiij declination ;
declination ; fo that from that declination in any place being once carefully obferved along with the latitude, the fame place and the fame latitude may be very eafly recognized afterward, even in the darkef night and in the thickejl mifi by a declination infirument. Wherefore to bring our oration at length back to you, mof eminent and learned Dr. Gilbert ( whom I gladly recognize as my teacher in this magnetick philofophy ), if thefe books of yours on the Magnet had contained nothing elfe, excepting only this finding of latitude from magnetick declination, by you now firfi brought to light , our Jhipmafiers , Britains , French, Belgians, and Danes, trying to enter the Britijh Channel or the Straits of Gibraltar from the Atlantick Ocean in dark weather, would fill mofi defervedly judge them to be valued at no fmall fum of gold. But that difcovery of yours about the whole globe of the earth being magnetic al, although perchance it will feem to many “ mofi paradoxical producing even a feeling of afionifhment , has yet been fo firmly defended by you at all points and confirmed by fo many experiments fo appofite and appropriate to the matter in hand, in Bk. 2, chap. 34 ; Bk. 3, chap. 4 and 1 2 ; and in almofi the whole of the fifth book , that no room is left for doubt or contradiction. I come therefore to the caufe of the magnetick variation, which hitherto has difir aCted the minds of all the learned ; for which no mortal has ever adduced a more probable reafon than that which has now been fet forth by you for the firfi time in thefe books of yours on the Magnet. The 6^9o/3opeohi^ig of the index magnetical in the middle of the ocean , and in the middle of continents (or at leaf in the middle of their fironger and more lofty parts') , its inclining near the fhore toward thofe fame parts, even by fea and by land, agreeing with the experiments Bk. 4, chap. 2, on an aClual terrella (made after the likenefs of the terrefirial globe, uneven, and rifing up in certain parts, either weak or wanting in firmnefs, or im- perfect in fome other way) , — this inclination having been proved, very certainly demonfirates the probability that that variation is nought elfe than a certain deviation of the magnetick needle toward thofe parts of the earth that are more vigorous and more prominent. Whence the reafon is readily efiablijhed of that irregularity which is often perceived in the magnetick variations , arifing from the inrequality and irregular- ity of thofe eminences and of the terrefirial forces. Nor of a furety have I any doubt, that all thofe even who have either imagined or admitted points attractive or points refpeCtive in the Jky or the earth , and thofe who have imagined magnetick mountains, or rocks , or poles, will immediately begin to waver as foon as they have perufed thefe books of yours on the Magnet, and willingly will march with your opinion. Finally , as to the views which you difcufs in regard to the circular motion of the earth and of the terrefirial poles, although to fome perhaps they will feem mofi fuppofititious, yet I do not fee why they Jhould not gain fome favour , even among the very men who do not recognize a fphcerical motion of the earth ; fince not even they can eafily clear themfelves from many difficulties, which necejfarily follow from the daily motion of the
whole
whole Jky. For in the JirJi place it is againji reafon that that Jhould be effected by many caufes , which can be ejfeBed by fewer ; and it is againf reafon that the whole Jky and all the fphceres (if there be any) of the fars , both of the planets and the fixed fiars , Jhould be turned round for the fake of a daily motion , which can be explained by the mere daily rotation of the earth. Then whether will it feem more prob- able, that the cequator of the terrefirial globe in a Jingle fecond (that is, in about the time in which any one walking quickly will be able to advance only a Jingle pace) can accomplijh a quarter of a Britijh mile (of which fixty equal one degree of a great circle on the earth), or that the cequator of the primum mobile in the fame time Jhould traverfe five thoufand miles with celerity ineffable ; and in the twink- ling of an eye Jhould fly through about five hundred Britijh miles, Jwifter than the wings of lightning, if indeed they maintain the truth who efpecially ajfail the motion of the earth) . Finally, will it be more
likely to allow fome motion to this very tiny terrefirial globe ; or to build up with mad endeavour above the eighth of the fixed fphceres thofe three huge fphceres, the ninth (I mean), the tenth, and the eleventh , marked by not a Jingle ftar, efpecially fince it is plain from thefe books on the magnet, from a comparifon of the earth and the terrella, that a circular motion is not fo alien to the nature of the earth as is commonly fuppofed. Nor do thofe things which are adduced from the facred Scriptures feem to be fpecially adverfe to the do Brine of the mobility of the earth ; nor does it feem to have been the intention of Mofes or of the Prophets to promulgate any mathematical or phyfical niceties, but to adapt themfelves to the underflanding of the common people and their manner of J'peech , jufi as nurfes are accuftomed to adapt themfelves to infants, and not to go into every unnecejfary detail. Thus in Gen. i. v. 16, and Pfal. 1 36, the moon is called a great light, becaufe it appears fo to us, though it it is agreed neverthelefs by thofe Jkilled in afironomy that many of the fiars, both of the fixed and wandering fiars, are much greater. There- fore neither do I think that any folid conclufion can be drawn againfi the earth' s mobility from Pfal. 1 04, v. 5 ; although God is faid to have laid the foundations of the earth that it Jhould not be removed for ever; for the earth will be able to remain evermore in its own and felf-fame place, fo as not to be moved by any wandering motion, nor carried away from its feat (wherein it was fir ft placed by the Divine artificer). We, therefore, with devout mind acknowledging and adoring the in- fcrutable wifdom of the triune Divinity (having more diligently invefii- gated and obferved his admirable work in the magnetical motions), induced by philofophical experiments and reafonings not a few, do deem it to be probable enough that the earth, though refiling on its centre as on an immovable circularly.
But pajjing over thefe matters (concerning which I believe no one has ever demonflrated anything with greater certainty), without any doubt thofe matters which you have difcujfed concerning the caufes of
*v the
bafe and foundation, neverthelejs is borne around
the variation and of the magnetick dip below the horizon , not to mention many other matters , which it would take too long to fpeak of here , will gain very great favour amongfl all intelligent men , and efpecially (to fpeak after the manner of the Chemifls ) among ft the fons of the magnetick doCtrine. Nor indeed do I doubt that when you have publijhed thefe books of yours on the Magnet , you will excite all the diligent and in- dufrious Jhipmaflers to take no lefs care in obferving the magnetick declination beneath the horizon than the variation. Since (if not certain) it is at leaf probable , that the latitude itfelf or rather the effett 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 ejfedl of the longitude from the variation , though the fun itfelf is Jhining brightly or all the fars are vifble , with the mof fkilful employ- ment likewife of all the mof exaCl inflruments . Nor is there any doubt but that thofe mof learned men , Peter Plancius (not more deeply verfed in Geography than in obfervations magnetic at) > and Simon Stevinus, the mojl diflinguijhed mathematician , will rejoice in no moderate degree , when they firf fee thefe magnetical books of yours , and obferve their XipeveupeTHcii, or Haven-finding Art, enlarged and enriched by fo great and unexpected an addition ; and without doubt they will urge all their own Jhipmafers (as far as they can) to obferve alfo everywhere the mag- netick declination below the horizon no lefs than the variation. May your Magnetical Philofophy , therefore , mof learned Dr. Gilbert , come forth into the light under the bef aufpices , after being kept back not till the ninth year only (as Horace prefcribes ), but already unto almof a fecond nine , a philofophy refcued at lafi by fo many toils, fudyings , watchings , with fo much ingenuity and at no moderate expenfe maintained continuoufy through fo many years , out of darknefs and denfe mif of the idle and feeble ph ilojoph izers , by means of endlefs experiments fkil- fully applied to it; yet without negleBing anything which has been handed down in the writings of any of the ancients or of the moderns , all which you did diligently perufe and perpend. Do not fear the boldnefs or the prejudice of any fupercilious and bafe philofophafer , who by either envioufy calumniating or fealthily arrogating to himfelf the invefigations of others feeks to fnatch a mof empty glory. Verily
Envy detracts from great Homer’s genius ; but
Whoever thou art, Zoilus, thou haft thy name from him.
May your new phyfology of the Magnet , I fay (kept back for fo many years), come forth now at length into the view of all, and your Philofophy, 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 feers), thefe 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.
Interpretation
Interpretation of certain words .
np'Errella, a globular loadftone.
A Verticity, polar vigour, not 7repi$lvYi<ng, but 7 re^lvturtog Svvupu;: not a vertex or 7 ToXog, but a turning tendency.
EleCtricks, things which attract in the fame manner as amber.
Excited Magnetick, that which has acquired powers from the loadftone.
Magnetick Verforium, a piece of iron upon a pin, excited by a loadftone.
Non-magnetick Verforium, a verforium of any metal, ferving for eleCtrical experiments.
Capped loadftone, which is furnifhed with an iron cap, or fnout.
Meridionally, that is, along the projection of the meridian.
Paralleletically, that is, along the projection of a parallel.
Cufp, tip of a verforium excited by the loadftone.
Crofs, fometimes ufed of the end that has not been touched and excited by a loadftone, though in many inftruments both ends are excited by the appropriate termini of the ftone.
Cork, that is, bark of the cork-oak.
Radius of the Orbe of the Loadftone, is a ftraight line drawn from the fummit of the orbe of the loadftone, by the fhorteft way, to the furface of the body, which, continued, will pafs through the centre of the loadftone.
Orbe of Virtue, is all that fpace through which the Virtue of any loadftone extends.
Orbe of Coition, is all that fpace through which the fmalleft magnetick is moved by the loadftone.
Proof, for a demonftration fhown by means of a body.
Magnetick Coition : fince in magnetick bodies, motion does not occur by an attractive faculty, but by a concourfe or concordance of both, not as if there were an eXKTixvj Svvctfjug of one only, but a <rw$popy of both ; there is always a coition of the vigour : and even of the body if its mafs fhould not obftruCt.
Declinatorium, a piece of Iron capable of turning about an axis, excited by a loadftone, in a declination inftrument.
INDEX
INDEX OF CHAPTERS.
Book i.
CHAP. i. Ancient and modern writings on the Loadftone, with certain matters of mention only, various opinions, & vanities.
Chap. 2. Magnet Stone, of what kind it is, and its difcovery.
Chap. 3. The loadftone has parts diftind in their natural power, & poles confpicuous for their property.
Chap. 4. Which pole of the ftone is the Boreal : and how it is diftinguilhed from the auftral.
Chap. 5. Loadftone feems to attrad loadftone when in natural pofition: but repels it when in a contrary one, and brings it back to order. Chap. 6. Loadftone attrads the ore of iron, as well as iron proper, fmelted & wrought.
Chap. 7. What iron is, and of what fubftance, and its ufes.
Chap. 8. In what countries and diftrids iron originates.
Chap. 9. Iron ore attrads iron ore.
Chap. 10. Iron ore has poles, and acquires them, and fettles itfelf toward the poles of the univerfe.
Chap. 11. Wrought iron, not excited by a loadftone, draws iron.
Chap. 1 2. A long piece of Iron (even though not excited by a loadftone) fettles itfelf toward North & South.
Chap. 13. Wrought iron has in itfelf certain parts Boreal & Auftral: a magnetick vigour, verticity, and determinate vertices or poles. Chap. 14. Concerning other powers of loadftone, & its medicinal properties. Chap. 1 5. The medicinal virtue of iron.
Chap. 16. That loadftone & iron ore are the fame, but iron an extrad from both, as other metals are from their own ores ; & that all mag- netick virtues, though weaker, exift in the ore itfelf & in fmelted iron.
Chap. 17. That the globe of the earth is magnetick, & a magnet; & how in our hands the magnet ftone has all the primary forces of the earth, while the earth by the fame powers remains conftant in a fixed diredion in the univerfe.
Book 2.
Chap. 1. On Magnetick Motions.
Chap. 2. On the Magnetick Coition, and firft on the attradion of Amber, or more truly, on the attaching of bodies to Amber.
Chap. 3. Opinions of others on Magnetick Coition, which they call Attradion.
Chap. 4. On Magnetick Force & Form, what it is ; and on the caufe of the Coition.
Chap. 5. How the Power dwells in the Loadftone.
Chap. 6 . How magnetick pieces of Iron and fmaller loadftones conform them- felves to a terrella & to the earth itfelf, and by them are difpofed.
Chap. 7. On the Potency of the Magnetick Virtue, and on its nature capable of fpreading out into an orbe.
Chap. 8. On the geography of the Earth, and of the Terrella.
Chap. 9. On the iEquinodial Circle of the Earth and of a Terrella.
Chap. 10. Magnetick Meridians of the Earth.
Chap. 11. Parallels.
Chap.
INDEX OF CHAPTERS.
Chap. 12. Chap. 13. Chap. 14.
Chap. 15.
Chap. 16.
Chap. 17. Chap. 18. Chap. 19. Chap. 20.
Chap. 21. Chap. 22.
Chap. 23. Chap. 24.
Chap. 25. Chap. 26.
Chap. 27.
Chap. 28.
Chap. 29. Chap. 30.
Chap. 31. Chap. 32.
Chap. 33.
Chap. 34.
Chap. 35.
The Magnetick Horizon.
On the Axis and Magnetick Poles.
Why at the Pole itfelf the Coition is ftronger than in the other parts intermediate between the aequator and the pole ; and on the proportion of forces of the coition in various parts of the earth and of the terrella.
The Magnetick Virtue which is conceived in Iron is more apparent in an iron rod than in a piece of Iron that is round, fquare, or of other figure.
Showing that Movements take place by the Magnetical Vigour though folid bodies lie between ; and on the interpofition of iron plates.
On the Iron Cap of a Loadftone, with which it is armed at the pole (for the fake of the virtue), and on the efficacy of the fame. An armed Loadftone does not indue an excited piece of Iron with greater vigour than an unarmed.
Union with an armed Loadftone is ftronger ; hence greater weights are raifed ; but the coition is not ftronger, but generally weaker. An armed Loadftone raifes an armed Loadftone, which alfo attracts a third ; which likewife happens, though the virtue in the firft be fomewhat fmall.
If Paper or any other Medium be interpofed, an armed loadftone raifes no more than an unarmed one.
That an armed Loadftone draws Iron no more than an unarmed one: and that an armed one is more ftrongly united to iron is fhown by means of an armed loadftone and a polifhed Cylinder of iron. The Magnetick Force caufes motion toward unity, and binds firmly together bodies which are united.
A piece of Iron placed within the Orbe of a Loadftone hangs fufpended in the air, if on account of fome impediment it can- not approach it.
Exaltation of the power of the magnet.
Why there fhould appear to be a greater love between iron & loadftone, than between loadftone & loadftone, or between iron & iron, when clofe to the loadftone, within its orbe of virtue.
The Centre of the Magnetick Virtues in the earth is the centre of the earth ; and in a terrella is the centre of the ftone.
A Loadftone attracts magneticks not only to a fixed point or pole, but to every part of a terrella fave the sequinodtial zone.
On Variety of Strength due to Quantity or Mafs.
The Shape and Mafs of the Iron are of moft importance in cafes of coition.
On long and round ftones.
Certain Problems and Magnetick Experiments about the Coition, and Separation, and regular Motion of Bodies magnetical.
On the Varying Ratio of Strength, and of the Motion of coition, within the orbe of virtue.
Why a Loadftone fhould be ftronger in its poles in a different ratio ; as well in the Northern regions as in the Southern.
On a Perpetual Motion Machine, mentioned by authors, by means of the attraction of a loadftone.
*vij Chap.
INDEX OF CHAPTERS.
Chap. 36. Chap. 37. Chap. 38. Chap. 39.
How a more robuft Loadftone may be recognized. Ufe of a Loadftone as it affeCts iron.
On Cafes of Attraction in other Bodies.
On Bodies which mutually repel one another.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Book 3.
1. On Direction.
2. The Directive or Verforial Virtue (which we call verticity): what it is, how it exifts in the loadftone ; and in what way it is acquired when innate.
3. How Iron acquires Verticity through a loadftone, and how that verticity is loft and changed.
4. Why Iron touched by a Loadftone acquires an oppofite verticity, and why iron touched by the true Northern fide of a ftone turns to the North of the earth, by the true Southern fide to the South; and does not turn to the South when rubbed by the Northern point of the ftone, and when by the Southern to the North, as all who have written on the Loadftone have falfely fuppofed.
5. On the Touching of pieces of Iron of divers ftiapes.
6. What feems an Oppofing Motion in Magneticks is a proper motion toward unity.
7. A determined Verticity and a difponent Faculty are what arrange magneticks, not a force, attracting them or pulling them together, nor merely a ftrongilh coition or unition.
8. Of Difcords between pieces of Iron upon the fame pole of a Load- ftone, and how they can agree and ftand joined together.
9. Figures illuftrating direction and lhowing varieties of rotations.
10. On Mutation of Verticity and of Magnetick Properties, or on alteration in the power excited by a loadftone.
1 1. On the Rubbing of a piece of Iron on a Loadftone in places mid- way between the poles, and upon the sequinoCtial of a terrella.
12. In what way Verticity exifts in any Iron that has been fmelted though not excited by a loadftone.
13. Why no other Body, excepting a magnetick, is imbued with ver- ticity by being rubbed on a loadftone, and why no body is able to inftil and excite that virtue, unlefs it be a magnetick.
14. The Placing of a Loadftone above or below a magnetick body fufpended in aequilibrio changes neither the power nor the verticity of the magnetick body.
1 5. The Poles, ^Equator, Centre in an entire Loadftone remain and continue fteady ; by diminution and feparation of fome part they vary and acquire other pofitions.
1 6. If the Southern Portion of a Stone be lefiened, fomething is alfo taken away from the power of the Northern Portion.
17. On the Ufe and Excellence of Verforia: and how iron verforia ufed as pointers in fun-dials, and the fine needles of the mariners’ compafs, are to be rubbed, that they may acquire ftronger ver- ticity.
Book
INDEX OF CHAPTERS.
Book 4.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
1. On Variation.
2. That the variation is caufed by the inasquality of the projecting
parts of the earth.
3. The variation in any one place is conftant.
4. The arc of variation is not changed equally in proportion to the diftance of places.
5. An ifland in Ocean does not change the variation, as neither do mines of loadftone.
6. The variation and direction arife from the difponent power of the earth, and from the natural magnetick tendency to rotation, not from attraction, or from coition, or from other occult caufe.
7. Why the variation from that lateral caufe is not greater than has hitherto been obferved, having been rarely feen to reach two points of the mariners’ compafs, except near the pole.
8. On the conftrudtion of the common mariners’ compafs, and on the diverfity of the compafles of different nations.
9. Whether the terreftrial longitude can be found from the variation.
10. Why in various places near the pole the variations are much more ample than in a lower latitude.
1 1 . Cardan’s error when he feeks the diftance of the centre of the earth from the centre of the cofmos by the motion of the ftone of Hercules ; in his book 5, On Proportions.
12. On the finding of the amount of variation: how great is the arc of the Horizon from its ardlick to its antardtick interfedlion of the meridian, to the point refpedlive of the magnetick needle.
13. The obfervations of variation by feamen vary, for the moft part, and are uncertain: partly from error and inexperience, and the imperfections of the inftruments: and partly from the fea being feldom fo calm that the fhadows or lights can remain quite fteady on the inftruments.
14. On the variation under the aequinodlial line, and near it.
1 5. The variation of the magnetick needle in the great iEthiopick and American fea, beyond the asquator.
1 6. On the variation in Nova Zembla.
17. Variation in the Pacifick Ocean.
18. On the variation in the Mediterranean Sea.
19. The variation in the interior of large Continents.
20. Variation in the Eaftern Ocean.
21. How the deviation of the verforium is augmented and diminifhed by reafon of the diftance of places.
Book 5.
1. On Declination.
2. Diagram of declinations of the magnetick needle, when excited, in the various pofitions of the fphere, and horizons of the earth, in which there is no variation of the declination.
3. An indicatory inftrument, fhowing by the virtue of a ftone the degrees of declination from the horizon of each feveral latitude.
#viii Chap.
INDEX OF CHAPTERS.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
Chap.
4. Concerning the length of a verforium convenient for declination on a terrella.
5. That declination does not arife from the attraction of the loadftone, but from a difpofing and rotating influence.
6. On the proportion of declination to latitude, and the caufe of it.
7. Explanation of the diagram of the rotation of a magnetick needle.
8. Diagram of the rotation of a magnetick needle, indicating mag- netical declination in all latitudes, and from the rotation and de- clination, the latitude itfelf.
9. Demonftration of direction, or of variation from the true direction, at the fame time with declination, by means of only a Angle motion in water, due to the difpofing and rotating virtue.
10. On the variation of the declination.
11. On the eflential magnetick adivity fphaerically effufed.
1 2. Magnetick force is animate, or imitates life ; and in many things furpafles human life, while this is bound up in the organick body.
Book 6.
Chap. 1. Chap. 2. Chap. 3.
Chap. 4. Chap. 5.
Chap. 6. Chap. 7.
Chap. 8.
Chap. 9.
On the globe of the earth, the great magnet.
The Magnetick axis of the Earth perfifts invariable.
On the magnetick diurnal revolution of the Earth’s globe, as a probable aflertion againft the time-honoured opinion of a Primum Mobile.
That the Earth moves circularly.
Arguments of thofe denying the Earth’s motion, and their confuta- tion.
On the caufe of the definite time of an entire rotation of the Earth. On the primary magnetick nature of the Earth, whereby its poles are parted from the poles of the Ecliptick.
On the Praecession of the ^Equinoxes, from the magnetick motion of the poles of the Earth, in the Ardick & Antardick circle of the Zodiack.
On the anomaly of the Prasceflion of the Equinoxes, & of the obliquity of the Zodiack.
WILLIAM
WILLIAM GILBERT
ON THE LOADSTONE, BK. I.
QHAP. I.
ANCIENT AND MODERN WRITINGS
on the Loadftone, with certain matters of mention only,
various opinions , & vanities .
T an early period, while philofophy lay as yet rude and uncultivated in the mills of error and ignorance, few were the virtues and properties of things that were known and clearly perceived : there was a briftling foreft of plants and herbs, things metallick were hidden, and the knowledge of Hones was un- 10 fooner had the talents and toils of many brought to light certain commodities necelfary for the ufe and fafety of men, and handed them on to others (while at the fame time reafon and experience had added a larger hope), than a thorough examination began to be made of forefts and fields, hills and heights ; of feas too, and the depths of the waters, of the bowels of the earth’s body ; and all things began to be looked into. And at length by good luck the magnet-flone was difcovered in iron lodes, probably by fmelters of iron or diggers of metals. This, on being handled by metal folk, quickly difplayed that powerful andftrong attraction for iron, a virtue not latent and obfcure, but ealily proved by all, and highly praifed and commended. And in after time when it had emerged, as it were out of darknefs and deep dungeons, and had become dignified of men on account of its flrong and amazing attraction for iron, many philo- fophers as well as phylicians of ancient days difcourfed of it, in fhort celebrated, as it were, its memory only ; as for inftance Plato in the Ioy Arillotle in the De Anima , in Book I. only, Theophraltus the Lefbian, Diofcorides, C. Plinius Secundus, and Julius Solinus. As handed down by them the loadltone merely attracted iron, the reft of its virtues were all undifcovered. But that the ftory of the load-
b ftone
2
WILLIAM GILBERT
ftone might not appear too bare and too brief, to this Angular and foie known quality there were added certain figments and falfehoods, which in the earlieft times, no lefs than nowadays, ufed to be put forth by raw fmatterers and copyifls to be fwallowed of men. As for inftance, that if a loadftone be anointed with garlick, or if a diamond be near, it does not attraCt iron. Tales of this fort occur in Pliny, and in Ptolemy’s Quadripartitum ; and the errors have been feduloufly propagated, and have gained ground (like ill weeds that grow apace) coming down even to our own day, through the writings of a hoft of men, who, to fill out their volumes to a proper bulk, write and copy out pages upon pages on this, that, and the other fubjeCt, of which they knew almoft nothing for certain of their own experience. Such fables of the loadftone even Georgius Agricola himfelf, moft diftinguifhed in letters, relying on the writings of others, has embodied as aCtual hiftory in his books De Natura Fojjilium. Galen noted its medicinal power in the ninth book of his De Simplicium Me die ament or um Facultatibus , and its natural property of attracting iron in the firft book of De Naturalibus Facultatibus ; but he failed to recognize the caufe, as Diofcorides before him, nor made further inquiry. But his commentator Matthiolus repeats the ftory of the garlick and the diamond, and moreover introduces Mahomet’s fhrine vaulted with loadftones, and writes that, by the exhibition of this (with the iron coffin hanging in the air) as a divine miracle, the public were impofed upon. But this is known by travellers to be falfe. Yet Pliny relates that Chinocrates the architect had commenced to roof over the temple of Arfinoe at Alexandria with magnet-ftone, that her ftatue of iron placed therein might appear to hang in fpace. His own death, however, intervened, and alfo that of Ptolemy, who had ordered it to be made in honour of his lifter. Very little was written by the ancients as to the caufes of attraction of iron ; by Lucretius and others there are fome fhort notices ; others only make flight and meagre mention of the attraction of iron : all of thefe are cenfured by Cardan for being fo carelefs and negligent in a matter of fuch importance and in fo wide a field of philofophizing ; and for not fupplying an ampler notion of it and a more perfeCt philofophy : and yet, beyond certain received opinions and ideas borrowed from others and ill-founded conjectures, he has not himfelf any more than they delivered to pofterity in all his bulky works any contribution to the fubjeCt worthy of a philofopher. Of modern writers fome fet forth its virtue in medicine only, as Antonius Mufa Brafavolus, Baptifta Montanus, Amatus Lufitanus, as before them Oribafius in his thirteenth chapter De Facultate Metallicorum , Aetius Amidenus, Avicenna, Serapio Mauritanus, Hali Abbas, Santes de Ardoynis, Petrus Apponenfis, Marcellus, Arnaldus. Bare mention is made of certain points relating to the loadftone in very few words by Marbodeus Gallus, Albertus,
Matthaeus
3
ON THE LOADSTONE, B K. I.
Matthaeus Silvaticus, Hermolaus Barbarus, Camillus Leonhardus, Cornelius Agrippa, Fallopius, Johannes Langius, Cardinal Cufan, Hannibal Rofetius Calaber; by all of whom the fubjedt is treated very negligently, while they merely repeat other people’s fidtions and ravings. Matthiolus compares the alluring powers of the load- ftone which pafs through iron materials, with the mifchief of the torpedo, whofe venom pafles through bodies and fpreads imper- ceptibly ; Guilielmus Puteanus in his Ratio Purgantium Medica- mentorum difcufles the loadftone briefly and learnedly. Thomas Eraftus, knowing little of magnetical nature, finds in the loadftone weak arguments againft Paracelfus; Georgius Agricola, like En- celius and other metallurgifts, merely ftates the fadts ; Alexander Aphrodifeus in his Problemata confiders the queftion of the load- ftone inexplicable ; Lucretius Carus, the poet of the Epicurean fchool, confiders that an attradlion is brought about in this way : that as from all things there is an efflux of very minute bodies, fo from the iron atoms flow into the fpace emptied by the elements of the loadftone, between the iron and the loadftone, and that as foon as they have begun to ftream towards the loadftone, the iron follows, its corpufcles being entangled. To much the fame effedt Johannes Coftaeus adduces a paflage from Plutarch ; Thomas Aquinas, writing briefly on the loadftone in Chapter VII. of his Phyjica, touches not amifs on its nature, and with his divine and clear intelledl would have publiflhed much more, had he been converfant with magnetick experiments. Plato thinks the virtue divine. But when three or four hundred years afterwards, the magnetick movement to North and South was difcovered or again recognized by men, many learned men attempted, each according to the bent of his own mind, either by wonder and praife, or by fome fort of reafonings, to throw light upon a virtue fo notable, and fo needful for the ufe of mankind. Of more modern authors a great number have ftriven to fhow what is the caufe of this diredtion and movement to North and South, and to underftand this great miracle of nature, and to difclofe it to others : but they have loft both their oil and their pains ; for, not being pradtifed in the fubjedts of nature, and being milled by certain falfe phyfical fyftems, they adopted as theirs, from books only, without magnetical experiments, certain inferences bafed on vain opinions, and many things that are not, dreaming old wives’ tales. Marfilius Ficinus ruminates over the ancient opinions, and in order to fhow the reafon of the diredtion feeks the caufe in the heavenly conftella- tion of the Bear, fuppofing the virtue of the Bear to prevail in the ftone and to be transferred to the iron. Paracelfus aflerted that there are ftars, endowed with the power of the loadftone, which attradt to themfelves iron. Levinus Lemnius defcribes and praifes the compafs, and infers its antiquity on certain grounds ; he does not divulge the hidden miracle which he propounds. In the kingdom
of
4
WILLIAM GILBERT
of Naples the Amalfians were the firft (fo it is faid) to conftruCt the mariners’ compafs : and as Flavius Blondus fays the Amalfians boaft, not without reafon, that they were taught by a certain citizen, Johannes Goia, in the year thirteen hundred after the birth of Chrift. That town is fituated in the kingdom of Naples not far from Salerno, near the promontory of Minerva ; and Charles V. bellowed that principality on Andrea Doria, that great Admiral, on account of his fignal naval fervices. Indeed it is plain that no invention of man’s device has ever done more for mankind than the compafs : fome notwithftanding confider that it was difcovered by others previoufly and ufed in navigation, judging from ancient writings and certain arguments and conjectures. The knowledge of the little mariners’ compafs feems to have been brought into Italy by Paolo, the Venetian, who learned the art of the compafs in the Chinas about the year MCCLX. ; yet I do not wilh the Amalfians to be deprived of an honour fo great as that of having firft made the con- ftrudtion common in the Mediterranean Sea. Goropius attributes the difcovery to the Cimbri or Teutons, forfooth becaufe the names of the thirty-two winds infcribed on the compafs are pronounced in the German tongue by all fhip-mafters, whether they be French, Britifh, or Spaniards ; but the Italians defcribe them in their own vernacular. Some think that Solomon, king of Judaea, was acquaint with the ufe of the mariners’ compafs, and made it known to his fhip-mafters in the long voyages when they brought back fuch a power of gold from the Weft Indies : whence alfo, from the Hebrew word Parvaim , Arias Montanus maintains that the gold-abounding regions of Peru are named. But it is more likely to have come from the coaft of lower .Ethiopia, from the region of Cephala, as others relate. Yet that account feems to be lefs true, inafmuch as the Phoenicians, on the frontier of Judaea, who were mod: fkilled in navigation in former ages (a people whofe talents, work, and counfel Solomon made ufe of in conftrudting Chips and in the aCtual expedi- tions, as well as in other operations), were ignorant of magnetick aid, the art of the mariners’ compafs: For had it been in ufe
amongft them, without doubt the Greeks and alfo Italians and all barbarians would have underftood a thing fo neceflary and made famous by common ufe ; nor could matters of much repute, very eafily known, and fo highly requifite ever have perifhed in oblivion ; but either the learning would have been handed down to pofterity, or fome memorial of it would be extant in writing. Sebaftian Cabot was the firft to difcover that the magnetick iron varied. Gonzalus Oviedus is the firft to write, as he does in his Hijioria , that in the fouth of the Azores it does not vary. Fernelius in his book De Abditis Rerum Caujis fays that in the loadftone there is a hidden and abftrufe cauie, elfewhere calling it celeftial ; and he brings forth nothing but the unknown by means of what is ftill more unknown.
For
5
ON THE LOADSTONE, BK. I.
For clumfy, and meagre, and pointlefs is his inquiry into hidden caufes. The ingenious Fracaftorio, a diftinguilhed philofopher, in feeking the reafon for the direction of the loadftone, feigns Hyper- borean magnetick mountains attradting magnetical things of iron : this view, which has found acceptance in part by others, is followed by many authors and finds a place not in their writings only, but in geographical tables, marine charts, and maps of the globe : dream- ing, as they do, of magnetick poles and huge rocks, different from the poles of the earth. More than two hundred years earlier than Fracaftorio there exifts a little work, fairly learned for the time, going under the name of one Peter Peregrinus, which fome confider to have originated from the views of Roger Bacon, the Englifhman of Oxford : In which book caufes for magnetick direction are fought from the poles of the heaven and from the heaven itfelf. From this Peter Peregrinus, Johannes Taifnier of Hainault extradted materials for a little book, and publifhed it as new. Cardan talks much of the riling of the ftar in the tail of the Greater Bear, and has attributed to its riling the caufe of the variation : fuppofing that the variation is always the fame, from the riling of the ftar. But the difference of the variation according to the change of polition, and the changes which occur in many places, and are even irregular in fouthern regions, preclude the influence of one particular ftar at its northern riling. The College of Coimbra feeks the caufe in fome part of the heaven near the pole : Scaliger in fedtion CXXXI. of his Exercitationes on Cardan fuggefts a heavenly caufe unknown to himfelf, and terreftrial loadftones nowhere yet difcovered. A caufe not due to thofe fideritic mountains named above, but to that power which falhioned them, namely that portion of the heaven which overhangs that northern point. This view is garnifhed with a wealth of words by that erudite man, and crowned with many marginal fubtilities ; but with reafonings not fo fubtile. Martin Cortes confiders that there is a place of attradtion beyond the poles, which he judges to be the moving heavens. One Beffardus, a Frenchman, with no lefs folly notes the pole of the zodiack. Jacobus Severtius, of Paris, while quoting a few points, fafhions new errors as to loadftones of different parts of the earth being different in diredtion : and alfo as to there being eaftern and weftern parts of the loadftone. Robert Norman, an Englishman, fixes a point and region refpedtive, not attradlive ; to which the magnetical iron is collimated, but is not itfelf attradted. Francifcus Maurolycus treats of a few problems on the loadftone, taking the trite views of others, and avers that the variation is due to a certain magnetical ifland mentioned by Olaus Magnus. Jofephus Acofta, though quite ignorant about the loadftone, neverthelefs pours forth vapid talk upon the loadftone. Livio Sanuto in his Italian Geographia , difcufles at length the queftion whether the prime magnetick
meridian
6
WILLIAM GILBERT
meridian and the magnetick poles are in the heavens or in the earth ; alfo about an inftrument for finding the longitude : but through not underftanding magnetical nature, he raifes nothing but errors and mills in that fo important notion. Fortunius Affaytatus philofophizes foolilhly enough on the attraction of iron, and its turning to the poles. Molt recently, Baptilta Porta, no ordinary philofopher, in his Magia Naturalis , has made the feventh book a cultodian and dillributor of the marvels of the loadltone ; but little did he know or ever fee of magnetick motions ; and fome things that he noted of the powers which it manifelted, either learned by him from the Reverend Maeltro Paolo, the Venetian, or evolved from his own vigils, were not fo well difcovered or obferved ; but abound in utterly falfe experiments, as will be clear in due place : Hill I deem him worthy of high praife for having attempted fo great a fubjeCt (as he has done with fufficient fuccefs and no mean refult in many other inftances), and for having given occafion for further refearch. All thefe philofophizers of a previous age, philofophizing about attraction from a few vague and untruftworthy experiments, drawing their arguments from the hidden caufes of things ; and then, feeking for the caufes of magnetick directions in a quarter of the heavens, in the poles, the liars, conllellations, or in mountains, or rocks, fpace, atoms, attractive or refpeCtive points beyond the heavens, and other fuch unproven paradoxes, are whole horizons wrong, and wander about blindly. And as yet we have not fet ourfelves to overthrow by argument thofe errors and impotent reafonings of theirs, nor many other fables told about the loadltone, nor the fuperllitions of impoltors and fabulilts : for inltance, Fran- cifcus Rueus’ doubt whether the loadltone were not an impolture of evil fpirits : or that, placed underneath the head of an unconfcious woman while alleep, it drives her away from the bed if an adulterefs : or that the loadltone is of ufe to thieves by its fume and Iheen, being a Itone born, as it were, to aid theft: or that it opens bars and locks, as Serapio crazily writes : or that iron held up by a loadltone, when placed in the fcales, added nothing to the weight of the load- llone, as though the gravity of the iron were abforbed by the force of the Itone : or that, as Serapio and the Moors relate, in India there exill certain rocks of the fea abounding in loadltone, which draw out all the nails of the fhips which are driven toward them, and fo flop their failing ; which fable Olaus Magnus does not omit, faying that there are mountains in the north of fuch great powers of attraction, that fhips are built with wooden pegs, left the iron nails fhould be drawn from the timber as they palled by amongft the magnetick crags. Nor this : that a white loadltone may be procured as a love potion : or as Hali Abbas thoughtlefily reports, that if held in the hand it will cure gout and fpafms : Or that it makes one
acceptable and in favour with princes, or eloquent, as PiCtorio has
fung ;
7
ON THE LOADSTONE, BK. I.
fung ; Or as Albertus Magnus teaches, that there are two kinds of loadftones, one which points to the North, the other to the South : Or that iron is directed toward the Northern ftars by an influence imparted by the polar ftars, even as plants follow the fun, as Helio- trope does : Or that there is a magnet-ftone fituated under the tail
of the Greater Bear, as Lucas Gauricus the Aftrologer ftated : He would even aflign the loadftone, like the Sardonyx and onyx, to the planet Saturn, yet at the fame time he afligns it with the adamant, Jafper, and Ruby, to Mars ; lb that it is ruled by two planets. The loadftone moreover is faid by him to pertain to the fign Virgo; and he covers many fuch lhameful pieces of folly with a veil of mathe- matical erudition. Such as that an image of a bear is engraved on a loadftone when the Moon faces towards the north, fo that when hung by an iron wire it may conciliate the influence of the celeftial Bear, as Gaudentius Merula relates : Or that the loadftone drew
iron and dire&ed it to the north, becaufe it is fuperior in rank to iron, at the Bear, as Ficinus writes, and Merula repeats : Or that
by day it has a certain power of attracting iron, but by night the power is feeble, or rather null : Or that when weak and dulled the virtue is renewed by goats’ blood, as Ruellius writes : Or that
Goats’ blood fets a loadftone free from the venom of a diamond, fo that the loft power is revived when bathed in goats’ blood by reafon of the difcord between that blood and the diamond: Or
that it removed forcery from women, and put to flight demons, as Arnaldus de Villanova dreams : Or that it has the power to
reconcile hulbands to their wives, or to recall brides to their hufbands, as Marbodeus Gallus, chorus-leader of vanities, teaches : Or that in a loadftone pickled in the fait of a fucking filh there is power to pick up gold which has fallen into the deepeft wells, according to the narratives of Cselius Calcagninus. With fuch idle tales and trumpery do plebeian philofophers delight themfelves and fatiate readers greedy for hidden things, and unlearned devourers of abfurdities : But after the magnetick nature fhall have been
difclofed by the difcourfe that is to follow, and perfected by our labours and experiments, then will the hidden and abftrufe caufes of fo great an effeCt ftand out, fure, proven, difplayed and demon- ftrated ; and at the fame time all darknefs will difappear, and all error will be torn up by the roots and will lie unheeded ; and the foundations of a grand magnetick philofophy which have been laid will appear anew, fo that high intellects may be no further, mocked by idle opinions. Some learned men there are who in the courfe of long voyages have obferved the differences of magnetick variation : the moft fcholarly Thomas Hariot, Robert Hues, Edward Wright, Abraham Kendall, all Englifhmen ; Others there are who have invented and produced magnetical inftruments, and ready methods of obfervation, indifpenfable for failors and to thofe travelling afar:
as
8
WILLIAM GILBERT
as William Borough in his little book on the Variation of the Compafs or Magneticall Needle, William Barlowe in his Supply , Robert Norman in his Newe Attractive. And this is that Robert Norman (a fkilful feaman and ingenious artificer) who firftdifcovered the declination of the magnetick needle. Many others I omit wittingly ; modern Frenchmen, Germans, and Spaniards, who in books written for the moft part in their native tongues either mifi- ufe the placets of others, and fend them forth furbifhed with new titles and phrafes as tricky traders do old wares with meretricious ornaments ; or offer fomething not worthy of mention even : and thefe lay hands on fome work filched from other authors and folicit fome one as their patron, or go hunting after renown for themfelves among the inexperienced and the young ; who in all branches of learning are feen to hand on errors and occafionally add fomething falfe of their own.
CHAP. II.
Magnet Stone, of what kind it is, and its
difcovery.
OADSTONE, the ftone which is commonly called the Magnet, derives its name either from the dif- coverer (though he was not Pliny’s fabulous herdf- man, quoted from Nicander,the nails of whofe fhoes and the tip of whofe ftaff Ruck faff in a magnetick field while he paftured his flocks), or from the region of Magnefia in Macedonia, rich in loadftones : Or elfe from the city Magnefia in Ionia in Afia Minor, near the river Meander. Hence Lucretius fays,
'The Magnet's name the obferving Grecians drew From the Magnetick region where it grew.
It is called Heraclean from the city Heraclea, or from the invincible Hercules, on account of the great ftrength and domination and power which there is in iron of fubduing all things : it is alfo called fiderite , as being of iron ; being not unknown to the moft ancient writers, to the Greeks, Hippocrates, and others, as alfo (I believe) to Jewifh and Egyptian writers ; For in the oldeft mines of iron, the moft famous in Afia, the loadftone was often dug out with its uterine brother, iron. And if the tales be true which are told of the people of the Chinas, they were not unacquainted in primitive times with magnetical experiments, for even amongft
them
9
ON THE LOADSTONE, B K. I.
them the fineft magnets of all are ftill found. The Egyptians, as Manetho relates, gave it the name Os Ori: calling the power which governs the turning of the fun Orus, as the Greeks call it Apollo. But later by Euripides, as narrated by Plato, it was defignated under the name of Magnet. By Plato in the Io , Nicander of Colophon, Theophraftus, Diofcorides, Pliny, Solinus, Ptolemy, Galen, and other inveftigators of nature it was recognized and commended ; fuch, however, is the variety of magnets and their points of unlike- nefs in hardnefs, foftnefs, heavinefs, lightnefs, denfity, firmnefs, and friability of fubftance: fo great and manifold are the differences in colour and other qualities, that they have not handed down any adequate account of it, which therefore was laid afide or left im- perfedt by reafon of the unfavourable character of the time ; for in thofe times varieties of fpecimens and foreign products never before feen were not brought from fuch diftant regions by traders and mariners as they have been lately, and now that all over the globe all kinds of merchandife, ftones, woods, fpices, herbs, metals, and ore in abundance are greedily fought after : neither was metallurgy fo generally cultivated in a former age. There is a difference in vigour ; as whether it is male or female : for it was thus that the ancients ufed often to diftinguifh. many individuals of the fame fpecies. Pliny quotes from Sotacus five kinds ; thofe from ./Ethiopia, Macedonia, Bceotia, the Troad, and Afia, which were efpecially known to the ancients: but we have pofited as many kinds of load- ftones as there are in the whole of nature regions of different kinds of foil. For in all climates, in every province, on every foil, the loadftone is either found, or elfe lies unknown on account of its rather deep fite and inacceflible pofition ; or by reafon of its weaker and lefs obvious ftrength it is not recognized by us while we fee and handle it. To the ancients the differences were thofe of colour, how they are red and black in Magnefia and Macedonia, in Bceotia red rather than black, in the T road black, without ftrength : While in Magnefia in Afia they are white, not attracting iron, and refemble pumice-ftone. A ftrong loadftone of the kind celebrated fo often nowadays in experiments prefen ts the appearance of un- polifhed iron, and is moftly found in iron mines : it is even wont to be difcovered in an unbroken lode by itfelf : Loadftones of this fort are brought from Eaft India, China, and Bengal, of the colour of iron, or of a dark blood or liver colour ; and thefe are the fineft, and are fometimes of great fize, as though broken off a great rock, and of confiderable weight ; fometimes fingle ftones, as it were, and entire : fome of thefe, though of only one pound weight, can lift on high four ounces of iron or a half-pound or even a whole pound. Red ones are found in Arabia, as broad as a tile, not equal in weight to thofe brought from China, but ftrong and good: they are a little darker in the ifland of Elba in the Tufcan fea, and together with
c thefe
10
WILLIAM GILBERT
thefe alfo grow white ones, like fome in Spain in the mines of Caravaca : but thefe are of leffer power. Black ones alfo are found, of lower ftrength, fuch as thofe of the iron mines in Norway and in fea-coaft places near the ftrait of Denmark. Amongft the blue- black or dufky blue alfo fome are ftrong and highly commended. Other loadftones are of a leaden colour, fiffile and not-fiffile, capable of being fplit like Hates in layers. I have alfo fome like gray marble of an afhen colour, and fome fpeckled like gray marble, and thefe take the fined: polifh. In Germany there are fome perforated like honeycombs, lighter than any others, and yet ftrong. Thofe are metallick which fmelt into the beft iron ; others are not eafily fmelted, but are burned up. There are loadftones that are very heavy, as alfo others very light ; fome are very powerful in catching up pieces of iron, while others are weaker and of lefs capacity, others fo feeble and barren that they with difficulty attradl ever fo tiny a piece of iron and cannot repel an oppofite magnetick. Others are firm and tough, and do not readily yield to the artificer. Others are friable. Again, there are fome denfe and hard as emery, or loofe-textured and foft as pumice ; porous or folid ; entire and uniform, or varied and corroded ; now like iron for hardnefs, yea, fometimes harder than iron to cut or to file ; others are as foft as clay. Not all magnets can be properly called ftones ; fome rather reprefent rocks ; while others exift rather as metallick lodes ; others as clods and lumps of earth. Thus varied and unlike each other, they are all endowed, fome more, fome lefs, with the peculiar virtue. For they vary according to the nature of the foil, the different admixture of clods and humours, having refpedt to the nature of the region and to their fubfidence in this laft-formed cruft of the earth, refulting from the confluence of many caufes, and the per- petual alternations of growth and decline, and the mutations of bodies. Nor is this ftone of fuch potency rare ; and there is no region wherein it is not to be found in fome fort. But if men were to fearch for it more diligently and at greater outlay, or were able, where difficulties are prefent, to mine it, it would come to hand everywhere, as we fhall hereafter prove. In many countries have been found and opened mines of efficacious loadftones unknown to the ancient writers, as for inftance in Germany, where none of them has ever afferted that loadftones were mined. Yet fince the time when, within the memory of our fathers, metallurgy began to flourifh there, loadftones ftrong and efficacious in power have been dug out in numerous places ; as in the Black Foreft beyond Helceburg ; in Mount Mifena not far from Schwartzenberg ; a fairly ftrong kind between Schneeberg and Annaberg in Joachimfthal, as was noticed by Cordus: alfo near the village of Pela in Franconia. In Bohemia it occurs in iron mines in the Leffa diftridt and other places, as Georgius Agricola and feveral other men learned in metallurgy
witnefs.
ON THE LOADSTONE, BK. I. n
witnefs. In like manner in other countries in our time it is brought to light ; for as the hone remarkable for its virtues is now famous throughout the whole world, fo alfo everywhere every land produces it, and it is, fo to fpeak, indigenous in all lands. In Eaft India, in China, in Bengal near the river Indus it is common, and in certain maritime rocks : in Perfia, Arabia, and the iilands of the Red Sea ; in many places in ./Ethiopia, as was formerly Zimiri, of which Pliny makes mention. In Alia Minor around Alexandria and the Troad ; in Macedonia, Bceotia, in Italy, the illand of Elba, Barbary ; in Spain Hill in many mines as aforetime. In England quite lately a huge power of it was difcovered in a mine belonging to Adrian Gilbert, gentleman ; alfo in Devonlhire and the Foreft of Dean ; in Ireland, too, Norway, Denmark, Sweden, Lapland, Livonia, Pruflia, Poland, Hungary. For although the terreftrial globe, owing to the varied humours and natures of the foil ariling from the continual fucceflion of growth and decay, is in the lapfe of time efflorefcing through all its ambit deeper into its furface, and is girt about with a varied and perilhable covering, as it were with a veil ; yet out of her womb arifeth in many places an offspring nigher to the more perfect body and makes its way to the light of day. But the weak and lefs vigorous loadftones, enfeebled by the flow of humours, are vilible in every region, in every ftrath. It is eafy to difcover a vaft quantity of them everywhere without penetrating mountains or great depths, or encountering the difficulties and hardlhips of miners ; as we fhall prove in the fequel. And thefe we fhall take pains fo to prepare by an eafy operation that their languid and dormant virtue fhall be made manifeft. It is called by the Greeks vj^diycXiog, as by Theophraltus, and poiyvriTig ; and fjcuyvng, as by Euripides, as quoted by Plato in the Io : by Orpheus too puyvyoa-a,, and o-i^iTvjg as though of iron : by the Latins magnes , Herculeus ; by the French aimant , corruptly from adamant ; by the Spaniards piedramant : by the Italians calamita; by the Englifh lOfltlftQn0 and anamant Clone, by the Germans magnefs and JiegelJiein: Among Englifh, French, and Spaniards it has its common name from adamant ; perhaps becaufe they were at one time milled by the name Jideritis being common to both : the magnet is called tn&pmjs from its virtue of attracting iron: the adamant is called cnSepiTvig from the brilliancy of polilhed iron. Ariftotle delignates it merely by the name of the Jlone : VE once de i cou QotXrig 6% uv cc7ropivvipt,ovEVov(rii x.iv7]tik6v ti Ty\v ipuxvv vnoXoifteiv, zIttep) rov XlQov e(pr] £%£*!', otl
tov <n'$v}f)ov xivei: De Anima , Lib. I. The name of magnet is alfo applied to another Hone differing from liderite, having the appearance of lilver ; it is like Amianth in its nature ; and lince it conlifts of laminae (like fpecular Hone), it differs in form: in German Katzenjilber and Talke.
4
CHAP.
I 2
WILLIAM GILBERT
CHAP. III.
The Loadftone has parts diftindt in their natural
power , & poles confpicuous for their property.
HE ftone itfelf manifefts many qualities which, though known afore this, yet, not having been well inveftigated, are to be briefly indicated in the firft place fo that ftudents may underftand the powers of loadftone and iron, and not be troubled at the outfet through ignorance of reafonings and proofs. In the heaven aftronomers aflign a pair of poles for each moving fphere : fo alfo do we find in the terreftrial globe natural poles pre- eminent in virtue, being the points that remain conftant in their polition in refpedt to the diurnal rotation, one tending to the Bears and the feven ftars; the other to the oppofite quarter of the heaven. In like manner the loadftone has its poles, by nature northern and fouthern, being definite and determined points fet in the ftone, the primary boundaries of motions and effedts, the limits and governors of the many adtions and virtues. However, it muft be underftood that the ftrength of the ftone does not emanate from a mathematical point, but from the parts themfelves, and that while all thofe parts in the whole belong to the whole, the nearer they are to the poles of the ftone the ftronger are the forces they acquire and fhed into other bodies : thefe poles are obfervant of the earth’s poles, move toward them, and wait upon them. Magnetick poles can be found in every magnet, in the powerful and mighty (which Antiquity ufed to call the mafculine) as well as in the weak, feeble and feminine ; whether its figure is due to art or to chance, whether long, flat, fquare, three-cornered, polifhed ; whether rough, broken, or unpolifhed ; always the loadftone contains and fhows its poles. But fince the fpherical form, which is alfo the moft perfedt, agrees beft with the earth, being a globe, and is moft fuitable for ufe and experiment, we accordingly wifh our principal demonftrations by the ftone to be made with a globe-fhaped magnet as being more perfedt and adapted for the purpofe. Take, then, a powerful load- ftone, folid, of a juft fize, uniform, hard, without flaw; make of it a globe upon the turning tool ufed for rounding cryftals and fome other ftones, or with other tools as the material and firmnefs of the ftone requires, for fometimes it is difficult to be worked. The ftone thus prepared is a true, homogeneous offspring of the earth and of the fame fhape with it : artificially poffeffed of the orbicular form which nature granted from the beginning to the common mother earth: and it is a phyfical corpufcle imbued with many virtues, by
means
*3
ON THE LOADSTONE, BK. I.
means of which many abftrufe and negledted truths in philofophy buried in piteous darknefs may more readily become known to men. This round ftone is called by us a fjuzpoyvi or 'Terrella. To find, then, the poles conformable to the earth’s, take the round ftone in hand, and place upon the ftone a needle or wire of iron: the ends of the iron move upon their own centre and fuddenly ftand ftill. Mark the ftone with ochre or with chalk where the wire lies and fticks: move the middle or centre of the wire to another place, and fo on to a third and a fourth, always marking on the ftone along the length of the iron where it remains at reft: thofe lines fhow the meridian circles, or the circles like meridians on the ftone, or terrella, all of which meet as will be manifeft at the poles of the ftone. By the circles thus continued the poles are made out, the Boreal as well as the fouthern, and in the middle fpace betwixt thefe a great circle may be drawn for an equator, juft as Aftronomers defcribe them in the heavens and on their own globes, or as Geo- graphers do on the terreftrial globe : for that line fo drawn on this our terrella is of various ufes in our demonftrations and experiments magnetical. Poles are alfo found in a round ftone by a verforium, a piece of iron touched with a loadftone, and placed upon a needle or point firmly fixed on a foot fo as to turn freely about in the following way:
On the ftone A B the verforium is placed in fuch a way that the verforium may remain in equilibrium : you will mark with chalk the courfe of the iron when at reft : Move the inftrument to another fpot, and again make note of the direction and alpedt: do the fame thing in feveral places, and from the concurrence of the lines of direction you will find one pole at the point A, the other at B. A verforium placed near the ftone alfo indicates the true pole ; when at right angles it eagerly beholds the ftone and feeks the pole itfelf diredtly, and is turned in a ftraight line through the axis to the
centre
H
WILLIAM GILBERT
centre of the ftone. For inftance, the verforium D faces toward A and F, the pole and centre, whereas E does not exactly refpedt * either the pole A or the centre F. A bit of rather fine iron wire, of the length of a barley-corn, is placed on the ftone, and is moved over the regions and furface of the ftone, until it rifes to the perpendi- cular: for it ftands ered: at the adtual pole, whether Boreal or auftral; the further from the pole, the more it inclines from the vertical. The poles thus found you fhall mark with a Sharp file or gimlet.
CHAP. IIII.
Which pole of the ftone is the Boreal : & how it is
diftinguijhed from the auftral .
NE pole of the earth turns toward the conftellation of the Cynofure, and conftantly regards a fixed point in the heaven (except fo far as it changes by the fixed ftars being Shifted in longitude, which motion we recognize as exifting in the earth, as we fhall hereafter prove) : While the other pole turns to the oppofite face of heaven, unknown to the ancients, now vifible on long voyages, and adorned with multitudinous ftars: In the fame way the loadftone has the property and power of directing itfelf North and South (the earth herfelf consenting and contributing force thereto) according to the conformation of nature, which arranges the movements of the ftone towards its native fituation. Which thing is proved thus : Place a magnetick ftone (after finding the
poles) in a round wooden veflel, a Bowl or difh, at the fame time place it together with the veflel (like a failor in a fkiff) upon water in fome large veflel or ciftern, fo that it may be able to float freely in the middle, nor touch the edge of it, and where the air is not dis- turbed by winds, which would thwart the natural movement of the ftone. Hereupon the ftone placed as it were in a fhip, in the middle of the Surface of the ftill and unruffled water, will at once put itfelf in motion along with the veflel that carries it, and revolve circularly, until its auftral pole points to the north, and its boreal pole to the fouth. For it reverts from the contrary pofition to the poles: and although by the firft too-vehement impulfe it over-pafles the poles ; yet after returning again and again, it refts at length at the poles, or at the meridian (unlefs becaufe of local reafons it is diverted fome little from thofe points, or from the meridional line, by fome fort of variation, the caufe of which we will hereafter ftate). However often you move it away from its place, fo often by virtue of nature’s noble dower does it feek again thofe fure and
determined
ON THE LOADSTONE, BK. I. 15
determined goals ; and this is fo, not only if the poles have been difpofed in the veffel evenly with the plane of the horizon, but alfo in the cafe of one pole, whether auftral or boreal, being raifed in the veffel ten, or twenty, or thirty, or fifty or eighty degrees, above * the plane of the horizon, or lowered beneath it : Still you fhall
fee the boreal part of the ftone feek the fouth, and the auftral part feek the north ; So much fo that if the pole of the ftone fhall be only one degree diftant from the Zenith and higheft point of the heaven, in the cafe of a fpherical ftone, the whole ftone revolves until the pole occupies its own fite ; though not in the abfolutely diredt line, it will yet tend toward thofe parts, and come to reft in the meridian of the diredtive adtion. With a like impulfe too it is borne if the auftral pole have been raifed toward the upper quarters, the fame as if the Boreal had been exalted above the Horizon. But it is always to be noted that, though there are various kinds of unlikenefs in the ftones, and one loadftone may far furpafs another in virtue and efficiency; yet all hold to the fame limits, and are borne toward the fame points. Further it is to be remembered * that all who before our time wrote of the poles of the ftone, and all the craftfmen and navigators, have been very greatly in error in confidering the part of the ftone which tended to the north as the north pole of the ftone, and that which verged toward the fouth, the fouth pole, which we fhall hereafter prove to be falfe. So badly hitherto hath the whole magnetick philofophy been cultivated, even as to its foundation principles.
CHAP. V.
Loadftone feems to attradf Loadftone when in natural
pofition: but repels it when in a contrary one, and brings
it back to order.
IRST of all we muft declare, in familiar language, what are the apparent and common virtues of the ftone ; afterward numerous fubtilities, hitherto abftrufe and unknown, hidden in obfcurity, are to be laid open, and the caufes of all thefe (by the un- locking of nature’s fecrets) made evident, in their place, by fitting terms and devices. It is trite and commonplace that loadftone draws iron ; in the fame way too does loadftone attract loadftone. Place the ftone which you have feen to have poles clearly diftinguifhed, and marked auftral and boreal, in its veffel fo as to float ; and let the poles be rightly arranged with refpedl to the plane of the horizon, or, at any rate not much raifed or awry : hold in your hand another ftone the poles of which are alfo known ; in
fuch
i6
WILLIAM GILBERT
fuch a way that its auftral pole may be toward the boreal pole of the one that is fwimming, and near it, lideways: for the floating ftone forthwith follows the other ftone (provided it be within its force and dominion) and does not leave off nor forfake it until it adhaeres ; unlefs by withdrawing your hand, you cautioufly avoid contact. In like manner if you fet the boreal pole of the one you hold in your hand oppoflte the auftral pole of the fwimming ftone, they rufh together and follow each other in turn. For contrary poles allure contrary. If, however, you apply in the fame way the northern to the northern, and the auftral to the auftral pole, the one ftone puts the other to flight, and it turns afide as though a pilot were pulling at the helm and it makes fail in the oppoflte ward as one that ploughs the fea, and neither ftands anywhere, nor halts, if the other is in purfuit. For ftone difpofeth ftone; the one turns the other around, reduces it to range, and brings it back to harmony with itfelf. When, however, they come together and are conjoined according to the order of nature, they cohere firmly mutually. For inftance, if you were to fet the boreal pole of that ftone which is in your hand before the tropic of Capricorn of a round floating load- ftone (for it will be well to mark out on the round ftone, that is the terrella, the mathematical circles as we do on a globe itfelf), or before any point between the asquator and the auftral pole ; . at once the fwimming ftone revolves, and fo arranges itfelf that its auftral pole touches the other’s boreal pole, and forms a clofe union with it. In the fame way, again, at the other fide of the aequator, with the oppoflte poles, you may produce fimilar refults ; and thus by this art and fubtilty we exhibit attraction, repulfion, and circular motion for attaining apofition of agreement and for declining hoftile encounters. Moreover ’tis in one and the fame ftone that we are thus able to demonftrate all thefe things and alfo how the fame part of one ftone may on divifion become either boreal or auftral. Let A D be an oblong ftone, in which A is the northern, D the fouthern pole ; cut this into two equal parts, then fet part A in its veflel on the water, fo as to float.
And
l7
ON THE LOADSTONE, B K. I.
And you will then fee that A the northern point will turn to the fouth, as before ; in like manner alfo the point D will move to the north, in the divided ftone, as in the whole one. Whereas, of the parts B and C, which were before continuous, and are now divided, the one is fouthern B, the other northern C. B draws C, delirous to be united, and to be brought back into its priftine continuity : for thefe which are now two ftones were formed out of one : and for this caufe C of the one turning itfelf to B of the other, they mutually attradt each other, and when freed from obftacles and relieved of their own weight, as upon the furface of water, they run together and are conjoined. But if you diredt the part or point A to C in the other ftone, the one repels or turns away from the other : for fo were nature perverted, and the form of the ftone perturbed, a form that ftridtly keeps the laws which it impofed upon bodies : hence, when all is not rightly ordered according to nature, comes the flight of one from the other’s perverfe pofition and from the difcord, for nature does not allow of an unjuft and inequitable peace, or compromife : but wages war and exerts force to make bodies acquiefce well and juftly. Rightly arranged, therefore, thefe mutually attract each other ; that is, both ftones, the ftronger as well as the weaker, run together, and with their whole forces tend to unity, a fadt that is evident in all magnets, not in the ^Ethiopian only, as Pliny fuppofed. The .Ethiopian magnets if they be powerful, like thofe brought from China, becaufe all ftrong ones fhow the effedt more quickly and more plainly, attract more ftrongly in the parts neareft the pole, and turn about until pole looks diredtly at pole. The pole of a ftone more perfiftently attracts and more rapidly feizes the correfponding part (which they term the adverfe part) of another ftone ; for inftance. North pulls South ; juft fo it alfo fummons iron with more vehemence, and the iron cleaves to it more firmly whether it have been previoufly excited by the magnet, oris untouched. For thus, not without reafon hath it been ordained by nature, that the parts nearer to the pole fhould more firmly attradt : but that at the pole itfelf fhould be the feat, the throne, as it were, of a confummate and fplendid virtue, to which magnetical bodies on being brought are more vehemently attracted, and from which they are with utmoft difficulty diflodged. So the poles are the parts which more particularly fpurn and thruft away things ftrange and alien perverfely fet befide them.
D
CHAP.
WILLIAM GILBERT
18
CHAP. VI.
Loadftone attracts the ore of iron, as well as iron
proper^ f melted and wrought.
RINCIPAL and manifeft among the virtues of the magnet, fo much and fo anciently commended, is the attraction of iron ; for Plato ftates that the magnet, fo named by Euripides, allures iron, and that it not only draws iron rings but alfo indues the rings with power to do the fame as the ftone ; to wit, draw other rings, fo that fometimes a long chain of iron objeCts, nails or rings is formed, fome hanging from others. The belt iron (like that which is called acies from its ufe, or chalybs from the country of the Chalybes) is belt and ftrongly drawn by a powerful loadftone ; whereas the lefs good fort, which is impure, rufty, and not thoroughly purged from drofs, and not wrought in fecond furnaces, is more feebly drawn ; and yet more weakly when covered and defiled with thick, greafy, and fluggifh humours. It alfo draws ores of iron, thofe that are rich and of iron colour ; the poorer and not fo productive ores it does not attraCt, except they be prepared with fome art. A loadftone lofes fome attractive virtue, and, as it were, pines away with age, if expofed too long to the open air inftead of being laid in a cafe with filings or fcales of iron. Whence it fhould be buried in fuch materials ; for there is nothing that plainly refifts this exhauftlefs virtue which does not deftroy the form of the body, or corrode it ; not even if a thoufand adamants were conjoined. Nor do I confider that there is any fuch thing as the Theamedes, or that it has a power oppofite to that of the loadftone. Although Pliny, that eminent man and prince of compilers (for it is what others had feen and difcovered, not always or mainly his own obfervations, that he has handed down to pofterity) has copied from others the fable now made familiar by repetition : That in India there are two mountains near the river Indus ; the nature of one being to hold faft all that is iron, for it confifts of loadftone ; the other’s nature being to repel it, for it confifts of the Theamedes. Thus if one had iron nails in one’s boots, one could not tear away one’s foot on the one mountain, nor ftand ftill on the other. Albertus Magnus writes that a loadftone had been found in his day which with one part drew to itfelf iron, and repelled it with its other end ; but Albertus obferved the faCts badly ; for every loadftone attracts with one end iron that has been touched with a loadftone, and drives it away with the other ; and draws iron that has been touched with a loadftone more powerfully than iron that has not been fo touched.
CHAP.
ON THE LOADSTONE, BK. I.
*9
CHAP. VII.
What Iron is, and of what fubftance,
and its ufes.
OR that now we have declared the origin and nature of the loadftone, we think it neceffary firft to add a hiftory of iron and to indicate the hitherto unknown forces of iron, before this our difcourfe goes on to the explanation of magnetick difficulties and demonftrations, and to deal with the coitions and harmonies of loadftone with iron. Iron is by all reckoned in the clafs of metals, and is a metal livid in colour, very hard, glows red-hot before it melts, being moft difficult of fufion, is beaten out under the hammer, and is very refonant. Chemifts fay that if a bed of fixed earthy fulphur be combined with fixed earthy quick- filver, and the two together are neither pure white but of a livid whitenefs, if the fulphur prevail, iron is formed. For thefe ftern mafters of metals who by many inventions twilling them about, pound, calcine, diffolve, fublime, and precipitate, decide that this metal, both on account of the earthy fulphur and of the earthy mercury, is more truly a fon of the earth than any other ; they do not even think gold or filver, lead, tin, or copper itfelf fo earthy ; for that reafon it is not fmelted except in the hotted: furnaces, with bellows; and when thus fufed, on having again grown hard it is not melted again without heavy labour ; but its flag with the utmoll difficulty. It is the hardeft of metals, fubduing and breaking all things, by reafon of the llrong concretion of the more earthy matter. Wherefore we ffiall better underftand what iron is, when we ffiall declare what are the caufes and fubftance of metals, in a different way from thofe who before our time have confidered them. Ariftotle takes the material of the metals to be vapour. The chemifts in chorus pronounce their adtual elements to be fulphur and quickfilver. Gilgil Mauritanus gives it as allies moiftened with water. Georgius Agricola makes it out to be water and earth mixed ; nor, to be fure, is there any difference between his opinion and the pofition taken by Mauritanus. But ours is that metals arife and efflorefce at the fummits of the earth’s globe, being dif- tinguiffied each by its own form, like fome of the other fubflances dug out of it, and all bodies around us. The earth’s globe does not confift of allies or inert dull. Nor is freffi water an element, but a more Ample confiftency of evaporated fluids of the earth. Undtuous bodies, freffi water devoid of properties, quickfilver and fulphur, none of thefe are principia of metals : thefe latter
things
20
WILLIAM GILBERT
things are the refults of a different nature, they are neither conftant nor antecedent in the courfe of the generation of metals. The earth emits various humours, not begotten of water nor of dry earth, nor from mixtures of thefe, but from the fubftance of the earth itfelf: thefe humours are not diftinguifhed by contrary qualities or fubftance, nor is the earth a fimple fubftance, as the Peripateticks dream. The humours proceed from vapours fublimated from great depths ; all waters are extracts and, as it were, exudations from the earth. Rightly then in fome meafure does Ariftotle make out the matter of metals to be that exhalation which in continuance thickens in the lodes of certain foils : for the vapours are condenfed in places which are lefs hot than the fpot whence they iffued, and by help of the nature of the foils and mountains, as in a womb, they are at fitting feafons congealed and changed into metals : but it is not they alone which form ores, but they flow into and enter a more folid material, and fo form metals. So when this concreted matter has fettled down in more temperate beds, it begins to take fhape in thofe tepid places, juft as feed in the warm womb, or as the embryo acquires growth : fometimes the vapour conjoins with fuitable matter alone : hence fome metals are occafionally though rarely dug up native, and come into exiftence perfect without fmelting : but other vapours which are mixed with alien foils require fmelting in the way that the ores of all metals are treated, which are rid of all their drofs by the force of fires, and being fufed flow out metallick, and are feparated from earthy impurities but not from the true fubftance of the earth. But in fo far as that it becomes gold, or filver, or copper, or any other of the exifting metals, this does not happen from the quantity or proportion of material, nor from any forces of matter, as the Chemifts fondly imagine ; but when the beds and region concur fitly with the material, the metals aflume forms from the univerfal nature by which they are perfected ; in the fame manner as all the other minerals, plants, and animals whatever : otherwife the fpecies of metals would be vague and undefined, which are even now turned up in fuch fcanty numbers that fcarce ten kinds are known. Why, however, nature has been fo ftingy as regards the number of metals, or why there fhould be as many as are known to man, it is not eafy to explain ; though the fimple-minded and raving Aftrologers refer the metals each to its own planet. But there is no agreement of the metals with the planets, nor of the planets with the metals, either in numbers or in properties. For what connexion is there of iron with Mars? unlefs it be that from the former numerous inftruments, particularly fwords and engines of war, are fafhioned. What has copper to do with Venus? or how does tin, or how does fpelter correfpond with Jupiter? They fhould rather be dedicated to Venus. But this is old wives’ talk. Vapour is then a remote caufe in the generation of the metals ; the fluid condenfed from
vapours
21
ON THE LOADSTONE, BK. I.
vapours is a more proximate one, like the blood and femen in the generation of animals. But thofe vapours and juices from vapours pafs for the moil: part into bodies and change them into marcaiites and are carried into lodes (for we have numerous cafes of wood fo tranfmuted), the fitting matrices of bodies, where they are formed as metals. They enter moil: often into the truer and more homo- geneal fubilance of the globe, and in the procefs of time a vein of iron refults ; loaditone is alfo produced, which is nought elfe than a noble kind of iron ore : and for this reafon, and on account of its fubilance being iingular, alien from all other metals, nature very rarely, if ever, mixes with iron any other metal, while the other metals are very often minutely mixed, and are produced together. Now when that vapour or thofe juices happen to meet, in fitting matrices, with efflorefcences deformed from the earth’s homogenic fubilance, and with divers precipitates (the forms working thereto), the remainder of the metals are generated (a fpecifick nature affecting the properties in that place). For the hidden primordial elements of metals and ftones lie concealed in the earth, as thofe of herbs and plants do in its outer cruil. For the foil dug out of a deep well, where would feem to be no fufpicion of a conception of feed, when placed on a very high tower, produces, by the incuba- tion of fun and fky, green herbage and unbidden weeds ; and thofe of the kind which grow fpontaneouily in that region, for each region produces its own herbs and plants, alfo its own metals.
Here corn exults , and there the grape is glad ,
Here trees and grafs unbidden verdure add.
So mark how Id molus yields his faffron Jlore ,
But ivory is the gift of Indian fhore ;
With incenfe foft the fofter She bans deal ;
The ft ark Chaly beans' element is Jieel:
With acrid caftor reek the Pontic wares ,
Epirus wins the palm of Elian mares.
But what the Chemifls (as Geber, and others) call fixed earthy fulphur in iron is nothing elfe than the homogenic earth-fubflance concreted by its own humour, amalgamated with a double fluid : a metallick humour is inferted along with a fmall quantity of the fubilance of the earth not devoid of humour. Wherefore the common faying that in gold there is pure earth, but in iron moflly impure, is wrong ; as though there were indeed fuch a thing as natural earth, and that the globe itfelf were (by fome unknown procefs of refining) depurate. In iron, efpecially in the beft iron, there is earth in its own nature true and genuine ; in the other metals there is not fo much earth as that in place of earth and precipitates there are confolidated and (fo to fpeak) fixed falts, which are efflorefcences of the globe, and which differ alfo greatly
in
22
WILLIAM GILBERT
in firmnefs and conliflency : In the mines their force rifes up along with a twofold humour from the exhalations, they folidify in the underground fpaces into metallic veins : fo too they are alfo connate by virtue of their place and of the furrounding bodies, in natural matrices, and take on their fpecific forms. Of the various con- ftitutions of loadflones and their diverfe fubflances, colours, and virtues, mention has been made before : but, now having Hated the caufe and origin of metals, we have to examine ferruginous matter not as it is in the fmelted metal, but as that from which the metal is refined. Quafi-pure iron is found of its proper colour and in its own lodes ; ftill, not as it will prefently be, nor as adapted for its various ufes. It is fometimes dug up covered with white filex or with other Hones. It is often the fame in river fand, as in Noricum. A nearly pure ore of iron is now often dug up in Ireland, which the fmiths, without the labours of furnaces, hammer out in the fmithy into iron implements. In France iron is very commonly fmelted out of a liver-coloured Hone, in which are glittering fcales ; the fame kind without the fcales is found in England, which alfo they ufe for craftfmen’s ruddle. In Suflex in England is a rich duiky ore and alfo one of a pale affien hue, both of which on being dried for a time, or kept in moderate fires, prefently acquire a liver- colour; here alfo is found a dufky ore fquare-fhaped with a black rind of greater hardnefs. An ore having the appearance of liver is often varioufly intermingled with other Hones : as alfo with the perfect loadflone which yields the beH of iron. There is alfo a ruHy ore of iron, one of a leaden hue tending to black, one quite black, or black mixed with true cobalt : there is another fort mixed either with pyrites, or with Herile plumbago. One kind is alfo like jet, another like bloodHone. The emery ufed by armourers, and by glaziers for glafs-cutting, called amongH the Engliffi Emerel- Hone, by the Germans Smeargel, is ferruginous ; albeit iron is extracted from it with difficulty, yet it attracts the verforium. It is now and then found in deep iron and filver diggings. Thomas Eraflus fays he had heard from a certain learned man of iron ores, of the colour of iron, but quite foft and fatty, which can be fmoothed with the fingers like butter, out of which excellent iron can be fmelted : fomewhat the fame we have feen found in England, having the afpedl of Spaniffi foap. Befides the number- lefs kinds of Hony ores, iron is extracted from clay, from clayey earth, from ochre, from a ruHy matter depofited from chalybeate waters ; In England iron is copioufly extracted in furnaces often from fandy and clayey Hones which appear to contain iron not more than fand, marl, or any other clay foils contain it. Thus in AriHotle’s book De Mirabilibus Aufcultationibus , “ There is faid ” (he Hates) “ to be a peculiar formation of Chalybean and Mifenian iron, for inflance the fort collected from river gravel; fome fay
that
23
ON THE LOADSTONE, BK. I.
“ that after being limply walked it is fmelted in the furnace ; others “ declare that it and the fediment which fubfides after feveral wafhings “ are call in and purified together by the fire ; with the addition of “ the ftone pyrimachus which is found there in abundance.” Thus do numerous forts of things contain in their various fubftances notably and abundantly this element of iron and earth. However, there are many ftones, and very common ones, found in every foil, alfo earths, and various and mixed materials, which do not hold rich fubftances, but yet have their own iron elements, and yield them to fkilfully-made fires, yet which are left afide by metallick men becaufe they are lefs profitable ; while other foils give fome fhow of a ferruginous nature, yet (being very barren) are hardly ever fmelted down into iron ; and being negledted are not generally known. Manufadtured irons differ very greatly amongft themfelves. For one kind is tenacious in its nature, and this is the beft ; one is of medium quality : another is brittle, and this is the worft. Some- times the iron, by reafon of the excellency of the ore, is wrought into fteel, as to-day in Noricum. From the fineft iron, too, well wrought and purged from all drofs, or by being plunged in water after heating, there iffues what the Greeks call o-Toptopa. ; the Latins acies ; others aciarium , fuch as was at times called Syrian, Parthian, Noric, Comefe, Spanifh ; elfewhere it is named from the water in which it is fo often plunged, as at Como in Italy, Bambola and Tarazona in Spain. Acies fetches a much larger price than mere iron. And owing to its fuperiority it better accords with the load- ftone, from which more powerful quality it is often fmelted, and it acquires the virtues from it more quickly, retains them longer at their full, and in the beft condition for magnetical experiments. After iron has been fmelted in the firft furnaces, it is afterward wrought by various arts in large workfteads or mills, the metal acquiring confiftency when hammered with ponderous blows, and throwing off the drofs. After the firft fmelting it is rather brittle and by no means perfedt. Wherefore with us (Englifh) when the larger military guns are caft, they purify the metal from drofs more fully, fo that they may be ftronger to withftand the force of the firing ; and they do this by making it pafs again (in a fluid ftate) through a chink, by which procefs it fheds its recremental matter. Smiths render iron fheets tougher with certain liquids, and by blows of the hammer, and from them make fhields and breaftplates that defy the blows of battle-axes. Iron becomes harder through fkill and proper tempering, but alfo by fkill turns out in a fofter condition and as pliable as lead. It is made hard by the adtion of certain waters into which while glowing it is plunged, as at Bambola and Tarazona in Spain : It grows foft again, either by the effedt of fire alone, when without hammering and without water, it is left to cool by itfelf ; or by that of greafe into which it is plunged ; or
(that
24
WILLIAM GILBERT
(that it may the better ferve for various trades) it is tempered varioufly by being fkilfully befmeared. Baptifta Porta expounds this art in book 13 of his Magia Naturalis. Thus this ferric and telluric nature is included and taken up in various bodies of ftones, ores, and earths ; fo too it differs in afpedt, in form, and in efficiency. Art fmelts it by various proceffes, improves it, and turns it, above all material fubft ances, to the fervice of man in trades and appliances without end. One kind of iron is adapted for breaftplates, another ferves as a defence againft fhot, another protects againft fwords and curved blades (commonly called fcimitars), another is ufed for making fwords, another for horfefhoes. From iron are made nails, hinges, bolts, faws, keys, grids, doors, folding-doors, fpades, rods, pitch- forks, hooks, barbs, tridents, pots, tripods, anvils, hammers, wedges, chains, hand-cuffs, fetters, hoes, mattocks, fickles, bafkets, fhovels, harrows, planes, rakes, ploughfhares, forks, pans, difhes, ladles, fpoons, fpits, knives, daggers, fwords, axes, darts, javelins, lances, fpears, anchors, and much fhip’s gear. Befides thefe, balls, darts, pikes, breaftplates, helmets, cuiraffes, horfefhoes, greaves, wire, firings of mufical inftruments, chairs, portcullifes, bows, catapults, and (pefts of human kind) cannon, mufkets, and cannon-balls, with endlefs inftruments unknown to the Latins : which things I have rehearfed in order that it may be underftood how great is the ufe of iron, which furpaffes a hundred times that of all the other metals ; and is day by day being wrought by metal-workers whofe ftithies are found in almoft every village. For this is the foremoft of metals, fubferving many and the greateft needs of man, and abounds in the earth above all other metals, and is predominant. Wherefore thofe Chemifts are fools who think that nature’s will is to perfect all metals into gold ; fhe might as well be making ready to change all ftones to diamonds, fince diamond furpaffes all in fplendour and hardnefs, becaufe gold excels in fplendour, gravity, and denfity, being in- vincible againft all deterioration. Iron as dug up is therefore, like iron that has been fmelted, a metal, differing a little indeed from the primary homogenic terreftrial body, owing to the metallick humour it has imbibed ; yet not fo alien as that it will not, after the manner of refined matter, admit largely of the magnetick forces, and may be affociated with that prepotent form belonging to the earth, and yield to it a due fubmiffion.
CHAP.
ON THE LOADSTONE, B K. I.
25
CHAP. VIII.
In what countries and diftri&s iron
originates .
LENTY of iron mines exift everywhere, both thofe of old time recorded in early ages by the moll ancient writers, and the new and modern ones. The earlieft and mod: important feem to me to be thofe of Alia. For in thofe countries which abound naturally in iron, governments and the arts flourifhed exceedingly, and things needful for the ufe of man were difcovered and fought after. It is recorded to have been found about Andria, in the region of the Chalybes near the river Thermodon in Pontus; in the mountains of Paleftine which face Arabia; in Carmania: in Africa there was a mine of iron in the Ille of Meroe ; in Europe in the hills of Britain, as Strabo writes ; in Hither Spain, in Can- tabria. Among the Petrocorii and Cubi Biturges (peoples of Gaul), there were workfteads in which iron ufed to be wrought. In greater Germany near Luna, as recorded by Ptolemy ; Gothinian iron is mentioned by Cornelius Tacitus ; Noric iron is celebrated in the verfes of poets ; and Cretan, and that of Euboea ; many other iron mines were palled over by thefe writers or unknown to them ; and yet they were neither poor nor fcanty, but moll extenlive. Pliny fays that Hither Spain and all the diftridt from the Pyrenees is ferruginous, and on the part of maritime Cantabria walhed by the Ocean (fays the fame writer) there is (incredible to relate) a pre- cipitoufly high mountain wholly compofed of this material. The mod: ancient mines were of iron rather than of gold, lilver, copper or lead; lince mainly this was fought becaufe of the demand; and alfo becaufe in every diftridt and foil they were eafy to find, not fo deep-lying, and lefs befet by difficulties. If, however, I were to enumerate modern iron workings, and thofe of this age and over Europe only, I Ihould have to write a large and bulky volume, and ffieets of paper would run Ihort quicker than the iron, and yet for one ffieet they could furnilh a thoufand workdeads. For amongft minerals, no material is fo ample ; all metals, and all ftones didindt from iron, are outdone by ferric and ferruginous matter. For you will not readily find any region, and fcarcely any country didridl over the whole of Europe (if you fearch.at all deeply), that does not either produce a rich and abundant vein of iron or fome foil con- taining or dightly charged with ferruginous duff; and that this is
e true
26
WILLIAM GILBERT
true any expert in the arts of metals and chemiftry will ealily find. Befide that which has ferruginous nature, and the metallick lode, there is another ferric fublfance which does not yield the metal in this way becaufe its thin humour is burnt out by fierce fires, and it is changed into an iron flag like that which is Separated from the metal in the firft furnaces. And of this kind is all clay and argil- laceous earth, fuch as that which apparently forms a large part of the whole of our ifland of Britain : all of which, if fubje&ed very vehemently to intenfe heat, exhibits a ferric and metallick body, or paffes into ferric vitreous matter, as can be eafily feen in buildings in bricks baked from clay, which, when placed next the fires in the open kilns (which our folk call clamps) and burned, prefent an iron vitrification, black at the other end. Moreover all thofe earths as prepared are drawn by the magnet, and like iron are attracted by it. So perpetual and ample is the iron offspring of the terreftrial globe. Georgius Agricola fays that almoft all mountainous regions are full of its ores, while as we know a rich iron lode is frequently dug in the open country and plains over nearly the whole of England and Ireland ; in no other wife than as, fays he, iron is dug out of the meadows at the town of Saga in pits driven to a two-foot depth. Nor are the Weft Indies without their iron lodes, as writers tell us ; but the Spaniards, intent upon gold, negledt the toilfome work of iron-founding, and do not fearch for lodes and mines abounding in iron. It is probable that nature and the globe of the earth are not able to hide, and are evermore bringing to the light of day, a great mafs of inborn matter, and are not invariably obftrufted by the fettling of mixtures and efflorefcences at the earth’s furface. It is not only in the common mother (the terreftrial globe) that iron is produced, but fometimes alfo in the air from the earth’s exhalations, in the higheft clouds. It rained iron in Lucania, the year in which M. Craffus was flain. The tale is told, too, that a mafs of iron, like flag, fell from the air in the Nethorian foreft, near Grina, and they narrate that the mafs was many pounds in weight ; fo that it could neither be conveyed to that place, on account of its weight, nor be brought away by cart, the place being without roads. This happened before the civil war waged between the rival dukes in Saxony. A fimilar ftory, too, comes to us from Avicenna. It once rained iron in the Torinefe, in various places (Julius Scaliger telling us that he had a piece of it in his houfe), about three years before that province was taken over by the king. In the year 1510 in the country bordering on the river Abdua (as Cardan writes in his book Be Rerum Varietate ) there fell from the fky 1200 ftones, one weighing 120 pounds, another 30 or 40 pounds, of a rufty iron colour and remarkably hard. Thefe occurrences being rare are regarded as portents, like the fhowersof earth and ftones mentioned in Roman hiftory. But that it ever rained other metals is not re- corded ;
ON THE LOADSTONE, BK. I. 27
corded ; for it has never been known to rain from the fky gold, lilver, lead, tin, or fpelter. Copper, however, has been at fome time noticed to fall from the Iky, and this is not very unlike iron ; and in fad. cloud-born iron of this fort, or copper, are feen to be im- perfectly metallick, incapable of being caft in any way, or wrought with facility. For the earth hath of her (tore plenty of iron in her highlands, and the globe contains the ferric and magnetick element in rich abundance. The exhalations forcibly derived from fuch material may well become concreted in the upper air by the help of more powerful caufes, and hence fome monftrous progeny of iron be begotten.
CHAP. IX.
Iron ore attracts iron ore.
ROM various fubftances iron (like all the reft of the -)£■ metals) is extracted : fuch fubftances being ftones, earth, and limilar concretions which miners call veins becaufe it is in veins, as it were, that they are generated. We have fpoken above of the variety of thefe veins. If a properly coloured ore of iron one (as miners call it) is placed, as foon as mined, upon water in a bowl or any fmall veffel (as we have fhown before in the cafe of a loadftone), it is attracted by a limilar piece of ore brought near by hand, yet not fo powerfully and quickly as one loadftone is drawn by another loadftone, but llowly and feebly. Ores of iron that are ftony, cindery, dufky, red, and feveral more of other colours, do not attract one another mutually, nor are they attracted by the loadftone itfelf, even by a ftrong one, no more than wood, or lead, lilver, or gold. Take thofe ores and burn, or rather roaft them, in a moderate fire, fo that they are not fuddenly fplit up, or fly afunder, keeping up the fire ten or twelve hours, and gently increafing it, then let them grow cold, fkill being fhown in the direction in which they are placed : Thefe ores thus prepared a loadftone will now draw, and they now fhow a mutual fympathy, and when fkilfully arranged run together by their own forces.
CHAP.
28
WILLIAM GILBERT
CHAP. X.
■fc Iron ore has poles, and acquires them, and fettles
it f elf toward the poles of the univerfe.
EPLORABLE is man’s ignorance in natural fcience, and modern philofophers, like thofe who dream in darknefs, need to be aroufed, and taught the ufes of things and how to deal with them, and to be induced to leave the learning fought at leifure from books alone, and that is fupported only by un- realities of arguments and by conjectures. For the knowledge of iron (than which nothing is in more common ufe), and that of many more fubftances around us, remains unlearned ; iron, a rich ore of which, placed in a veflel upon water, by an innate property of its own directs itfelf, juft like the loadftone, North and South, at which points it refts, and to which, if it be turned alide, it reverts by its own inherent vigour. But many ores, lefs perfeCt in their nature, which yet contain amid ftone or earthy fubftances plenty of iron, have no fuch motion ; but when prepared by fkilful treat- ment in the fires, as fhown in the foregoing chapter, they acquire a polar vigour (which we call verticity) ; and not only the iron ores in requeft by miners, but even earth merely charged with ferruginous matter, and many rocks, do in like manner tend and lean toward those portions of the heavens, or more truly of the earth, if they be fkilfully placed, until they reach the defired location, in which they eagerly repofe.
CHAP.
ON THE LOADSTONE, BK. I.
29
CHAP. XI.
Wrought Iron, not excited by a loadftone, %■
draws iron.
ROM the ore, which is converted, or feparated, partly into metal, partly into flag, by the intenfe heat of fires, iron is fmelted in the firft furnaces in a fpace of eight, ten, or twelve hours, and the metal flows away from the drofs and ufelefs matter, forming a large and long mafs, which being fub- -p hammering is cut into parts, out of which when reheated in the fecond hearth of the forge, and again placed on the anvil, the fmiths fafhion quadrangular lumps, or more fpecially bars which are bought by merchants and blackfmiths, from which in fmithies ufually it is the cuftom to fafhion the various implements. This iron we term wrought , and its attraction by the loadftone is manifeft to all. But we, by more carefully trying everything, have found out that iron merely, by itfelf alone, not excited by any loadftone, not charged by any alien forces, attracts other iron ; though it does not fo eagerly fnatch and fuddenly pluck at it as would a fairly ftrong loadftone ; this you may know thus : A fmall piece of cork, the fize of a hazel-nut, rounded, is traverfed by an iron wire up to the middle of the wire : when fet fwimming on ftill water apply to one end of it, clofe (yet fo as not to touch), the end of another iron wire; and wire draws wire, and one follows the other when flowly drawn back, and this goes on up to the proper boundaries. Let A be the cork with the iron wire, B one end of it raifed a little above the furface of the water, C the end of the
fecond wire, fhowing the way in which B is drawn by C. You may prove it in another way in a larger body. Let a long bright iron rod (fuch as is made for hangings and window curtains) be hung in balance by a (lender filken cord : to one end of this as it refts in the air bring a fmall oblong mafs of polifhed iron, with its proper
end
3°
WILLIAM GILBERT
end at the diftance of half a digit. The balanced iron turns itfelf to the mafs ; do you with the fame quicknefs draw back the mafs in your hand in a circular path about the point of equilibrium of the fufpenfion ; the end of the balanced iron follows after it, and turns in an orbit.
CHAP. XII.
A long piece of Iron, even though not excited by a
loadjlone, fettles itfelf toward North and South.
VERY good and perfedt piece of iron, if drawn out in length, points North and South, juft as the load- ftone or iron rubbed with a magnetical body does; a thing that our famous philofophers have little underftood, who have fweated in vain to fet forth the magnetick virtues and the caufes of the friendfhip of iron for the ftone. You may experiment with either large or fmall iron works, and either in air or in water. A ftraight piece of iron ftx feet long of the thicknefs of your finger is fufpended (in the way defcribed in the foregoing chapter) in exadt aequipoife by a ftrong and (lender filken cord. But the cord (hould be crofs-woven of feveral filk filaments, not twilled (imply in one way; and it (hould be in a fmall chamber with all doors and windows clofed, that the wind may not enter, nor the air of the room be in any way difturbed; for which reafon it is not expedient that the trial (hould be made on windy days, or while a ftorm is brewing. For thus it freely follows its bent, and (lowly moves until at length, as it refts, it points with its ends North and South, juft as iron touched with a loadftone does in (hadow-clocks, and in compafles, and in the mariners’ com- pa(s. You will be able, if curious enough, to balance all at the lame time by fine threads a number of fmall rods, or iron wires, or long pins with which women knit dockings ; you will fee that all of them at the fame time are in accord, unlefs there be fome error in this delicate operation: for unlefs you prepare everything fitly and (kilfully, the labour will be void. Make trial of this thing in water alfo, which is done both more certainly and more eafily. Let an iron wire two or three digits long, more or lefs, be pafted through a round cork, fo that it may juft float upon water ; and as foon as you have committed it to the waves, it turns upon its own centre, and one end tends to the North, the other to the South ; the caufes
of
ON THE LOADSTONE, B K. I. 31
of which you will afterwards find in the laws of the direction. This too you fhould underftand, and hold firmly in memory, that * as a ftrong loadftone, and iron touched with the fame, do not in- variably point exadtly to the true pole but to the point of the varia- tion ; fo does a weaker loadftone, and fo does the iron, which directs itfelf by its own forces only, not by thofe impreffed by the ftone ; and fo every ore of iron, and all bodies naturally endowed with fomething of the iron nature, and prepared, turn to the fame point of the horizon, according to the place of the variation in that particular region (if there be any variation therein), and there abide and reft.
CHAP. XIII.
Wrought iron has in itfelf certain parts Boreal and Auftral: -X- A magnetick vigour, verticity, and determinate vertices , or poles.
RON fettles itfelf toward the North and South ; not with one and the fame point toward this pole or that : for one end of the piece of ore itfelf and one extremity alfo of a wrought-iron wire have a fure and conftant deftination to the North, the other to the South, whether the iron hang in the air, or float ae iron large rods or thinner wires. Even if it be a little rod, or a wire ten or twenty or more ells in length ; one end as a rule is Boreal, the other Auflral. If you cut off part of that wire, and if the end of that divided part were Boreal, the other end (which was joined to it) will be Auftral. Thus if you divide it into feveral parts, before making an experiment on the furface of water, you can recognize the vertex. In all of them a Boreal end draws an Auftral and repels a Boreal, and contrariwife, according to the laws magnetical. Yet herein wrought iron differs from the loadftone and from its own ore, inafmuch as in an iron ball of any fize, fuch as thofe ufed for artillery or cannon, or bullets ufed for carbines or fowling-pieces, verticity is harder to acquire and is lefs apparent than in a piece of loadftone, or of ore itfelf, or than in a round load- ftone. But in long and extended pieces of iron a power is at once difcerned ; the caufes of which fa<5t, and the methods by which it acquires its verticity and its poles without ufe of a loadftone, as well as the reafons for all the other obfcure features of verticity, we fhall fet forth in defcribing the motion of direction.
CHAP.
32
WILLIAM GILBERT
CHAP. XIIII.
Concerning other powers of loadftone, and its
medicinal properties.
IOSCORIDES prefcribes loadftone to be given with fweetened water, three fcruples’ weight, to expel grofs humours. Galen writes that a like quantity of bloodftone avails. Others relate that loadftone perturbs the mind and makes folk melan- cholick, and moftly kills. Gartias ab Horto thinks it not deleterious or injurious to health. The natives of Eaft India tell us, he fays, that loadftone taken in fmall dofes preferves youth. On which account the aged king, Zeilam, is faid to have ordered the pans in which his victuals were cooked to be made of loadftone. The perfon (fays he) to whom this order was given told me fo him- felf. There are many varieties of loadftone produced by differences in the mingling of earths, metals, and juices ; hence they are al- together unlike in their virtues and effects, due to propinquities of places and of agnate bodies, and ariftng from the pits themfelves as it were from the matrices being foul. One loadftone is therefore able to purge the ftomach, and another to check purging, to caufe by its fumes a ferious fhock to the mind, to produce a gnawing at the vitals, or to bring on a grave relapfe ; in cafe of which ills they exhibit gold and emerald, ufing an abominable impofture for lucre. Pure loadftone may, indeed, be not only harmlefs, but even able to correct an over-fluid and putrefcent ftate of the bowels and bring them back to a better temperament ; of this fort ufually are the oriental magnets from China, and the denfer ones from Bengal, which are neither mifliking nor unpleafant to the aCtual fenfes. Plutarch and Claudius Ptolemy, and all the copyifts fince their time, think that a loadftone fmeared with garlick does not allure iron. Hence fome fufpedt that garlick is of avail againft any dele- terious power of the magnet : thus in philofophy many falfe and idle conjectures arife from fables and falfehoods. Some phyficians have opined that a loadftone has power to extraCt the iron of an arrow from the human body. But it is when whole that the loadftone draws, not when pulverized and formlefs, buried in plafters ; for it does not attract by reafon of its material, but is rather adapted for the healing of open wounds, by reafon of exficcation, doling up and drying the fore, an effedt by which the arrow-heads would rather be retained in the wounds. Thus vainly and prepofteroufly do the fciolifts
look
ON THE LOADSTONE, BK. I. 33
look for remedies while ignorant of the true caufes of things. The application of a loadftone for all forts of headaches no more cures them (as fome make out) than would an iron helmet or a fteel cap. To give it in a draught to dropfical perfons is an error of the ancients, or an impudent tale of the copyifts, though one kind of ore may be found which, like many more minerals, purges the ftomach ; but this is due to fome defedt of that ore and not to any magnetick property. Nicolaus puts a large quantity of loadftone into his divine plafter, juft as the Augfburgers do into a black plafter for frefh wounds and ftabs ; the virtue of which dries them up without fmart, fo that it proves an efficacious medicament. In like manner alfo Paracelfus to the fame end mingles it in his plafter for ftab wounds.
CHAP. XV.
The Medicinal Virtue of Iron.
OT foreign to our prefent purpofe will it be to treat briefly alfo of the medicinal virtue of iron : for it is a prime remedial for fome difeafes of the human body, and by its virtues, both thofe that are natural and thofe acquired by fuitable preparation, it works marvellous changes in the human body, fo that we may the more furely recognize its nature through its medicinal virtue and through certain manifeft experiments. So that even thofe tyros in medicine who abufe this most famous medicament may learn to prefcribe it with better judgment for the healing of the lick, and not, as too often they ufe it, to their harm. The belt iron, Stomoma, or Chalybs, Acies, or Aciarium, is reduced to a fine powder by a file ; the powder is fteeped in the fharpeft vinegar, and dried in the fun, and again foufed in vinegar, and dried; after- wards it is wafhed in fpring water or other fuitable water, and dried ; then for the fecond time it is pulverized and reduced on porphyry, palled through a very fine fieve, and put back for ufe. It is given chiefly in cafes of laxity and over-humidity of the liver, in enlarge- ment of the fpleen, after due evacuations ; for which reafon it reftores young girls when pallid, fickly, and lacking colour, to health and beauty ; fince it is very ficcative, and is aftringent without harm. But fome who in every internal malady always talk of obftrudtion
f of
34
WILLIAM GILBERT
of the liver and fpleen, think it beneficial in thofe cafes becaufe it removes obftruCtions, mainly trufting to the opinions of certain Arabians : wherefore they adminifter it to the dropfical and to thofe fuffering from tumour of the liver or from chronic jaundice, and to perfons troubled with hypochondrical melancholia or any ftomachic diforder, or add it to electuaries, without doubt to the grievous injury of many of their patients. Fallopius commends it prepared in his own way for tumours of the fpleen, but is much miftaken; for loadftone is pre-eminently good for fpleens relaxed with humour, and fwollen ; but it is fo far from curing fpleens thickened into a tumour that it mightily confirms the malady. For thofe drugs which are ftrong ficcatives and abforb humour force the vifcera when hardened into a tumour more completely into a quafi-ftony body. There are fome who roaft iron in a clofed oven with fierce firing, and burn it ftrongly, until it turns red, and they call this Saffron of Mars ; which is a powerful ficcative, and more quickly penetrates the inteftines. Moreover they order violent exercife, that the drug may enter the vifcera while heated and fo reach the place affeCted ; wherefore alfo it is reduced to a very fine flour ; otherwife it only flicks in the ftomach and in the chyle and does not penetrate to the inteftines. As a dry and earthy medicament, then, it is fhown by the moft certain experiments to be, after proper evacuations, a remedy for difeafes arifing from humour (when the vifcera are charged and overflowing with watery rheum). Prepared fteel is a medicament proper for enlarged fpleen. Iron waters too are effectual in reducing the fpleen, although as a rule iron is of a frigid and aftringent efficiency, not a laxative ; but it effeCts this neither by heat nor by cold, but from its own drynefs when mixed with a penetrative fluid : it thus difperfes the Eumour, thickens the villi, hardens the tiffues, and contracts them when lax; while the inherent heat in the member thus ftrengthened, being increafed in power, diffipates what is left. Whereas if the liver be hardened and weakened by old age or a chronic obftruCtion, or the fpleen be fhrivelled and contracted to a fchirrus, by which troubles the fleffiy parts of the limbs grow flaccid, and water under the fkin invades the body, in the cafe of thefe conditions the introduction of iron accelerates the fatal end, and confiderably increafes the malady. Amongft recent writers there are fome who in cafes of drought of the liver prefcribe, as a much lauded and famous remedy, the eleCtuary of iron flag, defcribed by Rhazes in his ninth book ad Almanforem , Chap. 63, or prepared filings of fteel ; an evil and deadly advice : which if they do not fome time underftand from our philofophy, at leaft everyday experience, and the decline and death of their patients, will convince them, even the fluggiffi and lazy. Whether iron be warm or cold is varioufly contended by
many.
35
ON THE LOADSTONE, BK. I.
many. By Manardus, Curtius, Fallopius and others, many reafons are adduced on both fides ; each fettles it according to his own fentiment. Some make it to be cold, faying that iron has the property of refrigerating, becaufe Ariftotle in his Meteorologica would put iron in the clafs of things which grow concreted in cold by emif- fion of the whole of their Heat : Galen, too, fays that iron has its confiftency from cold; alfo that it is an earthy and denfe body. Further that iron is aftringent, alfo that Chalybeate water quenches thirft : and they adduce the cooling effed of thermal iron waters. Others, however, maintain that it is Warm, becaufe of Hippocrates making out that waters are warm which burft forth from places where iron exifts. Galen fays that in all metals there is confider- able fubftance, or eflence, of fire. Paolo affirms that iron waters are warm. Rhazes will have it that iron is warm and dry in the third degree. The Arabians think that it opens the fpleen and liver ; wherefore alfo that iron is warm. Montagnana recommends it in cold affedions of the uterus and ftomach. Thus do the fmatterers crofs fwords together, and puzzle inquiring minds by their vague conjedures, and wrangle for trifles as for goats’ wool, when they philofophize, wrongly allowing and accepting properties : but thefe matters will appear more plainly by and by when we begin to difcufs the caufes of things ; the clouds being difperfed that have fo darkened all Philofophy. Filings, fcales, and flag of iron are, as Avicenna makes out, not wanting in deleterious power (haply when they are not well prepared or are taken in larger quantity than is fit), hence they caufe violent pain in the bowels, roughnefs of the mouth and tongue, marafmus, and fhrivelling of the limbs. But Avicenna wrongly and old-womaniftily makes out that the proper antidote to this iron poifon is loadftone to the weight of a drachm taken as a draught in the juice of mercurialis or of Beet ; for loadftone is of a twofold nature, ufually malefiant and pernicious, nor does it refill iron, fince it attrads it ; nor when drunk in a draught in the form of powder does it avail to attrad or repel, but rather inflids the fame evils.
CHAP.
36
WILLIAM GILBERT
CHAP. XVI.
That loadftone & iron ore are the fame, but iron an extraft from both , as other metals are from their own ores ; & that all magnetick virtues, though weaker , exifl in the ore itjelf & in fmelted iron.
ITHERTO we have declared the nature & powers of the loadftone, & alfo the properties & effence of iron ; it now remains to fhow their mutual affinities, & kinfhip, fo to fpeak, & how very clofely conjoined thefe fubftances are. At the higheft part of the terreftrial globe, or at its perifhable furface & rind, as it were, thefe two bodies ufually originate & are produced in one and the fame matrix, as twins in one mine. Strong loadftones are dug up by themfelves, weaker ones too have their own proper vein. Both are found in iron mines. Iron ore moft often occurs alone, without ftrong loadftone (for the more perfect are rarely met with). Strong loadftone is a ftone refembling iron ; out of it is ufually fmelted the fineft iron, which the Greeks call fomoma , the Latins acies , the Barbarians (not amifs) aciare , or aciarium. This fame ftone draws, repels, controls other loadftones, dired^s itfelf to the poles of the world, picks up fmelted iron, and works many other wonders, fome already fet forth by us, but many more which we muft demonftrate more fully. A weaker loadftone, however, will exhibit all thefe powers, but in a leffer degree; while iron ore, & alfo wrought iron (if they have been prepared) fhow their ftrength in all magnetick experiments not lefs than do feeble and weak loadftones; & an inert piece of ore, & one poffeffed of no magnetick properties, & juft thrown out of the pit, when roafted in the fire & prepared with due art (by the elimination of humours & foreign excretions) awakes, and becomes in power & potency a magnet. Occafionally a ftone or iron ore is mined, which attradls forthwith without being prepared : for native iron of the right colour attracts and governs iron magnetically. One form then belongs to the one mineral, one fpecies, one felf-fame effence. For to me there feems to be a greater difference, & unlikenefs, between the ftrongeft load- ftone,
37
ON THE LOADSTONE, BK. I.
ftone, & a weak one which fcarce can attradl a fingle chip of iron ; between one that is flout, flrong, metallick, & one that is foft, friable, clayey ; amidfl fuch variety of colour, fubflance, quality, & weight ; than there is on the one hand between the befl ore, rich in iron, or iron that is metallick from the beginning, and on the other the mofl excellent loadftone. Ufually, too, there are no marks to dif- tinguifh them, and even metallurgies cannot decide between them, becaufe they agree together in all refpedts. Moreover we fee that the beft loadftone and the ore of iron are both as it were diftreffed by the fame maladies & difeafes, both run to old age in the fame way & exhibit the fame marks of it, are preferved & keep their properties by the fame remedies & fafeguards ; & yet again the one increafes the potency of the other, & b) artfully devifed adjuncts marvelloufly intenfifies, & exalts it. For both are impaired by the more acrid juices as by poifons, & the aqua fortis of the Chemifts inflidts on both the fame wounds, and when expofed too long to harm from the atmofphere, they both alike pine away, fo to fpeak, & grow old ; each is preferved by being kept in the duft & fcrapings of the other ; & when a fit piece of fteel or iron is adjoined above its pole, the loadftone’s vigour is augmented through the firm union. The loadftone is laid up in iron filings, not that iron is its food; as though loadftone were alive and needed feeding, as Cardan philofophizes ; nor yet that fo it is delivered from the inclemency of the weather (for which caufe it as well as iron is laid up in bran by Scaliger; miftakenly, however, for they are not preferved well in this way, and keep for years their own fixed forms) : nor yet, fince they remain perfedt by the mutual adtion of their powders, do their extremities wafte away, but are cherifhed & preferved, like by like. For juft as in their own places, in the mines, bodies like to each other endure for many ages entire and uncorrupt, when furrounded by bodies of the fame fluff, as the leffer interior parts in a great mafs : fo loadftone and ore of iron, when inclofed in a mound of the fame material, do not exhale their native humour, do not wafte away, but retain their foundnefs. A loadftone lafts longer in filings of fmelted iron, & a piece of iron ore excellently alfo in duft of loadftone ; as alfo fmelted iron in filings of loadftone & even in thofe of iron. Then both thefe allied bodies have a true & juft form of one & the fame fpecies ; a form which until this day was confidered by all, owing to their outward unlikenefs & the inequality of the potency that is the fame innate in both, to be different & unlike in kind ; the fmatterers not underftanding that the fame powers, though differing in ftrength, exift in both alike. And in fadt they both are true & intimate parts of the earth, & as fuch retain the prime natural properties of mutually attracting, of moving, & of difpofing themfelves toward the pofition of the world,
and
38 WILLIAM GILBERT
and of the terreftrial globe ; which properties they alfo impart to each other, and increafe, confirm, receive, and retain each other’s forces. The ftronger fortifies the weaker, not as though aught were taken away from its own fubftance, or its proper vigour, nor becaufe any corporeal fubftance is imparted, but the dormant virtue of the one is aroufed by the other, without lofs. For if with a fingle fmall ftone you touch a thoufand bits of iron for the ufe of mariners, that loadftone attracts iron no lefs ftrongly than before ; with the fame ftone weighing one pound, any one will be able to fufpend in the air a thoufand pounds of iron. For if any one were to fix high up on the walls fo many iron nails of fo great a weight, & were to apply to them the fame number of nails touched, accord- ing to the art, by a loadftone, they would all be feen to hang in the air through the force of one fmall ftone. So this is not folely the adtion, labour, or outlay of the loadftone ; but the iron, which is in a fenfe an extradt from loadftone, and a fufion of loadftone into metal, & conceives vigour from it, & by proximity ftrengthens the magnetick faculties, doth itfelf, from whatever lode it may have come, raife its own inborn forces through the prefence & contadl of the ftone, even when folid bodies intervene. Iron that has been touched, adts anew on another piece of iron by contadt, & adapts it for magnetick movements, & this again a third. But if you rub with a loadftone any other metal, or wood, or bones, or glafs, as they will not be moved toward any particular and determinate quarter of heaven, nor be attradted by any magnetick body, fo they are able not to impart any magnetick property to other bodies or to iron itfelf by attrition, & by infedtion. Loadftone differs from iron ore, as alfo from fome weaker magnets, in that when molten in the furnace into a ferric & metallick fufed mafs, it does not fo readily flow & diffolve into metal ; but is fometimes burnt to allies in large furnaces ; a refult which it is reafonable to fuppofe arifes from its having fome kind of fulphureous matter mixed with it, or from its own excellence & Ampler nature, or from the likenefs & common form which it has with the common mother, the Great Magnet. For earths, and iron ftones, magnets abounding in metal, are the more imbued & marred with excrementitious metallick humours, and earthy corruptions of fubftance, as numbers of loadftones are weaker from the mine ; hence they are a little further remote from the common mother, & are degenerate, & when fmelted in the furnace undergo fufion more eafily, & give out a more certain metallick produdt, & a metal that is fofter, not a tough fteel. The majority of loadftones (if not unfairly burnt) yield in the furnace a very excellent iron. But iron ore alfo agrees in all thofe primary qualities with loadftone ; for both, being nearer and more clofely akin to the earth above all bodies known to us, have in themfelves
a
39
ON THE LOADSTONE, BK. I.
a magnetick fubftance, & one that is more homogenic, true & cog- nate with the globe of the earth ; lefs infected & fpoiled by foreign blemifh ; lefs confufed with the outgrowths of earth’s furface, & lefs debafed by corrupt products. And for this realon Ariftotle in the fourth book of his Meteora feems not unfairly to feparate iron from all the reft of the metals. Gold, he fays, filver, copper, tin, lead, belong to water ; but iron is of the earth. Galen, in the fourth chapter of De Facultatibus Simplicium Me die ament orum, fays that iron is an earthy & denfe body. Accordingly a ftrong loadftone is on our fhowing efpecially of the earth : the next place is occupied by iron ore or weaker loadftone ; fo the loadftone is by nature and origin of iron, and it and magnetick iron are both one in kind. Iron ore yields iron in furnaces ; loadftone alfo pours forth iron in the furnaces, but of a much more excellent fort, that which is called fteel or blade-edge ; and the better fort of iron ore is a weak loadftone, the beft loadftone being a moft excellent ore of iron, in which, as is to be fhown by us, the primary properties are grand and confpicuous. Weaker loadftone or iron ore is that in which thefe properties are more obfeure, feeble, and are fcarce percept- ible to the fenfes.
CHAP. XVII.
That the globe of the earth is magnetick, & a magnet ; &
how in our hands the magnet Jione has all the primary forces of the earth, while the earth by the fame powers remains conjlant in a fixed direction in the univerfe.
RIOR to bringing forward the caufes of magnetical motions, & laying open the proofs of things hidden for fo many ages, & our experiments (the true foun- dations of terreftrial philofophy), we have to eftab- lifh & prefent to the view of the learned our New & unheard of dodtrine about the earth ; and this, when argued by us on the grounds of its probability, with fubfequent
experiments
40
WILLIAM GILBERT
experiments & proofs, will be as certainly allured as anything in philofophy ever has been conlidered & confirmed by clever argu- ments or mathematical proofs. The terrene mafs, which together with the vafly ocean produces the fphasrick figure & conflitutes our globe, being of a firm & conflant fubflance, is not eafily changed, does not wander about, & fluctuate with uncertain motions, like the feas, & flowing waves : but holds all its volume of moiflure in certain beds & bounds, & as it were in oft-met veins, that it may be the lefs diffufed & diffipated at random. Yet the folid magnitude of the earth prevails & reigns fupreme in the nature of our globe. Water, however, is attached to it, & as an appendage only, & a flux emanating from it ; whofe force from the beginning is conjoined with the earth through its fmallefl parts, and is innate in its fubflance. This moiflure the earth as it grows hot throws off freely when it is of the greatefl poflible fervice in the generation of things. But the thews and dominant fluff of the globe is that terrene body which far exceeds in quantity all the volume of flowing flreams and open waters (whatever vulgar philofophers may dream of the magnitudes and proportions of their elements), and which takes up molt of the whole globe and almofl fills it internally, and by itfelf almofl fuffices to endow it with fphaerick fhape. For the feas only fill certain not very deep or profound hollows, fince they rarely go down to a depth of a mile and generally do not exceed a hundred or 50 fathoms. For fo it is afcertained by the obfervations of feamen when by the plumb-line and linker its abyfms are explored with the nautical founder ; which depths relatively to the dimenfions of the globe, do not much deform its globular fhape. Small then appears to be that portion of the real earth that ever emerges to be feen by man, or is turned up ; fince we cannot penetrate deeper into its bowels, further than the wreckage of its outer efflorefcence, either by reafon of the waters which gufh up in deep workings, as through veins, or for want of a wholefome air to fupport life in the miners, or on account of the vafl cofl that would be incurred in pumping out fuch huge workings, and many other difficulties ; fo that to have gone down to a depth of four hundred, or (which is of rareft occurrence) of five hundred fathoms as in a few mines, appears to all a flupendous undertaking. But it is eafy to underfland how minute, how almofl negligibly fmall a portion that 500 fathoms is of the earth’s diameter, which is 6,872 miles. It is then parts only of the earth’s circumference and of its prominences that are perceived by us with our fenfes ; and thefe in all regions appear to us to be either loamy, or clayey, or fandy, or full of various foils, or marls : or lots of flones or gravel meet us, or beds of fait, or a metallick lode, and metals in abundance. In the fea and in deep waters, however, either reefs, and huge boulders, or fmaller flones, or fands, or mud
are
4i
ON THE LOADSTONE, B K. I.
are found by mariners as they found the depths. Nowhere does the Ariftotelian element of earth come to light ; and the Peripa- teticks are the fport of their own vain dreams about elements. Yet the lower bulk of the earth and the inward parts of the globe con- fift of fuch bodies ; for they could not have exifted, unlefs they had been related to and expofed to the air and water, and to the light and influences of the heavenly bodies, in like manner as they are generated, and pafs into many diflimilar forms of things, and are changed by a perpetual law of fucceflion. Yet the interior parts imitate them, and betake themfelves to their own fource, on the principle of terrene matter, albeit they have loft the firft qualities and the natural terrene form, and are borne towards the earth’s centre, and cohere with the globe of the earth, from which they cannot be wrenched afunder except by force. But the loadftone and all magneticks, not the ftone only, but every magnetick homo- genic fubftance, would feem to contain the virtue of the earth’s core and of its inmoft bowels, and to hold within itfelf and to have conceived that which is the fecret and inward principle of its fubftance ; and it poflefles the adtions peculiar to the globe of attracting, directing, difpofing, rotating, ftationing itfelf in the univerfe, according to the rule of the whole, and it contains and regulates the dominant powers of the globe ; which are the chief tokens and proofs of a certain diftinguifhing combination, and of a nature moft thoroughly conjoint. For if among aCtual bodies one fees fomething move and breathe, and experience fenfations, and be inclined and impelled by reafon, will one not, knowing and feeing this, conclude that it is a man or fomething rather like a man, than that it is a ftone or a ftick ? The loadftone far excels all other bodies known to us in virtues and properties pertaining to the common mother : but thofe properties have been far too little underftood or realized by philofophers : for to its body bodies magnetical rufh in from all fides and cleave to it, as we fee them do in the cafe of the earth. It has poles, not mathematical points, but natural termini of force excelling in primary efficiency by the co-operation of the whole: and there are poles in like manner in the earth which our forefathers fought ever in the fky : it has an aequator, a natural dividing line between the two poles, juft as the earth has : for of all lines drawn by the mathematicians on the terreftrial globe, the aequator is the natural boundary, and is not, as will hereafter appear, merely a mathematical circle. It, like the earth, acquires Direction and liability toward North and South, as the earth does ; alfo it has a circular motion toward the pofition of the earth, wherein it adjufts itfelf to its rule : it follows the afcenfions and declinations of the earth’s poles, and conforms exadtly to the fame, and by itfelf raifes its own poles above the
g horizon
1
42
WILLIAM GILBERT
horizon naturally according to the law of the particular country and region, or links below it. The loadflone derives temporary properties, and acquires its verticity from the earth, and iron is affedted by the verticity of the globe even as iron is by a loadftone : Magneticks are conformable to and are regulated by the earth, and are fubjedt to the earth in all their motions. All its movements harmonize with, and flridtly wait upon, the geometry and form of the earth, as we fhall afterwards prove by moft conclulive experi- ments and diagrams; and the chief part of the vilible earth is alfo magnetical, and has magnetick motions, although it be disfigured by corruptions and mutations without end. Why then do we not recognize this the chief homogenic fubflance of the earth, likeft of fubftances to its inner nature and clofeft allied to its very marrow? For none of the other mixed earths fuitable for agriculture, no other metalliferous veins, nor Hones, nor fand, nor other fragments of the earth which have come to our view polfefs fuch conftant and peculiar powers. And yet we do not alTume that the whole interior of this globe of ours is compofed of Hones or iron (although Francifcus Maurolycus, that learned man, deems the whole of the earth’s interior to conliH of folid Hone). For not every loadflone that we have is a Hone, it being fometimes like a clod, or like clay and iron either firmly compacted together out of various materials, or of a fofter compofition, or by heat reduced to the metallick Hate ; and the magnetick fubflance by reafon of its location and of its furroundings, and of the metallick matrix itfelf, is diflinguifhed, at the furface of the terrene mafs, by many qualities and adventitious natures, juH as in clay it is marked by certain Hones and iron lodes. But we maintain that the true earth is a folid fubflance, homogeneous with the globe, clofely coherent, endowed with a primordial and (as in the other globes of the univerfe) with a prepotent form ; in which pofition it perflfls with a fixed verticity, and revolves with a neceflary motion and an inherent tendency to turn, and it is this conflitution, when true and native, and not injured or disfigured by outward defedts, that the loadflone poffeffes above all bodies apparent to us, as if it were a more truly homogenic part taken from the earth. Accordingly native iron which is fui generis (as metallurgifls term it), is formed when homogenic parts of the earth grow together into a metallick lode ; Loadflone being formed when they are changed into metallick Hone, or a lode of the finefl iron, or Heel : fo in other iron lodes the homogenic matter that goes together is fomewhat more im- perfedt ; jufl as many parts of the earth, even the high ground, is homogenic but fo much more deformate. Smelted iron is fufed and fmelted out of homogenic Huffs, and cleaves to the earth more tenacioully than the ores themfelves. Such then is our earth in its
inward
43
ON THE LOADSTONE, BK. I.
inward parts, poflefled of a magnetick homogeneal nature, and upon fuch more perfect foundations as thefe refts the whole nature of things terreftrial, manifefting itfelf to us, in our more diligent fcrutiny, everywhere in all magnetick minerals, and iron ores, in all clay, and in numerous earths and (tones ; while Ariftotle’s (imple element, that moft empty terreftrial phantom of the Peripateticks, a rude, inert, cold, dry, Ample matter, the univerfal fubftratum, is dead, devoid of vigour, and has never prefented itfelf to any one, not even in deep, and would be of no potency in nature. Our philofophers were only dreaming when they fpoke of a kind of (imple and inert matter. Cardan does not confider the loadftone to be any kind of (tone, “ but a fort of perfected portion of fome “ kind of earth that is abfolute ; a token of which is its abundance, “ there being no place where it is not found. And there is ” (he fays) “ a power of iron in the wedded Earth which is perfect in its “ own kind when it has received fertilizing force from the male, “ that is to fay, the (tone of Hercules” (in his book De Proportionibus ).
And later : “ Becaufe ” (he fays) “ in the previous proportion I “have taught that iron is true earth.” A ftrong loadftone (hows itfelf to be of the inward earth, and upon innumerable teds claims to rank with the earth in the poflefiion of a primary form, that by which Earth herfelf abides in her own (tation and is directed in her courfes. Thus a weaker loadftone and every ore of iron, and nearly all clay, or clayey earth, and numerous other forts (yet more, or lefs, owing to the different labefaction of fluids and (limes), keep their magnetick and genuine earth-properties open to view, falling fhort of the charaCteriftic form, and deformate. For it is not iron alone (the fmelted metal) that points to the poles, nor is it the loadftone alone that is attracted by another and made to revolve magnetically ; but all iron ores, and other (tones, as Rhenifh dates and the black ones from Avignon (the French call them Ardoifes ) which they ufe for tiles, and many more of other colours and fubftances, provided they have been prepared ; as well as all clay, grit, and fome forts of rocks, and, to fpeak more clearly, all the more folid earth that is everywhere apparent; given that that earth be not fouled with fatty and fluid corruptions; as mud, as mire, as accumulations of putrid matter ; nor deformate by the imperfec- tions of fundry admixtures ; nor dripping with ooze, as marls : all are attracted by the loadftone, when (imply prepared by fire, and freed from their refufe humour ; and as by the loadftone fo alfo by the earth herfelf they are drawn and controlled mag- netically, in a way different from all other bodies ; and by that inherent force fettle themfelves according to the orderly arrange- ment and fabric of the univerfe and of the Earth, as will appear
later
44
WILLIAM GILBERT
later. Thus every part of the earth which is removed from it exhibits by fure experiments every impulfe of the mag- netick nature ; by its various motions it ob- ferves the globe of the earth and the principle common to both.
BOOK
ON THE LOADSTONE, BK. II.
45
BOOK SECOND.
QHAP. I.
ON MAGNETICK Motions.
IVERS things concerning opinions about the magnet-ftone, and its variety, concerning its poles and its known faculties, concerning iron, concern- ing the properties of iron, concerning a magnetick fubftance common to both of thefe and to the earth itfelf, have been fpoken briefly by us in the former remain the magnetical motions, and their fuller philofophy, fhown and demonftrated. Thefe motions are incite- ments of homogeneal parts either among themfelves or toward the primary conformation of the whole earth. Ariftotle admits only two Ample motions of his elements, from the centre and toward the centre ; of light ones upward, heavy ones downward ; fo that in the earth there exifts one motion only of all its parts towards the centre of the world, — a rude and inert precipitation. But what of it is light, and how wrongly it is inferred by the Peripateticks from the Ample motion of the elements, and alfo what is its heavy part, we will difcufs elfewhere. But now our inquiry muft be into the caufes of other motions, depending on its true form, which we have plainly feen in our magnetick bodies ; and thefe we have feen to be prefent in the earth and in all its homogenic parts alfo. We have noticed that they harmonize with the earth, and are bound up with its forces. Five movements or differences of motions are then obferved by us : Coition (commonly called attraction), the in- citement
hook. There
WILLIAM GILBERT
46
citement to magnetick union ; Direction towards the poles of the earth, and the verticity and continuance of the earth towards the determinate poles of the world ; Variation, a deflexion from the meridian, which we call a perverted movement ; Declination, a defcent of the magnetick pole below the horizon ; and circular motion, or Revolution. Concerning all thefe we fhall difcufs feparately, and how they all proceed from a nature tending to aggregation, either by verticity or by volubility. Jofrancus Offufius makes out different magnetick motions ; a firft toward a centre ; a fecond toward a pole at feventy-feven degrees ; a third toward iron ; a fourth toward loadftone. The first is not always to a centre, but exifts only at the poles in a ftraight courfe toward the centre, if the motion is magnetick ; otherwife it is only motion of matter toward its own mafs and toward the globe. The fecond toward a pole at feventy-feven degrees is no motion, but is direction with refpeCt t;o the pole of the earth, or variation. The third and fourth are magnetick and are the fame. So he truly recognizes no magnetick motion except the Coition toward iron or loadftone, commonly called attraction. There is another motion in the whole earth, which does not exift towards the terrella or towards its parts ; videlicet, a motion of aggregation, and that movement of matter, which is called by philofophers a right motion, of which elfewhere.
CHAP. II.
On the Magnetick Coition, and firft on the Attraction of Amber, or more truly, on the Attaching of Bodies to Amber.
ELEBRATED has the fame of the loadftone and of amber ever been in the memoirs of the learned. Loadftone and alfo amber do fome philofophers invoke when in explaining many fecrets their fenfes become dim and reafoning cannot go further. In-
quifitive theologians alfo would throw light on the
divine myfteries fet beyond the range of human fenfe, by means of loadftone and amber; juft as idle Metaphyficians, when they are fetting up and teaching ufelefs phantafms, have recourfe to the load- ftone as if it were a Delphick fword, an illuftration always ap- plicable to everything. But phyficians even (with the authority of
Galen),
47
ON THE LOADSTONE, BK. II.
Galen), defiring to confirm the belief in the attraction of purgative medicines by means of the likenefs of fubftance and the familiarities of the juices — truly a vain and ufelefs error — bring in the loadftone as witnefs as being a nature of great authority and of confpicuous efficacy and a remarkable body. So in very many cafes there are fome who, when they are pleading a caufe and cannot give a reafon for it, bring in loadftone and amber as though they were perfonified witneffes. But thefe men (apart from that common error) being ignorant that the caufes of magnetical motions are widely different from the forces of amber, eafily fall into error, and are themfelves the more deceived by their own cogitations. For in other bodies a confpicuous force of attraction manifefts itfelf otherwife than in load- ftone ; like as in amber, concerning which fome things muft firft be faid, that it may appear what is that attaching of bodies, and how it is different from and foreign to the magnetical actions ; thofe mortals being ftill ignorant, who think that inclination to be an attraction, and compare it with the magnetick coitions. The Greeks call it yXetcrpov, becaufe it attracts ftraws to itfelf, when it is warmed by rubbing; then it is called ap7ra%; and xpvrotpopov , from its golden colour. But the Moors call it Carabe, becaufe they are accuftomed to offer the fame in facrifices and in the worfhip of the Gods. For Carab fignifies to offer in Arabic; fo Carabe, an offering: or feizing chaff, as Scaliger quotes from Abohalis, out of the Arabic or Perfian language. Some alfo call it Amber, efpecially the Indian and Ethiopian amber, called in Latin Succinum , as if it were a juice. The Sudavienfes or Sudini call it gemter , as though it were generated terreftrially. The errors of the ancients con- cerning its nature and origin having been exploded, it is certain that amber comes for the moft part from the fea, and the ruftics collect it on the coaft after the more violent ftorms, with nets and other tackle; as among the Sudini of Pruffia; and it is alfo found fometimes on the coaft of our own Britain. It feems, however, to be produced alfo in the foil and at fpots of fome depth, like other bitumens ; to be wafihed out by the waves of the fea ; and to become concreted more firmly from the nature and faltnefs of the fea-water. For it was at firft a foft and vifcous material ; wherefore alfo it contains enclofed and entombed in pieces of it, fhining in eternal fepulchres, flies, grubs, gnats, ants; which have all flown or crept or fallen into it when it firft flowed forth in a liquid ftate. The ancients and alfo more recent writers recall (experience proving the fame thing), that amber attracts ftraws and chaff. The fame is alfo done by jet, which is dug out of the earth in Britain, in Germany, and in very many lands, and is a rather hard concretion from black bitumen, and as it were a transformation into ftone. There are many modern authors who have written and copied from others about amber and jet attracting chaff, and about other fub-
ftances
WILLIAM GILBERT
48
fiances generally unknown ; with whofe labours the fhops of book- fellers are crammed. Our own age has produced many books about hidden, abfirufe, and occult caufes and wonders, in all of which amber and jet are fet forth as enticing chaff; but they treat the fubjeCt in words alone, without finding any reafons or proofs from experiments, their very ftatements obfcuring the thing in a greater fog, forfooth in a cryptic, marvellous, abfirufe, fecret, occult, way. Wherefore alfo fuch philofophy produces no fruit, becaufe very many philofophers, making no inveftigation themfelves, un- fupported by any practical experience, idle and inert, make no progrefs by their records, and do not fee what light they can bring to their theories ; but their philofophy refts fimply on the ufe of certain Greek words, or uncommon ones; after the manner of our goflips and barbers nowadays, who make fhow of certain Latin words to an ignorant populace as the infignia of their craft, and fnatch at the popular favour. For it is not only amber and *jet (as they fuppofe) which entice fmall bodies; but Diamond, Sapphire, Carbuncle, Iris gem, Opal, Amethyft, Vincentina, and Briftolla (an Englifh gem or fpar), Beryl, and Cryftal do the fame. Similar powers of attraction are feen alfo to be poffeffed by glafs (efpecially when clear and lucid), as alfo by falfe gems made of glafs or Cryftal, by glafs of antimony, and by many kinds of fpars from the mines, and by Belemnites. Sulphur alfo attracts, and maftick, and hard fealing-wax compounded of lac tinCtured of various colours. Rather hard refin entices, as does orpiment, but lefs ftrongly ; with difficulty alfo and indiftinCtly under a fuitable dry fky, Rock fait, mufcovy ftone, and rock alum. This one may fee when the air is fharp and clear and rare in mid-winter, when the emanations from the earth hinder eleCtricks lefs, and the eleCtrick bodies become more firmly indurated; about which hereafter. Thefe fubftances draw everything, not ftraws and chaff only, but all metals, woods, leaves, ftones, earths, even water and oil, and everything which is fubjeCt to our fenfes, or is folid ; although fome write that amber does not attraCt anything but chaff and certain twigs ; (wherefore Alexander Aphrodifeus falfely declares the queftion of amber to be inexplicable, becaufe it attracts dry chaff only, and not bafil leaves, but thefe are the utterly falfe and difgraceful tales of the writers. But in order that you may be able clearly to teft how fuch attraction occurs, and what thofe materials are which thus entice other bodies (for even if bodies incline towards fome of thefe, yet on account of weaknefs they feem not to be raifed by them, but are more eafily turned), make yourfelf a verforium of any metal you like, three or four digits in length, refting rather lightly on its point of fupport after the manner of a magnetick needle, to one end of which bring up a piece of amber or a fmooth
49
ON THE LOADSTONE, BK. II.
and polifhed gem which has been gently rubbed ; for the verforium turns forthwith. Many things are there- _sf ^ /p
by feen to attradt, both thofe which are ^ formed by nature alone, and thofe which are by art prepared, fufed, and mixed ; nor is this fo much a lingular property of one or two things (as is commonly fuppofed), but the manifefl nature of very many, both of limple fubflances, remaining merely in their own form, and of com- politions, as of hard fealing-wax, & of certain other mixtures belides, made of undtuous fluffs. We muff, however, invefligate more fully whence that tendency arifes, and what thofe forces be, concerning which a few men have brought forward very little, the crowd of philo- fophizers nothing at all. By Galen three kinds of attradlives in general were recognized in nature : a Firfl clafs of thofe fubflances which attradt by their elemental quality, namely, heat ; the Second is the clafs of thofe which attradt by the fucceflion of a vacuum ; the Third is the clafs of thofe which attradt by a property of their whole fubftance, which are alfo quoted by Avicenna and others. Thefe claffes, however, cannot in any way fatisfy us ; they neither embrace the caufes of amber, jet, and diamond, and of other limilar fubflances (which derive their forces on account of the fame virtue) ; nor of the loadflone, and of all magnetick fubflances, which obtain their virtue by a very diflimilar and alien influence from them, de- rived from other fources. Wherefore alfo it is fitting that we find other caufes of the motions, or elfe we muft wander (as in darknefs), with thefe men, and in no way reach the goal. Amber truly does not allure by heat, fince if warmed by fire and brought near flraws, it does not attradt them, whether it be tepid, or hot, or glowing, or even when forced into the flame. Cardan (as alfo Pidtorio) reckons that this happens in no different way than with the cupping-glafs, by the force of fire. Yet the attradling force of the cupping-glafs does not really come from the force of fire. But he had previoufly faid that the dry fubftance wifhed to imbibe fatty humour, and therefore it was borne towards it. But thefe flatements are at variance with one another, and alfo foreign to reafon. For if amber had moved towards its food, or if other bodies had inclined towards amber as to- wards provender, there would have been a diminution of the one which was devoured, juft as there would have been a growth of the other which was fated. Then why fhould an attradlive force of fire be looked for in amber ? If the attradlion exifled from heat, why fhould not very many other bodies alfo attradt, if warmed by fire, by the fun, or by fridtion ? Neither can the attradlion be on ac- count of the diflipating of the air, when it takes place in open air (yet Lucretius the poet adduces this as the reafon for magnetical mo- tions). Nor in the cupping-glafs can heat or fire attradt by feeding on air : in the cupping-glafs air, having been exhaufled into flame,
h when
5°
WILLIAM GILBERT
when it condenfes again and is forced into a narrow fpace, makes the fkin and flefh rife in avoiding a vacuum. In the open air warm things cannot attraCt, not metals even or ftones, if they fhould * be ftrongly incandefcent by fire. For a rod of glowing iron, or a flame, or a candle, or a blazing torch, or a live coal, when they are brought near to ftraws, or to a verforium, do not attract ; yet at the fame time they manifeflly call in the air in fucceflion ; becaufe they confume it, as lamps do oil. But concerning heat, how it is reckoned by the crowd of philofophizers, in natural philofophy and in materia medica to exert an attraction otherwife than nature allows, to which true attractions are falfely imputed, we will difcufs more at length elfewhere, when we fhall determine what are the pro- perties of heat and cold. They are very general qualities or kinfhips of a fubftance, and yet are not to be afligned as true caufes, and, if I may fay fo, thofe philofophizers utter fome refounding words ; but about the thing itfelf prove nothing in particular. Nor does this attraction accredited to amber arife from any Angular quality of the fubftance or kinfhip, fince by more thorough refearch we find the fame effeCt in very many other bodies ; and all bodies, moreover, of whatever quality, are allured by all thofe bodies. Similarity alfo is not the caufe; becaufe all things around us placed on this globe of the earth, fimilar and difiimilar, are allured by amber and bodies of this kind ; and on that account no cogent analogy is to be drawn either from fimilarity or identity of fubftance. But neither do fimi- lars mutually attraCt one another, as ftone ftone, flefh flefh, nor aught elfe outfide the clafs of magneticks and eleCtricks. Fracaftorio would have it that “ things which mutually attraCt one another are fimilars, “ as being of the fame fpecies, either in aCtion or in right fubjeCtion. “ Right fubjeCtion is that from which is emitted the emanation which “ attracts and which in mixtures often lies hidden on account of “ their lack of form, by reafon of which they are often different in “ aCt from what they are in potency. Hence it may be that hairs “ and twigs move towards amber and towards diamond, not becaufe “ they are hairs, but becaufe either there is fhut up in them air or “ fome other principle, which is attracted in the firft place, and “ which bears fome relation and analogy to that which attracts of “ itfelf ; in which diamond and amber agree through a principle “ common to each.” Thus far Fracaftorio. Who if he had obferved by a large number of experiments that all bodies are drawn to eleCtricks except thofe which are aglow and aflame, arfd highly rarefied, would never have given a thought to fuch things. It is eafy for men of acute intellect, apart from experiments and practice, to flip and err. In greater error do they remain funk who maintain thefe fame fubflances to be not fimilar, but to be fubftances near akin ; and hold that on that account a thing moves towards another, its like, by which it is brought to more perfection. But thefe are
ill-confidered
ON THE LOADSTONE, BK. II. 51
ill-confidered views ; for towards all eleCtricks all things move ex- cept fuch as are aflame or are too highly rarefied, as air, which is the universal effluvium of this globe and of the world. Vegetable fubftances draw moifture by which their fhoots are rejoiced and grow ; from analogy with that, however, Hippocrates, in his De Natura Hominis , Book I., wrongly concluded that the purging of morbid humour took place by the fpecifick force of the drug. Con- cerning the action and potency of purgatives we fhallfpeak elfewhere. Wrongly alfo is attraction inferred in other effeCts; as in the cafe of a flagon full of water, when buried in a heap of wheat, although well ftoppered, the moifture is drawn out ; fince this moifture is rather refolved into vapour by the emanation of the fermenting wheat, and the wheat imbibes the freed vapour. Nor do elephants’ tufks attraCt moifture, but drive it into vapour or abforb it. Thus then very many things are faid to attract, the reafonsfor whofe energy muft be fought from other caufes. Amber in a fairly large mafs allures, if * it is polifhed ; in a fmaller mafs or lefs pure it feems not to attract without friction. But very many eleCtricks (as precious ftones and fome other fubftances) do not attraCt at all unlefs rubbed. On the other hand many gems, as well as other bodies, are polifhed, yet do « not allure, and by no amount of fridtion are they aroufed ; thus the emerald, agate, carnelian, pearls, jafper, chalcedony, alabafter, por- phyry, coral, the marbles, touchftone, flint, bloodftone, emery, do not acquire any power ; nor do bones, or ivory, or the hardeft woods, as ebony, nor do cedar, juniper, or cy prefs ; nor do metals, filver, gold, brafs, iron, nor any loadftone, though many of them are finely polifhed and fhine. But on the other hand there are fome other polifhed fubftances of which we have fpoken before, toward which, when they have been rubbed, bodies incline. This we fhall underftand only when we have more clofely looked into the prime origin of bodies.
It is plain to all, and all admit, that the mafs of the earth, or rather the ftrudture and cruft of the earth, confifts of a twofold material, namely, of fluid and humid matter, and of material of more confiftency and dry. From this twofold nature or the more Ample compacting of one, various fubftances take their rife among us, which originate in greater proportion now from the earthy, now from the aqueous nature.- Thofe fubftances which have received their chief growth from moifture, whether aqueous or fatty, or have taken on their form by a Ampler compacting from them, or have been compacted from thefe fame materials in long ages, if they have a fufficiently firm hardnefs, if rubbed after they have been polifhed and when they remain bright with the friction — towards thofe fubftances everything, if prefented to them in the air, turns, if its too heavy weight does not prevent it. For amber has been compacted of moifture, and jet alfo. Lucid gems are made of water ; juft as Cryftal, which has been concreted from clear water, not
always
52
WILLIAM GILBERT.
always by a very great cold, as fome ufed to judge, and by very hard froft, but fometimes by a lefs fevere one, the nature of the foil fafhioning it, the humour or juices being fhut up in definite cavities, in the way in which fpars are produced in mines. So clear glafs is fufed out of fand, and from other fubftances, which have their origin in humid juices. But the drofs of metals, as alfo metals, (tones, rocks, woods, contain earth rather, or are mixed with a good deal of earth ;
* and therefore they do not attract. Cryftal, mica, glafs, and all eledtricks do not attradt if they are burnt or roafted ; for their pri- mordial fupplies of moifture perifh by heat, and are changed and exhaled. All things therefore which have fprung from a pre- dominant moifture and are firmly concreted, and retain the appear- ance of fpar and its refplendent nature in a firm and compadt body, allure all bodies, whether humid or dry. Thofe, however, which partake of the true earth-fubftance or are very little different from it, are feen to attradt alfo, but from a far different reafon, and (fo to fay) magnetically; concerning thefe we intend to fpeak afterwards. But thofe fubftances which are more mixed of water and earth, and are produced by the equal degradation of each element (in which the magnetick force of the earth is deformed and remains buried ; while the watery humour, being fouled by joining with a more plentiful fupply of earth, has not concreted in itfelf but is mingled with earthy matter), can in no way of themfelves attradt or move from its place anything which they do not touch. On this account metals, marbles, flints, woods, herbs, flefh, and very many other things can neither allure nor folicit any body either magnetically or eledtric- ally. (For it pleafes us to call that an eledtrick force, which hath
* its origin from the humour.) But fubftances confifting moftly of humour, and which are not very firmly compadted by nature (whereby do they neither bear rubbing, but either melt down and become foft, or are not levigable, fuch as pitch, the fofter kinds of refin, camphor, galbanum, ammoniack, ftorax, afafcetida, benzoin, afphaltum, efpecially in rather warm weather) towards them fmall bodies are not borne ; for without rubbing moft eledtricks do not
* emit their peculiar and native exhalation and effluvium. The refin turpentine when liquid does noc attradt ; for it cannot be rubbed ; but if it has hardened into a mastick it does attradt. But now at length we muft underfland why fmall bodies turn towards thofe fub- ftances which have drawn their origin from water ; by what force and with what hands (fo to fpeak) eledtricks feize upon kindred natures. In all bodies in the world two caufes or principles have been laid down, from which the bodies themfelves were produced, matter and form. Eledtrical motions become ftrong from matter, but magnetick from form chiefly ; and they differ widely from one another and turn out unlike, fince the one is ennobled by numerous virtues and is prepotent; the other is ignoble and of lefs potency, and
moftly
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moftly reftrained, as it were, within certain barriers ; and therefore that force muft at times be aroufed by attrition or fridtion, until it is at a dull heat and gives off an effluvium and a polifh is induced on the body. For fpent air, either blown out of the mouth or given * off from moifter air, chokes the virtue. If indeed either a fheet of paper or a piece of linen be interpofed, there will be no movement. But a loadftone, without fridtion or heat, whether dry or fuffufed with moifture, as well in air as in water, invites magneticks, even with the moft folid bodies interpofed, even planks of wood or pretty thick ilabs of ftone or fheets of metal. A loadftone appeals to magneticks # only ; towards eledtricks all things move. A loadftone raifes great weights ; fo that if there is a loadftone weighing two ounces and ftrong, it attradts half an ounce or a whole ounce. An eledtrical fubftance only attradts very fmall weights; as, for inftance, a piece of amber of three ounces weight, when rubbed, fcarce raifes a fourth part of a grain of barley. But this attradtion of amber and of elec- trical fubftances muft be further inveftigated ; and lince there is this particular affedtion of matter, it may be afked why is amber rubbed, and what affedtion is produced by the rubbing, and what caufes arife which make it lay hold on everything ? As a refult of fric- tion it grows flightly warm and becomes fmooth ; two refults which muft often occur together. A large polifhed fragment of amber or jet attradts indeed, even without fridtion, but lefs ftrongly ; but if it be brought gently near a flame or a live coal, fo that it equally becomes warm, it does not attradt fmall bodies becaufe * it is enveloped in a cloud from the body of the flaming fubftance, which emits a hot breath, and then impinges upon it vapour from a foreign body which for the moft part is at variance with the nature of amber. Moreover the fpirit of the amber which is called forth is enfeebled by alien heat ; wherefore it ought not to have heat excepting that produced by motion only and fridtion, and, as it were, its own, not fent into it by other bodies. For as the igneous heat emitted from any burning fubftance cannot be fo ufed that eledtricks may acquire their force from it ; fo alfo heat from the folar rays does not fit an eledtrick by the loofening of its * right material, becaufe it diffipates rather and confumes it (albeit a body which has been rubbed retains its virtue longer expofed to the rays of the fun than in the fhade ; becaufe in the fhade the effluvia are condenfed to a greater degree and more quickly). Then again the fervour from the light of the Sun aroufed by means of a * burning mirror confers no vigour on the heated amber; indeed it diffipates and corrupts all the eledtrick effluvia. Again, burning * fulphur and hard wax, made from fhell-lac, when aflame do not allure; for heat from fridtion refolves bodies into effluvia, which flame confumes away. For it is impoflible for folid eledtricks to be refolved into their own true effluvia otherwife than by attrition, fave
in
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in the cafe of certain fubftances which by reafon of innate vigour emit effluvia conftantly. They are rubbed with bodies which do not befoul their furface, and which produce a polifh, as pretty ftiff filk or a rough wool rag which is as little foiled as poffible, or the dry palm. Amber alfo is rubbed with amber, with diamond, and with glafs, and numerous other fubftances. Thus are eledtricks manipulated. Thefe things being fo, what is it which moves ? Is it the body itfelf, inclofed within its own circumference ? Or is it fomething imperceptible to us, which flows out from the fubftance into the ambient air ? Somewhat as Plutarch opines, faying in his Qucejliones Platonic ce : That there is in amber fomething flammable or fomething having the nature of breath, and this by the attrition of the furface being emitted from its relaxed pores attradts bodies. And if it be an effufion does it feize upon the air whofe motion the bodies follow, or upon the bodies themfelves ? But if amber allured the body itfelf, then what need were there of fridtion, if it is bare and fmooth ? Nor does the force arife from- the light which is refledted from a fmooth and polifhed body ; for a Gem of Vincent’s rock. Diamond, and clear glafs, attradt when they are rough ; but not fo powerfully and quickly, becaufe they are not fo readily cleanfed from extraneous moifture on the furface, and are not rubbed equally fo as to be copioufly refolved at that part. Nor does the fun by its own beams of light and its rays, which are of capital import- ance in nature, attradt bodies in this way ; and yet the herd of philo- fophizers conftders that humours are attradted by the fun, when it is only denfer humours that are being turned into thinner, into fpirit and air ; and fo by the motion of effuflon they afcend into the upper regions, or the attenuated exhalations are railed up from the denfer air. Nor does it feem to take place from the effluvia attenuating the air, fo that bodies impelled by the denfer air pene- trate towards the fource of the rarefadtion ; in this cafe both hot and flaming bodies would alfo allure other bodies ; but not even the lighted; chaff, or any verforium moves towards a flame. If there is a flow and ruffl of air towards the body, how can a fmall diamond of the fize of a pea fummon towards itfelf fo much air, that it feizes hold of a biggilh long body placed in equilibrio (the air about one or other very fmall part of an end being attradted)? It ought alfo to have flopped or moved more flowly, before it came into contadt with the body, efpecially if the piece of amber was rather broad and flat, from the accumulation of air on the furface of the amber and its flowing back again. If it is becaufe the effluvia are thinner, and denfer vapours come in return, as in breathing, then the body would rather have had a motion toward the eledtrick a little while after the beginning of the application ; but when eledtricks which have been rubbed are applied quickly to * a verforium then efpecially at once they adt on the verforium, and it is attradted more when near them. But if it is becaufe the rarefied
effluvia
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effluvia produce a rarefied medium, and on that account bodies are more prone to flip down from a denfer to a more attenuated medium; they might have been carried from the fide in this way or downwards, but not to bodies above them ; or the attradftion and apprehenfion of contiguous bodies would have been momentary only. But with a fingle fridtion jet and amber draw and attradt bodies to them ftrongly and for a long time, fometimes for the twelfth part of an hour, efpecially in clear weather. But if the mafs of amber be rather large, and the furface polifhed, it attracts without fridtion. Flint is rubbed and emits by attrition an inflammable matter that turns into {parks and heat. Therefore the denfer effluvia of flint producing fire are very far different from electrical effluvia, which on account of their extreme attenuation do not take fire, nor are fit material for flame. Thofe effluvia are not of the nature of breath, for when emitted they do not propel anything, but are exhaled with- out fenfible refiftance and touch bodies. They are highly attenuated humours much more fubtile than the ambient air ; and in order that they may occur, bodies are required produced from humour and concreted with a confiderable degree of hardnefs. Non-eledtrick bodies are not refolved into humid effluvia, and thofe effluvia mix with the common and general effluvia of the earth, and are not peculiar. Alfo befides the attraction of bodies, they retain them longer. It is probable therefore that amber does exhale fomething peculiar to * itfelf, which allures bodies themfelves, not the intermediate air. Indeed it plainly does draw the body itfelf in the cafe of a fpherical drop of water {landing on a dry furface ; for a piece of amber applied to it at a fuitable diftance pulls the neareft parts out of their pofition and draws it up into a cone ; otherwife, if it were * drawn by means of the air ruffling along, the whole drop would have moved. That it does not attradt the air is thus demonflrated: take a very thin wax candle, which makes a very fmall and clear flame ; bring up to this, within two digits or any convenient diftance, a piece of amber or jet, a broad flat piece, well prepared * and fkilfully rubbed, fuch a piece of amber as would attradt bodies far and wide, yet it does not difturb the flame ; which of neceffity would have occurred, if the air was difturbed, for the flame would have followed the current of air. As far as the effluvia are lent out, fo far it allures ; but as a body approaches, its motion is accelerated, ftronger forces drawing it ; as alfo in the cafe of mag- neticks and in all natural motion ; not by attenuating or by expel- ling the air, fo that the body moves down into the place of the air which has gone out; for thus it would have allured only and would not have retained ; fince it would at firft alfo have repelled approaching bodies juft as it drives the air itfelf ; but indeed a particle, be it ever fo fmall, does not avoid the firft application made very quickly after rubbing. An effluvium exhales from amber and is emitted by rubbing : pearls, carnelian, agate, jafper, chalcedony, coral, metals,
and
WILLIAM GILBERT
56
and other fubftances of that kind, when they are rubbed, produce no effeCl. Is there not alfo fomething which is exhaled from them by heat and attrition ? Moft truly ; but from grofler bodies more blended with the earthy nature, that which is exhaled is grofs and
* fpent ; for even towards very many eleCtricks, if they are rubbed too hard, there is produced but a weak attraction of bodies, or none at all ; the attraction is beft when the rubbing has been gentle and very quick ; for fo the fined: effluvia are evoked. The effluvia arife from the fubtile diffufion of humour, not from excefiive and tur- bulent violence ; efpecially in the cafe of those fubftances which have been compacted from unCtuous matter, which when the atmofphere is very thin, when the North winds, and amongft us (Englifh) the Eaft winds, are blowing, have a furer and firmer effeCt, but during
* South winds and in damp weather, only a weak one ; fo that thofe fubftances which attraCt with difficulty in clear weather, in thick weather produce no motion at all ; both becaufe in grofler air lighter fubftances move with greater difficulty ; and efpecially becaufe the effluvia are ftifled, and the furface of the body that has been rubbed is affeCted by the fpent humour of the air, and the effluvia are flopped at their very ftarting. On that account in the cafe of amber, jet, and fulphur, becaufe they do not fo eafily take up moift air on their furface and are much more plenteoufly fet free, that force is not fo quickly fupprefled as in gems, cryftal, glafs, and fubftances of that kind which colled on their furface the moifter breath which has grown heavy. But it may be afked why does amber allure water, when water placed on its furface removes its aClion ? Evidently becaufe it is one thing to fupprefs it at its
* very ftart, and quite another to extinguifh it when it has been emitted. So alfo thin and very fine filk, in common language
* Sarcenet , placed quickly on the amber, after it has been rubbed, hinders the attraction of the body ; but if it is interpofed in the intervening fpace, it does not entirely obftruCt it. Moifture alfo from fpent air, and any breath blown from the mouth, as well as water put on the amber, immediately extinguifh.es its force. But
* oil, which is light and pure, does not hinder it ; for although amber
* be rubbed with a warm finger dipped in oil, ftill it attracts. But if that amber, after the rubbing, is moiftened with aqua vitce or fpirits of wine, it does not attraCt ; for it is heavier than oil, denfer, and when added to oil finks beneath it. For oil is light and rare, and does not refill the moft delicate effluvia. A breath therefore, proceeding from a body which had been compacted from humour or from a watery liquid, reaches the body to be attracted ; the body that is reached is united with the attracting body, and the one body lying near the other within the peculiar radius of its effluvia makes one out of two ; united, they come together into the clofeft accord, and this is commonly called attraction. This unity, according to
ONTHE LOADSTONE, BK. II. 57
the opinion of Pythagoras, is the principle of all things, and through participation in it each feveral thing is faid to be one. For fince no adtion can take place by means of matter unlefs by contadt, thefe eledtricks are not feen to touch, but, as was neceffary, fomething is fent from the one to the other, fomething which may touch clofely and be the beginning of that incitement. All bodies are united and, as it were, cemented together in fome way by moifture ; fo that a wet body, when it touches another body, attradts it, if it is fmall.
So wet bodies on the furface of water attradt wet bodies. But the peculiar eledtrical effluvia, which are the moft fubtile material of diffufe humour, entice corpufcles. Air (the common effluvium of the earth) not only unites the disjointed parts, but the earth calls bodies back to itfelf by means of the intervening air ; other- wife bodies which are in higher places would not fo eagerly make for the earth. Eledtrical effluvia differ greatly from air ; and as air is the effluvium of the earth, fo eledtricks have their own effluvia and properties, each of them having by reafon of its peculiar effluvia a lingular tendency toward unity, a motion toward its origin and fount, and toward the body emitting the effluvia. But thofe fub- ftances which by attrition emit a grofs or vapourous or aeriform effluvium produce no effedt; for either fuch effluvia are alien to the humour (the uniter of all things), or being very like common air are blended with the air and intermingle with the air, wherefore they produce no effedt in the air, and do not caufe motions different from thofe fo univerfal and common in nature. In like manner * bodies ftrive to be united and move on the furface of water, juft as the rod C, which is put a little way under water. It is plain
that the rod E F, which floats on the water by realon of the cork H, and only has its wet end F above the furface of the water, is attradted by the rod C, if the rod C is wet a little above the furface of the water; they are fuddenly united, juft as a drop adjoining a drop is attradted. So a wet thing on the furface of water jfeeks union with a wet thing, fince the furface of the water is raifed on both ; and they immediately flow together, juft like drops or bubbles. But they are in much greater proximity than eledtricks, and are united by their clammy natures. If, however, the whole rod be dry * above the water, it no longer attradts, but drives away the ftick E F. The fame is feen in thofe bubbles alfo which are made on
1 water
WILLIAM GILBERT
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water. For we fee one drive towards another, and the quicker the nearer they are. Solids are impelled towards folids by the medium of liquid : for example, touch the end of a verforium with the end of a rod on which a drop of water is projecting ; as foon as the ver- * forium touches the top of the droplet, immediately it is joined ftrongly by a fwift motion to the body of the rod. So concreted humid things attraCt when a little refolved into air (the effluvia in the intermediate fpace tending to produce unity) ; for water has on wet bodies, or on bodies wet with abundant moifture on the top of water, the force of an effluvium. Clear air is a convenient medium for an eleCtrical effluvium excited from concreted humour. Wet bodies projecting above the furface of water (if they are near) run together fo that they may unite; for the furface of the water is raifed around wet fubftances. But a dry thing is not impelled to a wet one, nor a wet to a dry, but feems to run away. For if all is dry above the water, the furface of the water clofe to it does not rife, but fhuns it, the wave finking around a dry thing. So neither does a wet thing move towards the dry rim of a veffel ; but it feeks a wet rim. A B is the furface of the water ; C D two rods, which
ftand up wet above the water ; it is manifeft that the furface of the water is raifed at C and D along with the rods ; and therefore the rod C, by reafon of the water (landing up (which feeks its level and unity), moves with the water to D. On E, on the other hand, a wet rod, the water alfo rifes ; but on the dry rod F the furface is depreffed ; and as it drives to deprefs alfo the wave riling on E in its neighbourhood, the higher wave at E turns away from F ; for it does not fuffer itfelf to be depreffed. All eleCtrical attraction occurs through an intervening humour ; fo it is by reafon of humour that all things mutually come together ; fluids indeed and aqueous bodies on the furface of water, but concreted things, if they have been refolved into vapour, in air; — in air indeed, the effluvium of eleCtricks being very rare, that it may the better permeate the medium and not impel it by its motion; for if that effluvium had been thick, as that of air, or of the winds, or of faltpetre burnt by fire, as the thick and foul effluvia given out with very great force, from other bodies, or air fet free from humour by heat ruffling out through a pipe (in the inflrument of Hero of Alexandria, defcribed in his
book
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book Spirit alia ), then the effluvium would drive everything away, not allure it. But thofe rarer effluvia take hold of bodies and embrace them as if with arms extended, with the eledtricks to which they are united ; and they are drawn to the fource, the effluvia increafing in ftrength with the proximity. But what is that effluvium from cryftal, glafs, and diamond, fince thefe are bodies of confiderable hardnefs and firmly concreted ? In order that fuch an effluvium fhould be produced, there is no need of any marked or perceptible flux of the fubftance ; nor is it neceflary that the eledtrick fhould be abraded, or worn away, or deformed. Some odoriferous fubftances are fragrant for many years, exhaling con- tinually, yet are not quickly confumed. Cyprefs wood as long as it is found, and it lafts a very long time indeed, is redolent ; as many learned men atteft from experience. Such an eledtrick only for a moment, when ftimulated by fridtion, emits powers far more fubtile and more fine beyond all odours ; yet fometimes amber, jet, fulphur, when they are fomewhat eafily fet free into vapour, alfo pour out at the fame time an odour ; and on this account they allure with the very gentleft rubbing, often even without rubbing ; they alfo excite more ftrongly, and retain hold for a longer time, becaufe they have ftronger effluvia and laft longer. But diamond, glafs, rock-cryftal, * and numerous others of the harder and firmly concreted gems firft grow warm : therefore at firft they are rubbed longer, and then they alfo attradt ftrongly ; nor are they otherwife fet free into vapour. Everything rufhes towards eledtricks excepting flame, and flaming bodies, and the thinneft air. Juft as they do not draw flame, in like manner they do not affedt a verforium, if on any fide it is very near to a flame, either the flame of a lamp or of any burning matter. It is manifeft indeed that the effluvia are deftroyed by flame and igneous * heat ; and therefore they attradt neither flame nor bodies very near a flame. For eledtrical effluvia have the virtue of, and are analogous with, extenuated humour ; but they will produce their effedt, union and continuity, not by the external impulfe of vapours, not by heat and attenuation of heated bodies, but by their humidity itfelf attenuated into its own peculiar effluvia. Yet they entice * fmoke fent out by an extinguifhed light ; and the more that fmoke is attenuated in feeking the upper regions, the lefs ftrongly is it turned afide ; for things that are too rarefied are not drawn to them ; and at length, when it has now almoft vanifhed, it does not * incline towards them at all, which is eafily feen againft the light. When in fadt the fmoke has pafled into air, it is not moved, as has been demonftrated before. For air itfelf, if fomewhat thin, is not attradted in any way, unlefs on account of fucceeding that which has vacated its place, as in furnaces and fuch-like, where the air is fed in by mechanical devices for drawing it in. Therefore an effluvium refulting from a non-fouling fridtion, and one which
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WILLIAM GILBERT
is not changed by heat, but which is its own, caufes union and coherency, a prehenfion and a congruence towards its fource, if only the body to be