De Magnete

by William Gilbert

Overview

Much of modern science is based upon the theories and discoveries of William Gilbert, the brilliant English physician and physicist who was the first great experimental scientist. Gilbert was the first to use the word "electricity," to recognize mass as distinct from weight, to discover the effect of heat upon magnetic bodies, to differentiate clearly between static electricity and magnetism, and to explain phenomena of terrestrial magnetism in terms of the earth as a giant magnet.
In 1600 he published De Magnete in Latin. As lively and entertaining as it was scientifically scrupulous, it summarized everything that had previously been known about electricity and magnetism, founded a new science and earned Gilbert the title of "the father of modern electricity." In it Gilbert explores magnetism and electricity, lodestones, phenomena of magnetism, direction of the earth's magnetic lines of force, variation in the compass, dip, the concept of the earth as a giant magnet, and much else.
This Dover edition is a complete, unabridged reprinting of the definitive English translation of De Magnete prepared by Dr. P. Fleury Mottelay. Dr. Mottelay has added a number of footnotes that explain points that might be obscure to today's readers, who will find in this historically important text invaluable insights into the origins of modern science and physics. Translation by P. F. Mottelay. Biographical introduction. 90 illustrations.

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ISBN-13:	9780486163017
Publisher:	Dover Publications
Publication date:	01/03/2013
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DE MAGNETE

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By William Gilbert, P. Fleury Mottelay

Dover Publications, Inc.

Copyright © 1958 Dover Publications, Inc.
All rights reserved.
ISBN: 978-0-486-16301-7

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CHAPTER 1

WRITINGS OF ANCIENT AND MODERN AUTHORS CONCERNING THE LOADSTONE : VARIOUS OPINIONS AND DELUSIONS.

IN former times when philosophy, still rude and uncultured, was involved in the murkiness of errors and ignorances, a few of the virtues and properties of things were, it is true, known and understood : in the world of plants and herbs all was confusion, mining was undeveloped, and mineralogy neglected. But when, by the genius and labors of many workers, certain things needful for man's use and welfare were brought to light and made known to others (reason and experience meanwhile adding a larger hope), then did mankind begin to search the forests, the plains, the mountains and precipices, the seas and the depths of the waters, and the inmost bowels of earth, and to investigate all things. And by good luck at last the loadstone was found, as seems probable, by iron-smelters or by miners in veins of iron ore. On being treated by the metallurgists, it quickly exhibited that strong powerful attraction of iron—no latent nor obscure property, but one easily seen of all; one observed and commended with many praises. And after it had come forth as it were out of darkness and out of deep dungeons and been honored of men on account of its strong and marvellous attraction of iron, then many ancient philosophers and physicians discoursed of it, and briefly (but briefly only) made it matter of record: as, for instance, Plato in the Io, Aristotle only in his first book De Anima; likewise Theophrastus the Lesbian, Dioscorides, Caius Plinius secundus, Julius Solinus. These record only that the loadstone attracts iron : its other properties were all hid. But lest the story of the loadstone should be jejune and too brief, to this one sole property then known were appended certain figments and falsehoods which in the early time no less than nowadays were by precocious sciolists and copyists dealt out to mankind to be swallowed. For example, they asserted that a loadstone rubbed with garlic does not attract iron ; nor when it is in presence of a diamond. The like of this is found in Pliny and in Ptolemy's Quadripartitum; and errors have steadily been spread abroad and been accepted—even as evil and noxious plants ever have the most luxuriant growth—down to our day, being propagated in the writings of many authors who, to the end that their volumes might grow to the desired bulk, do write and copy all sorts about ever so many things of which they know naught for certain in the light of experience. Such fables about the loadstone even Georgius Agricola, a man that has deserved well indeed of letters, has inserted as truthful history in his books De Natura Fossilium, putting his trust in others' writings. Galen, in the ninth book of his De Simplicium Medicamentorum Facultatibus, recognizes its medicinal virtue, and its natural power of attracting iron, in the first book of his De Naturalibus Facultatibus; but he knew not the cause, any more than Dioscorides before him, nor did he seek further. But his translator Matthiolus furbishes again the garlic and diamond story, and further brings in the fable of Mahomet's shrine having an arched roof of magnets so that the people might be fooled by the trick of the coffin suspended in air, as though 'twere some divine miracle. But this is shown to be false by the reports of travellers. Pliny, however, records that the architect Chinocrates began to put an arched roof of loadstone on the temple of Arsinoe at Alexandria, so that her effigy in iron might seem to be suspended in air: in the meantime the architect died, as also Ptolemy, who had ordered the work to be done in honor of his sister. But little has been written by the ancients about the causes of the attraction of iron : some trifling remarks of Lucretius and others are extant ; other authors barely make slight mention of the attraction of iron : all these are berated by Cardan for being so heedless and indifferent about so notable a matter, so broad a field of philosophizing, and for not giving a fuller account or a more developed philosophy ; yet Cardan himself in his ponderous volumes has handed down to posterity, beyond a few commonplaces and quotations from other writers and false discoveries, naught that is worthy of a philosopher. Of later authors, some tell only of its efficacy in medicine, as Antonius Musa Brasevolus, Baptista Montanus, Amatus Lusitanus, as did before them Oribasius in book 13th of the De Facultate Metallicorum, Avicenna, Serapio Mauritanus, Abohali (Hali Abbas), Santes de Ardoniis, Petrus Apponensis, Marcellus, Arnaldus. Only a few points touching the loadstone are very briefly mentioned by Marbodeus Gallus, Albertus, Matthæus Silvaticus, Hermolaus Barbatus, Camillus Leonhardus, Cornelius Agrippa, Fallopius, Joannes Langius, Cardinal de Cusa, Hannibal Roserius Calaber: by all these the subject is handled in the most careless way, while they repeat only the figments and ravings of others. Matthiolus compares the attractive virtues of the loadstone, which pass through iron, to the mischief of the torpedo, whose poison passes through bodies and spreads in an occult way. Gulielmus Puteanus in his Ratio Purgantium Medicamentorum discusses the loadstone briefly and crudely. Thomas Erastus, knowing naught of the nature of the loadstone, draws from it weak arguments against Paracelsus. Georgius Agricola, like Encelius and other writers on metals, simply describes it. Alexander Aphrodiseus, in his Problemata, judges the question of the loadstone to be incapable of explication. Lucretius Carus, the Epicurean poet, deems the attraction to be due to this, that as there is from all things an efflux of minutest bodies, so there is from iron efflux of atoms into the space betwixt the iron and the loadstone—a space emptied of air by the loadstone's atoms (seeds); and when these begin to return to the loadstone, the iron follows, the corpuscles being entangled with each other. Something similar is said by Joannes Costæus, following Plutarch. Thomas Aquinas, in his Physica, Bk. 7, treating briefly of the loadstone, gets at the nature of it fairly well: with his godlike and perspicacious mind he would have developed many a point had he been acquainted with magnetic experiments. Plato holds the magnetic virtue to be divine. But when, some three or four hundred years ago, the magnetic movement to the north and the south was discovered or recognized anew, many learned men, each according to his own gifts, strove to honor with admiration and praise or to explain with feeble reasonings a property so curious and so necessary for the use of mankind. Of more recent authors, very many have striven to discover the cause of this direction and movement to north and south, and to understand this so great miracle of nature and lay it open to others: but they wasted oil and labor, because, not being practical in the research of objects in nature, being acquaint only with books, being led astray by certain erroneous physical systems, and having made no magnetical experiments, they constructed certain raciocinations on a basis of mere opinions, and old-womanishly dreamt the things that were not. Marcilius Ficinus chews the cud of ancient opinions, and to give the reason of the magnetic direction seeks its cause in the constellation Ursa: in the loadstone, says he, the potency of Ursa prevails and hence it is transferred into the iron. Paracelsus declares that there are stars which, gifted with the loadstone's power, do attract to themselves iron. Levinus Lemnius describes and praises the mariner's compass, and on certain grounds infers its antiquity; he does not divulge the hidden miracle which he makes profession to know. The people of Melfi, in the kingdom of Naples, first, 'tis said, constructed a mariner's compass; and, as Flavius Blondus says, the townsmen do not without reason boast, they were so taught by one Joannes Goia, a fellow-citizen, in the year 1300. This town is in the Kingdom of Naples, not far from Salerno, and near the promontory of Minerva. The sovereignty of the place was conferred by Charles V. on Andrea Doria, the great naval commander, in recognition of his splendid achievements. And that nothing ever has been contrived by the art of man nor anything been of greater advantage to the human race than the mariner's compass is certain: but many infer from ancient writings and from certain arguments and conjectures, that the compass was discovered earlier and received among the arts of navigation. Knowledge of the mariner's compass appears to have been brought into Italy by the Venetian Paolo [Paulum Venetum—Marco Polo] who about the year 1260 learned the art of the compass in China, still I do not want to strip the Melfitani of so great an honor, seeing that by them compasses were first commonly made in Mediterranean lands. Goropius ascribes the invention to the Cimbri or Teutons, on the ground that the thirty-two names of the winds inscribed on the compass are pronounced in German by all mariners, whether they be British or Spaniards, or Frenchmen. But the Italians give them names in their own vernacular. Some think that Solomon, King of Judea, was acquaint with the compass and taught the use of it to his pilots for their long voyages when they brought from the Western Indies such a quantity of gold : hence Arias Montanus holds that the regions in Peru that abound in gold got their name from the Hebrew word Paruaim. But it is more probable that the gold came from the coast of lower Ethiopia, or, as others declare, from the region called Cephala. The story seems less true for the reason that the Phœnicians, next neighbors of Judea, most skilful navigators in early times (whose talents, labor, and counsels Solomon employed in building ships and in his expeditions as well as in other ways), were ignorant of magnetic aids, of the use of the mariner's compass: for were it used by them, doubtless the Greeks, the Italians, and all the Barbarians would have known of a thing so necessary and so celebrated through common use ; nor would things famous, most easily known, and of the highest necessity, ever perish in oblivion ; on the contrary, the knowledge would have been handed on to posterity, or some memorial in writing would survive.

Sebastian Cabot first discovered that the magnetized iron (needle) varied. Gonzales Oviedo first made mention in his history that in the meridian of the Azores there is no variation. [Jean Francois] Fernel, in his book De Abditis Rerum Causis, says that in the loadstone is a hidden and abstruse cause : elsewhere he says this cause is celestial ; and he does but explain the unknown by the more unknown. This search after hidden causes is something ignorant, beggarly, and resultless. The ingenious Fracastorio, a philosopher of no common stamp, asks what gives direction to the loadstone [needle], and imagines the existence of hyperborean magnetic mountains, attracting objects of magnetic iron. This opinion, in some degree accepted by others also, many authors follow in their writings, their geographical maps, their marine charts, and their descriptions of the globe: dreaming [imagining to themselves the existence of] magnetic poles and mighty cliffs, apart from the earth's poles. Of date two hundred years or more earlier than Fracastorio, is a small work attributed to one Petrus Peregrinus, a pretty erudite book considering the time : many believe it owes its origin to the opinions of Roger Bacon, Englishman of Oxford. In this work the arguments touching the magnetic direction are drawn from the celestial poles and from the heaven itself. From this book of Petrus Peregrinus, Joannes Taisner Hannonius extracted the matter of a little volume, which he published for new. Cardan makes much of the star in the tail of Ursa Major ; the cause of variation he assigns to its rising, thinking that variation is always certain at the rising of the star. But the difference of variation for change of locality, and the mutations in many places—mutations that even in the southern regions are irregular—preclude this exclusive dominance of one star at its northern rising. The College of Coimbra seeks the cause in some region of the heavens nigh to the pole ; Scaliger, in the 131st of his Exercitationes on Cardan's work De Subtilitate, brings in a celestial cause to himself unknown, and terrestrial loadstones that have nowhere been discovered ; and seeks the cause not in the "siderite mountains" but in that force which formed them, to wit, in the part of the heavens which overhangs that northern point. This opinion the learned author dresses in abundant verbiage and crowns with many subtile observations in the margin : but his reasons are not so subtile. Martinus Cortesius holds that the seat of the attraction is beyond the poles, and that it is the heavens in motion. One Bessard, a Frenchman, studies the pole of the Zodiac, but to as little purpose. Jacobus Severtius, of Paris, after quoting a few observations of others, fashions new errors about loadstones of different regions being different in direction, as also about the eastern and western parts of a loadstone. Robert Norman, an Englishman, posits a point and place toward which the magnet looks (but whereto it is) not drawn : toward which magnetized iron, according to him, is collimated, but which does not attract it. Franciscus Maurolycus discusses a few problems regarding the loadstone, adopting the current opinions of others; he believes that the variation is caused by a certain magnetic island mentioned by Olaus Magnus. Josephus Costa, knowing nothing whatever of the subject, nevertheless pours out empty words about the loadstone. Livio Sanuto in his Geography (written in Italian) discourses at length of the prime magnetic meridian, of the magnetic poles, whether they are terrestrial or celestial ; treats also of an instrument for finding the longitude ; but as he does not understand the nature of the loadstone, he does but add errors and obscurities to his otherwise excellent treatise. Fortunius Affaitatus has some rather silly philosophizing about attraction of iron and the turning toward the poles. Very recently Baptista Porta, a philosopher of no ordinary note, makes the 7th book of his Magia Naturalis a very storehouse and repertory of magnetic wonders ; but he knows little about the movements of the loadstone, and never has seen much of them; much of what he has learned about its obvious properties, either from Messer Paolo, the Venetian, or through his own studies, is not very accurately noted and observed ; the book is full of most erroneous experiments, as will appear in fitting place; still I hold him worthy of praise for that he essayed so great a task (even as he has essayed many another task, and successfully too, and with no inconsiderable results), and that he has given occasion for further researches.

(Continues...)

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Excerpted from DE MAGNETE by William Gilbert, P. Fleury Mottelay. Copyright © 1958 Dover Publications, Inc.. Excerpted by permission of Dover Publications, Inc..
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

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Table of Contents

Translator's Preface
Biographical Memoir
Address by Edward Wright
Author's Preface
Explanation of some Terms used in this Work
Book I.
I. Writings of ancient and modern authors concerning the loadstone: various opinions and delusions
II. The loadstone: what it is: its discovery
III. "The loadstone possesses parts differing in their natural powers , and has poles conspicuous for their properties"
IV. Which pole is the north: how the north pole is distinguished from the south pole
V. One loadstone appears to attract another in the natural position; but in the oppposite position repels it and brings it to rights.
VI. The loadstone attracts iron ore as well as the smelted metal
VII. What iron is; what its matter; its use
VIII. In what countries and regions iron is produced
IX. Iron ore attracts iron ore
X. "Iron ore has and acquires poles, and arranges itself with reference to the earth's poles"
XI. "Wrought-iron, not magnetized by the loadstone, attracts iron."
XII. "A long piece of iron, even not magnetized, assumes a north and south direction"
XIII. "Smelted iron has in itself fixed north and south parts, magnetic activity, verticity, and fixed vertices or poles"
XIV. Of other properties of the loadstone and of its medicinal virtue
XV. The medicinal power of the iron
XVI. "That loadstone and iron ore are the same, and that ironis obtained from both, like other metals from their ores; and that all magnetic properties exist, though weaker, both in smelted iron and in iron ore"
XVII. "That the terrestrial globe is magnetic and is a loadstone; and, just as in our hands the loadstone possesses all the primary powers (forces) of the earth, so the earth by reason of the same potencies lies ever in the same direction in the universe"
BOOK II.
I. Of magnetic movements
II. "Of magnetic coition, and, first, of the attraction exerted by amber, or, more properly, the attachment of bodies to amber"
III. "Opinions of others concerning magnetic coition, which they call attraction"
IV. Of the strength of a loadstone and its form: the cause of coition
V. In what manner the energy inheres in the loadstone
VI. "How magnetized iron and smaller loadstones conform to the terrella, and to the earth itself, and are goverened thereby."
VII. "Of potency of the magnetic force, and of its spherical extension"
VIII. Of the geography of the earth and the terrella
IX. Of the equinoctial circle of earth and terrella
X. The earth's magnetic meridians
XI. Parallels
XII. The magnetic horizon
XIII. Of the magnetic axis and poles
XIV. Why the coition is stronger at the poles than in the parts between equator and pole; and the relative power of coition in different parts of the earth and the terrella
XV. "The magnetic force imparted to iron is more apparent in an iron rod, than in an iron sphere, or cube, or iron of any other shape"
XVI. That motion is produced by the magnetic force through solid bodies interposed: of the interposition of a plate of iron.
XVII. "Of the iron helmet (cap) of the loadstone, wherewith it is armed at the pole to increase its energy; efficiency of the same"
XVIII. An armed loadstone does not endow with greater force magnetized iron than does an unarmed one
XIX. "That unition is stronger with an armed loadstone: heavier weights are thus lifted: the coition is not stronger, but commonly weaker"
XX. "That an armed magnet lifts another, and that one a third: this holds good though there be less energy in the first"
XXI. "That when paper or other medium is interposed, an armed loadstone does not lift more than one unarmed"
XXII. "That an armed loadstone does not attract more than an unarmed one; and that the armed stone is more strongly united to the iron, is shown by means of an armed loadtone and a cylinder of polished iron"
XXIII. "The magnetic force makes motion toward union, and when united connects firmly"
XXIV. "That iron within the field of a loadstone hangs suspended in air, if on account of an obstacle it cannot come near"
XXV. Intensifying the loadstone's forces
XXVI. "Why the love of iron and loadstone appears greater than that of loadstone and loadstone, or iron and iron when nigh a loadstone and within its field"
XXVII. That the centre of the magnetic forces in the earth is the centre of the earth; and in the terrella the terrella's centre
XXVIII. "That a loadstone does not attract to a fixed point or pole only, but to every part of a terrella, except the equinoctial circle"
XXIX. Of difference of forces dependent on quantity or mass
XXX. The shape and the mass of an iron object are important magnetic coitions
XXXI. Of oblong and round stones
XXXII. "Some problems and magnetic experiments on the coition, and repulsion, and regular movement of magnetic bodies"
XXXIII. Of the difference in the ratio of strength and movement of coition within the sphere of influence
XXXIV. Why a loadstone is of different power in its poles as well in the north as in the south regions
XXXV. "Of a perpetual-motion engine actuated by the attraction of a loadstone, mentioned by authors"
XXXVI. How a strong loadstone may be recognized
XXXVII. Uses of the loadstone as it affects iron
XXXVIII. Of the attractions of other bodies
XXXIX. Of mutually repellent bodies
BOOK III.
I. Of direction
II. "Directive (or versorial) force, which we call verticity: what it is; how it resides in the loadstone; and how it is acquired when not naturally produced"
III. "How iron acquires verticity from the loadstone, and how this verticity is lost or altered"
IV. Why magnetized iron takes opposite verticity: and why iron touched by the true north side of the stone moves to the earth's north, and when touched by the true south side to the earth's south: iron rubbed with the north point of the stone does not turn to the south, nor vice versa, as all writers on the loadstone have erroneously thought
V. Of magnetizing stones of different shapes
VI. What seems to be a contrary movement of magnetic bodies is the regular tendence to union
VII. "A determinate verticity and a directive power make magnetic bodies accord, and not an attractional or a repulsive force, nor strong coition along, or unition"
VIII. Of disagreements between pieces of iron on the same pole of a loadstone; how they may come together and be conjoined
IX. Directional figures showing the varieties of rotation
X. "Of the mutation of verticity and magnetic properties, or of the alteration of the force awakened by the loadstone"
XI. "Of friction of iron with the mid parts of a loadstone between the poles, and at the equinoctial circle of a terrella"
XII. How verticity exists in all smelted iron not excited by the loadstone
XIII. Why no other bodies save the magnetic are imbued with verticity by friction with a loadstone; and why no body not magnetic can impart and awaken that force
XIV. "The position of a loadstone, now above, anon beneath, a magnetic body suspended in equilibrium, alters neither the force nor the verticity of the magnetic body"
XV. "The poles, equator, centre, are permanent and stable in the unbroken loadstone, when it is reduced in size and a part taken away, they vary and occupy other positions"
XVI. "If the south part of a loadstone have a part broken off, somewhat of power is taken away, they vary and occupy other positions"
XVII. Of the use of rotay needles and their advantages; how the directive iron rotary needles and their advantages; how the directive iron rotary needles of sun-dials and the needlesof the mariner's compass are to be rubbed with loadstone in order to acquire stronger verticity
BOOK IV.
I. Of variation
II. That variation is due to inequality among the earth's elevations
III. Variation is constant at a given place
IV. The arc of variation does not differ according to distance between places
V. An island in ocean does not alter in variation; neither do mines of loadstone
VI. "That variation and direction are due to the controlling force of the earth and the rotatory magnetic nature, not by an attraction or a coition or by other occult cause"
VII. "Why the variation due to this lateral cause is not greater than hitherto it has been observed to be, seldom appearing to amount to two points of the compass, except near the poles"
VIII. "Of the construction of the common mariner's compass, and of the different compasses of various nations"
IX. Whether terrestrial longitude can be found from variation
X. Why in various places near the pole the variations are much ampler than in lower latitudes
XI. "Cardan's error in seeking to determine the distance of the earth's centre from the centre of the world by means of the loadstone (in his De Proportionbus, V)"
XII. Of finding the amount of the variation; what the quantity is of the arc of the horizon from its arctic or antarctic intersection by a meridian to the point toward which the needle turns
XIII. "Observations made by seamen commonly vary and are untrustworthy, partly though mistakes and want of knowledge and the imperfectness of the instruments, and partly because the sea is seldom so calm but shadows or lights may rest of the instruments"
XIV. Of the variation under the equinoctial line and nearby
XV. "The variation of the magnetized needle in the great sea, Ethiopic and American, below the equator"
XVI. Of the variation in Nova Zembla
XVII. Variation in the South Sea
XVIII. Of the variation in the Mediterranean Sea
XIX. The variation in the interior of the great continents
XX. The variation in the Eastern Ocean
XXI. How the deviation of the needle is greater or less according to the distance of places
BOOK V.
I. Of the dip of the magnetic needle
II. Diagram showing dip of the magnetic needle in different positions of a sphere and horizons of the earth in which there is a variation of dip
III. An instrument for showing by the action of a loadstone the degree of dip below the horizon in any latitude. Description of the instrument; its uses
IV. Of a suitable length of needle on the terrella for showing the dip
V. That dip is not caused by the attraction of a loadstone but by its power of giving direction and rotation
VI. Of the ratio of the dip to latitude and the causes thereof
VII. Explanation of the diagram of the rotation of magnetized iron.
VIII. "Diagram of the rotation of magnetized iron showing the magnetic dip in all latitudes, and showing the latitude from the rotation and dip"
IX. "Demonstration of direction, or of variation from the true direction, together with dip, simply by the movement in water, due to the power of controlling and rotating"
X. Of variation of dip
XI. Of the formal magnetic act spherically effused
XII. "The magnetic force is animate,or imitates a soul; in many respects it surpasses the human soul while that is united to an organic body"
BOOK VI.
I. Of the globe of earth as a great loadstone
II. The magnetic axis of the earth remains invariable
III. "Of the daily magnetic revolution of the globes, as against the time-honored opinion of a primum mobile: a probable hypothesis"
IV. That the earth hath a circular motion
V. "Arguments of those who deny the earth's motion, and refutation thereof"
VI. Of the cause of the definite time of the total revolution of the earth
VII. Of the earth's primary magnetic nature whereby her poles are made different from the poles of the ecliptic
VIII. Of the precession of the equiuoxes by reason of the magnetic movement of the earth's poles in the arctic and antarctic circle of the zodiac
IX. Of the anomaly of the precession of the equinoxes and of the obliquity of the zodiac