Although people who compile such lists very often ignore it, there can be no doubt that William Gilbert’s De Magnete must be listed amongst the most important science books published in the Early Modern Period. It is the first printed book entirely dedicated to the study of the magnet, magnetism, and the magnetic compass and following Petrus Perigrinus de Maricourt’s Epistola de magnete only the second tome dedicated exclusively to the topic at all. It is a presentation of systematic, detailed, empirical, experimental science published thirty-eight years before Galileo’s Discorsi, often claimed to be the first such book.
Obviously the product of many years of dedicated research into all aspects of the magnet and magnetism, De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure (On the Magnet and Magnetic Bodies, and on That Great Magnet the Earth) was originally published in Latin by Peter Short in London in 1600. The English translation runs to three hundred and fifty pages. There appears to have been an edition in Amsterdam 1600, a new edition published in London in 1633, two editions published in Stettin in 1628 and 1633, two in Frankfurt 1629 and 1633, and one in Ferrara in 1629. The reception throughout Europe, which I will look at in some detail later, was generally very positive.
The book opens with an address to the author by Edward Wright (1561–1615) the leading English expert on navigation in the period and author of Certaine Errors in Navigation printed in London by Valentine Sims in 1599. Gilbert couldn’t have had a better recommendation for his text. I will look at this address in the next blog post in this series. This is followed by an Author’s Preface, in which Gilbert justifies his publication in rather flowery terms towards the end of which he slags off the Ancient Greeks. The work is divided into six books each of which deals with a different aspect of magnetism.
Book I, Writings of Ancient and Modern Authors Concerning the Loadstone: Various Opinions and Delusions, whereby “delusions” is Gilbert’s opinion of virtually everything that had been written about magnets and magnetism in the past. He debunks the myths about garlic and diamonds blocking magnetism as well as other less well known ones; naming and shaming the authors who perpetuated them. He gives a long list of authors who mentioned magnets and magnetism the writes:
…by all of these the subject is handled in a most careless way, while they repeat only the figments and ravings of others.
Having made negative comments about Fracastoro, all he has to say about Perigrinus is:
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:
Considering that Gilbert took the idea of experimenting with terrella, i.e. small spherical loadstones, and quite a few of the experiments he did with them, from Perigrinus this is a rather thin acknowledgement. Perhaps surprisingly, one author who gets a modicum of praise is Giambattista della Porta and Gilbert also repeats some of the experiments from Magia Naturalis in his research. He continues slagging off authors on magnetism right, left and centre before closing the chapter with the little piece of chauvinism that I brought in the first episode of this series:
There are other learned men who on long sea voyages have observed the difference of magnetic variation; as that most accomplished scholar Thomas Harriot, Robert Hues, Edward Wright, Abraham Kendall, all Englishmen; others have invented and published magnetic instruments and already methods of observing, necessary for mariners and those who make long voyages: as William Borough in his little work the Variations of the Compass, William Barlo (Barlow) in his Supplement, Robert Norman in his New Attractive–the same Robert Norman, skilled navigator and ingenious artificer, who first discovered the dip of the magnetic needle.Many others I pass by of purpose: Frenchmen, Germans, and Spaniards of recent times who in their writings, mostly composed in their vernacular languages, either misuse the teachings of others, and like furbishers send forth ancient things dressed with ne names and tricked in an apparel of new words as in prostitutes’ finery; or who publish things not even worthy of record; who, pilfering some book, grasp for themselves from other authors, and go a-begging for some patron, or go a-fishing among the inexperienced and the young for a reputation; who seem to transmit from hand to hand, as it were, erroneous teachings in every science and out of their own store now and again to add somewhat of error.[1]
With his opening chapter Gilbert basically says, all that went before was rubbish, now I’m going to deliver up the real story of magnets and magnetism. He devotes the next fifteen chapters of book one to the loadstone, iron and iron ore, starting with the history of the loadstone and then moving on to its properties, its poles, their basic attraction and repulsion. He then moves on to the relations between loadstone, smelted iron and iron ore basically arguing that they are one and the same, loadstone being ‘a noble kind of iron ore.’ In passing he rejects the then still prevalent Aristotelian theory of metals In the seventeenth and final chapter of book one he presents the central thesis of his book, its title:
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.
Gilbert argues that we can only infer this fact from the behaviour of magnets and compasses, as demonstrated in his experiments with his terrellas and versoria. A versorium was a miniature, adapted compass needle able to turn horizontally or vertically. We can not experience the earth’s loadstone nature directly because its surface, what we can the crust, is corrupted and degenerated.
The next five books of De Magnete are each devoted to one aspect of the movement of magnets and compass needles, so we have–magnetic attraction, the directional property of compass needles, variation, dip, and revolution.
Book II: Of Magnetic Movement is after a first chapter listing the five movement, dedicated to magnetic attraction, although Gilbert rejects the term attraction as too aggressive preferring instead the term coition:
Coition, we say, not attraction, for the term attraction has wrongfully crept into magnetic philosophy, through the ignorance of the Ancients; for where attraction exists, there force sems in and tyrannical violence rules.
Coition, a synonym for coitus, was a neologism meaning ‘coming together’ like two lovers’ bodies, by which Gilbert did no mean that two magnets made love but that their motions were governed by principles of mutual harmony. He demonstrates coition by placing two terrella on circular discs of wood that had hemispherical depressions in the centre to receive them and floating them on water. They begin to spin and circle each other until the opposing poles are drawn together. Interestingly Gilbert doesn’t think magnetic repulsion exists. If his two floating terrella repulse each other they continue to rotate until they come together in coition.
There is a long section in Book II devoted to static electrical attraction in order to explain why it is not the same as magnetic attraction. Today, this section gets as much attention as the rest of the book on magnetism and is regarded as the beginning of research into electricity, a term the coining of which Gilbert is indirectly given the credit for.
In the rest of book two he covers every possible aspect of magnetic attraction between loadstones, loadstones and iron, loadstones and the earth etc. Interestingly having dismissed the possibility that magnetic attraction is a force, Gilbert, who is generally anti-Aristotelian, turns to Aristotle’s four causes theory to explain it. Magnetic attraction is the form of the matter of the loadstone or the earth in the Aristotelian sense of the terms. Gilbert also investigated what we would call the magnetic field, which he called ‘Orbis Virtutis’ (the sphere of virtue). He carried out these investigations using his versoria.
Book III Of Direction, deals with the phenomenon that a magnetic compass needle, ignoring for the moment variation, always aligns in the same direction. He states that this is confirmed for the whole globe by the reports of mariners, naming dropping the personal reports of the circumnavigators, Francis Drake and Thomas Cavendish in the process. Once again Gilbert introduces his own terminology in the title of the second chapter:
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.
Sailing his miniature compass, the versorium around a terrella Gilbert demonstrates that, in terms of verticity, it behaves identically (ignoring variation) to the mariner’s compass on the terrestrial globe. In book two he had sliced loadstones and compasses into half to demonstrate that the two halves still have poles at both ends. Now he shows that his versorium behaves on a half terrellas exactly the same as on the complete one, the cut surface becoming the opposite pole, demonstrating that it is the poles towards which the versorium points. Gilbert uses these experiments and the real mariner’s compass behaviour data provided by the mariners to argue by analogy that the sphere of the Earth is indeed a compass. Gilbert believes that the magnetic poles of the Earth are identical to the geographical poles.
Book IV, Of Variation, opens with a confession:
Do far we have been treating of direction as if there were no such thing as variation; for we chose to have variation left out and disregarded in the foregoing natural history, just as if in a perfect and absolutely spherical terrestrial globe variation could not exist.
He now turns he attention to variation, systematically rejecting all the suggestions that had been put forth to explain it and such concepts as the zero variation meridian or graduated differences in variation around the globe, using the extensive empirical data available to do so. In this book. he surveys all the available information on variation. He dismisses the argument that variation could be used to determine longitude, well aware of the importance of finding a solution to the longitude problem.
Gilbert argues that variation is the result of damage or imperfection to the terrestrial globe, which is anything but a perfect sphere:
[The] globe of the earth is at its surface broken and uneven, marred by matters of diverse nature, and hath elevated and convex parts that rise to the height of some miles and that are uniform neither in matter nor in constitution … For this reason a magnetic body under the action of the whole earth is attracted toward a great elevated mass of land as toward a stronger body, so far as the perturbed verticity permits or abdicates its rights.
The variation takes place not so much because of these continental lands, as because of the inequalities of the magnetic globe and of the true earth substance which projects farther in continents than beneath the sea-depths.
He dismisses the argument that variation could be used to determine longitude, well aware of the importance of finding a solution to the longitude problem. However, having made the error of believing that variation is constant, the temporal changes in variation were not known at this time, Gilbert endorses the scheme of Simon Stevin (1548–1620) put forward in his De Havenvinding (1599), also published in English as The Haven-Finding Art in the same year and included as an appendix in later editions Edward Wright’s Certaine Errors in Navigation, to provide tables of the correctly measured variation to compare with measured observations as an aid to navigation. The thirteenth chapter of book four provides the best and most detailed description of how to determine variation published up till that time.
Book V, Of the Dip of the Magnetic Needle, is of course very much up to date, because although Georg Hartmann (1489–1564) had first discovered magnetic dip or inclination in 1544, the phenomenon had first become widely known in 1581 when Robert Norman published his The Newe Attractive. Gilbert mentions Norman and his book at the end of Book I and uses the illustration from The Newe Attractive in this Book V. Gilbert once again sets up experiments with his trusty terrella and versorium to demonstrate and measure magnetic dip. On his terrella he measures the dip for the latitude of London and shows it to be the same as the value measured by Norman for the city. He also discusses the possibility of using magnetic dip, as an alternative method for determining latitude. A scheme never realised.
The book closes in Book VI with the most spectacular claim of all, titled Of The Globe of Earth as a Loadstone, it contains the startling claim that the earth’s diurnal rotation is due to its being a loadstone, based on the false belief that a suspended terrella rotates freely about its polar axis. Gilbert has been called a Copernican and although he names Copernicus amongst those who claim that the earth moves he can at best be called a semi-Copernican, as he only argues for diurnal rotation, a position first argued by Heraclides Ponticus in the fourth century BCE. Gilbert makes no mention of the heliocentric theory of the earth’s orbit around the sun.
The above is merely a sketch of the highly detailed contents of De Magnete, but if you wish to know more then I recommend reading the book, which in the English translation is actually very readable and in the Dover edition very affordable.
The book was on the whole well received and became a central text on empirical methodology for the early decades of the seventeenth century. The strongest reactions came from Galileo, Kepler, and Francis Bacon.
Galileo appears to have acquired a copy very soon after publication from a philosopher who feared that keeping it on the shelf would infest the other books with the novelties it contained. and inspired by the book took up his own investigations into magnetism. He mentioned the book frequently in his correspondence with Giovanni Francesco Sagredo (1571–1620) and Paolo Sarpi (1552–1623). Paolo Sarpi in one of his letters, names Gilbert, with François Viète, as the only original writer among his contemporaries. We know from the only surviving letter from Gilbert, about which more in a later episode, that Sagredo wrote to Gilbert, presumably in February 1602:
… a Secretary of Venice, he came sent by that State, and was honourably received by her Majesty, he brought me a lattin letter from a Gentle-man of Venice that is very well learned, whose name is Iohannes Franciscus Sagredus, he is a great Magneticall man, and writeth that hee hath conferred with diuers learned men of Venice and with readers of Padua, and reporteth wonderfull liking of my booke…
Sagredo is one of the three figures, together with Salviati (Copernican, Galileo), and Simplicio (Aristotelian), discussing the Two Chief World Systems in Galileo’s Dialogo from 1632, he represents the supposedly neutral, intelligent layman.
On Day Three in the Dialogo Galileo includes a twenty-five page discussion of Gilberts theory that the Earth is a loadstone, initiated by Simplicio:
SIMPLICIO: Are you then one of those who subscribe to the magnetic philosophy of William Gilbert?
SALVIATI: I am indeed, and I think everyone who has read the book attentively and checked his experiments agrees with me.
Then Salviati goes off on a rant about thinkers who stick dogmatically to old ideas and are too cowardly to accept new ones. He then waxes lyrically about Gilbert and his ideas over many pages. However, towards the end of this section Salviati torpedoes Gilbert’s theory of diurnal rotation.
SALVIATI: […] Lest I forget, however, let me first tell you of one detail that I wish Gilbert had never considered. He allows that is a small sphere of loadstone could be perfectly balanced it would turn on its own axis; but there is no reason why it should do so.
Johannes Kepler was an even bigger fan of Gilberts theories than Galileo. Chapter 33 of his Astronomia Nova(1609) is titled, The power that moves the planets resides in the body of the sun and Chapter 34 The Sun is Magnetic, and Rotates. Here he writes:
The example of the magnet I have hit upon is a very pretty one, and entirely suited to the subject; indeed, it is little short of being the very truth. So why should I speak of the magnet as if it were an example? For, by the demonstration of the Englishman William Gilbert, the earth itself is a big magnet, and is said by the same author, a defender of Copernicus, to rotate once a day, just as I conjecture about the sun.
Chapter 57, Natural Principles of Reciprocation, presents Kepler’s proto-gravitational theory, which is based on magnetism. It is too complex to explain here but there are a couple of relevant Gilbert quotes:
What if all the bodies of the planets are enormous round planets? Of the earth (one of the planets for Copernicus) there is no doubt. William Gilbert has proved it.
For this magnetic power is corporeal, and divisible with the body, as the Englishman Gilbert, B. Porta, and others, have proved.
Whilst the leading natural philosophers on the continent were praising Gilbert to the heavens, in Kepler’s case quite literally, at home in England Francis Bacon (1561–1626) was of a very different opinion concerning Gilbert and his book. In his De Augmentis Scientiarum (1623) he wrote:
Gilbert has attempted to raise a general system upon the magnet, endeavouring to build a ship out of materials not sufficient to make the rowing-pins of a boat.
In The Advancement of Learning (1605), Novum Organum (1620) and repeated in De Augmentis Scientiarum(1623) he wrote:
The Alchemists have made a philosophy out of a few experiments of the furnace and Gilbert our countryman hath made a philosophy out of observations of the loadstone.
In his History of Heavy and Light Bodies published posthumously, he wrote:
[Gilbert] has himself become a magnet; that is, he has ascribed too many things to that force and built a ship out of a shell.
At least Gilbert is in good company, Bacon also rejected Copernicus’ heliocentricity and William Harvey’s discovery of the circulation of the blood. The best comment on Bacon’s approach was supposedly made by William Harvey, in his Brief Lives, John Aubrey tells us that Harvey:
“had been physitian to the Lord Chancellour Bacon, whom he esteemed much for his witt and style, but would not allow him to be a great Philosopher. Said he to me, ‘He writes Philosophy like a Lord Chancellour,’ speaking in derision, ‘I have cured him.’”
Inspired by Gilbert the Jesuits took up research of magnetism in a big way, largely to prove Gilbert wrong. Niccolò Cabeo (1586–1650) in his Philosophia magnetica (1629) accepted Gilbert’s proof that the earth is a loadstone but recast all of his theories about magnetism in Aristotelean terms, of course, rejecting his argument for diurnal rotation.
The Jesuit polymath Athanasius Kircher (1602–1680) published a massive tome on magnetism, Magnes (The Loadstone), which launched a massive attack on the heretics Gilbert, Stevin, and Kepler but added little of substance to the work of Cabeo.
Next up was Jacques Grandami (1588–1672) a professor at La Flèche the Jesuit college where both Descartes and Mersenne had studied. He published his Nova Demonstratio Immobilitatis Terrae (A new Demonstartion of the Earth’s Immobility) in 1645, which contained a new experiment, à la Gilbert, which disproved Gilbert’s magnetic diurnal rotation theory.
Grandami placed a terrella on a wooden disc in water, just as Gilbert had done, making sure that its axis was perfectly vertical. He marked the terrella’s equator with the 180° of longitude east and west. He set the terrella spinning having noted its orientation when it started and then again when it stopped. He repeated this experiment many times and each time the terrella stopped with the same east west orientation as when it started. He concluded that magnetism controlled not only North-South alignment but East-West alignment too. His conclusion:
…there is no doubt that the magnetic virtue that God gave to [the Earth] not only keeps its poles still and stable but also its other parts and points.[2]
He then tackled magnetic Copernicanism, which was:
…not only false, but clearly contrary to magnetic laws. They will have our demonstration, stick to their opinions more firmly, and refute opposing opinions more solidly. Then they can praise divine wisdom in earth’s magnetic quality, which causes its stability, and demolish the other useless and ridiculous effects of the Sun and other planets.
Grandami wrote up his claims in a manuscript that was circulated widely through Marin Mersenne’s network but which had very little resonance, although his experiment was widely repeated and found to be correct. The crunch came from a simple, rather obvious, comment from Mersenne, Jesuit educated but a Minim friar, provoked by Grandami’s conclusions. Mersenne pointed out that the analogy claims between the Earth and a terrella were invalid because the terrella was not free but was affected by the magnetic field of the Earth, torpedoing Grandami’s claims for a geo-static earth but at the same time Gilbert’s magnetic diurnal rotation. He published his thoughts in 1644, a year before Grandami finally commited his manuscript to print.
I do not even wish to pursue those ways by which others believe that the Earth’s stability is proved from magnetic directions, since exactly the same thing happens to the magnet whether the Earth stands still or moves. So far, nothing from magnetic laws, any more from projectiles and the fall of heavy bodies can or ought to prove the double or triple motion of the Earth, the double rest of the Earth or its immobility
Universae geometriae synopsis (1644)
I will close this very brief survey of the reception of De Magnete with Isaac Newton. Challenged on the action at a distance concept of his law of gravity, Newton proffered both magnetism and static electricity as attractive forces that displays action at a distance.
As Attraction is stronger in small Magnets than in great ones in proportion to their Bulk, and Gravity is greater in the Surfaces of small Planets than in those of great ones in proportion to their bulk, and small Bodies are agitated much more by electric attraction than great ones; so the smallness of the Rays of Light may contribute very much to the power of the Agent by which they are refracted. And so if any one should suppose that Æther (like our Air) may contain Particles which endeavour to recede from one another (for I do not know what this Æther is) and that its Particles are exceedingly smaller than those of Air, or even than those of Light: The exceeding smallness of its Particles may contribute to the greatness of the force by which those Particles may recede from one another, and thereby make that Medium exceedingly more rare and elastick than Air, and by consequence exceedingly less able to resist the motions of Projectiles, and exceedingly more able to press upon gross Bodies, by endeavouring to expand itself. (Opticks, Queries 21)
As I stated at the beginning, there can be no doubt that Gilberts De Magnete is one of the most important science books published in the Early Modern Period a fact that should be more widely acknowledged than it usually is.
[1] De Magnete by William Gilbert Translated by P. Fleury Mottelay, Dover Publications, NY, 1958, pp. 14-15
[2] This quote, and several others, is taken from Stephen Pumfrey’s excellent but frustrating biography of Gilbert, Latitude & The Magnetic Earth: The True Story of Queen Elizabeth’s Most Distinguished Man of Science, (Icon Books, 2002). Frustrating because it has no academic apparatus, no foot or endnotes, no references and above all no index!