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  William Gilbert (1544?–1603), by R. Clamp (after Harding, after unknown artist, 1591) William Gilbert (1544?–1603), by R. Clamp (after Harding, after unknown artist, 1591)
Gilbert, William (1544?–1603), natural philosopher, was almost certainly born in Colchester, Essex, the first of four children of Jerome Gilbert (d. 1583), lawyer and recorder of Colchester, and his first wife, Elizabeth Coggeshall. Jerome's father William was a weaver, appointed sewer (server) to the chamber to Henry VIII, who lived in Clare, Suffolk. Jerome moved to Colchester by the 1520s, and by 1558 he had married as his second wife Jane Wingfield, with whom he had nine more children. Excepting official records of Gilbert's university and medical career, biographical information about him is sparse. No record survives of Gilbert's baptism, but evidence converges strongly upon the year 1544. A later nativity relied upon the time and date of 2.20 p.m., 24 May 1544. The inscription on a monument erected in Holy Trinity Church, Colchester, by his stepbrothers Ambrose and William states that he ‘was born in the town of Colchester’, but unreliably gives his age at death as sixty-three (Munk, Roll; Gilbert, De magnete, xxiii).

Education and medical career

Nothing is known of Gilbert before he matriculated from St John's College, Cambridge, in May 1558. He might have attended the Royal Grammar School, Colchester, although his family was wealthy enough to employ a private tutor. His university career was unexceptional for an aspiring scholar and physician. He graduated BA and was admitted to the fellowship of the college in March 1561, proceeded MA in 1564, and served in the junior position of mathematical examiner in 1565 and 1566, before graduating MD in 1569. He was senior bursar in January 1570, but he subsequently left Cambridge to pursue a medical career in London. There is no evidence for Wood's oft-repeated claim that he first travelled or studied medicine abroad (Wood, Ath. Oxon., 1.737). There are likewise few clues as to why he came to reject much of the orthodox science (more properly, natural philosophy) of his day in his great work De magnete (‘On the lodestone’, 1600).

Gilbert must have built up a successful clientele among London's gentry and aristocracy during the 1570s. The inscription on his monument states that he practised ‘for more than thirty years at London’ (Munk, Roll; Gilbert, De mundo, xxiii). His place of residence in these early years is not known. Gilbert obtained a grant of arms in 1577, and was moving in court circles by January 1580 when, as was common for physicians in noble households, he acted as a trusted emissary from the earl of Leicester to the earl of Shrewsbury. About 1580 he was elected to one of the thirty odd fellowships of the College of Physicians in London, for he held the post of censor, regulating standards of practice, for eight years between 1581 and 1590.

By 1595 Gilbert had acquired and moved into Wingfield House in St Peter's Hill, a substantial property near St Paul's Cathedral possibly inherited from his stepmother. He moved from there to the court in February 1601, when he was selected to become one of the royal physicians. They were generally highly esteemed fellows of the College of Physicians, although court patronage and acceptance were also important. Gilbert had risen to become treasurer of the college (1587–94, 1597–9), elect (1596–7), consiliarius (1597–9), and finally president in 1600. He had also added to his patrons the powerful Cecil family. He attended at the deaths of William Cecil, Lord Burghley, Elizabeth I's chief counsellor, and his wife. A medical report to Robert Cecil, William's son and political successor, may be in Gilbert's hand (Roller, 81). The connections surely facilitated his formal appointment for life in April 1601 as a physician to Elizabeth I, with the usual stipend of £100 per year. She did not favour him especially, and there is no evidence for the scene painted by A. A. Hunt of Gilbert demonstrating experiments before her. He was re-appointed royal physician to James I, but died a few months afterwards.

Personal life

Very little is known of Gilbert's personal life. He did not marry. Judging from his will (printed by Houston) he was close to his family, especially to his half-sisters and half-brothers, one of whom edited his manuscript remains. His will mentions one godson, and two ‘good ffrends’, a Mr Harwood and, more significantly, John Chamberlain. Chamberlain, the famous gossipy correspondent, lodged with Gilbert in Wingfield House between c.1595 and 1601, and mentioned him respectfully. Gilbert, Chamberlain, and other habitués of Wingfield House made up a sociable circle or informal ‘college’ of uncertain composition. One candidate is Gilbert's fellow physician and defender of his magnetic philosophy, Mark Ridley. Ridley, to whose home Chamberlain moved, claimed that he was Gilbert's friend and had experimented with his apparatus (Ridley, preface; Letters of John Chamberlain, 1.5). Thomas Blundeville the mathematician was another ‘good friend’ and popularizer of Gilbert's discoveries. Lancelot Browne, the father-in-law of William Harvey, was a close acquaintance of both Gilbert and Blundeville. Browne's medical career paralleled Gilbert's, and he possessed an autographed copy of De magnete. Finally, Gilbert worked very closely with the mathematician Edward Wright (bap. 1561, d. 1615). The Wingfield ‘society’ must have discussed Gilbert's research, and probably also discussed religion. Giving the only available insight into Gilbert's private opinions, Chamberlain wrote, concerning outspoken preachers, that ‘yt is not good irritare crabrones, or to meddle with these pulpit-hornets, as our Doctor was wont to call them’ (Letters of John Chamberlain, 1.396). Gilbert's firm belief that theologians of all confessions had obstructed the development of true science and Copernican astronomy meant that his books did not follow this Erasmian counsel.

In his texts and in conversation Gilbert exhibited biting wit. This moderates the judgement of Thomas Fuller, who, relying on a relative and other sources some forty years after Gilbert's death, recounted that ‘[o]ne saith of him, “that he was stoical but not cynical”, which I understand reserved but not morose’. Fuller added (presumably of Gilbert's intellect) that he had ‘the clearness of Venice glass, without the brittleness thereof; soon ripe, and long lasting, in his perfections’. ‘His stature was tall, complexion cheerful; an happiness not ordinary in so hard a student and retired a person’ (Fuller, Worthies, 1.515). Wood responded identically to a portrait he saw in Oxford. Although it was destroyed, an engraving was made, from which derive modern reproductions of Gilbert in formal dress.

Maritime interests

Apart from his professional success, Gilbert's medical career seems unusual—though significantly so for a philosopher of magnetism—only in his connections with London's maritime community and naval explorers. In 1588 he and Browne were approached by the privy council to administer drugs to sailors struck down by an epidemic, being two of four ‘very fytt persons to be employed in the said Navye to have care of the helthe of the noblemen, gentlemen and others in that service’ (Roller, 79). If he was not one of the two selected, Gilbert nevertheless became acquainted with nautical practitioners, and wrote proudly of conversations with England's heroic circumnavigators Francis Drake and Thomas Cavendish. To Richard Hakluyt, the chronicler of Elizabethan voyages, he offered to compile a book on tropical medicine. He also advised Sir Francis Walsingham, Elizabeth's security chief during the hostilities with Spain, that a sick petitioner should be allowed to leave for a hot, dry country. His experience, unusual for an élite Galenic physician, of drug-based mass medicine might explain Gilbert's involvement between 1589 and 1594 in the college's first, controversial, and aborted attempts to produce a pharmacopoeia, which finally appeared in 1618.

Gilbert's acquaintance with English mariners and navigation experts was surely facilitated by his medical duties and interests, but it was also a crucial source of his burgeoning knowledge of terrestrial magnetism for which, far more than his medical career, he is remembered. A major achievement of Gilbert's magnetic philosophy was that it provided the first comprehensive and satisfactory explanation of the behaviour of the nautical magnetic compass. The correct recording and use of compass bearings made possible the ‘age of exploration’, and its concomitants of trade, naval capability, colonial imperialism, and missionary work. Recent naval successes had shaped the identity of Gilbert's England. Francis Bacon, Gilbert's contemporary both as courtier and as reformer of natural philosophy, made the compass, with printing and gunpowder, one of the three technologies that defined a modern age of progress beyond classical achievements. The new importance of the compass, the new availability of magnetic data, the new status of navigation experts in Elizabethan England, and a growing belief among the London scientific community that university learning was outdated, help to explain why Gilbert was the founder of a new science of magnetism.

The most important collaborator upon whose technical expertise Gilbert relied was Edward Wright, a mathematician who, under the patronage of the earl of Cumberland, had left Cambridge and theory for London and practical mathematics. He was an expert lecturer on navigation, and the author of the classic Certaine Errors in Navigation (1599), and of The Havenfinding Art (1599), a translation of a work by his Dutch counterpart Simon Stevin. Gilbert also exchanged knowledge of magnetism with William Barlow, a court chaplain and compass expert, who deferred to Gilbert's advanced research in his book The Navigators Supply (1597). In controversial terms that Bacon echoed, Gilbert asserted that navigational practitioners, metalworkers, and even farmers had a better knowledge of the nature of the earth than did professors of natural philosophy.

De magnete

Gilbert's enduring significance is secured by the one work published in his lifetime, De magnete, magneticisque corporibus, et de magno magnete tellure; physiologia nova, plurimis & argumentis, & experimentis demonstrata (‘A new natural philosophy of the lodestone, magnetic bodies, and the great lodestone the earth, proved by many reasonings and experiments’). It was printed by Peter Short of Bread Street, London, in 1600. The full title, announcing a new science of the earth, corrects the impression given by its universally used incipit De magnete that it was a treatise ‘on the magnet’. Unusually for a work of its period and genre, De magnete has no dedicatory epistle, suggesting that Gilbert did not seek, or failed to gain, patronage for his natural philosophical researches.

Evidence of Gilbert's long-standing and broad interests in natural philosophy comes from his other work. His half-brother William edited two more or less finished manuscripts into a handsome manuscript book entitled De mundo nostro sublunari, nova philosophia contra Aristotelem (‘A new philosophy of our sublunary world in opposition to Aristotle’), which he presented to Prince Henry, a patron of Barlow, Wright, and navigation in general. Previously placed in the Royal Library, it (or possibly a copy) is now in the British Library. A version found with some of Francis Bacon's manuscripts was published in Amsterdam in 1651. By then some of Gilbert's philosophical principles and style, though not his magnetic experiments and discoveries, were outmoded, and De mundo received limited attention. Nevertheless, the lack of evidence about how Gilbert came to produce De magnete, coupled with De mundo's very different style, makes the latter an invaluable source.

Despite the conventional success of his medical career, Gilbert's natural philosophy was at odds with conservative institutions such as Cambridge University and the College of Physicians that defended orthodox Aristotelian natural philosophy and Galenic medicine. He deplored the excessive authority accorded to Galen's texts, and emphasized the importance of experience. He rejected the traditional physician's habitual diagnosis of disease as a humoral imbalance of the qualities of heat, cold, wetness, and dryness, although he was also critical of the emerging alternative of Paracelsian or chemical medicine. He was especially hostile to the Galenic theory of attraction in which, significantly, Galen had explained the body's faculties by analogy with the magnet; both were apparently able to attract similar substances and to repel or expel harmful ones.

There is insufficient evidence to trace or explain the sources of Gilbert's profound hostility to Aristotelian and Galenic theory of matter. The Italian nature philosophers Bernardino Telesio and Francesco Patrizi both published self-consciously new and anti-scholastic natural philosophies during his formative period. They were influences, despite Gilbert's characteristic dismissals. He was more impressed by Giordano Bruno, whose advocacy of a vitalist, infinite universe contributed to his execution in Rome in 1600. But Gilbert certainly did not share Bruno's ‘Hermetic’ position that true philosophy was revealed in very ancient, pre-Hellenic texts. Indeed, Gilbert (and Bacon) pioneered the iconoclastic modern positions that knowledge progressed, and that science needed to begin anew on empirical and experimental foundations.

The philosophical core of Gilbert's hostility was, as for Patrizi and Bruno, his rejection of the traditional division by Christian Aristotelians of the cosmos into a superior celestial world and an inferior terrestrial one alone composed of the four elements. Gilbert particularly objected to the low status accorded to the terrestrial sphere of earth. Unlike the heavens, earthy matter was supposedly corrupt, and informed by the inactive qualities of coldness and dryness. Together with Aristotelian theories of gravity these properties explained why the earth had to be gathered as a motionless ball at the centre of the universe, maximally separated from the perfect heavens in which, according to a dominant theory, the planets were moved in endless circular orbits by indwelling motor souls. Gilbert was one of the very few sixteenth-century thinkers to promote a Copernican philosophy of the earth as a planet that was an integral part of a harmonious solar system. Proving this was the aim and climax of De magnete. Having rejected the authority of almost all previous natural philosophers, Gilbert set out to prove it with a brilliant series of magnetic experiments and inferences from them.

First, Gilbert established the modern science of magnetism by showing that magnetic attraction was a pervasive property of matter, specifically of all ‘true’ terrestrial and lunar matter. This challenged the dominant Aristotelian theory that elemental earth was cold, dry, and inert. To do so Gilbert distinguished magnetism from a plethora of highly specific occult sympathies, such as the electrostatic attraction of amber for chaff, or drugs for poisons, within which Renaissance philosophers had classified the pairing of lodestone and iron. Second, he discovered the foundations of geomagnetism, according to which the earth behaves like a giant dipole magnet. Third, he developed his geomagnetic theory into the first satisfactory explanation of the nautical compass. Since England and other European countries were fighting for military and commercial dominance on the seas, De magnete's applications to the problems of finding latitude and especially longitude were very attractive. Fourth, Gilbert provided controversial, if subsequently vindicated, arguments that magnetism was an immaterial force. Within their ‘sphere of activity’, magnets were capable of attracting and repelling ferrous bodies across empty spaces and through solid matter according to fixed laws.

Despite his claim to have broken with Renaissance philosophical traditions, Gilbert concluded from the lawlike and immaterial nature of terrestrial magnetism that it emanated from something akin to a magnetic soul in the earth. This fifth claim provoked the most criticism. To progressive seventeenth-century followers of Descartes, animate explanations were outdated. Galileo criticized Gilbert's ‘reasons’ for lacking mathematical rigour (Dialogue Concerning the Two Chief World Systems, trans. S. Drake, 1962, 406). Conservative opponents on the other hand did not object to planetary souls—they had been a standard explanation of the regular orbits of heavenly bodies. They opposed the principal thesis of Gilbert's magnetic philosophy, that the earth was not a passive, motionless body inferior to the planets, but a noble, self-moving equal.

Sixth, and in the controversial final book of De magnete, Gilbert argued that magnetism was the cosmic force that moved the earth. In doing so he was the first to offer a physical, dynamical rather than mathematical, astronomical proof of Copernicanism. This aspect of it was rendered unnecessary by seventeenth-century theories of inertia. As an adherent of disproofs of solid celestial spheres by the Danish astronomer Tycho Brahe, Gilbert was one of the first to assert that the earth moved effectively in a vacuum. He therefore argued that the fixed orientation of the earth's axis of daily rotation was also caused magnetically. He was almost certainly a thoroughgoing Copernican, but all his writings concerning the earth's annual rotation were skilfully evasive. He may have decided that there was no magnetic proof of it, or may have been restrained by theological concerns. English Copernicans like Gilbert and Thomas Harriot had reason to fear public ridicule and suspicion, if not religious persecution. In 1612 John Owen published two hostile epigrams about Gilbert. One read:
Stare negas terram; nobis miracula narras;
Haec cum scribebas, in rate forsan eras.
(You deny that the earth stands still; you tell us a miracle; Perhaps you were in a boat when you wrote this. Roller, 89)
Although a magnetic dynamics of celestial motion was rejected by post-Newtonian physicists, it was the most discussed aspect of magnetic philosophy in the first half of the seventeenth century.The enthusiasm of scientists like Kepler and Galileo shows that Gilbert's Copernicanism, if not his animism, was treated as a reasonable inference from his magnetic experiments. Modern commentators have tended to agree more with Francis Bacon. While Bacon shared Gilbert's impatience with traditional natural philosophers, his admiration for the knowledge of low-status practitioners such as metalworkers and navigators, and his interest in applied science, Bacon repeatedly reproved Gilbert for an approach that generalized and speculated too readily upon too narrow an observational base. The force must be conceded of Bacon's judgement that Gilbert ‘made a philosophy out of a few experiments of a lodestone’ (Bacon, Works, 1857, 1.169).

Although Gilbert did not articulate a formal scientific method of the kind explicit in Bacon's writings or implicit in Galileo's work, De magnete's experimentalism has impressed most readers from its publication to the present day. Gilbert's use of experiments was unprecedentedly thorough and innovative. As Gilbert himself noted, he surpassed the Italian natural magician Giambattista della Porta, whose unsystematic, over-spectacular, and sometimes unreliable collection was the previous fullest source for magnetic phenomena. He generally followed his rule to include nothing ‘that has not been investigated and again and again done and repeated under our eyes’ (Gilbert, De magnete, xlix), and he intended readers to replicate the experiments that he had performed or commissioned.

Gilbert's work on electricity, in book 2, chapter 2 of De magnete, is a typical example of his approach. He began, in Aristotelian fashion, with a review of past opinions, but with the post-Renaissance aim of ruthlessly exposing their inadequacy and ignorance of experimental facts. He then described apparatus and procedures for generating and detecting what is called electrostatic attraction. He indicated in the margin his many new discoveries. Key among these was identification of the numerous substances besides the traditional occult pair of amber and jet that would attract; the inability of electrostatic attraction to act through solid media; and its vulnerability to variables such as heat and humidity. Equally typically, Gilbert confidently and misguidedly explained that the cause of electrostatic effects was a ubiquitous aqueous humour or vapour. For coining the word electricitas (derived from the Greek word for amber) and for expanding the range of electrics and electrostatic experiments, Gilbert has been called the father of electricity. The designation misses the point that Gilbert's purpose was to distinguish succinctly magnetic attraction from its traditional occult partner by showing that electricity was a material property of many substances, whereas magnetism was immaterial and unique.

De magnete provided a huge repertory of experiments investigating the composition, shape, and strength of different magnets, but Gilbert's most important series used apparatus that he called terrellae and versoria. A terrella was a naturally occurring lodestone turned into a sphere. The name, meaning ‘little earth’, encapsulates his conclusion that a laboratory magnet reproduced terrestrial phenomena. The lack of experimental science before Gilbert is partially explained by the Aristotelian principle that a man-made object could not substitute for a natural one. Gilbert's success significantly weakened that objection. His concept of the terrella was almost certainly inspired by a few extraordinary experiments with a spherical magnet described in a letter of 1269 by a French engineer, Pierre de Maricourt, and in print in 1562. For Maricourt, however, the sphere imitated the heavens not the earth.

Gilbert modelled his innovative versorium, or ‘turn detector’, on the nautical compass. The miniature needle was mounted so that it could rotate freely in three dimensions. In modern terms it indicated the magnetic field vector. Gilbert moved versoria over the surface of his terrellae, in explicit imitation of ships' compasses travelling over the earth. His unprecedented strategy was to replicate and synthesize in the laboratory all the magnetic phenomena recorded by navigators, and hence to prove by analogy that the earth was a giant lodestone. Gilbert's intimate acquaintance with and respect for navigators and their skills were crucial.

A good example was Gilbert's use of the discovery of geomagnetic ‘dip’, or inclination, announced by the London compass maker Robert Norman in 1581. Unlike flat-mounted compasses, Gilbert's versorium indicated this vertical component of the earth's field. His method for identifying a magnet's poles was to find the places where the versorium's needle stood vertically. He discovered that dip increased steadily from 0° at a terrella's equator to 90° at its poles. Applied to the earth, this dip-latitude relation offered an alternative to astronomical methods for determining latitude, and De magnete included the description and instructions for use of such a dip instrument. Although the method was rarely tested or used at sea, its basic validity established the theoretical and practical credentials of magnetic philosophy.

Gilbert conducted similarly impressive investigations of magnetic variation. That compass needles rarely pointed true north was known to Europeans from the fourteenth century. Data gathered by 1600 had made the cause and geographical distribution of this bane of navigators into a major problem. Gilbert presented persuasive, though not reliably replicable, experiments using terrellae with prominences and depressions that modelled continents and oceans. These also generated variation, the needle seemingly attracted slightly away from the poles towards the ‘continents’. Gilbert concluded that variation was an artefact of geology, of the earth's slight departures from a perfect, homogeneous magnetic sphere. While only partially correct, it was the first convincing explanation, and it accorded with the empirical survey of variation published by Stevin in 1599. Gilbert's magnetic philosophy gave new and scientifically rigorous direction to Stevin's and other late sixteenth-century proposals for a solution to the longitude problem using compass observations. This, together with magnetic latitude finding, was a compelling practical reason for interest in Gilbert's work. Research into magnetic position finding continued for over a century, even after 1635 when a follower of Gilbert's, the Gresham professor Henry Gellibrand, presented evidence that variation changed over time. The inference was soon drawn that the earth's magnetic poles were separate from the geographical poles, and rotating around them.

Gilbert had rejected the theory of separate poles, because his magnetic astronomy required the earth's axis of rotation to be magnetically stabilized. Consequently, he interpreted variation as a circular motion away from true north. It was one of five magnetic motions. Dip was another, as was the basic rotation of any small magnet into alignment with the field of a larger one. The primary motion was the attraction of one magnet for another, although Gilbert coined the term ‘coition’ as a better description of the mutual interaction by which two magnets come into contact. He observed ‘attraction’ (he claimed never to see repulsion) using two magnets in water on floats, when they do appear to circle each other as if in a mating ritual.

These four ‘circular’ motions made more credible Gilbert's claim to a fifth magnetic rotation—that of the whole earth. Unlike Maricourt, Gilbert explicitly denied that he had seen carefully suspended terrellae imitate the earth's diurnal motion. Nevertheless, from the other four observable circular motions, he inferred that the earth's substance was capable of natural rotation, a possibility denied by Aristotelians and other geostatic astronomers. For Gilbert, the immateriality of the earth's magnetic virtue further confirmed that it did actually perform planet-like rotations.

De mundo

The posthumous compilation of the five books of De mundo means that it cannot be established when Gilbert wrote or revised their elements, or if he intended to publish them. Notwithstanding, the first two books comprise a ‘Physiologia nova contra Aristotelem’ (‘A new natural philosophy in opposition to Aristotle’) that is for the most part organized, polished, and built upon De magnete. Arranged according to scholastic natural philosophical topics (the four elements, qualities, place, light, the earth, moon, other heavenly bodies and their motions, etc.), it forms a complete natural philosophy in the same genre as Patrizi's. Gilbert developed his explanations of magnetism and electricity into a theory of sublunary matter that replaced the four elements with true magnetic earth and compounds of aqueous and oily humours. In his cosmology the magnetic virtues of the earth and moon, together with other specific planetary virtues, were excited by the sun's luminous virtue into harmonious Copernican orbits. A diagram, as deliberately ambiguous as his writings, strongly suggested that the earth moved in an empty, infinite universe. Because Gilbert concluded that the moon, as the earth's satellite, was also magnetic, he was especially interested in it: De mundo included the first map of the moon. Gilbert also proposed that the earth's tides were caused by the moon's magnetic attraction of water. In this, and in his general theory that the attractive power of the earth's and other virtues decreased with distance, his dynamic theory of cosmic attractions anticipated Newton's gravitational solution. Kepler freely acknowledged that it underpinned his magnetic explanation of the elliptical planetary orbits he discovered. But Gilbert believed that the complex interactions of the solar and planetary virtues would defeat mathematicians. This helps to explain why Gilbert maintained the conservative view that astronomers, even Copernicus, did not plot real orbits.

The most puzzling aspect of De mundo is its almost total lack of new experiments, experimental reasoning, instruments, and practical knowledge, especially practical mathematics—features that made De magnete impressively novel. One hypothesis is that Edward Wright ensured their prominence in De magnete. Mark Ridley wrote that Wright had admitted an editorial role, and authorship of parts of De magnete dealing with the mathematics and use of the dip instrument. Ridley also confided that Gilbert needed help with astronomy from a Joseph Jessop. It might be that the philosophical De mundo was the book that Gilbert wanted to write, while the influential combination in De magnete of theory and practice, natural philosophy and mathematics, was the synthesis of two men, sympathetic to each other's interests, but working in different disciplines.

De mundo's last three books make up a ‘Nova meteorologia contra Aristotelem’ (‘A new meteorology in opposition to Aristotle’). This too is organized around scholastic topics derived from Aristotle's own Meteorology. Gilbert discusses winds, rivers, and seas (the phenomena of elemental air and water that control the weather) as well as conventionally ‘aerial’ phenomena such as rainbows, shooting stars, and comets, in comparatively conventional ways. It declines into fragments. The ‘New meteorology’ does, however, afford some clues to the development of Gilbert's ideas. Dated weather observations suggest that in the late 1560s Gilbert had begun to seek new, anti-Aristotelian causes of the weather and its astrological correlation with planetary positions. The ‘New meteorology’ was most likely composed in the early 1580s and, while there are no references to magnetic experiments or compass observations, Gilbert did mention his big idea of the earth as a magnetic sphere. It may have originally occurred to him as a substitution for Maricourt's heavenly magnetic sphere. Wright claimed in his ‘laudatory address’ at the beginning of De magnete that Gilbert had held back his magnetic philosophy for eighteen years. This may refer to a prolonged period of experimental research and proofs, and collation of navigational data. Barlow wrote in 1597 that Gilbert ‘many years hath laboured in the consideration of the properties of that [lode] Stone’ (Barlow, The Navigators Supply, sig. C3r).

Last years

Between 1600 and his death Gilbert collaborated with grateful practical mathematicians to ensure that navigation was enhanced by his magnetic science. In 1602 Blundeville published a tract introducing English seamen to latitude-finding using a dipmeter sent to him by Gilbert. Tables calculated by Henry Briggs, the first professor of geometry at Gresham College, were appended by Wright, purportedly at Gilbert's suggestion. Gilbert also corresponded with Barlow, who, in order to establish his own credentials as a magnetic philosopher, published Gilbert's only surviving letter, which contained some praise of him. Gilbert told Barlow of his continuing magnetic research, a proposed addition to De magnete, and his receipt of a letter from Giovanni Sagredo, the Venetian friend of Galileo, who ‘reporteth wonderfull liking of my booke’ (Barlow, Magneticall Advertisements, appx).

This is the only evidence that Gilbert was aware before his death of the excitement De magnete was stimulating among continental philosophers. The English exile Nicholas Hill was the first to publish support for Gilbert's magnetic Copernicanism in 1601. In January 1603 Kepler wished he ‘had wings with which to travel to England to confer with him. I certainly think I can demonstrate all the motions of the planets with these same principles’ (J. Kepler, Gesammelte Werke, 1938, 14.352). The last generation of occult philosophers like Robert Fludd and Athanasius Kircher also used De magnete in doomed defences of a rational and experimental basis to magic.

Kepler's and Galileo's use of Gilbert's principles in their promotion of Copernicanism ensured that the cosmological aspects of De magnete were seriously discussed in the seventeenth century. Magnetic Copernicanism was controversial, and divided Gilbert's erstwhile colleagues Barlow and Ridley, who vied to communicate Gilbert's ideas in English. While Ridley was even more radical than his mentor, the clergyman Barlow admitted that only his respect for Gilbert's work had restrained him from theological criticism of the cosmology. After 1628, when pirate editions of De magnete first appeared, the most prolific magnetic philosophers were Catholic philosophers in the Society of Jesus, who were determined to harness magnetic science to their defence of the earth's immobility. Some surviving copies of De magnete have the Copernican book 6 mutilated or missing, according to the Roman inquisition's censorship practices, and Gilbert was cited as a perverse heretic in its prosecution of Galileo. The charge was not based on any particular knowledge. However, De mundo expanded upon Gilbert's hints in De magnete that theologians held primary responsibility for the erroneous state of contemporary natural philosophy. This was particularly true of the doctrine of solid celestial spheres which, in Gilbert's opinion, had begun as astronomers' calculating devices, had been given a spurious solidity by Aristotle, and was turned into virtual articles of faith by theologians. He wrote that ‘the theologians will cry out that I am impious and irreligious, but I show them to be insane and foolish, who defend this opinion borrowed from the Peripatetics’ (Gilbert, De mundo, 239).

According to his stepbrothers' inscription, Gilbert died on 30 November 1603: his will was proved on 3 December. He probably died in the severe plague epidemic in London that year. Sir Michael Hicks, the Cecils' secretary, recorded how, on 6 December 1603:
I heard as I was writing hereof that Doctor Gilbert, the physician, is dead, who was my neighbor at St. Peter's Hill. He was a learned physician, and an honest. The sickness is greatly decreased in London, and the citizens do return daily in great numbers. (Roller, 90)
He died a wealthy man. He bequeathed, mainly to Ambrose and William, his stepbrothers, nine houses with lands attached, five lots of real estate, and other tenements and leases. William junior also inherited his ‘heade house’ in Colchester, almost certainly the Tudor mansion called ‘Tymperley's’ that is now a Colchester museum. He passed Wingfield House to his sister Agnes, wife of William Smith (TNA: PRO, PROB 11/102, fol. 408rv). In 1646 it was purchased for £500 as a hall for the Worshipful Company of Upholders, and was destroyed in the fire of 1666. Fittingly, Crane Court, the future home of the Royal Society, was erected on the site. More seriously for Gilbert scholars, the fire also claimed the College of Physicians, to which Gilbert had bequeathed ‘all my bookes in my Librarye, my Globes, and Instrumentes, and my cabinet of myneralles’. The collection must have been substantial, because Gilbert willed £6 to cover their relocation to the college, almost as much as his bequest for a dinner for its fellows.


Gilbert has remained a heroic figure through many changes of fashion in the history and philosophy of science. To an early fellow of the Royal Society like Sir Christopher Wren he was, with Galileo, the liberator of natural philosophy from Aristotelianism. With the rise of positivism in the early nineteenth century William Whewell and others read him as the pioneer of an inductive experimental method who thereby founded the modern sciences of magnetism and electricity. This interpretation, which persists, struggles to explain his broader concern with natural philosophy and cosmology. Some analysts have attempted unsuccessfully to separate his ‘modern’ experimentalism from his ‘medieval’ speculation, although the Marxist historian Edgar Zilsel argued well that he was indebted to progressive craftsmen for his experimental method. By the 1960s the popularity of the ‘hypothetico-deductive’ school of scientific method saw Gilbert and his cosmological theories claimed as exemplary by this philosophical school too. In the early twenty-first century, historians are less confident of finding the origins of modern science in Gilbert's era, and have begun to locate him as a man of his time and place in the Elizabethan metropolis, and to explore his relationship with Renaissance magic. Our concern with context, however, should not obscure the revolutionary impact of Gilbert's magnetic experiments, hypotheses, and navigational applications. John Dryden, praising ‘th' asserters of free reason’, was half right when he versified in 1663 that
Gilbert shall live till loadstones cease to draw,
Or British fleets the boundless ocean awe.
(Gilbert, De magnete, xxvii)

Stephen Pumfrey


D. H. D. Roller, The ‘De magnete’ of William Gilbert (1959) · S. Pumfrey, ‘William Gilbert's magnetic philosophy, 1580–1684: the creation and dissolution of a discipline’, PhD diss., U. Lond., 1983 · S. Pumfrey, Latitude & the magnetic earth (2002) · S. Kelly, The ‘De mundo’ of William Gilbert (1965) · W. Gilbert, De magnete, trans. P. F. Mottelay (New York, 1958) · W. Gilbert, De mundo nostro sublunari philosophia nova (1651) · S. P. Thompson, ‘The family and arms of Gilbert of Colchester’, Transactions of the Essex Archaeological Society, new ser., 9 (1903–6), 197–211 · Munk, Roll · The letters of John Chamberlain, ed. N. E. McClure, 2 vols. (1939) · M. Ridley, Magneticall animadversions made by Mark Ridley, doctor in physicke, upon certain magneticall advertisements, lately published, from Maister William Barlow (1617) · W. Barlow, The navigators supply: conteining many things of principall importance belonging to navigation (1597) · W. Barlow, Magneticall advertisements (1616) · W. Barlow, A breife discovery of the idle animadversions of Marke Ridley doctor in phisicke, upon a treatise entituled, ‘Magneticall advertisements’ (1618) · CSP dom., 1595–1601; 1603–10 · Fuller, Worthies (1662) · Venn, Alum. Cant. · Wood, Ath. Oxon., new edn, vol. 1 · J. F. Houston, Featherbedds and flock bedds: notes on the history of the Worshipful Company of Upholders of the City of London (1993), pt 2


BL, Royal MS 12 F XI


A. A. Hunt, oils, c.1900, Colchester town hall, Essex · F. Daniell, oils, c.1902, Colchester town hall, Essex · L. J. Watts & Co.?, marble statue, c.1902, Colchester town hall, Essex · R. Clamp, stipple (after Harding, after unknown artist, 1591), NPG [see illus.] · Clamp?, engraving (after seventeenth-century portrait, now lost), repro. in Gilbert, De magnete, frontispiece · statue, St John Cam.

Wealth at death  

substantial: will, Houston, Featherbedds and flock bedds