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Gilbert, William

Gilbert, William

(b Colchester, Essex, England, 1544; d. London, England, 30 November 1603)

Magnetism, electricity.

Gilbert was born into a rising, middle-class family that had only recently acquired its well-to-do status. His great-grandfather, John Gilbert, had married Joan Tricklove, the only daughter of a wealthy merchant from Clare, Suffolk. Their son, William Gilbert of Clare, became a weaver and eventually sewer of the chamber to Henry VIII. This William married Margery Grey, and among their nine children was Jerome Gilbert. Jerome, who had some knowledge of law, moved from Clare to Colchester in the 1520’s became a free burgess and recorder there, and married Elizabeth coggeshall. The oldest of their five children was William Gilbert of Colchester. After Elizabeth’s death Jerome married Jane Wingfield, and after her death he married a third time. Little is known of this third marriage other than that the woman’s name was Margery.

Nothing is known of Gilbert’s early life and education. In May 1558 he was matriculated as a member of St. John’s College, Cambridge, where he received his A. B. 1n 1561, his M.A. in 1564, and his M.D. in 1569. During this time he was appointed pensioner (1558), fellow of Mr. Symson’s foundation (1561), mathematical examiner of St. John’s College (1565 and 1566), and senior bursar (1569 and 1570). Seven months after receiving his M. D. he was elected a senior fellow of his college.

Frequently writers have stated that after receiving his doctor’s degree, Gilbert went abroad to study. This is possible, but evidence for it is lacking; nothing is known of his life from the time he left Cambridge until he settled in London sometime in the mid-1570’s. There he practiced medicine, obtained a grant of arms in 1577, and sometime before 1581 became a member of the Royal College of Physicians. By 1581 Gilbert was one of the prominent physicians in London, and for the rest of his life he was consulted by influential members of the English nobility. In 1600 he became physician to Elizabeth I and after her death was appointed physician to James I.

While in London, Gilbert was active in the Royal College and held several offices in that organization. In 1588 he was one of the four College physicians requested by the Privy Council to care for the health of the men in the Royal Navy. In 1589 he was assigned the topic “Philulae” for the College’s Pharmacopoeia, and later in that year and again in 1594 he was mentioned among the examiners for this book on drugs. From 1582 on, Gilbert was an officer of the College and held the following positions; censor (1582, 1584–1587, 1589–1590); treasurer (1587–1594, 1597–1599); consiliarium (1597–1599); elect (1596- 1597). In 1600 he was elected president.

Gilbert never married. He lived in London at Wingfield House (presumably a legacy from his stepmother), St. Peters Hill. The house served as a laboratory but probably was not, as is sometimes stated, a center for the meetings of a ’scientific, group. Little is known about Gilbert’s life in London, for upon his death, presumably from the plague, he left his books, instruments, globes, and minerals to the Royal College of Physicians for their library. The Royal College, with its library, and Wingfield House were destroyed by the Great Fite in 1666.

Sometime during his life, presumably in the decade following his years at Cambridge, Gilbert studied magnetic phenomena. The results of these studies were published in 1600 under the title De magnete, magneticisque corporibus, et de magno magnete tellure; physiologia nova, plurimis & argumentis, & experimentis demonstrata. The book was an attempt to explain the nature of the lodestone and to account for the five movements connected with magnetic phenomena. It was well received both in England and on the Continent and was republished in 1628 and again in 1633.

Gilbert’s other writings were not published until almost half a century after his death. His younger half brother, William Gilbert of Melford, collected and possibly edited his brother’s papers and presented them, under the title De mundo nostro sublunari philosohia nova, to Prince Henry of England. Francis Bacon and Thomas Harriot were both acquainted with these writings, which were published at Amsterdam in 1651. The De mundo is, in part, an extension of the cosmological ideas Gilbert introduced in the last section of the De Magnete; it is dependent on the latter work for much of its vocabulary and basic assumptions but lacks its finish and completeness. It is Gilbert’s, work in the De magnete that gives him a place in the history of science.

During the fifteenth century the widespread interest in navigation had focused much attention on the compass. Since at that time the orientation of the magnetic needle was explained by an alignment of the magnetic poles with the poles of the celestial sphere, the diverse areas of geography, astronomy, and phenomena concerning the lodestone overlapped and were often intermingled. Navigators had noted the variation from the meridian and the dip of the magnetic needle and had suggested ways of accounting for and using these as aids in navigation. The connection between magnetic studies and astronomy was less definite; but so long as the orientation of the compass was associated with the celestial poles, the two studies were interdependent to some extent. There were suggestions in Thomas Digges and Nicolas Rymers that perhaps the magnetic property was somehow innate in the earth, but these were slight hints or passing remarks. Gilbert provided the only fully developed theory dealing with all five of the then known magnetic movements and the first comprehensive discussion of magnetism since the thirteenth century Letter on the Magnet of Peter Peregrinus.

Gilbert divided his De magnete books. The first deals with the history of magnetism from the earliest legends about the lodestone to the facts and theories known to Gilbert’s contemporaries. The nature, properties, and behavior of the lodestone are discussed and ways, of demonstrating them are suggested. Throughout the book Gilbert marked his own discoveries and experiments with asterisks; larger symbols were used for the more important discoveries and experiments, smaller asterisks for the less important ones. In the last chapter of book I, Gilbert introduced his new basic idea which was to explain all terrestrial magnetic phenomena: his postulate that the earth is a giant lodestone and thus has magnetic properties. The assertion is supported by a comparison of the earth and a lodestone (each has poles and an equator; each draws objects to itself), by an appeal to experience (lodestones are found in all parts of the earth; iron, the prime magnetic substance, lies deep within the earth), by a denial of the Aristotelian elements (elemental earth has never been found), and by ’Gilbett’s repeated statements that this new idea is so.

The remaining five books of the De magnete are concerned with the five magnetic movements: coition, direction, variation” declination and revolutian. Before he began his discussion of coition, however, (Gilbert carefully distinguished the attraction due to the amber effect from that caused by the lodestone. This section, chapter 2 of book II, established the study of the amber effect as a discipline separate from that of magnetic phenomena, introduced the vocabulary of electrics, and is the basis for Gilbert’s place in the history of electricity.

Gilbert’s distinction between magnetic phenomena and the amber effect was based upon the difference between their causes. He used a material cause to explain the amber effect and a formal one for magnetic attraction. That is, substances which had been formed from the fluid and humid matter in the earth would, after they had become solid, behave as amber does when it is rubbed. Gilbert’s explanation was that the fluidity was never completely lost, and thus such substances emitted an effluvium which seized small particles and pulled them inward. Magnetic materials were those substances which shared in the specific, primary form of the earth. This form, implanted in the globe by the Creator, gave the earth its magnetic property. All parts of the earth which maintained a principal share in this form, i.e., lodestones and iron, were magnetic bodies. Unlike the electrics, magnetics did not depend on the emission of effluvia to draw bodies to themselves.

Having distinguished the magnetic and amber effects, Gilbert presented a list of many substances other than amber which, when rubbed, exhibit the same effect. These he called electrics. All other solids were nonelectrics. To determine whether a substance was an electric, Gilbert devised a testing instrument, the versorium. This was a small, metallic needle so balanced that it easily turned about a vertical axis. The rubbed substance was brought near the versorium. If the needle turned, the substance was an electric; if the needle did not turn, the substance was a nonelectric.

After disposing of the amber effect, Gilbert returned to his study of the magnetic phenomena. In discussing these, Gilbert relied for his explanations on several assumptions: (1) the earth is a giant lodestone and has the magnetic property; (2) the magnetic property is due to the form of the substance; (3) every magnet is surrounded by an invisible orb of virtue which extends in all directions from it; (4) pieces of iron or other magnetic materials within this orb of virtue will be affected by and will affect the magnet within the orb of virtue; and (5) a small, spherical magnet resembles the earth and what can be demonstrated with it is applicable to the earth. This small spherical magnet he called a terrella.

Gilbert was more negative than positive in his assertions about the form which accounts for the magnetic property. He tried to distinguish it from the commonly accepted forms of his time . Thus he denied that this form was the formal cause of Aristotle’s four causes, or the specific cause alchemists associated with mixtures, or the secondary form of the philosophers, or the propagator of generative bodies. Yet when he attempted to describe or define this form, he could assert only that there is a primary, radical, and astral form that is unique to each body and that orders its own proper globe; for the earth this form was the anima of the earth and was associated with the magnetic property.

One of the effects of this primary form was the surrounding of the magnetic body with an orb of virtue. The orb extended in all directions from the body, and its extent and strength depended on the perfection and purity of the magnetic body. Magnetics within the orb would be attracted to the body; those outside would be unaffected. Thus Gilbert used this orb to eliminate the necessity for attraction at a distance in regard to the magnet just as he had used the effluvium in his explanation of the amber effect. Yet he was unable or unwilling to account for the magnetic effect solely in terms of substance, as he had done for the electrics. The primary form, once accepted, went beyond a material explanation and so, for Gilbert, provided another essential difference between the two phenomena. Once this was established as a fundamental part of his theory, he was free to discuss the five magnetic movements.

In discussing coition Gilbert was careful to distinguish magnetic coition from other attractions. For him magnetic coition was a mutual action between the attracting body and the attracted body. At the beginning of the De magnete he explained several terms that were necessary for understanding his work. One of these was “magnetic coition,” which he said he “used rather than attraction because magnetic movements do not result from attraction of one body alone but from the coming together of two bodies harmoniously (not the drawing of one by the other)” (P. Fleury Mottelay, William Gilbert of Colchester ... on the Great Magnet of the Earth [Ann Arbor, 1893], p. liv).

The coition occurred only if the bodies were within the orb of virtue of the magnet, and the action was dependent upon the size and purity of the magnet and the object. Larger and purer magnets were stronger than smaller and less pure ones. The removal of part of a lodestone would weaken it, while the addition of an iron cap would strengthen the orb of virtue.

Book III of the De magnete contains Gilbert’s explanation of the orientation taken by a lodestone that is balanced and free to turn, that is, the behavior of the magnetic compass. Since the earth was a giant lodestone, it was surrounded by an orb of virtue; and magnetic substances within this orb behaved as they did in the orbs of small magnets. Thus the orientation of the compass was simply an alignment of the magnetic needle with the north and south poles of the earth. Gilbert gave numerous demonstrations of this with the terrella as well as directions for magnetizing iron.

By the end of the sixteenth century, navigators were well acquainted with variations from the meridian in the orientation of the compass. Thus, after discussing orientation, Gilbert turned in book IV to the variations in that orientation. Here he again used the comparison of the phenomena that can be demonstrated with the terrella and those that occur on the surface of the globe. Just as a very small magnetic needle will vary its orientation if the terrella on which it is placed is not a perfect sphere, so will the compass needle vary its orientation on the surface of the earth according to the proximity or remoteness of the masses of earth extending beyond the basic spherical core. Also, the purity of these masses (the amount of primary magnetic property retained by them) will affect the orientation of the compass just as stronger lodestones have greater attractive powers than weaker ones.

The next magnetic movement that Gilbert discussed was declination, the variation from the horizontal. This phenomenon had been described by Robert Norman in his book on magnetism, The New Attractive (1581). Although Norman had also given an effective means of constructing the compass needle so that it would not dip but would remain parallel to the horizontal, he had made no attempt to account for this strange behavior. As with the other magnetic effects of the compass, Gilbert explained declination in terms of the magnetic property of the earth and the experiments with the terrella. The small needle placed on the terrella maintained a horizontal position only when placed on the equator. When moved north or south of this position, the end of the needle closer to one pole of the terrella dipped toward that pole. The amount of dip increased as the needle was moved nearer the pole, until it assumed a perpendicular position when placed on the pole. A compass on the earth, according to Gilbert, behaved in a similar manner.

In discussing the variations from the meridian and the horizontal, Gilbert suggested practical applications of his theory. Navigators of the period were concerned with determining the longitude and latitude of their positions on the open seas. Since the deviation from the meridian was constant at a given point, Gilbert thought that if the seamen would record these variations at many points, an accurate table of variation for various positions could be compiled and the problem would be solved. He included detailed instructions for the construction of the instruments necessary for this task.

Gilbert thought that the variations from the horizontal could be obtained by means of experimentation with the terrella, since the dip depended on the position of the needle between the equator and the pole rather than on the configuration of the surface of the magnet. He does not seem to have had much data from navigators in this regard, as he did concerning the variation from the meridian, and was satisfied with his theoretical considerations.

The final book of the De magnete, book VI, deals with rotation and in this section Gilbert expounded his cosmological theories. Without discussing whether the universe is heliocentric or geocentric, Gilbert accepted and explained the diurnal rotation of the earth. From the time of Peter Peregrinus’ Letter on the magnet, written in the thirteenth century, rotation had been considered one of the magnetic movements. The assumption was that a truly spherical, perfectly balanced lodestone, perfectly aligned with the celestial poles, would rotate on its axis once in twenty-four hours. Since the earth was such a lodestone, it would turn upon its axis in that manner and thus the diurnal motion of the earth was explained. The theory was taken from Peter’s Letter; the application to the earth was a Gilbert’s addition.

In advancing his theory Gilbert denied the existence of the solid celestial spheres, stated that the fixed stars were not equally distant from the earth, and accounted for the precession of the equinoxes and the tides in terms of the magnetic property of the earth. These statements were in general weakly, if at all, supported and were not well developed. Much of the criticism directed by Bacon and others against Gilbert’s writing was based upon the sixth book of the De magnete, where Gilbert extended to the cosmos his magnetic theory and the results obtained from his experiments.

Throughout the De magnete, Gilbert discussed and usually dismissed previous theories concerning magnetic phenomena and offered observational data and experiments which would support his own theories. Most of the experiments are so well described that the reader can duplicate them if he wishes, and the examples of natural occurrences which support his theory are well identified. Where new instruments are introduced (for example, the versorium, to be used in identifying electrics), directions for their construction and use are included. The combination, a new theory supported by confirming evidence and demonstrations, is a pre-Baconian example of the new experimental philosophy which became popular in the seventeenth century.

Gillbert’s other writings, those in the De mundo, do not follow this pattern. When the younger William Gilbert collected his half brother’s papers for presentation to Prince Henry and eventual publication, he divided them into two sections. The first of these, “Physiologiae nova contra Aristotelem,” is an expansion of the cosmology of the De magnete; the second, “Nova meterorologia contra Aristotelem,” follows the general pattern of Aristotle’s Meteorology. There is nothing in the two works to indicate that William Gilbert of Colchester considered the two to be one work. Internal evidence indicates that the “Nova meteorologia” was written during the 1580’s and left unfinished, while the “Physiologia nova” must have been written after the early 1590’s Also, since it is assumed in the “Physiologia nova” that the reader is familiar with the content of the De magnete, it appears that much of this work was written after the major portion of the De magnete was completed.

At the beginning of the “Physiologia nova” Gilbert denied the existence of the four terrestrial elements—earth, water, air, and fire—and replaced them with one element, earth. This earth was the one substance from which all terrestrial bodies were made; its primary attribute was its magnetic property; solids not exhibiting this property were degenerate forms of the element; and moist fluid substances on the earth were effluvia of this basic element. The surface of the globe consisted primarily of these degenerate forms and effluvia. The lodestones and iron were purer forms of this one element.

Gilbert also postulated a similar structure for all of the heavenly globes. Each consisted of a substance with a primary form and effluvia surrounding it. He then placed a void between the effluvia from one globe and that from the next. While the general scheme was the same for all, each globe or type of globe had its own distinguishing characteristics. Gilbert gave a more detailed description of the moon than of any other celestial body. This “Companion of the Earth,” as he called it, was described as a miniature earth and possessed seas, continents, and islands. These Gilbert named and charted; the lighter parts of the moon were assumed to be bodies of water, the darker parts land masses. Since the moon was within the orb of virtue of the earth, there was a mutual attraction between the two bodies. Because the earth was larger, it held the moon in its power and thus the moon revolved around it. The lesser effect of the moon on the earth was seen in the tides.

The sun was designated as the center for the orbits of the five wandering stars and was the cause of motion for all the globes within its orb of virtue. Although the earth was located within this orb, Gilbert excluded it from those bodies affected by the sun. There are indications that he considered the planets to be earthlike bodies with continents and seas, but this was never definitively stated. The fixed stars were placed in the same category as the sun, the light-giving bodies, while moon, planets, and earth belonged to the group of light-reflecting bodies. The causes for the differences were not stated.

From the structure of the earth and the other globes, Gilbert moved to the structure of the universe. While he repeated his belief, expressed in the De magnete, that the earth had a diurnal rotation and that the fixed stars were not all equally distant from the earth, and while he discussed the motions of the earth according to Copernicus and Giordano Bruno, he did not affirm or deny the heliocentric system. At tines he dismissed the system as not pertinent to the topic he was discussing; at other times he indicated that it would be taken up in another place. Gilbert dismissed the third motion described in the De revolutionibus as “no motion.” This treatment of the motions of the earth is only one of the many indications that the De mundo was left in a fragmentary state.

Scattered throughout the latter part of the “Physiologia nova” are references to and statements about spices, twilight, putrefaction, the polarity of magnets, the buoyancy of a leaden vessel, the comparative densities of solid and liquid forms of the same substance, and light. All of these are mere statements or partial discussions. It seems as if the younger William Gilbert included everything he found, regardless of its relevance to the rest of the papers or its internal completeness.

The second part of the De mundo, the “Nova meteorologia,” contains Gilbert’s discussion of comets, the Milky Way, clouds, winds, the rainbow, the origin of springs and rivers, and the nature of the sea and tides. Most of these are summaries of other theories with Gilbert’s ideas interspersed among them.

Comets, Gilbert considered, could be either above or below the moon. They were wandering bodies without polarity and with uncertain paths. He listed the various positions the vapor of a comet might take but said nothing about the centers of comets or the causes of their motions.

Several theories and mythological explanations for the Milky Way were reviewed and denied by Gilbert; then the hypothesis that the Milky Way is a collection of stars so numerous and so far from the earth as to appear to be a mist or cloud was given but was neither accepted nor denied. The section ends with a suggestion that the reader look at the Milky Way through a “specillis.” The instrument is not described, and it is uncertain whether Gilbert meant a lens, a small mirror, or some other instrument.

Clouds, in Gilbert’s meteorology, were exhalations and effluvia from the earth which rose to varying heights according to the density of their content. Some methods were given for estimating the heights of clouds, but there was little new information in this section.

Like the clouds, winds were part of the effluvia of the earth. They were described as expanding and swollen exhalations which escaped from the interior of the earth in search of more room in the region above the earth. The specific properties of any wind were determined by the location and circumstances of its origin and also by the positions of various stars at the time. Gilbert mentioned a “Table of Winds” he had composed, but this table was missing from the manuscript used for the printed edition. The editor inserted the table from Francis Bacon’s “Historia ventorum,” but since Bacon had four secondary winds and Gilbert mentioned five, it is unlikely that the two tables were similar.

In the section on the rainbow Gilbert included elaborate drawings showing the position and colors of both primary and secondary rainbows and the conditions necessary for the rainbow to be visible; he discussed the necessity for moisture, a dense object, and proper conditions in the air for the rainbow and digressed a little on the subject of mirror images. Again all the explanations are general and incomplete.

The last part of the “Meteorologia” concerns water phenomena—springs, rivers, the sea, and tides. Gilbert considered water to be a humor from the earth, and the motions of springs and rivers were explained in terms of water returning to its source; the tides were the results of the combined actions of the diurnal motion of the earth and the magnetic coition between the earth and the moon.

Throughout the “Nova meteorologia” Gilbert included numerous examples of specific instances of the phenomena he was describing. Some of these observations were his own, some he had received from others. There is an indication of an interest in astrology and, as in the De magnete, a concern for observational data to support his ideas. It appears that at one time Gilbert planned a detailed study of meteorology that would replace the existing theories, but he never completed the project.

The De mundo did not have the influence of the De magnete, since Gilbert’s cosmology was less acceptable than either his magnetic theory or his electric theory. Gilbert’s contemporaries generally praised the earlier work both for its content and for its methodology, and the idea of the earth’s magnetism was incorporated into arguments for the support of the Copernican theory. Johann Kepler tried to use Gilbert’s magnetic theory, with its orb of virtue, as a motive force for his astronomical theory but needed so many ad hoc postulates to do so that others found this use of magnetism unacceptable. Kepler also expressed interest in seeing Gilbert’s theory of the void in the De mound, but we do not know whether he did so.

Certainly the De magnete was the far more influential of Gilbert’s books. The theory of the magnetic orb of virtue and the explanation of the amber effect in terms of an emitted effluvium provided mechanistic explanations for these phenomena and a starting point for the study of the two disciplines in the following centuries.


I. Original Works. Gilbert’s writings are De magnete, magneticisque corporibus, et de magno magnete tellure; physiologic nova, plurimis & argumentis, & experimentis demonstrata (London, 1600), Eng. trans., P. Fleury Mottelay,William Gilbert of Colchester ... on the Great Magnet of the Earth (Ann Arbor, 1893); and De mundo nostro sublunari philosophia nova, collected by his half brother, William Gilbert of Melford (Amsterdam, 1651).

II. Secondary Literature. On Gilbert or his work, see Suzanne Kelly, The De mundo of William Gilbert (Amsterdam, 1965); and Duane H. D. Roller, The De magnete of William Gilbert (Amsterdam, 1959).

Suzanne Kelly

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Gilbert, William (1544–1603)


GILBERT, WILLIAM (15441603), English scientist and physician. Gilbert is best known for his revolutionary theories on magnetism, published in his book De Magnete (or De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure ; On the loadstone and magnetic bodies, and on the great magnet the Earth) in 1600. Remarkably little is known of Gilbert's life. Born in Colchester to a prosperous magistrate, he received a B.A. from Cambridge University in 1561, an M.A. in 1564, and an M.D. in 1569. By the mid-1570s, he was practicing medicine in London, where he became a member of the Royal College of Physicians (and was elected president of the group in 1600). There, he also came into contact with navigators, compass makers, and practical mathematicians, and pursued his research on magnetism. In his successful medical practice, he was consulted by members of the aristocracy, was appointed as one of Elizabeth I's personal physicians (16001603), and, after her death in 1603, served as James I's physician until a plague epidemic that November took his own life.

Navigational accuracy assumed greater importance with the overseas explorations by the Spanish and Portuguese in the fifteenth century, and during the sixteenth century Dutch and English navigators compiled observations that were of significant use to Gilbert. It was not lost on Gilbert or his contemporaries that discoveries about magnetism would be politically and commercially useful. Despite the widespread use of nautical compasses on Spanish, English, Dutch, and French ships, none of his contemporaries understood why compass needles behaved as they did: attraction, repulsion, variation, dip, bipolarity, and the discovery of latitude were recognized empirically, but poorly understood. Through his experiments on magnets and magnetic bodies (especially the lodestone, that is, naturally magnetized iron ore), Gilbert methodically investigated a wide range of magnetic behaviors.

In fact, Gilbert's book went far beyond being a useful navigational treatise, and represented the first comprehensive analysis of magnetism, featuring a revolutionary new theory about the Earth's magnetic force. In formulating his views, Gilbert insisted on using his own empirical data rather than relying on past scientific authorities. His book is full of carefully contrived laboratory experiments that he urged his readers to replicate. He assailed credulous acceptance of myths (such as the power of a magnet to detect adultery), rejected Aristotelian explanations, and invented his own language to describe magnetic phenomena, including the terms electricity, electric force, electric attraction, and magnetic pole. To explain the phenomena he investigated, he concluded that the Earth was alive with magnetic potency or force, and he likened this to sexual attraction. Hence, for him, magnetism was an immaterial, innate force operating in the universe, with occult and vital properties.

The stunning claim of Gilbert's book was that the Earth behaves in the heavens as a spherical magnet does on earth. He based this assertion on his experiments with spherical magnets and on his deduction that the Earth itself was a giant spherical magnet. Reasoning by analogy, he stated boldly that the Earth rotated daily on its own axis by its magnetic power, just as a perfectly spherical lodestone aligned with the Earth's poles would spin on its axis. Declaring himself an adherent of astronomer Nicolaus Copernicus (14731543), whose theory about the Earth's rotation around the heavens had been published in 1543, Gilbert added new magnetic arguments to the arsenal of the Copernican polemic.


Subsequent natural philosophers including Francis Bacon (15611626) and Galileo Galilei (15641642) hailed Gilbert's handling of empirical and experimental evidence, and others applauded his rejection of Aristotle's erroneous ideas about physics and astronomy. Johannes Kepler (15711630) and Sir Isaac Newton (16421727) pondered Gilbert's magnetic forces before devising their own physical explanations of astronomical motions. And, although many parts of Gilbert's new magnetic theories were soon rejected, including his analogy of the Earth and the spherical lodestone, he is still acknowledged for some of his discoveries about electricity and magnetism (such as the distinction between magnetic and static electricity), and for correctly recognizing that the fixed stars are not all the same distance from the earth.

See also Astronomy ; Bacon, Francis ; Copernicus, Nicolaus ; Exploration ; Galileo Galilei ; Kepler, Johannes ; Newton, Isaac ; Shipbuilding and Navigation.


Gilbert, William. On the Loadstone and Magnetic Bodies, and on the Great Magnet the Earth. Translated by P. Fleury Mottelay. New York, 1958.

Pumfrey, Stephen. Latitude and the Magnetic Earth. Cambridge, U.K., 2002.

Roller, Duane H. D. The De Magnete of William Gilbert. Amsterdam, 1959.

Martha Baldwin

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William Gilbert

William Gilbert

The English physician and physicist William Gilbert (1544-1603), an investigator of electrical and magnetic phenomena, is principally noted for his "Demagnete," one of the first scientific works based on observation and experiment.

William Gilbert was born in Colchester, Suffolk, on May 24, 1544. He studied medicine at St. John's College, Cambridge, graduating in 1573. Four years later he began practicing in London. He was prominent in the College of Physicians and became its president in 1599. The following year he was appointed physician to Queen Elizabeth I, and a few months before his death on Dec. 10, 1603, physician to James I.

In 1600 Gilbert published De magnete (On the Magnet, on Magnetic Bodies, and Concerning That Great Magnet, the Earth: A New Physiology), in Latin. The first major scientific work produced in England, it reflected a new attitude toward scientific investigation. Unlike most medieval thinkers, Gilbert was willing to rely on sense experience and his own observations and experiments rather than the authoritative opinion or deductive philosophy of others. In the treatise he not only collected and reviewed critically older knowledge on the behavior of the magnet and electrified bodies but described his own researches, which he had been conducting for 17 years.

In electrostatics Gilbert coined the word "electricity," greatly extended the number of known materials exhibiting electric attraction, and suggested that static electric attraction was due to a subtle electric effluvium emitted by electrified bodies. The greater bulk of the work, however, is devoted to magnetism. Although the compass had been known in Europe for at least 4 centuries, Gilbert's was the first important study on the detailed behavior of compass needles, their variation from true north, and the tendency of the north pole of the needle to dip. From experiments involving a spherical lodestone, the most powerful magnet then available, Gilbert concluded that the earth was a huge magnet, with a north and south magnetic pole coinciding with the rotational poles. The variation in compass readings from true north, he believed, was due to land masses.

Gilbert also speculated on the nature of magnetism, suggesting that magnetic bodies had a kind of soul which spontaneously attracted other bodies. He pointed out that gravity might be a sort of magnetism, or was at least analogous to it, and that the motions of the planets might well be explained by considering their mutual influence.

Gilbert's studies were so complete and comprehensive that as late as 1822 it was asserted that De magnete contained almost everything known about magnetism. Today the unit of magnetomotive force is called the gilbert.

Further Reading

Gilbert's De magnete (On the Magnet) is available in several translations, such as those of S. P. Thompson and P. Fleury Mottelay. The only complete biography of Gilbert is Silvanus P. Thompson, Gilbert of Colchester: An Elizabethan Magnetizer (1891), which is now difficult to obtain. Romano Harré, Early Seventeenth Century Scientists (1965), has a full chapter on Gilbert. A brief biography is given in George Sarton, Six Wings: Men of Science in the Renaissance (1957). Most standard histories of science discuss Gilbert's contributions. See particularly Abraham Wolf, A History of Science, Technology, and Philosophy in the 16th and 17th Centuries (2 vols., 1939; 2d ed. 1959). □

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Gilbert, William

William Gilbert, 1544–1603, English scientist and physician. He studied medicine at Cambridge (M.D., 1569), where he was elected a Fellow of St. John's College, and set up practice in London, becoming president of the College of Physicians (1599) and court physician to Queen Elizabeth I (1600) and later also to James I. He is best known, however, for his studies of electricity and magnetism. He coined the word electricity (from the Greek for "amber" ), was the first to distinguish clearly between electric and magnetic phenomena, and published (1600) De Magnete, the most important work on magnetism until the early 19th cent. In it he described his methods for strengthening natural magnets (lodestones) and for using them to magnetize steel rods by stroking; he also outlined his investigations of the earth's magnetic field, from which he concluded that the earth as a whole behaves like a giant magnet with its poles near the geographic poles. He found that an iron bar that is left in alignment with the earth's magnetic field will slowly become magnetized, and that sufficient heating will cause a magnet to lose its magnetism.

See translations of his De Magnete by P. F. Mottelay (1893, repr. 1958) and S. P. Thompson (1901, repr. 1958).

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Gilbert, William

Gilbert, William ( Gilberd, William) (1540–1613) A natural philosopher and physician to Elizabeth I, Gilbert studied terrestrial magnetism. In his book De Magnete Magneticisque Corporibus, et de Magna Magnete Tellure (1600) he made a firm distinction between magnetism and electricity. He explained the Earth's magnetic field by likening the Earth to a vast spherical magnet.

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"Gilbert, William." A Dictionary of Earth Sciences. . 24 Jun. 2017 <>.

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Gilbert, William

Gilbert, William (1544–1603) English physicist and physician to Queen Elizabeth I. In De Magnete, he was the first to recognize terrestrial magnetism, and coined the terms magnetic pole, electric attraction, and electric force. He was the first to recognize terrestrial magnetism and coined the terms magnetic pole, electric attraction and electric force.

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"Gilbert, William." World Encyclopedia. . 24 Jun. 2017 <>.

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