GILBERT, or GILBERD, WILLIAM, was born in 1540 at Col chester, Essex, of which borough his father was After passing through the grammar school of his native place, he proceeded to Cambridge, and thence, according to Anthony b, Wood, to Oxford. Having decided on adopting medicine as a profession, he went to a foreign university to prosecute his medical studies, and whilst abroad received the degree of Doctor of Physic. He was elected a fellow of the College of Physicians, London, in 1573. As a physician, lie attained great celebrity, and the eminence he had acquired by his ssiontific pursuits, both in England and on the Continent, appears to have rather assisted than hindered his professional progress. Queen Elizabeth appointed him her physician in ordinary, conferred on him many marks of her favour, and gave him an annual pension to encourage his studies. (Fuller, from the information "of his near kinsman, Mr. William Gilbert of Brental-Ely.") Ilia early scientific etudies had been chiefly in chemistry; but eventually his attention was devoted principally to the subject of magnetism, and iu 1600 he published his great work, on which he had been for eighteen years engaged—a folio volume of 210 pages, entitled 'De Magnate, Magneticisque corporibus, at de magno magnete tellure ; physiologia nova, pluriruis et argumentis et experitnentis demon strata.' In this work, after giving an account of all that had been previously written on the subject, he propounds his own views, which not only were full of novelty and of remarkable comprehensiveness, but in fact served as the basis of most subsequent investigations on the important subject of tollurio magnetism, and forestalled many of the discoveries of comparatively recent experimenters and theorists. Whewell, indeed, in the last edition of his 'History of the Inductive Sciences,' vol. iii. p. 49, says that Gilbert's "work contains all the fundamental facts of the science, so folly examined, indeed, that even at this day we have little to add to them." He establishes as his fundamental principle the magnetic nature of the earth ; demon strates the affinity of magnetism and electricity, while he clearly dis tinguishes between them : and recognising electric action as the operation of a natural force or power allied to magnetism, he regards magnetism and electricity as two emanations of one fundamental force pervading all matter. He treats at length of the attraction, direction, and variation of the magnetic force. He pointed out too the cardinal fact on which all our generalisations rest—that the magnet has poles, which, he says, we may call north and south poles, and that in two magnets the north pole of each attracts the south pole and repels the north pole of the other. He proposed to deter mine latitudes by means of the inclination of the 'magnetic needle, and invented two instruments for the purpose ; but lie did not per ceive that the method is not generally applicable. The work created a powerful impression at the time, especially among the learned in other parts of Europe. Galileo expressed the highest admiration of the work and its author, and Erasmus pronounced him to be "great to a degree that is enviable." In his own country he was scarcely
so highly appreciated ; even Bacon, though he praises Gilbert as a philosopher, speaks with little respect of his theory. After awhilo his speculations came to be more esteemed, though perhaps not fully understood ; but the great superiority of Gilbert over all who had previously treated of magnetism, and "the extent to which he had anticipated by his conjectures much of our present knowledge," has only been perceived since the study of magnetism has assumed some thing like its present systematic and compreheneive character. "William Gilbert," says Humboldt, "regarded the earth itself as a magnet, and the lines of equal declioation and inclination as having their inflections determined by distribution of mass, or by the form of continents and the extent of the deep intervening oceanic) basins. It is difficult to reconcile the periodic variation which characterises the three elementary forms of the magnetic phenomena (the isoclinal, isoginic, and isodyuamio lines) with this rigid distribution of force and maas, unless we imagine the attractive force of the material particles modified by similar periodical variations in the interior of the globe. In Gilbert's theory, as in gravitation, the quantity of material particles only is estimated, without regard to the specific heterogeneity of sub stances. This circumstance gave to his work, in the period of Galileo and Kepler, a character of comical grandeur. By the unexpected discovery of 'rotation magnetism' by Arago (1825), it has been practically proved that all kinds of matter are susceptible of mag netism ; and Faraday's researches on diamagnetic substances have, under particular conditions of axial or equatorial direction,' and of solid, fluid, or gaseous inactive conditions of the bodies, confirmed this important result. Gilbert had so clear an idea of the imparting of the telluric magnetic force, that be already ascribed the magnetic state of iron bare in the crosses on old church towers or steeples to this cir cumstance." (' Kesmos,' ii. 332, Sabine's translation.) It is deserving of remark that Gilbert, in this work, was the first to use the terms "electric force," "electric emanations," and "electric attraction;" also to point out that amber was not the only substance which had the faculty, when rubbed, of attracting light objects of any kind, but that it was common to all the resins, to sealing-wax, sulphur, glass, rock crystal, the precious stones, etc. ; and he describes how, by means of an iron needle moving freely on a point, to measure the excited electricity.
After the death of Elizabeth, Gilbert was continued in his office of physician in ordinary by James, but lie survived his royal mistress only a few months. He died on the 30th of November 1603, and was buried in the church of the parish in which he was born, Trinity's, Colchester. Gilbert was never married, and he bequeathed his books, philosophical instruments, globes, and collection of minerals to the College of Physicians. Gilbert left in manuscript another treatise, which was not printed till forty-eight years after his death : 'De Mundo nostro subluuari Philosophic Nova,' 4to, Amsterdam, 1651.