GILBERT, William, English physician and physicist: b. 1540 at Colchester; d. 1603. At the age of 18 he entered Saint John's College, Cambridge, from which he graduated in 1560. In 1601, he was elected president of the Royal College of Physicians, an honor which was fol lowed by his appointment as chief physician to Queen Elizabeth.
Gilbert's fame rests on the discoveries which he made in electricity and magnetism and which he tersely recorded in his work on the magnet Magnete magneticisque Corporibus,' pub lished in London in 1600. He devoted all the time he could spare from his professional duties during a period of 18 years to the researches described in this remarkable treatise, which re searches he informs the "candid cost him over E5,000. By way of distinction, he marks his discoveries with marginal asterisks, large ones denoting important discoveries and small ones those of minor note. Of the former, there are 21; of the latter 178. Besides a re markable titlepage, the work contains 84 illus trations.
In magnetism, Gilbert recognizes the mag netic field, the effects of heat, magnetic induc tion and magnetic screening; but his cardinal discovery is that the earth itself is a great mag net with its magnetic poles, equator and axis. He was led to this generalization by prolonged experiments with globular magnets, or terrellas, on which he poised small magnetic needles, find ing that, however placed, they always pointed to the poles. He confirmed his theory by refer
ence to the prevalence of magnetic materials in the crust of the earth, the behavior of the com pass-needle and the dip circle, and also by the magnetic condition of vertical masses of iron such as the crosses of church-steeples.
Gilbert was an ardent advocate of the Coper nican theory, and there is reason to believe that his magnetic work was undertaken in its de fense, convinced as he was that the revolution of the earth round the sun and its suspension in space would follow at once from the magnetic attraction of the other planets provided the earth itself could be proved to be a colossal magnet. Gilbert was belittled in De Augmentis Scienti orum by Chancellor Ba.on, who was a staunch anti-Copernican, but was praised and admired by Galileo and Kepler. Two translations of 'De Magnete> have been made, the first by P. Fleury Mottelay of New York (1893), and the second by the Gilbert Society of London (1900). Gilbert's work stands out as the second land mark on magnetic philosophy, the first being a treatise on the lodestone by Peregrinus (q.v.) A.D. 1269.