Concept
De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure (On the Magnet and Magnetic Bodies, and on That Great Magnet the Earth) is a scientific work published in 1600 by the English physician and scientist William Gilbert. A highly influential and successful book, it exerted an immediate influence on many contemporary writers, including Francis Godwin and Mark Ridley. In De Magnete, Gilbert described many of his experiments with his model Earth called the terrella. Gilbert made the claim that gravity was due to the same force and he believed that this held the Moon in orbit around the Earth. The work then considered static electricity produced by amber. Amber is called elektron in Greek, and electrum in Latin, so Gilbert decided to refer to the phenomenon by the adjective electricus. De Magnete consists of six books. Historical survey of magnetism and theory of Earth's magnetism. The lodestone in antiquity from Plato onwards and the gradual identification of iron ores. The south pole of a lodestone points to the north pole of the Earth and vice versa as the terrestrial globe is magnetic. Distinction between electricity and magnetism. An amber stick when rubbed affects a rotating needle made of any type of metal (a versorium) and attracts paper, leaves and even water. But electricity is different from heat and to magnetism which only attracts iron-bearing materials (he calls it coition). He shows the effects of cutting a spherical lodestone (which he calls a terrella) through the poles and equator and the direction of attraction at different points. Magnets act at a distance but the force has no permanent presence and is not hindered like light. Materials including gold, silver and diamonds are not affected by magnets, nor can one produce perpetual motion. The Earth's normal magnetism. He proposes (incorrectly) that the angle of the ecliptic and precession of the equinoxes are caused by magnetism. A lodestone cut out of rock and floated in water returns to the same direction.
