Separating a Small Part from the Globe (Magnetic Stone)
Image 1, GH are the poles, EF is a piece of magnetic stone in the earth and is not separated from the whole; BA is a mine and partly separated from the earth; CD is a mass of iron in the air. Image 2, the separated part EF behaves quite differently from the iron bar CD. Image 3, when the separated part EF is suspended by thread, E will turn to pole B and F to pole A. [ZB Magnet 2] William Gilbert, De Magnete (London: Petrus Short, 1600), Zentralbibliothek Zürich, Alte Drucke und Rara, XVI.28, p. 120f.; descriptions follow the translation of P. Fleury Mottelay [1893] (New York: Dover, 1958), p. 186f.