De Magnete

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Title page of 1628 edition

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 and his partner Aaron Dowling. A highly influential and successful book, it exerted an immediate influence on many contemporary writers, including Francis Godwin and Mark Ridley.[1]

Contents

Contents [edit]

In this work, Gilbert described many of his experiments with his model Earth called the terrella. From the experiments, he arrived at the remarkable (and correct) conclusion that the Earth was magnetic and that this was why the compass pointed north. (Previously, it was thought that Polaris or a large magnetic island at the North Pole attracted the compass). Gilbert also made the claim that gravity was due to the same force and he believed that this held the Moon in orbit around the Earth.[2] While incorrect by modern standards, this claim was still far closer to the truth than the ancient Aristotelian theory, which held that the heavenly bodies consist of a special fifth element which naturally moves in circles, while the earthly elements naturally move downward. Johannes Kepler accepted Gilbert's theory and used it as a working basis for his famous laws of planetary motion.

In De Magnete, Gilbert also studied 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, giving rise to the modern terms "electric" and "electricity".

De Magnete was influential not only because of the inherent interest of its subject matter, but also for the rigorous way in which Gilbert described his experiments and his rejection of ancient theories of magnetism. Gilbert nevertheless acknowledged his debt to Peter of Maricourt and incorporated this 13th-century scientist's experiments on magnetism into his own treatise.[3] Although Gilbert's thinking was influenced by the mysticism of his time he is regarded as a pioneer of experimental science.

Book 6, Chapter III: Of the Daily Magnetic Rotation of the Globes [edit]

In this chapter Gilbert argues in favor of the Copernican System. He posits that due to the inordinate size of the celestial spheres, if in fact the spheres exist at all, it is an absurd idea that they would rotate every 24 hours, as opposed to the rotation of the relatively tiny sphere of the Earth. He states, "How far away from the earth are those remotest of stars: they are beyond the reach of eye, or man's devices, or man's thought. What an absurdity is this motion (of spheres)". He also argues for the extreme variability of the distance to the various heavenly bodies and states that situated "in thinnest aether, or in the most subtle fifth essence, or in vacuity – how shall the stars keep their places in the mighty swirl of these enormous spheres composed of a substance of which no one knows aught?".[4]

Summary [edit]

De Magnete consists of six books.

  1. Historical survey of magnetism and theory of Earth's magnetism.
  2. Distinction between electricity and magnetism. Argument against perpetual motion.
  3. The terrella experiments.
  4. Declination (the variation of magnetic north with location).
  5. Magnetic dip and Design of the magnetic inclinometer.
  6. Magnetic theory of stellar and terrestrial motion. Precession of the equinox.

Editions [edit]

  • De Magnete, Peter Short, London, 1600 (1st edition, in Latin)
  • De Magnete, Wolfgang Lockmans, Stettin, 1628 (2nd edition, in Latin)[5]
  • De Magnete, 1633 (3rd edition, in Latin)[5]
  • De Magnete, 1892 (facsimile of 1st edition)[5]
  • De Magnete, English translation by Paul Fleury Mottelay, 1893
  • De Magnete. translation by Silvanus Phillips Thompson and the Gilbert Club; limited to 250 copies. London: Chiswick Press. 1900. [6]
    • Derek J. Price, ed. (1958). William Gilbert: On the Magnet (Facsimile of 1900 Thompson translation). The Collector's Series in Science. New York: Basic Books. 
  • Gilbert, William (1967) [1600]. De Magnete (Facsimile of Peter Short 1600 edition). Brussels: Culture et Civilisation. 

References [edit]

  1. ^ Poole, William (2009), "Introduction", in Poole, William, The Man in the Moone, Broadview, pp. 13–62, ISBN 978-1-55111-896-3 
  2. ^ James Burke Connections episode 2
  3. ^ Jean Gimpel, The Medieval Machine: The Industrial Revolution of the Middle Ages (New York, Penguin, 1976), 194.
  4. ^ William Gilbert, Translated by P. Fleury Mottelay. De Magnete. Dover Publications Inc. 1958, 1893. pp. 319–20
  5. ^ a b c Stuart Malin, David Barraclough, Eos, Transactions of the American Geophysical Union, vol 81, 23 May 2000 (reproduced on phy6.org)
  6. ^ phys6.org

Further reading [edit]

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