De Magnete

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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.

In this work Gilbert describes many of his experiments with his model earth called the terrella. From the experiments, he arrived at the remarkable 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). In his book, he 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 and the noun electricitas, 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 thirteenth century scientist's experiments on magnetism into his own treatise.^[1] Although his thinking was heavily influenced by the mysticism of his time, Gilbert was also one of the pioneers of experimental physics.

Contents 1 Summary 2 Editions 3 Notes 4 References

[edit] Summary

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.

[edit] Editions

• De Magnete, Peter Short, London, 1600 (original Latin)
• De Magnete, English translation by Paul Fleury Mottelay, 1893
• De Magnete, translation by Silvanus P Thompson, Chiswick Press, 1900
• De Magnete, facsimile of Thompson translation, Basic Books, New York, 1958
• De Magnete, facsimile of Mottelay translation, Dover Books, 1991, ISBN 0-486-26761-X

[edit] Notes

1. ↑  Jean Gimpel, The Medieval Machine: The Industrial Revolution of the Middle Ages (New York, Penguin, 1976), 194.

[edit] References

• Review by Stuart Malin and David Barraclough
• Cambridge Scientific Minds, chapter on Gilbert (PDF) - available in print as ISBN 0-521-78100-0 (hardback), ISBN 0-521-78612-6 (paperback)
• The active-matter signal theory of De Magnete