Geomagnetism: Historical introduction

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Geomagnetism, the study and use of the magnetic field of the Earth, is one of the oldest branches of science and can be said to have begun with the discovery that a piece of lodestone (a naturally occurring, and usually naturally magnetized, form of magnetite, Fe3O4), when freely suspended or supported in some manner, always came to rest in a roughly north-south direction. The fact that lodestone attracts small pieces of iron was widely known by about the middle of the first millennium B.C., but its directional property in the Earth's magnetic field was not discovered until much later.

This article is a roughly chronological sketch of the most significant events in the history of geomagnetism from the discovery of this directive property until the end of the nineteenth century. For the present century no attempt has been made to be at all comprehensive and the choice of topics is no doubt strongly influenced by my own interests.

The Magnetic Compass in China