The Magnetic Field 1. Historical

The writings of Thales, the Greek, establish that the power of loadstone, or magnetite, to attract iron was known at least as long ago as 600 B.C. It has been claimed that the Chinese used the compass sometime before 2500 B.C. That magnetite can induce iron to acquire attractive powers, or to become magnetic, was mentioned by Socrates. Thus permanent and induced magnetism represent two of man's earliest scientific discoveries. However, the only real interest in magnetism in antiquity appears to be concerned with its use in the construction of the compass. For example, it is illuminating that it was not until many centuries later that Gilbert (1540-1603) realized that the earth was a huge magnet, even though the operation of the compass depends on this very fact. The discovery of two regions called magnetic poles, or sometimes just "poles, " which attracted a piece of iron more strongly than the rest of the magnetite, was made by P. Peregrines about 1269 A.D. Coulomb (1736-1806), in accurate quantitative experiments with the torsion balance