Magnetic Monopoles

In 1269 Petrus Peregrinus observed lines of force around a lodestone and noted that they were concentrated at two points which he designated as the north and south poles of the magnet. Subsequent observation has confirmed that all magnetic objects have paired regions of'' opposite polarity, that is, all magnets are dipoles. It is easy to conceive of an isolated pole, which J.J. Thomson did in 1904...