Long one of nature's most fascinating phenomena, magnetism was once the subject of many superstitions. Magnets were thought useful to thieves, effective as a love potion or as a cure for gout or spasms. They could remove sorcery from women and put demons to flight and even reconcile married couples. It was said that a lodestone pickled in the salt of sucking fish had the power to attract gold. Today, these beliefs have been put aside, but magnetism...