In olden times, magnets were known as lodestones because, give or take a vowel or two, when used as a compass they would "lead" the way. But lodestones were alleged to have other mysterious and very useful properties as well. It was believed, for example, that placed upon the pillow of a guilty wife, the lodestone would make her confess her indiscretions while she slept.
Modern research has revealed why this clever ploy might work for errant wives, but not, apparently, in the case of guilty husbands: women, it seems, are more magnetically sensitive than men.
It is well known that certain birds and animals can use the Earth's magnetic field to navigate. Pigeons are the most notable example, but up to 60 other species with the same gift have been identified. Some large fish, for example, appear to detect the Earth's magnetic field by using electrical sensors, called the ampullae of Lorenzini, located in their snouts. And other creatures have tiny crystals of an iron oxide called magnetite embedded in their brains; these, rather like iron filings near a magnet, orientate themselves in the direction of a magnetic force.
Speculation that some human beings may possess this gift was kindled some years ago when scientists discovered tiny crystals of magnetite in the human brain.
Shortly afterwards, experiments were carried out which, in their simplest form, consisted of driving blindfolded volunteers to unfamiliar locations. It was found that, still blindfolded, some of them could indicate their direction relative to home. They were unable to do so, however, when magnets were held near their heads.
Further research has revealed interesting variations with regard to age and sex. This intuitive sense of direction, sometimes called magneto-reception, is found to be particularly strong in some female subjects, developing gradually from the age of about nine years, reaching a plateau of ability at 18, and persisting until its decline after the age of 40.
By contrast, those males who possess the gift at all have it for only a relatively short interlude in life - and even then it is much weaker than in females.
But ladies, panic not. There is an antidote to the lodestone's power to extract your indiscretions. It was also believed in ancient times that magnetic forces could be countered by the influence of onions or of garlic. And perhaps, indirectly, this accounts for the other rumoured property of the lodestone - that as a contraceptive it was sans pareil.