Scrutinising the glass under a microscope (after treating it with appropriate chemicals) would make it clear if a monopole had turned up or not.

ECONOMIST: Magnetic monopoles: Absence of evidence | The

The path of a monopole would have a distinctive pattern lots of damage at the beginning of its journey and very little towards the end of it.

ECONOMIST: Magnetic monopoles: Absence of evidence | The

Although the grand prize of all this searching would be to find a monopole, a close second would be a conclusive result that they do not exist.

ECONOMIST: Magnetic monopoles: Absence of evidence | The