In 1861, James Clerk-Maxwell published Part II of his four-part series 'On physical lines of force'. In it, he attempted to construct a vortex model of the magnetic field but after much effort neither he, nor other late nineteenth century physicists who followed him, managed to produce a workable theory. What survived from these attempts were Maxwell's four equations of electrodynamics together with the Lorentz force law, formulae that made no attempt...