ABSTRACT
When Ampere heard of Hans Christian Oersted’s discovery that the electric current sets a magnetic needle in motion, he suspected that electric currents would exhibit moving forces between themselves. The essential step in the reasoning is the assumption that only one kind of magnetic force exists; that therefore the magnetic forces exerted by currents are in all their effects equivalent to equal and equally directed forces produced by magnetic poles. when the electric forces that act on the ring-magnet are due, not to electric charges, but to a second ring-magnet of diminishing moment, their distribution is the same as if they were due to an electric double layer. Magnetic currents act on each other according to the same laws as electric currents; in absolute magnitude the action between magnetic currents of S magnetic units is equal to that between electric currents of S electrical units. The system of the electromagnetic action of closed currents is in its present state certainly incomplete.
