chapter  4
25 Pages

Station 1 (1856–1858)

On Faraday’s lines of force
ByGiora Hon, Bernard R. Goldstein

Maxwell’s first contribution to the study of electromagnetism is the most revolutionary, although each of the four contributions is innovative in its own way. In Station 1 Maxwell transformed the traditional methodology of analogy, perfected by Thomson, into a powerful new technique that draws a parallel between a set of physical phenomena and an imaginary arrangement, entirely contrived by the physicist. The move was to imagine the lines of force as tubes, fill them with an incompressible fluid complete with sources and sinks. Maxwell then developed an imaginary hydrodynamics to turn the geometrical scheme of Faraday into a “physical” one, which now included both the direction of the force and its intensity. This novel imaginary physics served as an analog which, in turn, facilitated the construction of a new formalism. It was assumed as a vehicle of mathematical reasoning. Faraday’s scheme of lines of force had the power to unify electromagnetic phenomena, but only geometrically; Maxwell rendered this scheme as physical. This was done by appealing—surprisingly—to imagination; indeed, that was the strength of the new methodology. The use of analogy in scientific discourse goes back to Antiquity, but making an analogy between observable phenomena and imaginary physics was something new and unexpected. We call this methodology “contrived analogy,” for Maxwell constructed an analogy which worked, as he explicitly put it, in one direction only: from his imaginary physical scheme to the physics of electromagnetism.