Jan Hendrik van Swinden (1746-1823) en het probleem van de analogie tussen elektriciteit en magnetisme

Jan Hendrik van Swinden (1746-1823) and the problem of the analogy between electricity and magnetism In the 18th century electricity and magnetism flourished as new branches of experimental physics. From about 1750 onwards their relationship became a matter of special interest. Comparison of similarities and differences in their effects raised the question as to what extent these effects, and also the mechanisms and the causes of these two 'natural forces' were analogous. Theorizing was mainly embedded in the frame of imponderable-fluids theories of light, heat, electricity and magnetism. During the years 1770-1784 Jan Hendrik van Swinden (1746-1823), professor at the university of Franeker in Friesland (closed down in 1811), spent much time on this topic, in the end resulting in his "Memoire sur l'analogie de l’electricite et du magnetisme" of 1784. Van Swinden's approach is strikingly different from the one used by most of his contemporaries. To Van Swinden analogy between objects means that they behave according to the same pysical rules; whether this is the case or not, can only be investigated and established in a strictly empirical way. He constantly sets apriorism and unwarranted hypothesizing against his own unbiased approach of the phenomena, exercising fundamental criticism on colleagues like F.U.T. Aepinus (1724-1802, Petersburg) and G.F. Cigna (1734-1790, Turin). Contrary to the then current opinion he concludes that electricity and magnetism are totally different in almost every respect; there is no mutual influence either. This point of view, based on and justified by exhaustive and detailed treatment of the observational and experimental knowledge of his time, was, however, soon definitively superseded by Charles Coulomb, who experimentally confirmed the validity of similar inverse-square laws for both electricity and magnetism (1785), and Hans Christian Oersted, who discovered the influence of an electric current on a magnetic needle (1820). It is pointed out that Van Swinden on the one hand favoured the efforts to transform electricity and magnetism into mathematical-physical disciplines, but on the other vindicated a baconian primacy of experiential data. Because of this methodological point of view he was unable to follow the new and from the 1780's onwards very successful mathematical approach, initiated by Aepinus and Coulomb.