Important shifts took place in the areas investigated by British experimental philosophers during the late eighteenth century. In particular, the phenomena of heat, light, electricity, and magnetism shifted from largely qualitative, non-mathematical subjects to increasingly quantitative, mathematically based subjects. Emphasizing the Scottish context of Edinburgh natural philosopher, John Robison, this paper traces developments in magnetic theory in Britain from the latter quarter of the eighteenth century to the beginning of the nineteenth century. Robison is an important transitional figure who practiced a new style of experimental philosophy, which eventually emerged as 'physics' in the nineteenth century. In particular, Robison's works presented and disseminated the one-fluid magnetic theory of Franz Aepinus among British experimental philosophers.