The magnet served three interests of Restoration mechanical philosophers: it provided a model of cosmic forces, it suggested a solution to the problem of longitude determination, and evidence of its corpuscular mechanism would silence critics. An implicit condition of William Gilbert's ‘magnetic philosophy’ was the existence of a unique, immaterial magnetic virtue. Restoration mechanical philosophers, while claiming descent from their compatriot, worked successfully to disprove this, following an experimental regime of Henry Power. Magnetic philosophy lost its coherence and became subsumed (...) in the study of effluvia. This contradiction of a distinct, yet mechanical magnetic philosophy came to a head in 1684 in an argument between Robert Hooke and Martin Lister. An effluvial explanation of magnetism introduced great complexity to the North-seeking behaviour of compass needles, and undermined the already troubled longitude programme. Thus magnetic philosophy no longer furthered the interests which had maintained it, and it was abandoned. (shrink)