Diagrams, circuits by Philip Cardew Three diagrams, labelled figures I-III, showing circuits used by Cardew in his investigations into the possibility of obtaining a unidirectional current to earth from the mains of an alternating current system. Subject: Electricity A version of this paper was published in volume 56 of the Proceedings of the Royal Society as 'Note on the possibility of obtaining a unidirectional current to earth from the mains of an alternating current system'. 1894