The invention relates to a method of and an apparatus for compensating the magnetic fields in adjacent rows of transversely arranged igneous electrolysis cells.In this method, the distribution of current in the conductors feeding the anode of a downstream cell from the cathode of the adjacent upstream cell is modified in such a way as to superimpose upon the cell an electrical loop which produces an additional magnetic field substantially equal to that created by the adjacent row and opposite in direction.The invention is applicable to the compensation of the magnetic fields of adjacent rows of transversely arranged igneous electrolysis cells and, more particularly, to cells for the production of aluminium.