The principles are set forth for the use of inductive methods (at low frequency) for the prospecting of conductive ores in the galleries of the mines. As these conductive ores in the gallery pillars are bodies limited in space (veins, plates, etc.) attention is given to the problem of the inductor in connection, for instance, with a plane conductive plate of limited dimensions. This problem is essentially reducible to the solution of an integral equation of the second type, integrable by approximation.