Abstract: The method of measuring local rock inhomogeneities on the wall of a borehole is disclosed. The method of measurement includes the step of generating microelectric fields in a conductive way on an area of the wall of the borehole insulated from the drilling mud by an insulating pad which carries electrodes and excludes direct electrical contact between the electrodes and the conductive borehole liquid. The local current intentities are measured at, at least two, different places perpendicularly to the wall of the borehole and the measured current intensities are compared to each other. Alternatively, a local voltage difference created by current flowing first parallel to the wall of the borehole and then an absolute voltage created by the same current in another section of flow where the current is perpendicular to the wall of the borehole may be measured and the measured voltages compared to each other.