A brief review is presented of simple forms of electrical layout which are used in resistivity investigations on the upper surface of a two-layered medium of which the crust of the earth is assumed to be an example. The associative formulas for resistivity are given.The necessity for equalization in magnitudes of the source and the sink in all experimental methods of resistivity investigation is emphasized in order to be in accord with the basis of development of the formula, and in order to eliminate experimentally pseudo anomalies which may appear in homogeneous media.Formulas are developed for use in conjunction with experimental results obtained by the use of drill holes whereby the source and sink are embedded in a two-layered medium. Distinction is made in the cases where the source and sink are remote from, or are in the neighborhood of, the plane of separation of the layers.Some experimental results on the values of the interbowl résistance,R, are presented in comparison with the values ofRthat would be obtained from a medium of two homogeneous layers of a suitably chosen resistivity ρ. The local anomalies in these layers appear clearly.