The analysis in the quoted paper is an attempt to calculate the induced polarization response of a two-layer flat earth. The upper layer is a homogeneous overburden of thickness h with a resistivity ρ1 and a dielectric constant of e1. The lower (semi-infinite) medium which is the “aquifer” has a resistivity ρ2 and dielectric constant ε2. The value of the relaxation voltage as seen at the potential electrodes “immediately after” the current is shut off is designated Δφ. The A's of the above paper present a method for calculating the ratio Δφ/V where V is the steady voltage across the potential electrodes during the time of current flow.