Abstract
S. Chapman and T. T. Whitehead calculated, first, the earth potential gradients induced by the magnetic variations, considering the earth core enveloped by the non-conducting layer, but the calculated gradients differed from the observed ones, much in amplitude (the latter was 5 or 6 times larger) and little in phase.
Latley, H. Ertel made the amplitude-difference clear, due to non-uniform conductivity of the earth crust varying rapidly with depth.
The author extends Ertel's idea to the anisotropic earth crust which is regarded as the isotropic when it is averaged over the sufficiently wide regions and generalises the Chapman's and Ertel's solutions. We see that the solution answers the existence of the vertical potential gradient and the phase-difference between the calculated and observed potential gradients.
