In the near zone apparent resistivity formula of central loop and coincident loop in layered ground, the power n of time delay t was formerly regarded as a constant. In fact, it is a variable. This paper has proved through inference that its Δn-value is equivalent to the logarithmic difference of apparent longitudinal conductances. Therefore it can be used to interpret the direct division of strata. For this purpose, the authors made quite a lot of mathematical model calculations, and the result shows that under certain circumstances the strata can be rather satisfactorily divided; nevertheless, the observation precision should be very high.