The geomagnetic daily variations at the Niegerian dip equator are analyzed to find the thickness of the nonconducting layer in this zone. To do so, the external current system was determined from the external part of the geomagnetic daily variations by using a method discussed in a previous work. The field induced by this system was calculated assuming a two-layer model for the earth conductivity. Fitting this induced field to the internal part of of the geomagnetic daily variations yielded a thickness of 500 km for the nonconducting layer in the internal of 100 km south to 500 km north of the dip equator. However, there is evidences showing a latitudinal gradient in the thickness of this interval.