Measurements of the value of the large-scale (4050 km) mean earth potential between California and Hawaii are reported as determined over a one year interval in 1990--91. The mean electric field measured during quiet geomagnetic intervals, 0.183¿0.056 mV/km, is about six times larger than that reported for a shorter interval over a slightly longer distance in the Atlantic [Lanzerotti et al., 1985>, but of the same sign. The present results are also about three standard deviations from a null value, in contrast to the previous results, which were consistent with a null mean. If the mean potential is entirely attributable to leakage of a poloidal electric field from the core-mantle boundary, then under some models of the mantle conductivity one can conclude that the deduced toroidal magnetic field intensity in the core would be of the same order as the poloidal magnetic field at the core-mantle boundary. The measured potential gradient is smaller than that which might be expected from thermoelectric emfs at the core-mantle boundary. The potential could also correspond to a south to north quasi-steady water flow of ~0.6 cm/sec. ¿ American Geophysical Union 1992