Energetic particle detectors on the Vela satellites have the capability of making three-dimensional measurements of particle fluxes. We report observations, using these instruments, of directional anisotropies of solar proton flux in the high-latitude magnetotail (i.e., the lobes of the magnetotail). The anisotropies last for several minutes and are associated with sudden changes in the intensity of the proton flux. The measurements suggest that the gradients in the proton flux are perpendicular to the magnetic field and move past the satellites toward the midplane of the tail, i.e., toward the plasma sheet. Our observations constitute the first measurements of the E¿B drift of energetic protons in the tail lobes and provide a means for measuring the associated electric field. Measured values of the electric field fall in the range ~0.5-1.3 mV/m, which would drive convection at ~30--80 km/s in a typical magnetotail magnetic field of ~15 &ggr;. The observations are consistent with an open model of the magnetosphere which has magnetic field lines from the earth's polar regions extending into the solar wind and, along with solar proton fluxes that are associated with these field lines, being convected into the magnetosphere as they are pulled downstream by the solar wind.