We have measured the temperature dependence of conductance of electrons in 2D sodium induced impurity bands in silicon inversion layers from 4.2 to 80 K observing both activation of electrons to a mobility edge. E1, and nearest neighbor hopping, E3 in magnetic fields up to 25 T. The results are that E1 decreases slightly between 0 and about 20 T and then increases slightly. The prefactor decreases by about a factor of four. E3 increases monotonically. None of these results was expected. © 1984.