The experimental results of Palmer, Morrison, and Dauenbaugh on the conductivity of cleaved surfaces of silicon are reinterpreted in terms of a large density of states below the center of the forbidden energy gap. This new interpretation shows that the conductivity measurements and the work function and photoelectric threshold measurements are not in disagreement. If a Shockley-type band of surface states is present at the surface, it is possible to estimate an upper bound for the mobility of its carriers. The value of the mobility is found to be less than 0.01 ${\mathrm{cm}}^{2}$/volt sec.