The saturated emission currents from uranium carbide in cesium vapor were measured for four different bath temperaturesT: 167°, 197°, 227°, and 250°C (the cesium arival rates &mgr;a, in 1019atoms/cm2, were 0.3, 1, 3, and 6, respectively). The measurements were made with a ``plasma anode'' tube at constant temperature. The plot of log&mgr;avs 1000/Twas used to extrapolate the electron emission ``S'' curves to arrival rates that differed by a factor of ten. Since calculations based on the assumption of a homogeneous surface yields unexpectedly high binding energies and surface coverages, it seems likely that some surface patchiness exists.