A short time after Rinehart presented his mechanism, Geis (1966, 1968) presented a different mechanism to explain the behavior of Old Faithful. Rinehart's theory falls into the "critical column" class, while Geis' theory falls into the "steam chamber" class. It is proposed to show, using the available data, that Rinehart's mechanism does not apply to Old Faithful, while Geis' mechanism, modified slightly, is better able to explain the eruption cycle of Old Faithful.