A column of ionized mercury vapor is placed in a parallel plate transmission line and the resulting reflection coefficient observed. From the measurement of reflection coefficient as a function of discharge current, plasma resonance is demonstrated. In accordance with the theory applied, but in contrast to the results of other investigators, resonance is found at only one value of discharge current. The discharge current required to produce resonance is measured as a function of frequency. The functional dependence observed is as predicted by theory, but the current is higher than the theoretical value. The discharge current required to produce resonance is measured as a function of gas pressure. The dependence that is found follows that predicted theoretically at higher gas pressures, but deviates sharply from the theoretical form at lower gas pressures.
