With monochromatic light, the photoelectric threshold wave-length for solid mercury, freshly distilled and frozen in vacuum, was 2750 +25A for all temperatures between -190°C and the melting point. For room temperature it was 2735 + 10A, confirming Kazda's value.The photoelectric current excited by each of the lines 2537A, 2653A and 2700A was independent of temperature between -190°C and ca. -125°C. Between ca.-125°C and -39°C there was a gradual small decrease in the current with increasing temperature, but this was not reproducible at definite temperatures and is attributed mostly to contamination and other secondary causes. With the possible exception of this decrease in current, there was no indication of an allotropic change in the mercury between -190°C and the melting point. The photoelectric current for the solid phase was always higher than that for the liquid at room temperature, possibly due to a change in the optical absorptivity of mercury with change in phase. Between -39°C and 0°C the emission curves show so much hysteresis that conclusions regarding this region are impossible.