Considerable variation occurs at one aseismic location in the emission rate of mercury and emanation rate of random from the earth. Improvements are made in the use of seasonal parameters to explain variance in mercury emission. The rate of emission of mercury and radon have contrasting seasonal fluctuations. This may be the result of radon emanation being dominated by diffusion and possible convection processes, whereas mercury emission is strongly influenced by sorption of mercury by soil particles. An understanding of the non-seismic induced variation in gas emission processes may allow reliable application of these techniques to earthquake prediction. The data presented suggest randon offers more promise than mercury in this application.