The results of the air temperature and dew point measurements at the top of the shaft are shown in Figs. and. In Fig. is shown the fluctuation of the temperature, and its frequency distribution in Fig. . The latter figure includes also the accuracy of the dew point. From Fig. , the average temperature was found to be 11.090 ± 0.005 • C or 284.240 ± 0.005 K. The dew point was 10.8 • C , and there was essentially no fluctuation. Neither the peak positions nor the widths of the frequency distributions were affected by the NaCl aerosol injection. This observation that the dew point at the end point of the updraft was lower than the temperature implied that macroscopically speaking the humidity stayed below the saturation level throughout the droplet formation and growth process by the cooling due to expansion in the updraft. From the dew point and the temperature, it is reckoned that the relative humidity was in the range 98.09 ± 0.03%.