Saturated ethanol vapour in an atmosphere of nitrogen was expanded in a cloud chamber. The condensation arising thereby was shown by light scattering. At the same time the temperature curve occurring after the expansion was measured by means of a resistance thermometer. Experiments with twenty different expansion ratios (from E=1,083 to E= 1,324) were carried out at room temperature. The expansions were polytropic at n = 1,24. Supersaturations were obtained at about 1,3 and 1,5 regardless of E and never attained the critical value of 2,1. Nevertheless a condensation was shown every time, although nuclei were not present. The cloud vanished shortly after its appearence, long before the initial temperature could be reached again. The formation as well as start and finish of the evaporation of this “subcritical fog” can be traced exactly in the registered temperature curves. The simultaneous light scatteringand temperature measurement make a stronger interpretation of the temperature curves recorded by STACHORSKA also possible.