Two communications on this subject have been published recently. Sechrist1 found that water containing dissolved carbon dioxide, or surrounded by an atmosphere of this gas, evaporated 15-50 per cent more rapidly than water in the presence of air. Kingdon2 measured the rates of evaporation of water in the presence of 11 different gases, including hydrogen, oxygen, argon, carbon dioxide and butane. Rates varied over a range of 15 per cent in all gases except hydrogen and helium, which produced rates about 40 per cent less. Kingdon defined a corrected rate of evaporation as the measured rate divided by the diffusion coefficient of water vapour in the surrounding gas. The corrected rate in butane was double that found in oxygen or nitrogen. Other gases also augmented the corrected rate relative to oxygen or nitrogen, except hydrogen or helium, which reduced it five-fold.