The paper contains the result of the comparative observations of soil temperature at the depths of 30, 40 and 50 cms. with the electrical resistance thermometers and Symons' earth-thermometers for ascertaining the eventual faults of the latter. The english version of this paper by the author himself appeared in Vol. VIII. No. 10. of the Proceedings of the Tôkyô Mathematico-physical Society.

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When air-temperature near the earth's surface is below the freezing point the precipitation takes generally the form of snow. But there are many instances of the falling of ordinary raindrops in the hours during which the mercury stands far below the freezing point. The author has picked out 36 cases in all from the meteorological registers kept at the meteorological observatories at Hakodate, Sapporo and Nemuro for the 15 years from 1897 to 1912. In the large majority of the cases air-temperature was ranging between 0°and-2°C. There were 3 cases in which the temperature was below-5°C. In one instance it was as low as-7°.8C.
The phenomenon under consideration occurs mostly in the early morning or at night, and is rarely observed in the daytime. Its duration is mostly less than 30 minutes, and the amount reaches scarcely a milimetre. This phenomenon occurs mostly with strong winds or gales from the east.
In the thirty-six cases referred above, eight cases were preceded by snowfall; two cases by soft-hailfall and seven cases by sleetfall. in two cases it occurs with fogs. In the remaining fourteen cases it was raining from beginning to end.
According to the author there are two causes of this abnormal phenomenon. In the most cases it may be explained by assuming the existence of the inversion in the vertical distribution of air-temperature. In some cases the raindrops are supposed to have been formed in the warm upper current of air and have fallen to the earth's surface where air-temperature is below the freezing point. In the other cases this phenomenon may be explained by assuming that the raindrops have been formed in the ascending current of air highly supersaturated with aqueous vapour. From thermodynamical consideration the author has shown that when the condensation takes place continuously in the highly supersaturated air, both snow-crysta_??_s and raindrops are formed even though the air-temperature is many degrees below the freezing point.

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