It has long been noticed that the effect of wind velocity acts to diminish the amount of rainfall by a rain-gauge. Thus the rain-gauge installed at a higher elevation is considered to generally measure the smaller amount of rainfall compared with that at the lower elevation, since the wind velocity increases rapidly with height near the earth's surface. In the present paper this windeffect is examined statistically by inspecting the observational materials for the year 19.3-1929 at the Zinsen Meteorological Observatory. In this observatory one rain-gauge is installed 0.3m high above the ground surface and the other automatic recording rain-gauge 3m high. The author has made a carefull study on the difference of precipitation-amount between the above two gauges. The result thus obtained may approximately be expressed by the formula:
y=1.2-1.6x (see Fig. 1), in which y denotes the difference of amount of precipitation between the two gauges in mm per day and x the mean wind velocity in m/s measured by the Robinson's cup anemomenter at 14m elevation. The same research has been extended to the Saisyu and the Genzan observatory and the analogous results have been obtained.