The electric charges and masses of single raindrops

Raindrops were admitted by a cone‐shaped opening into an insulated vessel connected to a valve amplifier for measuring the drop charge Q. Drop radius a was found by the absorbent paper method. The field at the ground and the point discharge current I were also measured. Most often, but not always, the signs of the drop charge and field were opposite. During point discharge, 173 drop charges and masses were measured, and statistical analysis showed a definite correlation between Q and I—, a probable correlation between Q/—I and a and a possible correlation between a and —Q. By grouping drops according to radius, and taking averages within the groups, the approximate relationship Q/—I ∞ a was obtained. In one period when the radius was nearly constant, the observations gave the connection Q ∞ — I without taking averages. The observed relation between Q and I corresponds to the results of Simpson (1949) for the charge on a volume of rain. The observed charges were mostly much higher than predicted on Wilson's ion‐capture theory, unless the field increases considerably with height in the atmosphere.