Abstract
A series of detailed measurements was made of the concentration of small ions near the ground. It was found that for values of the atmospheric potential gradient exceeding some ยฑ 500 v m^โ1^ the electrode effect in the small ions was readily observable, and that when rain fell in a large electric field, there took place a large production of ions of sign opposite to that of the field. The latter effect was examined in some laboratory experiments which showed that the release of charge in the form of ions was associated with splashing. The mechanism by which the ions were produced was found and a determination made of the dependence of the charge released by individual drops on the field, drop mass and drop speed at impact.
To determine the importance of the charge released by splashing at the ground, another series of observations was made including the measurement of space charge. It was found that in fine weather the field was sometimes controlled by clouds of charge near the ground. In disturbed weather natural point discharge gave rise to considerable values of the space charge, and in comparison with these, the charges produced by the splashing of rain only became important during heavy rain.