Some observations of low-level ion clouds

Simultaneous measurements have been made of the atmospheric potential at 33 meters, 21 meters, and 8 meters above ground level, using three radioactive probes. The current from each probe to ground passed through a number of 100,000 megohm resistors and the i-r drop across a terminal resistor of 400 megohms was measured. These measurements indicate that clouds of ions whose net charge was sometimes positive and sometimes negative frequently passed over-head at altitudes of ten meters and less. The origin of the ion clouds is uncertain, but it appears that some, if not all, were produced by motor vehicles, particularly diesel-powered vehicles.