The electrical current accompanying any specified source of point discharge. In the electrical budget of the earth–atmosphere system, point discharge currents are of considerable significance as a major component of the supply current. Estimates made by Schonland (1928) of the point discharge current from trees in arid southwest Africa suggest that this process accounts for about 20 times as much delivery of negative charge to the earth during typical thunderstorms as do lightning discharges. Although the great height of thundercloud bases in arid regions, such as that referred to in Schonland's study, tends to favor point discharge over lightning charge transfer, point discharge still seems more significant than lightning even in England, where Wormell (1953) found for Cambridge a ratio of about 5:1 in favor of point discharge over lightning charge transfer.