Eskdalemuir ion measurements 1909-1916

The electrical conductivity of atmospheric air depends on the positive and negative cluster ions (or 'small ions') it contains. Here, intermittent daily ion measurements are presented from Eskdalemuir observatory in Scotland (55.314° N, 356.794° E), in initial work beginning soon after the observatory opened in 1908. These early ion measurements were made using an Ebert sampling apparatus. Air pollution reduces air ion concentrations, hence ion information can provide an indirect measure of air pollution. As air ion measurements were made before routine air pollution monitoring began, ion measurements provide an indirect – and quantitative – source of early pollution information for comparisons. Eskdalemuir is now a background air pollution site. Some entries in the air ion record book containing the original data were initialled by the then Eskdalemuir superintendent, Lewis Fry Richardson.