In a recent issue of the JOURNAL OF THE FRANKLIN INSTITUTE, Koller 1 discusses the question whether the number of small ions in the atmosphere at a given locality has a seasonal as well as a daily variation. He states, among other things, that the number present is greater during the day than at night and is greater during the summer than during the winter. Recent work by the Department of Terrestrial Magnetism of the Carnegie Institution of Washington indicates this statement is open to some question, consideration being given the atmospheric-electric data accumulated by the Department at several different localities over sufficiently long periods to permit statistical analysis. Thus, in addition to the data taken aboard the Carnegie over the Atlantic, Pacific, and Indian oceans, there are the measurements of the electrical conductivity of the atmosphere (ionic content not being observed) made at Watheroo in Western Australia, Huancayo in Peru, Tucson in Arizona (in co6peration with the United States Coast and Geodetic Survey), and Washington in the District of Columbia. For the last station, conductivity of one sign only is recorded for a given time, but positive and negative conductivities have been recorded alternately since January 193o, while for the other stations simultaneous records of the positive and negative conductivity are available.
During cruises IV and VI (I916-2I) of the Carnegie 2 there were obtained six complete diurnal-variation series of positive ionic content of the atmosphere made over the Atlantic, eight over the Indian, and 4 Β° over the Pacific (see '5 2:,6*Z
600
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