THE LARGE‐ION AND SMALL‐ION CONTENT OF THE ATMOSPHERE AT WASHINGTON, D. C.

Abstract

By means of automatic recorders, the small‐ion and large‐ion content of the atmosphere at Washington, D. C., have been secured. The number of large‐ions have been continuously recorded over a period of nineteen months and the small‐ions over a period of twelve months. Curves of diurnal variation of large ions and of small ions for the various months of the year are drawn. During the cold season of the year, the large ions pass through maxima in the morning and in the evening. During the warm season, only the evening maximum is present which shows a seasonal variation in time of occurrence. The small‐ion variation through the day is more or less reciprocal to the large‐ion variation, but is considerably smaller when regarded on a percentage basis. This is largely attributable to the fact that a portion of the current in the small‐ion counter is contributed by intermediate ions present in the atmosphere. The large ions and relative humidity vary directly during the cold season and in an inverse manner during the warm season. This change in character from one season to another will be a contributing factor to the daily and yearly changes that occur. The mobility of the large ions, as determined in this investigation, is noticeably greater than that ascribed to them by Langevin, thus indicating that the ions in the two places are not identical in size, unless the difference may be attributed to a difference in experimental conditions.