On the nature of Atmospherics-II

Abstract

In a previous paper we gave a preliminary account of an experimental method of determining the intensity and duration of those naturally occurring electric waves known as atmospherics. The method consisted in examining, by means of a sensitive cathode-ray oscillograph, the potential variations developed across a condenser or resistance included in a damped antenna, the time constant of which was small compared with the duration of the atmospheric pulse. A summary of the chief characteristics of the first six hundred atmospherics investigated by this method was also given, but, as the work was obviously of a preliminary nature, the detailed discussion of the results was not considered profitable at such an early stage and was accordingly postponed. Since that time the observations have been systematically continued, and many alterations and improvements have been made in the experimental apparatus which tend to make the oscillographic trace a still more faithful representation of the electric field changes. In particular, the development and use of a new form of oscillograph time base, which is both linear and unidirectional, has eliminated the distortion and ambiguity as to time-sense which was associated with the use of the simple harmonic time base of the earlier experiments. Also, as the apparatus for the delineation of atmospheric wave-forms is now more or less in its final form, and as the circuit ultimately developed is somewhat complicated, a series of station tests has been devised which enable the observer rapidly to ascertain at any moment if the aerial and internal insulation is satisfactory and the required quality of amplification is being maintained. The oscillographic observations have been supplemented by simultaneous and independent determinations of the measurable semi-permanent changes of the earth’s electric field which have been found to be associated with a small percentage of atmospherics. It may be noted that the possibility of such net changes of field was purposely excluded from our first account of the method.