Summary The waveforms of atmospherics having long-continued trains of pulses, and the systematic modifications associated with time of recording, storm distance and the presence of a low-frequency component, are described. Their interpretation is discussed and the results of analysis—assuming the simple ionospheric reflection mechanism—are presented. Estimates of reflection height and storm distance show the applicability of the theory to the temporal parameters of the waveforms, and the origins of two groups of atmospherics having calculated ranges of 4500 and 7000 km are considered. The variation of pulse amplitude with reflection order is shown to lead to the postulation of horizontal radiating elements in the channel during the later stages of the return stroke, although difficulties arise in reconciling this concept with considerations of the magnitude and orientation of the horizontal elements.