ELECTRICITY, ATMOSPHERIC. phenomena divide themselves into two main classes : those which we shall call Normal Phenomena—phenomena which prevail at all times, even in the absence of abnormal meteorological condi ditions—and those more particularly associated with thunder storms, which we shall class as Thunderstorm Phenomena. A class of phenomena associated with the motion of electricity in the upper atmosphere and capable of investigation only by indirect means is becoming more and more important in view of the part they play in wireless telegraphy.