THUNDER and lightning are the most
-L impressive natural phenomena that occur in our normal experience, and their impressiveness is not lessened if we know what they really are-an enormous electric spark and the noise made by a cataclysmic disturbance of air molecules. In the last talk in his present series Mr. Eric Parker will describe how thunder and lightning happen, what is meant by being ' struck by lightning,' and the distance at which lightning can be seen and thunder heard.
