Franklin's lightning experiment, historical artwork. This 1752 experiment, by the American scientist Benjamin Franklin (1706-1790), was to study the nature of lightning. Franklin, assisted by his son, flew a kite during a thunderstorm. Franklin held a Leyden jar (and early capacitor) next to a key attached to the wet string. The electric charges in the air caused the Leyden jar to charge, proving that lightning is an electrical phenomenon. Several other scientists died attempting to repeat this experiment. Franklin invented the lightning rod after his experiments.