Franklin thought lightning was a discharge phenomenon. In order to prove this point, he risked being struck by lightning on a thunderstorm day in July 1752, and released a kite with a long metal wire into the thunderstorm cloud, and tied a string of copper keys at the end of the metal wire. When the thunder and lightning happened, Franklin's hand was close to the key, and a string of electric sparks burst out on the key. My hands are still numb.