Franklin's lightning experiment. Illustration of the US scientist Benjamin Franklin (1706-1790) and his son William, performing their famous lightning experiment. On 15th June 1752 they flew a kite during a thunderstorm, with a metal wire on the kite attracting a lightning strike. Electricity flowed down the string to a key, charging a Leyden jar (capacitor). This experiment proved that lightning was an electrical phenomenon, and supported Franklin's invention of lightning rods. Some scientists died repeating the experiment. Image published in New York, USA, by Currier and Ives, c1876.