Franklin's lightning experiment. US scientist Benjamin Franklin (1706-1790) and his 21-year-old son William, performing their famous lightning experiment. On 15 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) seen near Franklin's hand. This experiment proved that lightning was an electrical phenomenon, and supported Franklin's invention of lightning rods. Artwork from 'Electricite' (1911) by Max de Nansouty, part of the 'Les merveilles de la science' series of 1867-1891 by Louis Figuier.