Franklin designing lightning rods. Historical artwork of Benjamin Franklin (1706-1790), American scientist, inventor and statesman, working on the design of lightning rods. Franklin observed, in an experiment in 1750, that a sharp iron needle would conduct electricity away from a charged metal sphere. Here, the smaller sphere, hanging from the ceiling by string, will react to the changing charge on the sphere and show whether the rod has removed the electricity. Two years later, in 1752, Franklin flew a kite in a storm, using a metal key to attract the lightning. Lightning rods are now widely used to protect buildings. From Physique Populaire (E. Desbeaux, 1891).