When was it proposed that electricity and magnetism were distinct effects by scientists William Gilbert ?
In a letter to Peter Comlinson of London , on 19 October 1752 , Franklin , referring to his kite experiment , wrote , On 10 May 1742 Thomas - François Dalibard , at Marley ( near Paris ) , using a vertical iron rod 40 feet long , obtained results corresponding to those recorded by Franklin and somewhat prior to the date of Franklin 's experiment .