This collection consists primarily of letters exchanged between Edison and Secretary of the Navy Josephus Daniels, along with related correspondence. Many of the typewritten letters are accompanied by drafts in Edison's hand. The one item in this folder is from April 30, 1917. It pertains to Edison's idea of using a mercury column operated by a telephone as a tuner to prevent lightning or other natural phenomena from interfering with signals from wireless stations. Courtesy of Charles Hummel.