The letters in these six folders primarily cover the years 1917-1920, although there are some items from 1914-1916 and a few from 1921, 1927, 1930, and 1931. In addition to Edison and Daniels, the correspondents include their spouses, Mina Miller Edison and Addie Worth Bagley Daniels; their personal assistants, William H. Meadowcroft and Frank Smith; and longtime Edison associates Frank J. Sprague and T. Comerford Martin. The wartime correspondence, which constitutes the bulk of the collection, consists primarily of typewritten copies of Edison's incoming letters that Daniels kept in his personal file, along with carbon copies of his own outgoing letters. There are also a few items in Edison's hand. Many of the letters discuss Edison's wartime research projects for the U.S. Navy. Since a more complete set of research reports can be found in the Edison Wartime Research Reports (Charles Hummel Collection), these letters have selected only in cases where there is no copy in the Hummel Collection. Among the research projects discussed in the selected reports are Edison's sea anchor (or kite rudder) for the rapid turning of merchant ships threatened by enemy torpedoes; smoke bombs to hide merchant ships from enemy submarines; searchlights for use on U.S. submarines; and various submarine detection experiments. The letters from the summer of 1917 also discuss the difficulties experienced by Edison in securing a private yacht on which to conduct his experimentsa situation that was ultimately remedied when the Navy gave him the use of the USS Sachem.
The Daniels Papers also contains numerous letters dealing with Edison's role as chairman (later president) of the Naval Consulting Board. The original signed copy of Daniels's letter of July 7, 1915, inviting Edison to head a civilian advisory board is in the Edison National Historical Park archives. However, two earlier versions of this letter, both dated May 31, 1915, as well as a draft of the July 7 letter with handwritten changes by Daniels, can be found in the Daniels Papers. Among the topics discussed in the wartime letters are Edison's concern that his research be kept secret, his dissatisfaction with the career officers of the U.S. Navy, the acrimonious debate over the location and purpose of the Naval Research Laboratory, and his strenuous objection to the decision to locate the laboratory in Washington, D.C. A handwritten letter marked "personal & private," written by Edison two weeks before the end of the war, warns Daniels that he is "being systematically deceived" by the heads of the various Navy bureaus and urges the secretary to "get suspicious."
Despite the bitter tone of many of Edison's letters, the correspondence also reveals the friendly personal relationship that developed between Edison and Daniels. Included are periodic birthday greetings by Daniels, invitations by Edison for Daniels to participate in his summer camping trips, and other social invitations tendered by both men. The letters also indicate that Edison used his connection with Daniels to obtain delays in a federal antitrust suit against the Edison Phonograph Works and a damage suit against the Edison Storage Battery Co. arising from the January 1916 explosion of the E-2 submarine. The last item is a telegram of condolence that Daniels sent to Mina Miller Edison after her husband's death on October 19, 1931.