This folder contains correspondence and other documents relating to the Darby Mine. The letters are to or from Edison, Charles Edison, and John V. Miller. The documents pertain to the proposed sale or option of the mine, as well as changes in the demand for cobalt. One item by Miller is entitled "Report of Visit to Sudbury, Ont., Mining District -- July 2 & 3, 1929."

Approximately 30 percent of the documents have been selected.