This folder contains correspondence and other documents relating to the Darby Mine and other cobalt-bearing properties in the Sudbury district of Ontario. The correspondents include Edison and Horace M. Wilson, mining scout and manager of the Darby Mine. The letters deal with Edison's decision to abandon his search for cobalt and close the Darby Mine and with negotiations for the sale of the property and machinery. There are also letters concerning operations at the mine and the transmittal of ore samples.

Approximately 40 percent of the documents have been selected. Most of the selected items contain Edison marginalia.