This notebook covers the period December 1887-November 1889. All entries are by Edison. The book contains drawings and several long notes relating to filament experiments. There are also phonograph drawings; notes on battery solutions; and notes, drawings, and cost calculations regarding ore milling and hydroelectric power production at Niagara Falls. On the inside back cover is a list of points to include in an electric railway caveat. The pages are unnumbered. Approximately 120 pages have been used. Courtesy of Thomas Edison National Historical Park.