This undated notebook was probably used during the 1890s, but it could have been used during the early 1900s. All entries are by Edison. The book contains notes and drawings probably relating to either ore milling or Portland cement plant operations. Included are several rough drawings of gearing and gear ratios. The pages are unnumbered, and several pages have been removed from the book. Approximately 50 pages have been used. Courtesy of Thomas Edison National Historical Park.