This notebook covers the period January-December 1890. All entries are by Edison. At the beginning of the book is a list of iron mines in New York, New Jersey, and Pennsylvania. The book also contains drawings of the phonograph and the electric railway; notes regarding the technical and commercial development of the electric light, including notes on the contractual arrangement between the laboratory and the manufacturing company (possibly the Edison General Electric Co.); lists and drawings for an ore milling operation; and an enumeration of salaries and other operating expenses at the West Orange laboratory. There are also hypotheses on conductivity and resistance and notes on filament experiments. The front cover is labeled "#581." The inside front cover is inscribed "#581 T A Edison Jan 4. 90." The pages are unnumbered, and the book has been used in both directions. Several pages have been removed from the middle of the book. Approximately 125 pages have been used. Courtesy of Thomas Edison National Historical Park.