The entries in this notebook contain only the month and the day. The book probably covers the period April 1880-January 1881. Its author is unknown. Included are notes relating to tests of insulating materials, primarily glass, quartz, and calcite; notes on magnetism experiments; and notes on chemical experiments. There are also a few drawings of circuits. The label on the front cover is marked "107" and "Apr 1880." The pages are unnumbered, and the book has been used in both directions. Approximately 100 pages have been used. Courtesy of Thomas Edison National Historical Park.