This notebook covers the period August 1880. Most of the entries are by William J. Hammer. There are also a few entries by Francis Jehl. The book contains notes, along with a few drawings, relating to tests of experimental lamps. The label on the front cover is marked "Hammer" and "Experimental Lamps." There is an index on the inside front cover. The book contains 284 numbered pages.
Blank pages: 26-35, 40-197, 200-269, 272-279. Courtesy of Thomas Edison National Historical Park.