According to an inscription by Clarke at the front of the book, this notebook was used in 1890-1891 for research into the "prior art" in defense of Edison's U.S. Patents 369,280 and 264,668. The entries consist primarily of summaries of books on electricity and articles in scientific and engineering journals. The books consulted include George B. Prescott's History, Theory, and Practice of the Electric Telegraph (1860) and The Speaking Telephone, Electric Light, and Other Recent Electrical Inventions (1879), Hippolyte Fontaine's Electric Lighting (1878 translation), John T. Sprague's Electricity: Its Theory, Sources, and Applications (1875), and Franklin L. Pope's Modern Practice of the Electric Telegraph (1871). The journals include Engineering, Nature, Philosophical Transactions of the Royal Society of London, Telegraphic Journal & Electrical Review, and Van Nostrand's Engineering Magazine.There are also two pages of notes and drawings concerning the Edison "Z" dynamo, along with summaries of British and American patents. The label on the front cover is inscribed "Multiple Arc Distribution," "U.S. Patent 369280. Edison," and "Compound Winding U.S. Patent 264668. Edison." Clarke's name and address are also inscribed on the label. The pages are unnumbered; approximately 65 pages have been used. Courtesy of the Henry Ford Museum and Greenfield Village Research Center.