This letterbook covers the period July 1889-May 1890. The book contains correspondence, technical reports, and draft manuscripts by Arthur E. Kennelly. Included is material regarding a variety of electrical experiments, such as tests of meters, batteries for the phonograph, the carrying capacity of copper wire, and various insulation compounds. In addition, there are items relating to alternating current experiments and plans for the Niagara Falls hydroelectric power system. The book contains 468 numbered pages. Some pages have been removed from the book. The book is water damaged, and many pages are discolored and wrinkled; the ink on the pages near the end of the book is smeared. Approximately 30 percent of the documents have been selected. Courtesy of Thomas Edison National Historical Park.