This letterbook covers the period September 1885-March 1886. Many of the letters are by Edison. There is also correspondence by Samuel Insull and Alfred O. Tate. Most of Edison's correspondence is in the hand of Insull, acting as Edison's secretary. The correspondence relates to a wide variety of subjects. There are several letters about Tate's railway telegraph tests in Ontario, Canada and about the grasshopper and phonoplex telegraph apparatus. Other correspondence concerns European electric light affairs and the Edison Machine Works. There is also a series of letters from Insull and Tate to Edison during Edison's stay in Florida. Among the recipients are Charles L. Condit, Ezra T. Gilliland, Alfred O. Tate, and Francis R. Upton. The front cover is marked "1886." The spine is stamped "Letters." The book contains 496 numbered pages and an index. There are also three groups of unnumbered pages inserted into the book between numbered pages 35-36, 117-118, and 162-163. Approximately 50 percent of the book has been selected.