This notebook was used by Edison and an unidentified experimenter during October 1918. At the beginning of the book is a table "showing composition of cylinders." The remainder of the book contains descriptions of cylinders for chalk telephones prepared with various compounds. Inserted into the book are several loose pages relating to the same topic. The front cover is labeled "Chalk Telephone." The book contains 196 numbered pages, some of which are blank, and an index on pages 180-181. The index appears first. Courtesy of Thomas Edison National Historical Park.