This notebook was used during April-May 1919 and May 1920. The entries from 1919 are by Benjamin F. Sorin and pertain to his construction of pressed chalk cylinders and "buttons" for Edison's experiments. Each entry describes the composition and construction of a batch of cylinders, sometimes indicating when Ludwig F. (Louis) Ott or other laboratory employees supplied chemicals or materials and occasionally noting when the results were shown to Edison. The entries from 1920 are all by Edison and indicate that he "just returned to expmtg with chalk phone." The notes relate to experiments with electromotograph (chalk) telephones using different chalks in various circuits. Included are descriptions of experiments with manganese oxide chalks, some of them faced with various metallic washers, made with varying amounts of pressure. The entries indicate that Frederick P. Ott assisted Edison in some cases. Inserted into the book are notes by Edison, Sorin, and William Walter Dinwiddie. The front cover is marked "Note Book." The book contains 100 numbered pages; pages 54-100 are blank. Courtesy of Thomas Edison National Historical Park.