This undated notebook was used by Edison in July 1918. It contains entries on the preparation of metallic and other compounds for use in the chalk telephone. Several of the early entries are crossed out and noted as "Entrd." Some of these were entered into N-18-07-18.2. The front cover is labeled "Chalk Telephone {Rough Notes}." The pages are unnumbered. Only 14 pages have been used.

Courtesy of Thomas Edison National Historical Park.