The one dated entry in this pocket notebook is from May 1919. However, the book was probably begun late in 1918 or early in 1919. It was used by Edison to record ideas about business matters, experiments to be tried, and other tasks to be performed. Many of the entries pertain to Edison's idea of using lithium hydroxide in the Lalande primary battery, his interest in locating new sources of lithium, and his plans to construct a lithium hydroxide plant to supply his own needs and to meet the growing industrial demand. At the beginning of the book is the address of an unworked lithium mine in South Dakota, along with a notation to "increase Capital stock Mining Exploration Co to pay my expenditures at Par." There are also entries regarding mica mines in western New Jersey, as well as Edison's renewed interest in the regeneration of used storage battery components and the development of a process to extract potash (used in batteries) from feldspar.
In addition, there are numerous entries relating to electromotograph ("EMG") experiments and to the use of the device in the chalk telephone. One entry contains a reminder to "look up old note books for all notes on chalk phone & copy," while another mentions Edison's plan to "retry the old Etheric & use phone & chalk phone." Also included are notes on disc records and test recordings, along with entries indicating Edison's continuing interest in submarine detection and other military topics. The inside front cover is inscribed "Ent in final book May 6th 1919." The pages are unnumbered. Approximately 160 pages have been used. Courtesy of Thomas Edison National Historical Park.