This notebook covers the periods July 1871-Nebruary 1872 and April 1874-August 1875, with the majority of entries falling in 1875. The notes and drawings are in the hand of Thomas Edison and Charles Batchelor and deal with the development of the electric pen, electromotograph, automatic printing and chemical telegraphy, and multiple telegraphy. There are many tests of chemical solutions and a few notes on battery and other experiments. Tapes treated with chemicals are affixed to pages 204-206, 208-210, and 212-213; examples of printed tape are on pages 289 and 290; samples of reproductions done by the electric pen are glued onto pages 228, 236, 238, and 254. Some of the experiments are signed and dated by Edison and Batchelor, and the names of Joseph Murray, Edward H. Johnson, Samuel Edison, James Adams, and Ezra T. Gilliland appear as witnesses. The book contains 294 numbered pages.

Blank pages: 34-35, 44-59, 94-125, 128-133, 136-157, 182-199, 242-243, 292-293.

Missing pages: 215-216, 251-252, 277-278.