This notebook covers the period April-October 1879. The entries are by Edison and John W. Lawson. Included are notes, drawings, and calculations for a series of experiments on thermoelectricity. The experiments were made with bars of metal alloys and are probably related to the alloy experiments in Menlo Park Notebook #18. The label on the front cover is marked "Thermo Experiments." The book contains 284 numbered pages.

Blank pages: 158-161, 202-203, 208-215, 218-271, 274-277.

Missing page numbers: 7, 9-13, 15, 17 [pages 7, 13, 15, 17 were renumbered as 2, 3, 4, 5].