This notebook covers the period April-August 1881. Most of the entries are by Francis Jehl. A few entries are by Edison. All of the material relates to electric light and power. There are notes, calculations, and drawings concerning dynamo experiments and tests, including Edison's notes on commutator brushes for the South American dynamo and Jehl's tests of these brushes, based on Edison's instructions. There are also notes by Jehl on changes made in dynamo design as a result of tests conducted at the Edison Machine Works. Other material relates to tests of meters, conductors, steam engines, and motors. The label on the front cover is marked "Francis Jehl" and "Edison Machine Works N.Y." The book contains 280 numbered pages.

Blank pages: 30-35, 94-95, 230-231, 256-265.