This notebook covers the period March-May 1880. Most of the entries are by Charles L. Clarke. Much of the book relates to the development of generators, including the jumbo dynamo. There are notes, calculations, and drawings of shafting and belting for dynamos; calorimeter tests of dynamos; and notes on jumbo dynamos for the Pearl Street central station, including a memorandum on questions to be asked of Charles T. Porter, whose steam engine was to be used for the jumbo. Also included are notes by Clarke on Henry Rowland\'s report on the electric light, draft letters by both Edison and Clarke in response to the American Machinist\'s article on Edison\'s dynamo, and a report by Clarke on Sidney H. Short\'s telephone. The label on the front cover is marked \"Clarke.\"" The book contains 280 numbered pages and has been used in both directions.

The notebook pages appear in the following order: pp. 1-201, 275-210 [in reverse page-number order], 272-280. Blank pages: 202-209."