This notebook covers the period July 1881. The entries are by Charles L. Clarke and relate to dynamos. Included are notes, calculations, and drawings of the London C dynamo, the Z dynamo, and various central station dynamos. Several loose pages were found in the book, including calculations and notes by Clarke and Gustav Soldan on dynamo design and a note from Edison to Clarke asking for the size of wire used on the Z dynamo for the Edison Machine Works. The label on the front cover is marked "Magnets." The book contains 278 numbered pages.

Blank pages: 643, 66-278.