The dated entries in this book begin on page 75 and cover the period April-November 1879. The earliest entries are a series of undated notes by Edison relating to the work of Sir William Crookes on vacuums, which are followed by drawings of vacuum pumps. These entries probably relate to a series of vacuum experiments for electric lamps, conducted in February and March 1879. The rest of the book is by Francis Upton and relates to electric light experiments. Included are notes, calculations, and tests on generators, motors, and batteries; drawings of generators; calculations about electric light systems; and notes on a regulator \"to make a ten ohm lamp equal to an 100 ohm.\"" The label on the front cover is marked \""Theory\"" and \""Upton.\"" The book contains 284 numbered pages.

Blank pages: 20-21 46-47, 234-249, 280, 283.

Missing page numbers: 281-282."