This notebook covers the period July-December 1880. The entries are by Francis Upton and Francis Jehl. Some entries are probably by William Hammer. The book contains calculations and notes regarding insulation for underground cables and the electric railroad. The label on the front cover is marked "Lines Insulat" There are 284 numbered pages.

Blank pages: 88-91, 140-143, 146-149, 152-253, 262-267.

Missing page numbers: 111-114, 271-272.

Courtesy of Thomas Edison National Historical Park.