This notebook covers the period June-July 1880. It is a continuation of Menlo Park Notebook #42 and includes a summary of lamp experiments from that book. Most of the entries are by Francis Upton. There are also occasional entries by other laboratory staff members. Most of the book relates to experiments with bast fibers and, occasionally, with paper or bamboo. There are also notes and drawings relating to dynamo tests and to tests of insulation for electric railroad tracks and underground cables. The label on the front cover is marked "Upton." The book contains 282 numbered pages.

Blank pages: 278-279.