The dated entries in this book begin on page 165 and cover the period March-April 1879. However, the book was probably begun in December 1878. Most of the entries are by Francis Upton. There are also entries by Edison, Charles Batchelor, and Francis Jehl. Included are notes, drawings, and tests of lamps; notes, drawings, and calculations about generators; notes and calculations about meters and electric power distribution; notes and drawings of dynamometers; drawings of the telephone; and notes, drawings, and calculations about electrolysis. There are also notes by Edison on a law of "Proportion of Resistance." The book contains 282 numbered pages.

Blank pages: 54-55.

Missing page numbers: 123-134, 235-238, 243-246.

Courtesy of Thomas Edison National Historical Park.