This notebook covers the periods December 1885 and February 1886. All of the entries are by Edison. The names of John F. Ott and Martin Force appear frequently as witnesses. The first page of the notebook contains a notation by Edison that "this book is to contain ideas as to the discovery of a new mode of motion or energy and also to the conversion of heat directly into electricity." He apparently called this potential new source of energy "XYZ." The one entry from February 1886 relates to carbons for arc lights. The spine is labeled "26." The book contains 288 numbered pages.

Blank pages: 66-199, 204-288.