This notebook covers the periods April-October 1907 and February-April 1920. All entries are by Edison. The book contains notes and drawings regarding projects to be undertaken and hypotheses to be tested, along with other theoretical speculation pertaining to electricity, physics, and cosmology. Included are entries relating to x-rays and "xyz rays," the electromotograph, storage batteries, and incandescent lamps. There is scattered material dealing with improvements to the phonograph and kinetoscope, including a one-page entry about a proposed "kinetophonograph," as well as a brief notation detailing a high-voltage direct current dynamo. The book appears to have been used primarily at Fort Myers, Florida. At the end of the book, Edison's youngest son, Theodore, signed his name in November 1906. The front cover is labeled "Ideas Theory." The book contains 408 numbered pages; many pages are blank.