This notebook was used by William A. Hayes during the periods October 1918 and October 1920-March1922 for experimental notes on a variety of subjects. At the beginning and end of the book are a few notes from 1918 describing experiments with depth meters for ships. The remaining entries, covering the years 1920-1922, pertain primarily to experiments with recorders for disc phonographs involving a variety of diaphragms, gaskets, and recording arms. There are also experiments on wax master blanks with varying ingredients. Many of the phonograph entries include notations by Hayes regarding Edison's instructions, comments, or opinions. Numerous items, including some with notations by Edison, have been affixed onto or between the notebook pages. In addition, several loose items from 1922 (by Hayes) and 1925-1926 (by F. C. Burt) have been inserted into the book. The book contains 4 unnumbered pages, followed by 127 numbered pages (some blank), and 23 additional unnumbered pages. Courtesy of Thomas Edison National Historical Park.