This notebook was used by George E. Hart during the period April 1920-July 1921 for experimental notes on a variety of subjects. The experiments are numbered from 562 to 660. The first part of the book consists of notes on primary battery experiments, similar to those in N-20-01-12.1 [not selected] in Battery Experiments -- Experimenters' Books -- H. E. Thayer Books. Beginning with Experiment 606 is a series of entries pertaining to annealing work with storage batteries. These are followed by experiments (613-632) to improve the wax master for disc records. At the end of the book is a series of notes describing experiments to develop a method of purifying commercial graphite for use in disc record manufacture. The notes indicate that Edison was directing Hart's work, and some of the entries include notations by Hart regarding Edison's instructions, comments, or contributions. A communication from Edison to Hart has been inserted into the book. The front cover is labeled "George E Hart #3." The pages are unnumbered. Approximately 100 pages have been used.