This notebook was used by Edison and Peter C. Christensen during the period August 1913-May 1914 for a sequence of numbered "tracking tests," which are continued in N-14-06-09. These tests involved evaluating the hardness, surface tension, and other characteristics of experimental preparations of wax compounds and metallic soaps, probably in an effort to improve the quality of the "white master" records onto which recordings were made. The masters formed the base for subsequent molds used in the disc record production process. Intermixed with the tracking tests are entries by Christensen alone [not selected] relating to tests of the viscosity and purity of rosin, varnish, graphite, and various waxes used in the manufacture of phonograph records. Related wax experiments by Christensen, with comments by Edison, can be found in Notebooks by Other Experimenters -- General Experiment Books -- P. C. Christensen Book, N-12-04-19. The spine is labeled "Testings #1." The book contains 197 numbered pages and has been used to page 196. Courtesy of Thomas Edison National Historical Park.