This is the last record by sound ranging of artillery activity on the American front near the River Moselle. It is the reproduction of a piece of recording tapeas it issued from an American sound-ranging apparatus when the hour of 11 o'clock on the morning of November 11, 1918, brought the general order tocease firing, and the great war came to an end. Six seconds of sound recording are shown. The broken character of the records on the left indicates greatartillery activity; the lack of irregularities on the right indicates almost complete cessation of firing, two breaks in the second line probably being dueto the exuberance of a doughboy firing his pistol twice close to one of the recording microphones on the front in celebration of the dawn of peace. The twominutes on either side of the exact armistice hour have been cut from the strip to emphasize the contrast. Sound ranging was an important means of locatingthe positions and calibers of enemy guns. A description of these wonderful devices, which were a secret with America and the Allies, is given in BookIII, chapter 4.