The results already obtained were got by means of a roughly made apparatus designed for the purpose of testing the method used, so that only a single instance, to show their general character, need now be given. When a wooden block of 10 lbs. mass fell through a height of 18¼14 inches on a rounded lump of gutta-percha, the time of impact was found to be somewhere about 0.001 sec, and the coefficient of restitution was 0.26.