The general form is shown in Figure I, and suggests that of the broken petrified trees in some of the national parks. A cross-section, as in Figure 2, shows bands of vesicles that are much like the growth rings of trees. Close examination shows that the bands do not go completely around and close on themselves as tree rings do. The greatest and least diameters of the ellipsoidal cross-section are about 41 and 3 feet. The total length shown n Figure i is about 40 feet, but fragments totaling as much more have rolled down the sides of the small ridge that is surmounted by the parts still in alignment. The long axis is parallel to the local slope of the lava flows. There is a very slight tendency toward radial jointing.