diameter of one at 68,000 feet, and of the other at 110,000 feet. The growth of the diameters . of the two rings is plotted in Figure 6.7. The diameters of the twobells observed areplotted in Figure 6.8. The heights of the ' bells were measurable on only one film, which shows the base of the lower bell at approx- °. imately 30,000 feet and the upper at 40,000 to 45,000 feet throughout the measurable range, from 2 to 15 minutes. The stem could be measured from only one film, between 10 and 14 minutes. During that interval, its diameter increased from 9,000 feet to 14,000 feet. 6.3 SHOT 4 Six condensation rings were visible on three films from this shot. Figure 6.9 shows all six rings distinctly. Their diameters are plotted in Figure 6.10, together with the Ice _ CONDENSATION a RINGS Woo THUNDERHEAD ’ Figure 6.1 Idealized sketch of cloud phenomena from multimegation bomb with top view showing early cloud stage and bottom view at later time. diameters of the shock wave and the Wilson cloud chamber, which were visible in one of the films. All the rings except No. 3 remained at approximately the same height throughout the period measured. The rings were all measurable from about 0.3 minute to 0.6 28 SECRET