The activity of the liquid and of the solid was measured separately in the 4-pi gamma high-pressure ionization chamber.” The decay was plotted on appropriate log-log paper. The ionization chamber utilized argon gas under a pressure of 600 psi; the ionization current was impressed across a high resistance. The resulting voltage was measured with a vibrating reed electrometer.’? Its calibration with respect to energy and linearity agreed closely with published values, RESULTS AND DISCUSSION The data have been summarized in Table 1 and the exponent values, k, computed for the decay equation. The observed decay curves are plotted in Figs. 3 through 8. It has been noted* that these data are within a few percent of the gamma decay curves calculated from radiochemical analysis. The values of k for all the samples except two were greater than l.2. The range and’magnitude of the exponents are greater than those reported from Operation TEAPOT.? The exponent values derived from the fallout collected at Operation TEAPOT ranged from 0.9 to 1.3 while the values from CASTLE ranged from 1.1 to 2.03. It is interesting to note that beta decay measurements made on rain water collected at Harvard University‘ after Operation CASTLE gave exponents of the same order of magnitude as those reported here, Approved by: E.R. TOMPKINS Head, Chemical Technology Division For the Scientific Director * Personal communication from C.F. Miller of this laboratory. -3.- UNCLASSIFIED