er daebeste tome? 12 a 3-inch lead Anton pig with a Nuclear-Chicago Model 181 Scaler. Background varied from 18 to 32 c/min. Correction Factors: To convert counts to disintegrations per unit volume or weight, corrections were made for sample size, self-absorption, geometry, backscatter and decay. The correc- tion factor for counting efficiency, which includes self-absorption, geometry and backscatter, was determined from counting plates of known weights of potassium chloride with known disintegration rates for x0, For plankton this factor ranged from 3.4 to 3.8; and was for filter paper, 3.3; and for water samples, 4.0. All samples counting background or less were taken as zero. The samples counted aboard ship were counted within a few hours from time collected and therefore were not corrected for decay. The samples counted at EMBL were corrected to the day of- collection. For samples collected west of Eniwetok (sections 1 to 5 inclusive) one decay curve was used and for sections 6 to 10 @ second curve was used (Fig. 9). For the former the half life was less than two days for the early part of the curve and about six days for the end of the observation period. curve the half life was about four days. For the latter The maximum correction factor for decay was 15 but the factor usually was much less. Fish samples were corrected to the day of collection using the plankton decay curves and absorption factors. Contours: Contours have been used to show distribution of radioactivity, but the contours have limited significance. The use of contours adequately shows the relationships between the radioactivity of the plankton and water samples, but the contours py yes