10 by using a 100/110-ml cassia volumetric flask instead of a4 graduated cylinder. All samples except fish were processed aboard ship immediately after being collected. Fish were frozen aboard ship, dissected and dried at the Eniwetok Marine Biological Laboratory, and ashed and counted at the University of Washington. The water supply for the probe tank for continuous monitoring, instead of being taken from the fire mains as on the Walton, was supplied by 4 Marlow Centrifugal Pump, Model No. 12, HEL-9, operated at its full capacity of 50 gallons per minute. Chemical pumrs of lesser capacity which had been furnished with the tank were tried but were inadequate. used for intake and discharge. and hull of the One and one-half-inch pipe was The pipe was welded to the deck ship and the free end of the intake pipe was held against the force of the water by a chsin leading to 4 stanchion on deck. Even with these precautions and generally good sailing conditions, the pipe broke on the last day of the cruise. METHODS OF ANALYSIS All counting, with the exception of fish samples, was done aboard ship within a few hours after the time of collection. Counting Equipment. Samples were prepared on 14-inch stain- less steel plates and counted with 2-inch Anton tubes in a 3-inoh lead Anton pig with Nuclear-Chicago Model 181 scalers. Baok- ground varied from 17.3 to 37.1 c/min. Correction Factors. The same correction factors were used as for the Walton data, the details of which are given in UWFL-46. ot le ey ba a.