clam shells and corals which were held at 600°C for thirty minutes. (5) After cooling, the ash was slurried with ethyl alcohol and a clean glass rod to distribute it evenly on the plate. var, Following drying, a weightless amount of form- ina s-percent solution of ethylene dichloride was added to prevent ash from being blown off the plate. After drying under a heat lamp the plate was ready for counting. 3.3 Counting The samples were counted in two Nucleometer internal gas flow (pure methane) counting chambers. Counting time. counting time, | A compromise was made as to length of since there were many plates to be counted, only two counters were available and it was desirable to keep the correction factor for decay to a minimum. The counting time for each plate was determined by its approximate counting rate, including a 50 c/m background, in accordance with the following schedule: Counting Rate (c/n) £500 500-1000 1000-2000 >2000 Counting time (minutes) : | 20 10 5 2 The counting period for practically all samples collected after the Mike test (Nov. 1) was from November 24 to December 12. Most of the samples from the pre-test collections were counted -8- Sp ary