~28- constant at l1l:1l. 6. The ratio of Co5//zn65 at Bikini and Eniwetok Atolls was 0.06:1.0. Similar ratios occurred 200 miles south and west of Eniwetok Atoll. north. Slightly higher ratios occurred to the The center of high Co>7/zn65 ratio (5.5:1.0) was found approximately 480 miles west and slightly north of Eniwetok Atoll and did not coincide with the center of high total radioactivity in plankton, which was located 110 miles north of Eniwetok Atoll. 7. The changes in ratio of Co5!/Pe25 with change in geo- graphical location were similar to those of C057 /zn®5, DOE ARCHIVES 33