420 SALTER sphere are suggested from the data for April 1963 at 90,000 ft and also those for May and June. Although Starfish debris moving northward from the southern polar stratosphere was present at both 90,000 and 105,000 ft at 34°S in equal amounts by April 1963, it is apparent that debris from the 1961 25-Mt test and/or other 1962 shots which stabilized in the high stratosphere moving southward across the equator was present in relatively larger quantities at 105,000 ft than at 90,000 ft. With the beginning of the southern-hemisphere winter season in May 1963, the absence of ‘Cd in the May and June samples suggests that not only did the equatorward movementof Starfish debris halt but that this material actually retreated to latitudes higher than 34°S. At the same time, the southward movement of even larger quantities of debris from the other shots continued, as is noted by the high *4Mn levels at 105,000 ft in May. Finally, this latter material subsided to lower altitudes, accounting for the high "Sr levels at 77,000 and 86,000 ft in June and at 65,000 ft in September and October. CONCLUSIONS Fission-product data have been used to trace debris from the 1961 U.S.S.R. weapons tests at 34°S in 1962 and1963. This material may account, in part, for the high activity levels at 105,000 ft observed at the end of 1962 and at lower altitudes in mid-1963. It is suggested that this may be attributed to the 25-Mt detonation, the debris from which reached into the high stratosphere and then moved across the equator and mixed downward in the southern hemisphere. Early data on '%cq indicate that material from Starfish Prime behaved similarly to that from Orange. Rapid lateral mixing at high altitudes followed by subsidence in the polar regions and then movement into lower latitudes in the summer months appear to be dominant factors in the transport of this debris. Additional data on Cd and other activation products produced in the 1961 to 1962 test series and on actual formation ratios of fission products in weapons tests should help in future evaluation of radioactive materials in the stratosphere. The failure of a satellite device earlier this year’® containing 17 kc of *88pu may provide yet another tracer for studying movements of stratospheric materials if burnup of this device occurred. REFERENCES 1. Health and Safety Laboratory, Fallout Program Quarterly Summary Report, USAEC Report HASL-115, p. 70, October 1961. 2. Health and Safety Laboratory, Fallout Program Quarterly Summary Report, USAEC Report HASL-124, p. 151, July 1962.