RADIOACTIVITY IN THE SOUTHERN STRATOSPHERE 417 altitudes. An upper limit for the amount of Sr from the 55-Mt test may be determined by assumingthatthe total °“in found in the sample came from this device and applying the calculated value of 100 for the 4vin/sr ratio. These results, given in the fifth column of Table 3, indicate that this detonation can at most account for only a small frac- tion of the Sr attributed to the whole series. If the 1961 debris is in- deed present to the extent shown, it is probable that the major source was, therefore, the 25-Mt device. This is consistent with the hypothesis presented earlier that most of the material from this device reached altitudes considerably above 100,000 ft from where it spread laterally across the equator and then mixed downward, appearing in significant amounts at 105,000 ft in late 1962 and at successively lower altitudes in 1963. CONTRIBUTIONS FROM STARFISH Cadmium-109 was first observed in samples collected from 105,000 ft at 34°S in December 1962. This markedtheinitial appearance of debris from Starfish in the balloon sampling-program range about five months after its injection into the ionosphere at 17°N. Con- centration profiles for ‘Cd through mid-1964 are summarized in Fig. 3. All 'Cd data have been corrected to July 9, 1962. The 'Cd to total observed *Sr activity ratios are given under the ‘Cd concentra- tion values. The results for ‘cq at 34°S show that Starfish debris had de- scended as low as 90,000 ft in early 1963 and then apparently shifted completely outside the sampling range in May. It reappeared in July, and, by the end of the year, debris was present at all altitudes sampled at 34°S in significant amounts. By mid-1963, one year after its pro- duction, only traces of 'cd had been detected at 31°N, but a few results in samples collected from 45°N and 65°N at that time indicated 199Cq concentrations comparable to those observed earlier at 34°S. In March 1964, 'Cd concentrations at 34°S showed a decrease with altitude from 40 dis/min per 10° scf at 70,000 ft to 25 dis/min per 10° scf at 105,000 ft; at 31°N they ranged from less than 2 dis/min per 10° scf at 65,000 ft to 18 dis/minper 10° scf at 105,000 ft. In June 1964, 1080q was present in slightly higher concentrations in the northern polar stratosphere than at 31°N. The '%cq data delineating the movement of debris from Starfish are generally consistent with that for ‘Rh produced in the Orange rocket shot, the U. S. high altitude test of Aug. 11, 1958, at 17°N during Operation Hardtack I which has been discussed by Kalkstein’? and Telegadas and List,!! Although ‘"Rh data above 70,000 ft are not available for the first year after the Orange shot, high '“Cce/"sr ratios!!-!2 from 90,000 ft at