30 ~~ 20 ~ sy Oo mh oO — ~ ~O ~ “~. O _ Oo ON a, Ue ~ x “93 Oo DO ~ Og, Ss ~*~. _ Oo sy 144 /dpm Sr 90 ~ — dpm Ce ONG — QL 4 On 6 Oo“ Dw _ ~ oO ° MiAImlu{yvlA;/S{O|N{O]ylE[Mlaimlu fu fAl/Sfo{[NiDO{[JIFIMIAIM fu 1958 1959 1960 Fig. 2 -- Variation with time of the monthly average for Cel44/5r90 in samples collected between 60,000 and 70, 000 feet in the trop- ical stratosphere (30°N - 30°S)