6928933 in the atrnosphere will alter the falling rates of the particles. Corrections for these effects can be made wh-n adequite metecrological data are avail~ 2ble, The local fallout as defined bere will be down in 4.5 days or less, leaving aloft an aypgregzte of particles ranging from about 25-micron diameter dewn to submicron size. For small shots the majority of this will be.in the troposphere but for megaton-range yields a large propor tion will be deposited in the stratospkere. Hence, in discussing world- wide fallout, it is desirable to consider it as subdivided into two classes identified as tropospheric, or intermediate, fallcut and stratespheric, or delayed, fallout (Reference 23). The miterial left in the troposphere is thought to remain 2loft up te forty days and to circle the carth 2 few times before reaching level. ground It deposits in relatively narrow bards, centered on the detoretion latitude, with little evidence of diffusion acress the stable air barrier located in the troposphere north of the equator. It is probably brought down largely by the scavenging effect of rainfall or other precipitztion (Reference 23). These particles which do not fall out within the first few weeks will remain suspended in the stmosphsere for z prolonged period — 2 matter 1A S * * ed f ad tanta stm Lei tes LE LE 4b of zround seven vears on the average, Ths meteriz] oripinates exclusive- Sohie a s s eer Enereys vcActof ee <