0018933 of the radiomeclide composition of local fallout as determined from the rocket samplese The influence of the enviroment on fallout partition was to be inves- tigated by participation in events over land and water surfacese The basic hypothesis on which the determination of fallout partition by the measurement of relative enrichment is based is that the increase of a volatile material with respect to a refractory material (eoges Kr 88 with respect to Mo?9) occurs principally as a result of fallout of the refractory material (i.e., the only force producing separation is gravitation). If this hypothesis is correct, then the Mo?9 left in the cloud region sampled compared to the Kr 88 nay be interpreted as the fraction of refractory debris which will be distributed in"world-wide™ fallout. This fraction is given by _ fR°°(e8)] 5 [n°9(e8)] c If, however, other forces operate on the particles, particularly centrifugal forces which exist during the initial phase of cloud rise or turbulent forces which may exist for several hours due to temperature inequalities, the possibility exists that separation of gases or small particles from large particles ‘may cccur without requiring real fallout of refractory materiale It is also possible that separation of the more volatile products from the less volatile may occur in the gas phase. as a function of altitude in the cloud without requiring separation of large particles from small particles or particles from permanent gasese If these processes occur, even a large enrichment of volatile material near the top of the cloud would not necessarily be attributable principally to fallout. To help determine whether these elternative processes are important, it is considered necessary to obtain very early data for R values of relatively volatile