of recent tropospheric origin, this northward movems r£ coulée be fue to surface winds, 3 However, the high percentage of Sr“~ : . 93 levels in the troposphere are not uniform over the incicates that the 5 > 2 r A Unites States, However, when areas are chosen which are small enough to have neariy the same tropospheric activity levels, the Sr“~90 in rain water is proportional to the amount of precipitation. There is some justification for accepting the theory that a selective entrance zone for stratospheric fallout exists. This is demonstrated in the initial separation of data, where northern sites show little correlation although they have a higher mean level psr inch of rain. Rainout for the southern stations is definitely proportional to the amount of rainfall, suggesting a more uniform activity level in the atmosphere, It should be noted that no correlation for southern stations existed in July, when there was fresh fellout, SUGGESTIONS The validity of the assumptions made from this data suffer from In the event a more comprehensive study is ck several sources of errore undertaken in the future, there ere several changes that should be made. (1) The scope of the experiment should be extended to operate over a larger area and a longer period of tims: (2) Sampling methods should be improved to preclude missing parts of the rain sample, = 25 = ““ ~ AQ 2 . => ~ Ps LOR ~ > ae ° 5 ORAL ao> a - BY Sad oe s y = 0 es 7