The patterns of Sr90 distribution in the equatorial Atlantic are described for the years 1957, 1958, 1960, and 1961. Evidence is drawn from analysis of surface samples and of vertical profiles. The concentration distributions bear no resemblance to patterns of fall-out delivery on land; it is concluded that hydrographic processes are responsible for seawater concentration patterns. The data provide evidence for two otherwise unobserved, high fallout incidents over the Atlantic Ocean....