29 January 2.5 days later. The cloud from Baker-1l shot fired at 0845 ZST on 26 January was estimated to pass over BNL at 0600 EST on 31 January, 2.8 days later. The cloud from Easy shot fired 1 February 1951 was estimated to require about 7 days to reach BNL; arrived about the same time. that from Baker-2 fired 2 February § The cloud from Freddy missed BNL entirely. kinds of observations were made: Two one on the collection of radio-activity of snowfall precipitation and the other on filters drawing ten cubic meters at : air per sample. From the snowfall activity of 1.4 x i974 curies per cc 1 was estimated that about .9 curies per sq. mi. of snowfall activity was brought down with the snow on 31 January (presumably Baker-1 shot). some allowance for neptunium content, ’ Making ; it appears that the total bomb debris, - about a fraction of 5 x 107? per sq. mi. was deposited at Brookhaven, residuum from about 2 x 107? fissions per sq. mi. per kT. or the The filters reported an average activity of around 1800 disintegrations per minute. It is interesting to note that if activity of this density is uniform in the atmosphere and if, furthermore, the precipitation brings down all activity from ; ell 2, height of around 5000 meters that the activity deposited would be about Pe 1.4 curies per sq. mi. eo et! The evidence from the material settling out on the & csround at times when there is no precipitation indicates that the particles ”™ from a height of only ten to fifty meters are deposited. The NRL investigators report gathering of fission debris from roofs of labs at Denver, Pensacola and Washington, D. C. Their technique is particularly accurate in that the activity of the fission product molybdenum 99 was separated and measured, allowing one to.-compute that a fraction of 5 x 19" per sqe mi. of the debris from Baker-1 shot was precipitated at Denver; 5x i071 per sq. mi. of the Baker-2 shot settled at Pensacola; and 8 x 107? per sq- mi. of the Able shot settled at NOEEee s . While these numbers are valuable the samples were not collectedat places where major fall out occurred. “KAPL reports that dispersion of 3 x i971 curies per cc of snow from Baker-1 shot is about 1/6 of that reported by BNL. As an exploratory calculation the following figures are assumed: 1) fall out density is 5 x 104 of bomb debris per sq. mi., 2) that a fraction 1073 of strontium is ingestible pererr,