At about 2000Z, 26 May 1953 the District of Columbia area experienced a hailstorm in which individual hailstones ranged up to the size of tennis balls. Determinations of the radioactive count of the water content of these hailstones and of roof gravels indicate that considerable material was brought to earth by the hailstorm from the explosion of the atomic cannon shell 29 hours earlier some 2000 airline miles away in Nevada. The air-flow pattern at upper levels proves to have been around a high-pressure ridge located between the two sites. Such a pattern permitted the arrival of such radioactive material over the District of Columbia area within the time noted.

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