ee Ae Ze Sampling en Observers at each typical fixed station collected 2h hour samples by ex- posing duplicate one foot squares of gummed film. Cne hundred twenty sucn stations throughout the world mailed samples daily to the Health and Safety Laboratory where the activity was measured. The program began February 157. and is still in effect as this is written. except that a few stations which were m-r-' only temporarily during the weapons tests have dropped out. Samp? ing and- analysis techniques were the same as those used during Operation UpsnoteFr-oth-Lle and other test series and they are described in ear- lier reports 1,2,3. ] 3. Results The maps, Figures 1 to 18, show the total fallout of beta activity at the fixed stations for each of six periods, the five between consecutive ex- plosions and the sixth beginning the day of the last explosion and ending 18 days later. Each period begins on the day of a burst. Figures 19 to 21 show the totals for all six periods. is shown in Figures 22 to 30. Fallout for June, July and August The data are in millicuries per square mile extrapolated to January 1, 1955. For the purpose of extrapolation the activity was attributed tc test explosions according to an arbitrary rule adopted in advance, Fallout at stations in the 900 series, the nearest to the proving grounds, and fallout on ships was attributed to the latest burst preceding sampling. Fallout at other stations was attributed to the durst before the latest except that all fallout between the first and second bursts was assigned to the first. Beginning in August the activity was assumed to have originated on April 10th, about the midpoint of the series. As usual the activity was assumed inversely proportional to the 1l.< power of the age. Total world fallout, excluding the vicinity of the test site, from th- . beginning of the series mnti? 13 days after the Last burst, is estin::e?3 4. megacuries, In the vicinity of the tests the network was not dense enough to furniz> an estimate of fal. o:t Measurements of radiation from the open s2:.-. reported elsewhere, 4 temonstrated that activity of a higher orcer fits out over small spots .. the ocean. Estimated world fallout is 0.7 and 0,8 megacuries for June and July. The estimate for August is 1.2 megacuries, an increase of 50% over Juiz. The average monthly fallout for the three months of the weapons tests was only slightly greater, 1.5 megacuries.