water are obtained by considering the 10 rainfall sampling stations nearest New Haven, Pittsburgh, and New York, The best comparison between rain water data and total fallout should be obtained using gummed film data, since the gummed film network covers the same area as the rain water stations and was operated over the same sampling period. The positioning of the two sampling networks is shown in Fig. 4. Because only 14 of the stations are duplicated, geographic exTATOOSH ISLE + SPOKANE T SALEM +GLASCOW © BILLINGS BOISE 8 RED BLUFF * + WINNEMUCCA UPSAN FRANSISCO ¥ SHERIDAN RAPID Ci vy GRAND JUNCTION SANTA mania DECELES ty o ALBUQUERQUE RSA st i BURLINGTON x CONCORD ST. CLOUD + MINNEAPOLIS& NEWTON Ss. BANY ©+o“westN L Pyne R gana HURON @ SCOTTSBLUFF ° FRESNO LAS VEGAS, na * SAN DIEGO TBISMARK + SALT LAKE CIT Y * 2 +HELENA @MEOFORD MNearipou INTERNATIONAL ’s FALLS ONE aorsbnDETROIT? SCLEVELANOW* CHICAGO GRAND -SLANO+ wonrouviig INNAT| NOIANAPOLSs NCINNA covumai atv? ® os ST Lou's WICHI ~ 0 KNOXVILLE AGREENWILLE art ant LAaANTA FORT WORTH +0 DALLES JACKSON + +SAN ANGELO LAKE CHARLES os Lanepok+ 9 coeSE b BROWNSVILLE f we 3 HARLESTON + MONTGOMERY/ MOBILE 7-4 % ~-SOLOUISVILLE ROANOKE yoot @ HATTERAS NASHVILLE PHI LITTLE ROCK ° JOMEMPHIS TUSCON NEW YORK PHILADELPHIA RKRON“Ai PITTSBURGHhoameron Dc. + + GOODLAND + AMARILLO a OY" NANTUCKET ON Praga 2JNEW HAVEN @! JACKSONVILLE *~ TALLAHASSEE -_ NEW ORLEANS TAMPA + 0 50400 200 300 400 Pt MILES —_g, WEST . PALM BEACH MIAMI Fig. 4— Location of rain water and gummed film sampling sites in the United States. +, Air Force site, ©, gummed film site. trapolation is employed to obtain values for the rain water sites that are not covered by gummed film stations. Distances of 100, 150, 200, and 300 miles were used as extrapolation radii, but it was found that the distance used madelittle difference in the final correlation. The optimum distance was chosen as 150 miles because, when circles of this radius were drawn around the rain water sites, a maximum number of gummed film stations fell within the given areas with a minimum number of circles overlapping. With this scheme there are 11 results that may be compared in March, 30 in April; 20 in May; 25 in June; and 23 in July. The highest correlation coefficient obtained, using the gummed film data’ as predicted Sr®’ and rain water data as measured Sr*’, is 0.49. This relation is shown in Fig. 5, using May 1956 as an illustration. The ratios of average Sr” in rain to average Sr” in gummed film range from 1.9 to 45. Table 6 is a summary of this comparison. 4 CONCLUSIONS The relation between fallout in rainfall with total fallout measurements using the pot type of collector is good, but there is poor agreement between the rain water data and gummed film measurements. It is believed that the Sr*’ values calculated from gummedfilm activity are low owing to incorrect arbitrary burst assignments uSed in the calculations.® Considering only the rainfall data, no over-all correlation exists between rainfall and the level of Sr*” activity. It is interesting that, although the testing of atomic weapons takes place in southern latitudes, the Sr’? deposition is higher at northern latitudes. If the fallout were of recent tropospheric origin, this northward movement could be due to surface winds. However, the high percentage of Sr®° indicates that the debris is old and entered the troposphere from the stratosphere.