3 [ | x EK e 6 z S2 - _ ~ Lad a = e og vn ~ s e e e 4 ° 3. Oo —s e e e ; | “° 0 2 [| 4 6 8 419 42 44 RAINFALL, IN. Fig. 3d— Regression of sr™ in rain water on the amountof rainfall collected March through July 1956 at Mobile, Lake Charles, Jackson, and Little Rock. From these plots it is obvious that activity is proportional to the amount of rainfall within each area. Correlation coefficients for all graphs are summarized in Table 4. Table 4—CORRELATION COEFFICIENTS FOR THE REGRESSION OF Sr®® ON INCHES OF RAINFALL Time of sampling Fraction of total sampling area March Total sampling area Above 40° latitude Below 40° latitude Northeast Northwest Southeast July March— July 0.31 0.47 0.60 0.37 0.42 0.43 0.66 0.37 0.72 0.77 0.78 0.77 April May June 0.77 0.57 0.86 0.46 0.45 0.63 0.95 0.87 0.90 Southwest eyes 0.87 The next step in the analysis of the rain water data is made by comparing Sr*® in rain to that measured by various pot type collectors. However, most of these devices collect total fallout and have sampling networks that do not coincide with the rain water stations. Therefore, a comparison of these results can only indicate the relative levels of rainout to total fallout. This comparison is shown in Table 5 in which the average values of fallout in rain Table 5— COMPARISON OF FALLOUT (MC/SQ MILE/MONTH) IN RAIN WATER TO TOTAL FALLOUT® Alr Force rain water Average Sampling month New York New Haven roof pots dustfall total 8 Average Total 8 activity sr” activity sr*® Total B activity Sr? Srin Pittsburgh rainfall March 20 1.3 46 1.9 April May 45 21 1.3 1.2 83 71 0.8 1.0 63 42 2.3 0.6 1.0 1.5 June July 17 27 0.8 1.5 27 77 0.8 0.6 28 0.6 1.4 0.6 351 1.3