Station Abingdon Milford Haven Kinloss Liverpool Snowdon Felixstowe 90 88 BO 106 100 102 89 B4 409 68 100 42 Relative specific activity of rainfall Relative rainfall rates The specific activity of the rain is apparently insensitive to the amount of rain which falls, and there are therefore very good grounds for believing that the cumulative deposition of Sr*° at any point in the U. K. will be proportional to rainfall. The results of Bryant et al.° obtained from the radiochemical analysis of soils confirm this. It appears that over a reasonable averaging period, each site receives its rain in showers of a sufficiently random nature that the effects which might otherwise be expected from the results of Fig. 1 do not arise. Table 3— QUARTERLY DEPOSITION OF Sr’® IN VARIOUS PARTS OF THE WORLD (mc /km? OF Sr?) 1955 Station 3 1956 4 1 2 Kinloss 0.72 0.43 Liverpool Snowdon Abingdon Milford Haven Felixstowe 0.60 0.85 Ottawa Gibraltar Port Harcourt Singapore Suva Melbourne Ohakea 1957 3 4 0.56 0.60 0.76 1.40 0.58 0.75 0.27 2,44 0.39 0.57 0.59 3.22 0.33 0.85 0.36 0.22 0.25 0.76 0.76 0.62 0.62 0.62 0.71 No rain 0.97 2.44 0.19 0.055 1.69 0.39 0.055 0.49 0.19 0.33 0.093 0.091 0.13 0.31 0.52 0.20 0.11 0.20 0.25 0.23 0.32 0.32 0.29 0.12 0.20 0.19 0.60 <0.014 0.055 <O.11 0.14 0.35 Port Stanley 1 2 0.52 1.01 0.66 0.11 The total Sr®° fallout at Milford Haven between June 1, 1955, and April 1, 1957, determined by quarterly samples is within 3% of the value obtained on the monthly sampling system. This is not only a satisfactory check on the radiochemical analysis but on the sampling procedures which differ in that carrier is not added to the quarterly samples until they are returned to the laboratory for analysis. 6 RESULTS OF DEPOSITION MEASUREMENTS ON WORLD NETWORKS The amounts of Sr*” deposited in three-monthly periods in the world network are given in the lower part of Table 3. The most striking features are the consistently very low values for the fallout at Singapore, which is nearly on the equator, and the relatively low values in the southern hemisphere. Since the stations were commissioned at different times, it is not possible to plot the total fallout figures in a straightforward manner. In Fig. 5a the total deposition of Sr*? during 1956 is plotted against latitude at each station where observations were continuous throughout the year. Also plotted are figures derived from stations where observations were made for nine months only, but here each station has been allocated a value whose ratio to the mean value at Milford Haven and Abingdon for the twelve month period is the same as the ratio determined over the shorter common period. The specific activity of the rain water has been averaged over the total period of sampling at each station and the type of normalizing procedure described in the last paragraph used to derive the values plotted in Fig. 5b. In this instance the specific activities at stations in the J 239