21 The radionuclide content of leachates collected in the field agrees with these results (Cole et al. 1961). Leachates from young soil contained only spt25 and sr?°, while leachates from better developed soils contained mainly sr?° and est 37, with traces of other gamma-emitters. Depth Gradient of sr?° The relative sr?° content of depth increments of the two soil types is given in Table IV, There is a rapid decrease in the amount of sr?° with depth, and the differences in sr? content between soils probably are not significant. The extreme values from the results of sr?° analyses of subsamples of replicate samples taken from small areas differ by a factor of more than ten (Table II). It is likely that the variability is due largely to the spotty nature of the distribution of the fallout radionuclides, which is evident in the radioautographs discussed below and from X-ray films that were exposed at the soil surface and just below the surface (Fig. 11), and to small differences in the characteristics of the soil within a single soil type. Sampling by 1/8-inch increments in 1959 of an undisturbed old soil, (Fig. 4 and Table I ) on Rongelap Island indicates a gradient of sr?? levels in the top inch of soil (Table v). The levels in the second inch are about one tenth those in the