from about -1 to about -2. The.differences among the Tumbler-Snapper lines are probably artifactitious, however, because the yields and scaled heights of burst of all four shots were quite similar. In particular, the two points at 1.0 and 1.5 um for Tumbler-Snapper 6 appear anomalous, in which case the points from all four shots probably fall on the same correlation line within the precision of the measurements. That is, the points below 5 um may be correlated by a single line with a slope of about ~2. — The significant observation is that a general rule appears to obtain for the particle size dependence of the specific activity. Starting at about 1 wm and moving towards larger particle sizes, the specific activity of particles from tower shots decreases with a slope which may vary from about -l to about -2. At a particle size of about 5 to 20 um, the specific activity becomes independent of the particle size, then begins to increase at about 150 to 250 um. A maximum is reached at a size of several hundred micrometers, after which the specific activity decreases continuously to the largest particles for which activity data have been obtained. Plutonium data have been obtained by Nathans (unpublished) for two shots from the Redwing series. Figure 10 shows the data. The major difference between the two shots was the scaled heights of burst, which was much greater for Shot 2 than for Shot 1, which actually began to approach a surface burst. CONCLUSION The major trends in the particle size dependence of specific activities has been rather well established for above-surface shots. Further work on this subject will deal with surface and subsurface bursts. In addition to the particle properties discussed in this paper, a review will be conducted of principal-constituent concentrations and activity translocation in soil. It is expected that this work will be completed in about three to four months, and that a report can be presented at a later meeting. 579