PARTICLE ANALYSIS PROGRAM AT LRL 157 because they may be of some general interest. The additional information required will derive from Sedimentation runs in media of different density than the »-butyl alcohol and on particle size measurements on the individual fractions. Although these analyses are in process, the data from them are not available at the time of this writing. Further analyses of the Sedan particle samples to obtain distribution data on individual isotopes must await the installation and calibration of low-background high-resolution gamma-—gamma and beta— gamma coincidence counting systems. The final pieces of the equipment are now being installed at the laboratory. It is expected that, by the time the counting systems are operational, a steady input of particle fractions prepared from filter samples covering a variety of events from previous years can be maintained. A substantial amount of useful data should be produced.