scaler unit Radiec Computer Indicator CP-79/UD (NavShips 91892). The detector assemhly mounted inside a commercial lead castle consists of a@ cylindrical sodium iodide crystal 1.5.in. in diameter and 0.5 in. thick, an ROA 5319 photomultiplier tube, and a pre-anvlifier unit. The crystel is shielded from the sample chamber by 0.25 in. of aluminum, The counters used were completely evalusted for coincicence loss by using six paired sources and employing a least square evalvation.?/ Coincidence loss varied from 1 per cent: at 100,000 c/m'to 10 per cent: at 2,000,000 c/n. * . All differentiel fallout collections were counted under fixed geometry and corrected for background and counter coincidence losses. No attempt was made to obtain any more than relative counts between sammles. 4elelel Totsl Collectors Many of the total collectors contained cconsicerable quantities of rain water which fell during the relatively long period between place- ment and recovery of the instruments but not during the period of fallout. In these cases there was leaching of the fallout activity into the liquid. Preliminery separations of the liquids and solids were achieved by decantine the gross samples. Final separations were then obtained by centrifuging which left the resultirg liquid clear or, in some cases, containing colloids. The liquid volumes were measured and the solids dried and weirhed. The samples were placed in 100-ml lusteroid centrifuge tubes and gamma activity measurements were made on these samples with a 41 gamma ionization chamber. In instances where the liquid fraction exceeded 100 ml, these samples were concentrated to the desired volune after acidification. 4.1.1.2 Gummed Paper Collectors The acetate-backed 1-ft squares of gummed paper were renoved from their cardboard mounts and folded to fit into 100-ml lusteroid tubes, Their gamma activities were measured with a 47 gamma ionization chamber. 4.1.1.3 Differentiel Fallout Collectors Each of the 40 volyethylene collecting jars was removed from the collector and decontaminated on the outside. The jer openings were then canped with cellovhane 0,001 in. thick held in positisn with a rubber band. Ganma counts were then made rith : scintillation counter. 4.1.2 Particle Size Measurements The particles were fixed with Krylon cn a framed cellophane membrans. Contact autoradiographs were made using Eastman Ccmmercial Ortho film. The outer island analysis employed nuclear emulsion stripping film with the particles fixed to the non-enulsion side of the film 45