C coseoe) Project 12.1 - Threshold Detectors - W. A. Riggers J-12 participation on Osage consisted of placing gcld samples at four stations, Two of these were land stations at approximately ground zero and 700 yards south of ground zero, The samples were placed from surface level to about 20 inches below the surface. Two stations were in the water on the larsoon side of the island, one being about 100 yards west of ground zero andi the other about 700 yards south of zero. These samples also were placed from the water surface to a point about 20 inches below the surface, One of the main items of interest was to find the difference in the water end grouni for absorption of thermal neutrons, This is for future calculations of neutron distribution in space where the As two medium problem is considered.