II. INSTRUMENTATION, DATA COLLECTION AND ANALYSIS A high pressure ionization chamber and a y-ray spectrom- eter system were used to obtain in situ exposure rates and spectra. The spectra were then analyzed to determine the individual exposure rates contributed by each major y-ray emitting isotope in the soil. Because of the bulk and weight of the analyzer system, ionization chamber, and related power supplies, and the resultant difficulty in transporting the equipment from the ship via small boats to the shore and thence in many cases through heavy brush to a survey Site. these types of measurements were limited to 16 sites on the three major islands. In ail some 29 field spectra were obtained. A small scintillation counter survey meter and a number of rugged G-M counter survey meters were used to extend the total exposure rate measurements over these islands and to survey the smaller islands. Although the data obtained with these instruments is less accurate for a particular location, their use enabled us to extend our measurements over a fairly large area convenientiy and consequently obtain a more complete picture of the variation of radiation levels across the major islands and from island to island. In addition to these measurements, thermoluminescent dosimeters were placed at a large number of locations on Bikini and Eneu Islands at the beginning of the survey and collected about ten days later and returned to the United States for readout. These passive dosimeters were employed to provide an independent check on the data obtained with the other instrumentation. Soil samples were also taken at various locations exhibiting unusually high or low activity. Ail of these samples were returned to the United States for laboratory analysis, however, several were also spectrally analyzed on our 4 in. x 4 in. NaI(T1l) detector abcard ship to obtain identification of the major y~ray emitters in the sample. At several locations a complete depth profile set of soil ~4- Dor ARCTire he