action of wind and waves. There is evidence that mixing may be complete within a few hours to a depth, in this area, of 300 feet or more. The lower boundary of this mixed layer frequently appears as an abrupt drop in temperature. Mixing is thorough in the upper layers as evidenced by the remarkable uniformity of temperature betweenthis boundary, called the thermocline, and the surface. It was expected therefore that the radioactive fallout would also become evenly distributed throughout the mixing layer to an extent which might permit estimation of the amount of fallout by measurementof the radioactivity of oceanwater in the mixed layer. The portion of the above investigations organized and performed underthe direction of Task Unit 13, Program 2, was established as a separate joint SIO and NRDL project, Project 2.7. SIO has evaluated the direct gamma measurements. NRDL has analyzed the water samples. In this report an attempt has been madeto construct approximate fallout contours and calculate zammafield intensities on the basis of the data obtained by these two methods. 16