The ship assigned by the Task Force to the first of the two surveys was the USS WALTON (Destroyer Escort 361), a 306-foot vessel whose range and accommodations were considered adequate for oceanographical work in open waters. The WALTON arrived at Eniwetok on June 5, and shortly thereafter the survey equipment llaaele as a was installed on board. The survey was begun on Monday, June 11, and completed on Thursday, June 2l. The success of the survey is attributable to the support of the Division of Biology and Medicine, particularly Dr. W. R. Boss, and to the coordinated assistance given to the field team by the operational groups within Joint Task Force 7, particularly Task Group 7.3 (Navy). Members of the staff are es- pecially grateful for the intelligent interest in the project demonstrated by Commander Arthur T. Emerson, Jr., captain of the WALTON, and for the very great understanding and assistance afforded by officers and members of the crew of the vessel. The probe for continuous water monitoring was developed and constructed by the Instruments Branch of the Health and Safety Laboratory, New York Operations Office, under the direction of Mr. Harris D. LeVine, Chief. The use at Eniwetok of a gamma ray spectrometer was made possible through the kindness of TRAE reenenenD Mr. Robert Graveson, Chief Engineer of the Electronics Section, Instruments Branch, HASL, who also assisted and instructed members of the staff in its operation. The Eniwetok Marine Bio- logical Laboratory of the Division of Biology and Medicine was used as a headquarters, and shared with HASL personnel who were most cooperative in the exchange of the use of equipment and Supplies, ath