firing and assembly equipment. Electrical equipment for both checkout and firing was purchased as regular device components or designed and fabricated by project personnel. Nuclear components were obtained from standard production through the AEC. One of the major phases of the project's activities was coordination with DOD agencies and other support groups to devise a workable emplacement and firing system. This included taking part in various conferences and tests from the initial planning stages through preliminary sea trials of the suspension system and dry run activities prior to detonation. Checkout and assembly were completed prior to placing the devices in firing position. The device case and underwater signal cables were water-pressure tested before acceptance from the manufacturer. The electrical equipment for firing was tested on numerous dry runs for satisfactory operation. The two devices were detonated satisfactorily without any major difficulties or delays. Some trouble was encountered on the Wahoo event from fairly rough seas which made the rero instrument platform (LCM hull) very unstable. This was not only uncomfortable for personnel but created very unfavorable working conditions and caused deterioration of equipment. These conditions were corrected on the Umbrella event through the use of a larger platform (LCU hull) in an anchored position. A few trouble spots developed in the fabrication of equipment such as the zero instrument platform, which was to be used by several agencies. These conditions were brought about by poor coordination between the users and fabrication agencies. For any future test of a similar nature, the following recommendations are offered concerning the activities of Project 34.3: 1. Although the emplacement, suspension, and firing system as used during Operation Hardtack was employed successfully on the two underwater events, a different system, which should include a more stable platform for the zero firing and instrumentation system, would be desired. 2. More time should be allowed for the various support groups to determine their requirements and procure and fabricate special equipment. This action would permit better coordination for preparation of facilities. The primary purpose of Project 34.4 was to measure blast waves from the Teak and Orange events. High temperatures or wind speeds in the upper atmosphere may cause portions of a blast wave to be returned to the ground at great distances. Microbarograph stations at Johnston Island; Lualualef, Oahu; and French Frigate Shoals were to record these refracted sounds, arrival time, and incidence angles. From these records it is anticipated that winds and temperatures at 100,000 to 180,000 ft, where the blast waves were returned to the ground, may be interpreted. The secondary purpose of Project 34.4 was to measure blast waves generated near the ground at the Eniwetok Proving Ground. These waves are bent by refraction as they propagate through the upper atmosphere and were recorded at microbarograph stations located at Eniwetok, Bikini, Kwajalein, Utirik, Wotho, and Ujelang. The microbarograph station at Johnston Island recorded an overpressure of : Arrival time for the blast wave at the recording instrument was approximately 193 sec. These data were ob- tained for the Teak event and together with the Orange data will be evaluated in terms of wind speed and temperature. The same will apply to the recorded data from Lualualei and French Frigate Shoals. The microbarograph 54