inches wide by five feet six inches high for passage of personnel. The second experiment on Engebi, which was added to the program later, subjected the power house to considerably more pressure than that for which it was designed, and the structure was not oriented properly for this experiment, A check on design calculations indicated that if it was mounted over with earth on all sides the equipment would probably be saved but some structural damage might occur, (See Chapter 5,27 of this volume for an account of blast damage.) Two ventilated fans were provided near the ceiling in each power plant, The air was taken from outside through intake ducts from above the roof and was directed toward the front of the building and exhausted through openings in the rear wall near the floor. It was a requirement that the power plants on the experiment islands operate unattended for several hours before zero hour and that they then be shut down automatically a few seconds after zero. One air inlet and one air exhaust were each provided with blind flanges which were bolted over the openings before the operators left the plant, while the other air inlet and outlet were each provided with electrically operated butterfly valves. When the operators left the plant after shutting down one ventilating fan and bolting the blind flanges on to one intake and one exhaust opening, the blast doors were tightly closed and the engines were supplied with air by the fan still running. The piping from the engine exhausts was so arranged that they normally exhausted through the building roof, but during an unattended operation the exhaust pipes through the roof were closed and the engines exhausted directly in front of the air exhaust port remaining open. At H-hour minus 30 seconds, a time signal was received in the power plant from the sequence timer which was operated from the control building on Parry Island. This time signal energized a timing system in the power plant which was designed by Holmes & Narver, At H-hour minus 15 seconds, the timing system shut down the ventilating fan and started to close the electrically operated butterfly valves on both the air intake and the air exhaust, The closing. of these valves required 10 seconds, From H-hour minus 5 seconds to H-hour plus 5 seconds, the engines operated on the air inside the sealed building and then shut down by another signal that electrically closed the fuel valves, Bogallua Island. When it was planned in 1949 to use Bogallua for an experiment, a blastproof power plant was designed for this island. The plant was to be in an area of high pressure, and to keep the cost as low as possible, the blastproof building was designed to house only the 118 kw diesel generating unit. An 85-gallon distillation unit, a steam boiler, and the necessary auxiliary units for water distillation were to be located outside the blastproof building, and it was planned to remove these from the island after storing a supply of fresh water, prior to the experiment. The 85-gallon per hour distillation unit was a selfcontained, skid mounted piece of equipment, The building housing the diesel unit with its auxiliaries was to be located partially underground for protection from the blast, The engine piping was typical, except for exhaust piping which, for protection, was to be carried in an 5-215