Dual installations of sensing instruments were .made at ali stations on the blast line for Mike shot.'* Sensing elements were standard variable-reluctance Bourdon type gauges (Model SPAD) manufactured by the Wiancko Engineering Company,'* mounted either in standard ground and side-onbaffles’ or in pitot static tubes.'* Pressures predicted for the first three stations, on Teiteir, Bogairikk, and Bogon, madeit advisable to use Wiancko gauges mounted in ground baffles (Fig. 2). At Noah both installations were Wiancko gauges mounted in side-on baffles (Fig. 3). At the remaining seven stations one gauge at each location was mounted in a side-on baffle; at two stations the second gauge was also mounted in a side-on baffle, whereas at the remaining five locations the second gauge was mounted in a pitot static tube. The Wiancko gauges in side-on baffles were mounted 10 ft above the surface, either on single pipe stands (Fig. 4) or on goal-post type pipe stands (Fig. 5), depending on whether other types of instrumentation were to be mounted at the same locations. The pitot static tubes were mounted on the goal-post type stands in each instance. Before the side-on type baffle was used on Operation Ivy, some extensive wind-tunnel tests were made to determinethe influence of baffle orientation on the data obtained.'’ All side-on baffles were carefully aligned with ground zeroin the belief that any error introduced by this orientation would be negligible and could safely be ignored. Powerto all gauges was supplied by a standard Consolidated Engineering Corporation 3-kce carrier system, and the outputs of the gauges were recorded on magnetic tape by a multichannel Ampex recording system.’ Recording shelters were placed at convenient locations to serve all end instruments used; seven shelters (Table 1) were used on Mike shot, 602, 605, and 606 having one recorder each and the remainder having two recorders each. .° 4.2 King Shot Since it was planned to install blast lines over both land and water on King shot, intended ground zero was fixed at a point off the north end of Runit (Fig. 6) to gain the advantage of a land blast line as long as possible. The land blast line comprised four stations, all on Runit, whereas the blast line over water had nine stations. Eight of the stations for the blast line over water were placed on a coral reef along the northeast edge of Runit (Fig. 6), and the ninth was on the northern tip of Parry. All except the two most remote stations (617.08 and 612.02) were on a radial line from intended ground zero (Table 2). The station on Parry comprised two gauges, at the same locations as were used on Mike shot. All stations on the land blast line were necessarily at different azimuths from the refer- ence line passing through ground zero, and, although the blast line was predominantly over land, the shock wave had to traverse paths made up of varying percentages of land and water to reach the individual stations. Each of the land-line stations corresponded to one of the stations over water so far as its predicted overpressure and distance from intended ground zero were concerned (Table 2). The pattern followed in choosing station locations was the same as for Mike shot: it was attempted to choose locations such that overpressures would be halved at each successive measuring point. Wiancko pressure gauges were again used for all air-pressure measurements on King shot. Those at the land-line stations were mounted in ground baffles (Fig. 2), and those over water in side-on baffles. The stations over water were single pipe stands mounted in con- crete footings atop the coral reef (Fig. 7). The gauge in its baffle was thus effectively placed approximately 10 ft above the surface of the water, inasmuch as the feoting was submerged the greater part of the time. Unfortunately, however, the movementof the tide caused the footings for someof the gaugeinstallations to be exposed part or all of the time. Elevations of the footings for the various stations above the mean low water spring tide are presented in Table 3. The carrier and recording systems for King shot were the same as those used for Mike shot. Outputs of all land-line gauges on Runit and all gauges over water near Runit were re14