result that the mechanism was jammedprior to operation. The recorders so affected were the Able recorders on Bogon and Bokon and the Baker recorder on Aomon. Noneof the air--pres- sure gauges was connected to the Baker recorder on Aomon, but, since the primary air-~pres- sure gauges at Stations 614, 615.01, 615.02, and 611.03 were connected to the first two re- corders, no records were obtained from these gauges. Three additional recorders on Mike shot ran properly only until the air shock front struck the shelter. One of these was the Baker recorder on Bogon, to which the gauges at Station 610 (Noah) were connected. Because this station was farther from ground zero than was the recorder shelter, the records from it were worthless. However, a low-range pressure gauge at Station 615.02 was also connected to this recorder and did provide information on arrival time since this station was nearer ground zero than was the shelter. At the time that the shock struck the shelter on Bokon, a small amount of slack developed in the tape on the Baker re- corder, causing it to wind up on the capstan. Although the recorder continued to run for sey- eral seconds thereafter, the tape did not wind up on the take-up spool but became snarled in- side the cover over the recorder. Although the speed at which the tape crossed the recorder head might have changed, information from the gauges at Aitsu, placed on the tape during this interval, apparently gave reliable arrival times and pressures which were only slightly re- duced, if at all. When the shock struck the shelter on Muzin, it caused some tape “wow”or fluctuation of the speed at which the tape passed the heads of the recorder. Since this wow occurred as the pressure was decreasing in the positive phase, and since the speed had returned to normal before the crossover point into the negative phase was reached, the record was rather easily interpolated. Determination of arrival times on the records from recordersat two of the shelters, those on Runit and Parry, was again a matter of judgment. The Blue Boxes at these locations failed, with the result that no signal was placed on the tape at zero time. Although the Blue Box on Bokon also failed, an electromagnetic signal at zero time appeared on the records at this shelter. A fairly accurate value for arrival time could be obtained from the other two records by counting from the start time of the tape at -15 sec. On King shot all recorders ran properly, precautions having been taken to remove the brake bands and repair the brakes so that the recorders ran free. Actually, the brakes were not used during operation of the recorder (the Ampex recorder was designed for other applications in which it is desirable to start and stop the recording system quickly). Since the number of recorders required on King shot was not so great as on Mike shot, it was possible to take the added precaution of installing dual or backup recorders, Two of these dual instal- lations were on Runit, and the other was on Parry. Both recorders at each dual installation ran during the test; thus, if one failed, a record was obtained on the other. Perhaps the most serious difficulty experienced in obtaining intelligence from the airpressure gauges on King shot was the tape wow which obscured all records from the recorders on Runit at about the time the air shock struck the shelter. Some records began in the middle of the wow, whereas others were in the crossover period from the positive to the negative phase. Fortunately some of the records —those from the first two gauges over water, which broke off, and those from two gauges considerably farther from ground zero than the shelter — were at balance during this period. Thus the signal that did appear on these channels during the period in question could be attributed solely to tape wow. The records that recorded the wow alone could be used as a standard for comparison in subtracting the wow from channels which did record gauge signals during this period. This procedure madeit possible to obtain highly satisfactory records despite interference by tape wow, although on two records it was impossible to resolve either the shape of the pressure-time curve in the negative phase or the ending of the negative phase. Several of the gauges over water failed completely or partially, but, even though those at Stations 617.01 and 617.02 broke off from their mounts, peak pressures and arrival times were obtained. The baffles for the gauges at Stations 617.03 and 617.04 rotated about 45° from the side-on position (presumably during the blast), but peak pressures could be read, and a fair 22 a