BOMBS AT BIKINI 



Wave Motion Section of the Oceanographic Group.* 

 Much reliance was placed on photography. Tower cam- 

 eras on Bikini, Amen, and Enyu Islands were synchro- 

 nized in a w^ave photography network controlled by 

 radio. Cameras on three photographic planes were 

 brought into the same network. Each camera was to 

 take a photograph every three seconds. 



Television was used also. Two transmitters, operat- 

 ing in the 200 megacycle band, were placed in the Bikini 

 towers ; ten receivers were used, several of them being 

 mounted in PBM planes. 



Many direct-reading wave-height gages were read- 

 ied. Thirty of these, called turtles, were laid directly 

 on the lagoon bottom. When a wave crest passed, the 

 hydrostatic pressure on the bottom increased. Water 

 was forced into the instrument through a fine capillary 

 tube, a Bourdon-type pressure element was actuated, 

 and a small pen drew a significant line on a slowly- 

 revolving chart. Use of the capillary tube frequenc}'' 

 filter was essential; it prevented the apparatus from 

 being wrecked by the extremely intense underwater 

 shock wave, which reached the apparatus a few mo- 

 ments before the water waves themselves swept past. 

 The underwater shock wave came and went within a 



* Lieutenant Commander F. G. Mo7-ris was officer in charge of 

 the Wave Measurement Section. Group leaders were Dr. W. K. 

 Lyon, Lieutenant C. Sklaw (Navy), Mr. H. W. Iversori, Prof. Alex- 

 ander Forbes, and Mr. A. C. Vine. Very important parts in this 

 work were played by Dean M. P. O'Brien, Mr. J. D. Isaacs, and 

 Lieutenant J. H. Chamblin. 



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