TEST B: UNDERWATER EXPLOSION 



Six of the eight submarines used were placed in 

 submerged positions, since it appeared certain that the 

 bomb would deliver its greatest punch underwater. 

 Placing the submarines in submerged positions some 

 distance above the bottom was not easy. The Navy had 

 never before had occasion to attempt such a feat. Not 

 only must the submarines be fixed at the right depth 

 and in normal horizontal position, but the arrangement 

 must be secure enough to last for weeks if necessary ; 

 and the submarines were to be raised again after the 

 explosion. A method of submerging which was found 

 satisfactory was to flood certain ballast tanks and then 

 attach heavy weights to the submarine 's bow and stern 

 by means of long chains of carefully chosen length. The 

 weights overcame the submarine's residual positive 

 buoyancy and drew her down until the weights them- 

 selves rested on the bottom, leaving the submarine at 

 the desired depth. The submarine Could be surfaced 

 later by pumping air back into the flooded ballast tanks. 

 The entire operation was controlled from a salvage 

 ship. The illustration Plate XVII shows the submarine 

 APOGON in the process of submerging. 



For the underwater explosion, elaborate prepara- 

 tions were made for measuring wave heights. Waves of 

 unprecedented height were expected, and a unique 

 opportunity was j^resented for studying generation and 

 propagation of giant waves. 



Preparing the highly-specialized instruments was 

 the responsibility of Mr. N. J. Holter, head of the 



147 



