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Impulse. On the other hand, when a mine is at the "best" 

 location (about 20 ft. above the sea bed for a depth, say, 

 of 100 fto), then the shock wave peak pressixre at the sur- 

 face is increased about 25 percent over that of the sea bed 

 position since the pressure at the surface Is inversely 

 proportional to the distance from the explosion. 



2. The principle of stabilization . 



The best location of the mine is determined by the 



following Principle of Stabilization: For a given mass of 



explosive, the maxlioim peak pressure in the secondary pulse 



is obtained if the gas bubble produced by the explosion is 



kept motionless at the time of its minimmn size . This 

 stabilization can be attained for mines by suitably balancing 



the upward buoyant force on the bubble against the dovmward 



attractive force due to the sea bed. In other cases, the 



repulsive force of the surface, as well as additional factors, 



could be utilized. 



In part II, a mathematical demonstration of the principle 



of stabilization is given. The following plausible argument 



also points to the same result. In general, the total energy 



of the bubble and water is divided into two parts, namely, 



the kinetic energy of the water surrounding the bubble, and 



the Internal energy of the gas inside the bubble. If the 



bubble is moving at the time of its minimum size, then some 



of the total energy is diverted into kinetic energy of the 



water and thus less is available for the Internal energy 



«• [9] reports no change in the shock wave for a mud bottom. 

 Experiments in Woods Hole for a sand bottom show an increase 

 of 12 percent, according to an oral discussion. Theoretically, 

 if the sea bed were perfectly rigid, the peak pressure would 

 be multiplied by the factor ^f2 , which means an increase of 

 26 percent. Actually, however, the explosion tears a hole in 

 the sea bed and also transmits a shock into ito 



