20 



247 



of the Incident and reflected waves as they become superposed upon each other 

 at various points and at various times. The pressure in each wave is assumed 

 to decrease in inverse proportion to the distance from its point of origin, 

 real or assumed; and allowance must be made for the time of propagation. It 

 Is unnecessary to give details of the rather tedious calculations, which were 

 carried out only roughly. 



By trial, It is found that the total pressure should first reach 

 the value of -600 pounds per square inch at a point situated directly over 

 the charge and about 1 foot under the surface. Cavitation will begin at this 

 point, according to the assumption made here, and from this point a closed 

 breaking-front will sweep out, moving at supersonic velocity. The upper side 

 of this front must obviously halt almost at once, for a tension of 600 pounds 

 per square inch cannot occur close to the surface; but the lower side may de- 

 scend to a considerable depth. 



In Figure 14 are shown the estimated distributions of pressure 

 along a vertical line through the charge at two different times, distin- 

 guished by the numbers 1 and 2. Heavy curves are drawn to represent the ac- 

 tual pressures; light curves above the axis represent the component pressures 

 due to the incident wave, those below the axis the components due to the re- 

 flected wave. 



Pressure 



Posit ion 

 of Surface 



-600 



Figure 1U - Diagram illustrating the Distribution of Pressure below 

 the Surface of the Sea, as explained in the Text 



