SCIENTIFIC OFFENSIVE 



a simple matter, after an explosion has occurred, to 

 inspect the foil, pick out the smallest area which burst, 

 and thus compute the peak pressure. Hundreds of 

 these gages were used. Typically, they were bolted to 

 ''Christmas trees,'' sturdy 9-ft.-high structures of 

 heavy steel pipes. The Christmas trees were ordinarily 

 welded to the upper decks of the target vessels. 



5. Deformed Plate Peak-Pressure Gage. This gage 

 was used to measure fairly high pressure. It somewhat 

 resembles the ruptured foil gage in operating prin- 

 ciple, but employs a thicker foil or diaphragm, which 

 ordinarily deforms without actually rupturing. A va- 

 riety of designs were used to accommodate different 

 pressure ranges. 



6. Indentation Peak-Pressure Gage. This gage also 

 was capable of measuring very high pressures. Pres- 

 sure is recorded in terms of indentation produced by 

 a small steel ball forced against a sheet of lead. The 

 greater the pressure, the deeper the indentation. 



In addition, various gages of more conventional 

 type were used for measuring more moderate pres- 

 sures. Some of these were of the familiar aneroid- 

 barometer type. Others were of a liquid-trap type, in 

 which the pressure wave depresses the liquid in a tube 

 and causes some of the liquid to become trapped. 



Most elaborate of the pressure gages were those de- 

 signed to trace the entire rise and fall of the pressure, 

 i.e., the whole life history of the pressure wave as it 

 swept past a given point. In some of these pressure- 



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