1411 
(111) As the angle is decreased, durations first begin to 
deviate from the theoretical predictions, and only when the 
angle is further decreased does pressure deviation become 
significant. 
(iv) If the charge is very close to the surface, there is 
a diminution of peak pressure even when the rarefaction cuteoff 
is steep. This may possibly indicate that some of the pressure 
effects might be due to venting of the gaseous explosion products, 
Although there is no theoretical formulation which covers 
these conclusions at this time, the general manner in which 
deviations from ordinary acoustic theory occur is in agreement 
with fae description of finite amplitude effects presented by 
Cole>), and the deviations are in the direction that Cole 
indicates, 
Throughout the results presented above, standard deviations 
appear which are higher than might have been expected, This 
would seem to indicate that the methods of measuring depths 
were not so accurate as was believed, or simply that the number 
of shots was so limited that significant results could not be 
expected, In any case, the need for further investigation is 
apparent. For example, additional work may enable one to define the 
boundaries of the noneacoustic region, and to describe the na- 
ture of the shock wave emitted by shallow explosions. 
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