764 
Le) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 
Time t (msec) 
Fig. 1. The pressure-time curve from an underwater explosion. 
Gauge 20 ft from charge. Timing frequency 5 kc/sec. 
(Shot RE-111, film R-305.) 
This is a photographic projection of an actual piezoelectric-gauge record. 
Note the base line at the left before the sbock wave reaches the gauge, the 
‘instantaneous pressure rise to the "peak pressure", and the gradual decay of 
pressure with increasing time. The row of dots is the record of the time 
calibration and also serves to align the curve with respect to the axes. 
