564 
Fig. 2. 
Oscillogram of the pulse due to a submarine explosion. 
Pressure bar :- length = 22 ft.; diameter zx 1% inch. 
:- cylindrical type, measuring the longitudinal 
Condenser unit 
displacement of the end of the bar. 
Upper trace :- timing wave of period 0.0525 millisecs. 
Lower trace :- amplified p.d- from condenser unit. 
