1391 
GLOSSARY OF SYMBOLS 
Pn Peak pressure at gauge position as obtained from 
Kirkwood's similitude curves (OSRD 3949) for 
free water (psi) 
P Apparent peak pressure of shock wave at gauge 
position: the highest visible point on photographic 
record (psi) ; 
P> Derived peak pressure: an approximation to 
extrapolated peak pressure (psi) 
Ps Peak pressure at a given point on the water's surface, 
as obtained from Kirkwood's similitude curves 
(OSRD 3949) for free water (psi) 
t Calculated shock-wave duration time between the arrival 
' of the directly propagated pressure wave and the 
subsequent arrival of the reflected tension wave (microsec) 
T Experimental shock-wave duration time as measured on the 
piezoelectric record (microsec) 
Tg Gauge crossing time of the positive shock wave (microsec) 
a Gauge crossing time of the reflected tension wave (microsec) 
D Depth from the center of the charge or gauge to the surface 
(ft or in. , as specified) 
R Charge-to-gauge distance (ft or in., as specified) 
Surface point of incidence of that part of the shock 
front which is reflected in such a way as to strike 
the gauge, assuming equal angles of incidence and 
reflection 
w/3/R Scaling constant for similitude curves in terms of 1/3 
charge weight, W, and charge-to-gauge distance, R (1b /ft) 
X eunle of incidence of shock front at point S (degrees) 
angle between ocean surface and the line from S to 
the charge) 
8 Time constant; time required for pressure to drop to 1/e 
of its initial value (microsec) 
o Standard deviation of a single observation from the mean (%) 
