429 
z (5.6) 
Detailed numerical calculations, based upon the isothermal Tait 
equation and the Hugoniot conditions, have been carried out for the proper- 
ties of water at the shock front up to a pressure of 50 kilobars (1 kilobar 
= 986.9 atmospheres), They show that ae very small in comparison with u 
and that the change in adiabatic along the Hugoniot curve is slight. Except 
for the sound velocity @ at the higher pressures the approximate formas 
54, 525, and 5.6, based upon the modified Tait equation 5.2 integrated 
along the initial adiabatic, yield results which are not significantly dif- 
ferent from the numerical calculations based on Eq. 5.1. Since the Hugoniot 
curve for water crosses the liquid-ice VII phase boundary :-at about 25,000 
atm., extrapolation into a metastable liquid region inaccessible to measure- 
ment is necessary. The occurrence of the transition during the short time 
of passage of a shock wave seems entirely excluded on the basis of Bridgmen's 
experiments. 
We return now to the asymptotic theory of the pressure-time curve. 
The retarded time 7, (Ft) at the shock front is given by 
R R 
ay’ ar! 
t, (A) = Fi a Cru y (5.7 
UG e) alt) ) 
o 
obtained from Eq. 3.34 with the substitution C=C+u. The time-spread 
parameter » a measure of the broadening of the t = 5: seale relative to 
the eB scale, was defined by 
