have been derived through correlation of fireball-growth parameters with the total energy-release of fission bombs as determined by radiochemical means. On the other hand, theoretical studies have given the scaling con- stants in terms of the gamma (ratio c,/c, of the specific heats) for air at elevated pressures and temperatures; comparison of the two methods has actually thrown much light upon these characteristics of the medium in regions of strong shock. It was shown, prior to the first atomic explosion at New Mexico, that the energy release may be expressed by E = Kp Rt? (1) where R is the radius of the spherical shock wave in an ideal medium, t is the time after the explosion, P, is the atmospheric density, and K is a dimensionless parameter dependent upon the gammaof the medium inside the fireball. This relation was published by its originator, Sir Geoffrey I. Taylor! » in a pair of articles that also compared the theoretical prediction with the experimental observations obtained during the New Mexico (Trinity) shot of 1945. The observations obtained for the first several test shots of the USAEC showed that equation (1) was generally not satisfied until the latter phases of visible shock propagation; but that after a preliminary period of deviant growth it did indeed settle down and obey equation (1) for a time interval long enough to permit the empirical evaluation of the parameter K, in terms of the radiochemical yield. From this observation it follows that the gamma of air remains approximately constant for a considerable range of fireball temperatures and pressures, | When the quantities in equation (1) are expressed in CGS units, the first determination based on about six shots was K = 1.740. After a few years it appeared that the value K = 1.709 gave a better fit with the radiochemical data. This value continues to be good to this day, when applied to the prescribed portion of the hydrodynamic-growth curve. 3. Taylor Theory Taylor considers the total energy release to consist of two parts: LG. I. Taylor, Proc. Roy. Soc. 201A, 159, 175 (1950), -4.-