Simple equations are used to infer approximate values of the major parameters of an unusual plasma which was used by Rashleigh and Marshall to accelerate 3‐g macroparticles to high velocities (5.9 km/s). Subject to the assumptions made here, these results indicate that for the applied current of 300 kA and generated pressure of 1.1×108N/m2, the temperature of the ionized copper plasma was 4413 kK and the electron number density was (81)×1025m−3. It is recommended that future experiments of this type should incorporate instrumentation techniques which can provide direct experimental evidence on these parameters.