The data of Dunn and Martin (1978), Is reanalyzed using a rigorous applicat
ion of Hertzian theory to the, impact process. The Young's modulus of steel
, required to fit their data to the theory is a factor of about 10(3), too
low compared to the values quoted for steels. Thus, doubt is thrown on the
validity of their experimental technique, and it is possible that their val
ues for maximum impact force and stress are far too low.