The non-quadratic behaviour of the specific-heat enhancement below 5 K as measured by Novoty, Meincke, and Watson for 22 lead particles [ Phys. Rev.Lett. 28, 901 ( 1972 )] is explained by rigorously summing the contributions of all the 183 vibrational modes of the respective free sphere problem. In addition a maximum of the enhancement is predicted near 8 K. The usual asymptotic surface term fails. The mean squared frequency < omega^2 > is calculated.