  We show that part of the empirical formula describing the gross features of
the measured yrast energies of the natural parity even multipole states for
even-even nuclei can be related to the rotational energy of nuclei. When the
first term of the empirical formula, $\alpha A^{-\gamma}$, is regarded as the
otational energy, we can better understand the results of the previous analyses
of the excitation energies. We show that the values of the parameters $\alpha$
and $\gamma$ newly obtained by considering the $\alpha A^{-\gamma}$ term as the
rotational energy of a rigid rotor are remarkably consistent with those values
extracted from the earlier `modified' $\chi^2$ analyses, in which we use the
logarithms of the excitation energies in defining the `modified' $\chi^2$
values.
