  The magnitude of the powder spin susceptibility of an optimally doped
superconductor HgBa$_2$CuO$_{4+\delta}$ (Hg1201) in the normal state is found
to be nearly the same as that of La$_{2-x}$Sr$_{x}$CuO$_{4}$ near the optimally
doped level. The Stoner enhancement factor of Hg1201 is larger than that of
La$_{2-x}$Sr$_{x}$CuO$_{4}$. The magnitude correlation of the Stoner
enhancement factor is inconsistent with the effect of the recent theoretical
Coulomb repulsion between 3$d$ electrons and that of the superexchange
intereraction of a charge transfer type.
