  We examine quenched chiral logarithms in lattice QCD with overlap Dirac
quark. For 100 gauge configurations generated with the Wilson gauge action at $
\beta = 5.8 $ on the $ 8^3 \times 24 $ lattice, we compute quenched quark
propagators for 12 bare quark masses. The pion decay constant is extracted from
the pion propagator, and from which the lattice spacing is determined to be
0.147 fm. The presence of quenched chiral logarithm in the pion mass is
confirmed, and its coefficient is determined to be $ \delta = 0.203 \pm 0.014
$, in agreement with the theoretical estimate in quenched chiral perturbation
theory. Further, we obtain the topological susceptibility of these 100 gauge
configurations by measuring the index of the overlap Dirac operator. Using a
formula due to exact chiral symmetry, we obtain the $ \eta' $ mass in quenched
chiral perturbation theory, $ m_{\eta'} = (901 \pm 64) $ Mev, and an estimate
of $ \delta = 0.197 \pm 0.027 $, which is in good agreement with that
determined from the pion mass.
