  We present results of a high statistics calculation of hadron masses and
meson decay constants in the quenched approximation to lattice QCD with Wilson
quarks at $\beta=$ 5.85 and 6.0 on $24^3 \times 54$ lattices. We analyze the
data paying attention in particular to the systematic errors due to the choice
of fitting range and due to the contamination from excited states. We find that
the systematic errors for the hadron masses with quarks lighter than the
strange quark amount to 1 --- 2 times the statistical errors. When the lattice
scale is fixed from the $\rho$ meson mass, the masses of the $\Omega^{-}$
baryon and the $\phi$ meson at two $\beta$'s agree with experiment within about
one standard deviation. On the other hand, the central value of the nucleon
mass at $\beta=6.0$ (5.85) is larger than its experimental value by about 15\%
(20\%) and that of the $\Delta$ mass by about 15\% (4\%): Even when the
systematic errors are included, the baryon masses at $\beta=6.0$ do not agree
with experiment. Vector meson decay constants at two values of $\beta$ agree
well with each other and are consistent with experiment for a wide range of the
quark mass, when we use current renormalization constants determined
nonperturbatively by numerical simulations. The pion decay constant agrees with
experiment albeit with large errors. Results for the masses of excited states
of the $\rho$ meson and the nucleon are also presented.
