  We report results from high-resolution particle-mesh (PM) N-body simulations
of structure formation in an $\Omega=1$ cosmological model with a mixture of
Cold plus Hot Dark Matter (C+HDM) having $\Omega_{\rm cold}=0.6$,
$\Omega_\nu=0.3$, and $\Omega_{\rm baryon}=0.1$. We present analytic fits to
the C+HDM power spectra for both cold and hot ($\nu$) components, which provide
initial conditions for our nonlinear simulations. In order to sample the
neutrino velocities adequately, these simulations included six times as many
neutrino particles as cold particles. Our simulation boxes were 14, 50, and
200~Mpc cubes (with $H_0=50$ km s$^{-1}$ Mpc$^{-1}$); we also did comparison
simulations for Cold Dark Matter (CDM) in a 50~Mpc box. C+HDM with linear bias
factor $b=1.5$ is consistent both with the COBE data and with the galaxy
correlations we calculate. We find the number of halos as a function of mass
and redshift in our simulations; our results for both CDM and C+HDM are well
fit by a Press-Schechter model. The number density of galaxy-mass halos is
smaller than for CDM, especially at redshift $z>2$, but the numbers of
cluster-mass halos are comparable. We also find that on galaxy scales the
neutrino velocities and flatter power spectrum in C+HDM result in galaxy
pairwise velocities that are in good agreement with the data, and about 30\%
smaller than in CDM with the same biasing factor. On scales of several tens of
Mpc, the C+HDM streaming velocities are considerably larger than CDM. Thus
C+HDM looks promising as a model of structure formation.
