  We have analyzed the clustering of C IV and Mg II absorption-line systems on
comoving scales from 1 to 16 \hMpc, using an extensive catalog of heavy-element
QSO absorbers with mean redshift 2.2 (C IV) and 0.9 (Mg II). We find that, for
the C IV sample as a whole, the absorber line-of-sight correlation function is
well-fit by a power law with index $\gamma = 1.75 ^{+0.50}_{-0.70}$ and
comoving correlation length $r_0 = 3.4 ^{+0.7}_{-1.0}$ \hMpc ($q_0=0.5$). The
clustering of absorbers at high redshift is thus of a form like that of
galaxies and clusters at low redshift, and of amplitude such that absorbers are
correlated on scales of galaxy clusters. We also trace the evolution of the
mean amplitude $\xi_0(z)$ of the correlation function from $z=3$ to $z=0.9$. We
find that, when parametrized as $\xi_0(z)\propto (1+z)^{-(3+\epsilon)+\gamma}$,
the amplitude grows rapidly with decreasing redshift, with maximum-likelihood
value for the evolutionary parameter of $\epsilon = 2.05 \pm 1.0$ ($q_0=0.5$).
When extrapolated to zero redshift, the correlation length is $r_0 = 30
^{+22}_{-13}$ \hMpc . This suggests that the strong C IV and Mg II absorbers,
on megaparsec scales, are biased tracers of the higher-density regions of
space, and that agglomerations of strong absorbers along a line of sight are
indicators of clusters and superclusters. This is supported by recent
observations of ``Lyman break'' galaxies. The rapid growth seen in the
clustering of absorbers mimics that expected in a a critical universe from
linear theory of gravitational instability, and is consistent with
gravitationally induced growth of perturbations.
