  A mean field method to study heteroepitaxial thin film growth is applied to
growth, intermixing and surface reconstructions of $Au$ on $Ag(110)$. The
results are in accordance with experimentally observed ``burrowing'' at
submonolayer coverages and growth of elongated, $(1 \times 3)$ reconstructed,
$Au$ clusters at higher coverages. At coverages of few monolayers the surface
between the clusters has a high concentration of $Ag$, and ordered rows of $Au$
are formed just beneath the surface.
