  Clean metallic superlattice systems composed of alternating layers of
superconducting and normal materials are considered, particularly aspects of
the proximity effect as it affects the critical temperature. A simple model is
used to address the question of when a finite--sized system theoretically
approximates well a true infinite superlattice. The methods used in the
analysis afford some tests of the approximation used that the pair amplitude of
the Cooper pairs is constant over a superconducting region. We also use these
methods to construct a model of a single superconducting layer which intends to
incorporate a more realistic form of the pair amplitude than a simple constant.
