  Using a conventional BCS -- Fermi liquid model we calculate the c-axis
optical reflectivity of the layered high temperature cuprate superconductors by
obtaining the finite temperature dynamical dielectric function in a microscopic
self-consistent gauge invariant formalism. We get good semi-quantitative
agreement with all the existing experimental data by using the measured normal
state $dc$ resistivities as the input parameters in obtaining the c-axis
hopping amplitude and the normal state level broadening in our microscopic
calculation.
