  Using deep Hubble Space Telescope imaging, color-magnitude diagrams are
constructed for the globular clusters 47 Tuc and NGC 6397. As expected, because
of its lower metal abundance, the main sequence of NGC 6397 lies well to the
blue of that of 47 Tuc. A comparison of the white dwarf cooling sequences of
the two clusters, however, demonstrates that these sequences are
indistinguishable over most of their loci - a consequence of the settling out
of heavy elements in the dense white dwarf atmosphere and the near equality of
their masses. Lower quality data on M4 continues this trend to a third cluster
whose metallicity is intermediate between these two. While the path of the
white dwarfs in the color-magnitude diagram is nearly identical in 47 Tuc and
NGC 6397, the numbers of white dwarfs along the path are not. This results from
the relatively rapid relaxation in NGC 6397 compared to 47 Tuc and provides a
cautionary note that simply counting objects in star clusters in random
locations as a method of testing stellar evolutionary theory is likely
dangerous unless dynamical considerations are included.
