  In order to specify a foliation of spacetime by spacelike hypersurfaces we
need to place some restriction on the initial data and from this derive a way
to calculate the lapse function $\alpha$ which measures the proper time and
interval between neighbouring hypersurfaces along the normal direction. Here we
study a prescribed slicing known as the Constant Mean Curvature (CMC) slicing.
This slicing will be applied to the Reissner-Nordstr\"{o}m metric and the
resultant slices will be investigated and then compared to those of the
extended Schwarzschild solution.
