  Intrinsic c-axis tunnelling in the superconducting state has been measured in
zero and finite fields in small mesa structures fabricated on the surface of
2212-BSCCO single crystals. The temperature dependence of the zero-field
critical current and quasi-particle conductance is related to microscopic
d-wave models in the presence of impurity scattering. The strong field
dependence of the c-axis critical current provides information on the
correlation of flux pancakes across adjacent superconducting bi-layers. An
instability in the IV characteristics is observed below 20K, which accounts for
the apparent drop in critical current at low temperatures previously reported.
