  The far-infrared (FIR) c axis conductivity of a Bi2223 crystal has been
measured by ellipsometry. Below T$_c$ a strong absorption band develops near
500 cm $^{-1}$, corresponding to a transverse Josephson-plasmon. The related
increase in FIR spectral weight leads to a giant violation of the
Ferrell-Glover-Tinkham sum-rule. The gain in c axis kinetic energy accounts for
a sizeable part of the condensation energy. We also observe phonon anomalies
which suggest that the Josephson-currents lead to a drastic variation of the
local electric field within the block of closely spaced CuO$_2$ planes.
