  We have recently derived two-fluid hydrodynamic equations for a trapped
weakly-interacting Bose gas. In this paper, we use these equations to discuss
first and second sound in a uniform Bose gas. These results are shown to agree
with the predictions of the usual two-fluid equations of Landau when the
thermodynamic functions are evaluated for a weakly-interacting gas. In a
uniform gas, second sound mainly corresponds to an oscillation of the
superfluid (the condensate) and is the low frequency continuation of the
Goldstone-Bogoliubov symmetry-breaking mode.
