  A normal-fluid component varying as T$^{2}$ is observed at very low
temperatures in superfluid $^4$He and $^3$He-$^4$He mixture films adsorbed in
alumina powder. The normal fluid appears to arise from thermally excited third
sound that has one-dimensional propagation characteristics. A Landau model of
third sound excitations in an infinite cylindrical pore by Saam and Cole
provides good agreement with the experimental measurements over a wide range of
$^4$He and $^3$He coverages. However, it is unclear why the powder substrate
can be modeled as having cylindrical pores.
