  We evaluate the small-amplitude excitations of a spin-polarized vapour of
Fermi atoms confined inside a harmonic trap. The dispersion law
$\omega=\omega_{f}[l+4n(n+l+2)/3]^{1/2}$ is obtained for the vapour in the
collisional regime inside a spherical trap of frequency $\omega_{f}$, with $n$
the number of radial nodes and $l$ the orbital angular momentum. The low-energy
excitations are also treated in the case of an axially symmetric harmonic
confinement. The collisionless regime is discussed with main reference to a
Landau-Boltzmann equation for the Wigner distribution function: this equation
is solved within a variational approach allowing an account for
non-linearities. A comparative discussion of the eigenmodes of oscillation for
confined Fermi and Bose vapours is presented in an Appendix.
