We study the spectrum of the Laplacian acting on 1-forms for a surface
of revolution diffeomorphic to S-2 and obtain, for the S-1 invariant
spectrum, a trace formula for the eigenvalues of its Green's operator.
The trace formula is used to ''hear'' negative curvature for some met
rics and to prove the existence of metrics on S-2 with rather unusual
spectral characteristics.