  The twin peaks in the nucleus of M31 have been interpreted by Tremaine as a
thick, eccentric, disk of stars orbiting a massive dark object; the required
alignment of the apoapsides of the stellar orbits could be maintained by
self-gravity, and the whole structure might be a discrete, nonlinear eigenmode.
The pattern speed of this mode could, in principle, be determined by the
Tremaine-Weinberg (TW) method, which requires measurements of the surface
brightness, and radial velocity along a strip parallel to the line of nodes.
However, spectroscopic observations along the line of nodes are not available.
We propose a variant of the TW method, which exploits a basic feature of the
eccentric disk model, to extract estimates of the pattern speed from {\it
Hubble Space Telescope} spectroscopic data, taken along the line joining the
two peaks. Within limitations imposed by the data, we estimate that the pattern
rotates in a prograde manner and, for an assumed disk inclination of
$77^{\circ}$, the pattern speed $|\Omega_p| < 30 {\rm km s^{-1} pc^{-1}}$, or
period more than $200,000$ years.
