  We relate Gaussian curvature to the gyroscopic force, thus giving a
mechanical interpretation of the former and a geometrical interpretation of the
latter. We do so by considering the motion of a spinning disk constrained to be
tangent to a curved surface. It is shown that the spin gives rise to a force on
the disk which is equal to the magnetic force on a point charge moving in a
magnetic field normal to the surface, of magnitude equal to the Gaussian
curvature, and of charge equal to the disk's axial spin. In a special case,
this demonstrates that the precession of Lagrange's top is due to the curvature
of a sphere determined by the parameters of the top.
