  We consider an uniformly charged incompressible nuclear fluid bounded by a
closed surface. It is shown that an evolution of an axisymmetric surface
$\Gamma(\bbox{r},t)\equiv \sigma - \Sigma(z,t) = 0,\quad
\bbox{r}=(\sigma,\phi,z)$ can be approximately reduced to a motion of a curve
in the $(\sigma,z)$-plane. A nonlinear integro-diffrerential equation for the
contour $\Sigma(z,t)$ is derived. It is pointed on a direct correspondence
between $\Sigma(z,t)$ and a local curvature, that gives possibility to use
methods of differential geometry to analyze an evolution of an axisymmetric
nuclear surface.
