The dynamical properties of the surface density of a constant-energy e
nsemble are discussed. An equilibrium surface density is introduced an
d used to calculate single- and multivariable distributions for first-
and second-order Hamiltonians. In particular the distribution of inter
sections in a Poincare surface of section for a second-order Hamiltoni
an is obtained. The results an applied to the special case of one simp
le harmonic oscillator, two uncoupled simple harmonic oscillators, and
the Henon-Heiles system.