  The dynamics of the soliton in a self-attractive Bose-Einstein condensate
under the gravity are investigated. First, we apply the inverse scattering
method, which gives rise to equation of motion for the center-of-mass
coordinate of the soliton. We analyze the amplitude-frequency characteristic
for nonlinear resonance. Applying the Krylov-Bogoliubov method for the small
parameters the dynamics of soliton on the phase plane are considered.
Hamiltonian chaos under the action of the gravity on the Poincar\'e map are
studied.
