  An explicit Lorentz covariant formulation of the canonical theory for
classical fields is established on a space-like hypersurface. Hamilton's
equations and a Poisson bracket are defined on the space-like hypersurface. The
Poisson bracket relations between total momentum and total angular momentum
satisfies the Poincar{\'e} algebra. It is shown that our Poisson bracket has
the same symplectic structure that was brought in the covariant symplectic
approach.
