Abstract
An exact derivation of HAMILTON's principle has been shown for the non-viscous fluid dynamics. The principie of virtual work has been applied to the LAGRANGE-type dynamic equation of the fluid. The conservation laws of mass and energy as well as the geometrical boundary condition have been treated as subsidiary conditions. In the present variational method, a new concept of substantial variations of the state variables has been introduced in order to describe the subsidiary conditions in the correct forms. By use of this concept, it has been found that HAMILTON's principle for the fluid dynamics can be exactly derived from the principle of virtual work through the familiar manner in the classical dynamic problems. And also the theoretical foundation has been given to HERIVELLIN's principle.
