The equations of motion and the principle of equilibrium determine the signes of viscosity, heat conductivity, mass, elastic modulus and heat capacity in terms of the sign of absolute temperature. Furthermore, these thermodynamic conditions show that light velocity is the upper limit for the velocity of elastic waves. The equations of motion contain the 2nd time derivative of the velocity of substance, in perfect analogy to Dirac's theory of the point election. The linear approximation of the

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... uations is discussed. The equilibrium for a rotating fluid and for a fluid in a gravistatic field are given. In particular, a method is used (see annex), which shows that the use of Lagrange Multipliers is valid not only for an extremum but also for a maximum (or minimum), if the functionals involved are of the density type.