Page:Zur Dynamik bewegter Systeme.djvu/24

 mass of the body, while on the other hand, the derivative $$\frac{dG}{dq}$$ is the "longitudinal" mass. In the longitudinal mass is, however, the "isothermal-isochoric" mass to be distinguished from the "adiabatic-isobaric" mass, etc.; because the derivative has only one definite value when the path of differentiation is given. For the special speed q = 0, transverse and longitudinal masses of all forms become the same, i.e. they become (48).

The mass of a stationary cavity radiation is, therefore, given by (5):

the transverse mass of a moving cavity radiation:

the longitudinal isothermal isochoric mass of that

the longitudinal adiabatic isochoric mass:

the longitudinal adiabatic-isobaric mass, on the contrary:

Especially notable in relation (48) is the close connection of the mass of a body with the thermal function R0. Since mass M can easily be measured in grams, then the quantity of R0 immediately can be given by the absolute CGS system. But this value can not be tested directly by thermodynamic means; because an additive constant of the thermal function, as well as of energy, remains unspecified by pure thermodynamics. In this respect, relation (48) is essentially a complement to the thermodynamic definition of energy.

In contrast, there arises a possibility of an experimental test of the theory by taking into account the variability of the