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is only very slightly larger than the ponderable mass which is quite independent of temperature. In any case, however, a notable reduction in the latent energy would also result in a notable reduction of the ponderable mass. The future will teach us whether such an influence will ever be directly detected.

Fourth Section. Introduction of new independent variables.

§ 19.

The expression (38) for the kinetic potential H found in the previous section has the same form as that for the kinetic potential of a single material point moving with constant mass M, which was found by me in a previous study^[1]:

$-Mc^{2}{\sqrt {1-{\frac {q^{2}}{c^{2}}}}}+const$

(49)

However, the agreement is not complete: for that it would be necessary that $M=-{\frac {H'_{0}}{c^{2}}}$, which according to equation (48) is not at all the case. The reason for this apparent contradiction is that the quantity H which was denoted as the kinetic potential, means something different than there, as can be seen most easily by considering the equations of motion (6). These equations can be found in my earlier paper in exactly the same form as here, but there the differential quotients ${\frac {\partial H}{\partial {\dot {x}}}},\ {\frac {\partial H}{\partial {\dot {y}}}},\ {\frac {\partial H}{\partial {\dot {z}}}}$ have a different meaning, because in that place the differentiation was not to be given in a isothermal but in a adiabatically-isobar way. As the material point moves without external heat supply under the constant external pressure zero, then according to § 6 it has variable volume and variable temperature. To make that difference clear, I will at this place refer by K to the former size H, so that we have the equations:

$\left({\frac {\partial K}{\partial {\dot {x}}}}\right)_{p,S}=\left({\frac {\partial H}{\partial {\dot {x}}}}\right)_{V,T}$, etc.

(50)

1. Verhandlungen der Deutschen Physikalischen Gesellschaft 8, p. 140, 1906.