On the Variation of the Electromotive Force in a Photoactive Cell, Containing a Fluorescent Electrolyte, with the Intensity of Illumination.

With regard to the second law of thermodynamics, as given by equation (6), it should be noted that the sign "is greater than" applies to the case of a system which is approaching the condition of thermodynamic equilibrium and implies a difference between "forward" and "backward" directions for the time-like coordinate x4. The equality sign, on the other hand, may characterize either a system which is in a condition Qf thermodynamic equilibrium, or one in which changes in the direction of equilibrium are not taking place. To distinguish the important case of thermodynamic equilibrium from one of mere delayed change is usually not difficult, since it is merely necessary to see if zero is the maximum possible value for the integral in equation (6).